Showing papers on "Electric potential published in 1999"
TL;DR: The physical mechanisms underlying the transport of ions across a model potassium channel, which corresponds closely to that deduced from crystallography, and the conductance exhibits the saturation property observed experimentally are described.
210 citations
TL;DR: In this article, electric potential variations, radon emanation and deformation measurements recorded since 1995 in the French Alps in the vicinity of two artificial lakes which have strong seasonal variations in water level of more than 50 metres.
Abstract: Two of the most often cited earthquake precursors are radon emanation and electric potential variations, but these few reported examples have generally been deemed questionable. If a mechanism relating crustal deformation to radon emanation or electrical signals does indeed exist, it is thought to involve fluids. Some preliminary insight has been gained into these processes from the study of natural systems under controlled mechanical and hydrological conditions. Here we report electric potential variations, radon emanation and deformation measurements recorded since 1995 in the French Alps in the vicinity of two artificial lakes which have strong seasonal variations in water level of more than 50 metres. We observe that electric potential variations and radon emanations are repeatedly associated with transient deformation events induced by variations in lake levels. These events are characterized by a change in ground tilt which deviates from the expected elastic response, and are associated with periods of accelerating strain, which suggests that accelerated loading can enhance fluid transport properties. Qualitatively, this behaviour can be accounted for by a model in which straining induces fluid overpressure and dynamic flow in cracks. These observations may shed light on the sensitivity of rock transport properties to deformation.
174 citations
TL;DR: In this article, a self-excited vertical oscillation of dust particles in a Coulomb crystal has been observed near the plasma-sheath boundary of a dc plasma operated at a low plasma density and gas pressure.
Abstract: A self-excited vertical oscillation of dust particles in a Coulomb crystal has been observed. It occurs near the plasma-sheath boundary of a dc plasma operated at a low plasma density and gas pressure. The excitation of this spontaneous oscillation is attributed to the finite charging time of particles. As particles move, their charge varies with the local plasma conditions, but with a delay due to the charging time. As particles traverse the vertical electric potential gradient in the sheath, they gain energy. A model of this mechanism is developed to predict the instability threshold and the energy gain.
147 citations
TL;DR: In this paper, a three-dimensional, stationary, two-fluid plasma model for electrons and one ion species was developed to understand the local interaction of Io's atmosphere with the Io plasma torus and the formation of Io ionosphere.
Abstract: A three-dimensional, stationary, two-fluid plasma model for electrons and one ion species was developed to understand the local interaction of Io's atmosphere with the Io plasma torus and the formation of Io's ionosphere. Our model calculates, self-consistently, the plasma density, the velocity and the temperatures of the ions and electrons, and the electric field for a given neutral atmosphere and imposed Io plasma torus conditions but assumes for the magnetic field the constant homogeneous Jovian field. With only photoionization in a pure SO2 atmosphere it is impossible to correctly model the plasma measurements by the Galileo spacecraft. With collisional ionization and photoionization the observations can be successfully modeled when the neutral atmospheric column density is Ncol = 6 × 1020 m−2 and the atmospheric scale height is H = 100 km. The energy reservoir of the Io plasma torus provides via electron heat conduction the necessary thermal energy for the maintenance of the collisional ionization process and thus the formation of Io's ionosphere. Anisotropic conductivity is shown numerically as well as analytically to be essential to understand the convection patterns and current systems across Io. The electric field is very greatly reduced, because the ionospheric conductances far exceed the Alfven conductance ΣA, and also strongly twisted owing to the Hall effect. We find that the electric field is twisted by an analytic angle tan Θtwist = Σ2/(Σ1 + 2ΣA) from the anti-Jupiter direction toward the direction of corotation for constant values of the Pedersen and Hall conductances Σ1 and Σ2 within a circle encompassing Io's ionosphere. Because the electron velocity is approximately equal to the E × B drift velocity, the electron flow trajectories are twisted by the same angle toward Jupiter, with E and B the electric and magnetic fields, respectively. Since Σ1 ∼ Σ2, the electron flow is strongly asymmetric during convection across Io, and the magnitude of this effect is directly due to the Hall conductivity. In contrast, the ions are diverted slightly away from Jupiter when passing Io. Large electric currents flow in Io's ionosphere owing to these substantially different flow patterns for electrons and ions, and our calculations predict that a total electric current of 5 million A was carried in each Alfven wing during the Galileo flyby. We also find a total Joule heating rate dissipated in Io's ionosphere of P = 4.2 × 1011 W.
144 citations
TL;DR: In this paper, small-scale solitary electric potential structures are commonly observed on auroral field lines with the Polar Electric Field Instrument (EFI) and the velocities of these "ion" solitary structures are estimated, using spaced EFI measurements, to be distributed within the range of ∼75 − 300 km s−1.
Abstract: Small-scale solitary electric potential structures are commonly observed on auroral field lines with the Polar Electric Field Instrument (EFI). This study focuses on observations of solitary structures in the southern hemisphere auroral zone at altitudes between 5500 and 7500 km. Some of the potential structures are similar to those observed previously by the S3-3 and Viking satellites and are inferred to be negative potential pulses traveling upward along the auroral magnetic field lines, associated with upgoing ion beams and upward currents. The velocities of these “ion” solitary potential structures are estimated, using spaced EFI measurements, to be distributed within the range of ∼75 – 300 km s−1. In addition to these structures, a different type of solitary potential structure with.opposite polarity has been observed with faster propagation velocities. These faster structures (termed “electron” solitary potential structures) are distinguishable from the slower, ion solitary structures in that their distinctive bipolar electric field signature, common to both types of solitary structure, is reversed. The ultimate distinction for the electron solitary potential structures is that they are observed on auroral field lines in conjunction with magnetically field-aligned upflowing electron beams. The electron solitary potential structures propagate up the field line in the same direction as the electron beam. An example is shown of the polarity reversal from ion to electron solitary potential structures coincident with a simultaneous shift from upgoing ion beams to upgoing electron beams.
112 citations
20 Jul 1999
TL;DR: In this article, the relations between electrohydrodynamic variables at moving and deformable interfaces of immiscible liquids in the presence of surface electrical charge and a double electrical layer are derived.
Abstract: The relations between electrohydrodynamic variables at moving and deformable interfaces of immiscible liquids in the presence of surface electrical charge and a double electrical layer are derived. Received relations at the interfaces can be used as boundary conditions in solving the problems of electrohydrodynamics both with still and with moving and deformable boundaries. The presence of the double electrical layer on the interface between liquids can be a reason for electric field formation at flows in contacting immiscible liquids. The problem of variable electric potential occurrence at the pulsation of a drop of one liquid in the other liquid is investigated.
111 citations
TL;DR: In this article, the electric potential distribution in the dark in nanocrystalline porous semiconductor electrodes, in full depletion conditions, was investigated and a model based on a columnar shape was developed to overcome the limitations of results based on these geometries.
Abstract: This study concerns the electric potential distribution in the dark in nanocrystalline porous semiconductor electrodes, in full depletion conditions. Since band bending in a single colloidal particle is small, the idea is to develop a model that accounts for the total potential drop resulting from the equilibration between the Fermi level and the redox potential in the solution. As preliminary steps, the band bending and potential distribution in a planar electrode and also in a colloidal semiconductor particle are reviewed. In order to overcome the limitations of results based on these geometries, a model based on a columnar shape is developed. The Poisson equation is solved in the columnar electrode, with careful consideration of the boundary conditions. A large potential drop is shown to take place at the back contact. To complete the study, the effect of the depletion zone in the transparent conducting oxide is analysed. Simple expressions are derived that permit evaluation of how the total potential drop is distributed between the electrode and the substrate. From this, the strength and spatial range of the electric field in the electrode can be estimated.
105 citations
TL;DR: In this article, the structure of the Taylor meniscus and emitted jet is studied by perturbation methods in the limit of low flow rates, and an asymptotic system of governing equations is derived from the basic equations of electrohydrodynamics, taking into account the inertia and viscosity of the liquid as well as the surface ion mobility.
Abstract: In this paper the structure of the Taylor meniscus and emitted jet is studied by perturbation methods in the limit of low flow rates. An asymptotic system of governing equations is derived from the basic equations of electrohydrodynamics. They rigorously take into account the inertia and viscosity of the liquid as well as the surface ion mobility. The solutions to the asymptotic equations in the meniscus, jet and surrounding gas regions are found, matched with each other, and applied to study distributions of electric and hydrodynamic variables. Such an approach allows the liquid velocity, surface charge, and meniscus-jet radius as well as electric potential inside and outside the liquid to be calculated. We also derive the theoretical dependences of the current carried by the jet and its diameter on the liquid properties and flow rate. These dependences are consistent with the scaling laws found experimentally by Fernandez de la Mora & Loscertales (1994) and data obtained by Chen & Pui (1997).
86 citations
TL;DR: In this paper, the structure of the non-neutral region is shown to vary significantly with the ratio of the negative ion and electron densities at the core edge, the ratios of ion and ion temperatures, and the ratio for the electron Debye length to the ion mean free path.
Abstract: In three component electronegative discharges a parameter regime can be found in which the positive ions reach the local ion sound velocity at a position where the negative ion density may be significant compared to the electron density. For this regime a quasineutral electronegative core breaks down and a space charge region forms. Solutions in the space charge region are obtained in collisionless and collisional cases, neglecting ionization and positive-negative ion recombination. The structure of the non-neutral region is shown to vary significantly with the ratio of the negative ion and electron densities at the core edge, the ratio of ion and electron temperatures, and the ratio of the electron Debye length to the ion mean free path. If the first ratio is not too large the non-neutral region displays potential oscillations on the electron Debye length spatial scale, which damp away on the scale of the ion–neutral mean free path. The non-neutral region then terminates within the plasma. The change in electric potential across this region is several times the negative ion temperature, which is sufficient to confine the negative ions to the core. The non-neutral region merges with a quasineutral halo containing essentially only positive ions and electrons. If the negative ion density is sufficiently high compared to the electron density the electropositive halo disappears and the non-neutral region extends from the ion sound velocity threshold to the wall. For intermediate values of the negative ion density, a space charge double layer forms between the electronegative and electropositive regions.
78 citations
TL;DR: In this article, an electrostatic potential between the droplet formation device and the collecting solution is applied to obtain smaller droplets which are desirable for many applications, and droplet size is mainly determined by the jet instability (theory of Rayleigh)
Abstract: Microcapsules are produced by a dropwise addition of one solution into a solidifying bath By applying an electrostatic potential between the droplet formation device and the collecting solution, it is possible to obtain smaller droplets which are desirable for many applications Droplet formation may be divided into two phases Under a certain critical value of the electric potential Uc, liquid exits the nozzle as droplets The surface tension decreases with increasing electric potential resulting in a reduction of droplet diameter to approximately 200 μm At higher electric potential, liquid exits the nozzle as a jet which subsequently breaks into droplets, which are smaller than 200 μm In this case, droplet size is mainly determined by the jet instability (theory of Rayleigh)
78 citations
TL;DR: In this article, the theory of electrostatic dispersion of polyelectrolyte solutions is elaborated in order to describe the effect of the applied electric potential U and different physico-chemical factors on the droplet size.
TL;DR: In this article, the authors describe nanometer scale characterization of piezoelectric thin films of lead-zirconate-titanate and show that it is possible to form and subsequently image ferroelectric domains using the cantilever in resonant mode.
Abstract: In this article, we describe nanometer scale characterization of piezoelectric thin films of lead-zirconate-titanate. Using the electric field from a biased conducting atomic-force microscope tip, we show that it is possible to form and subsequently image ferroelectric domains. Using the cantilever in resonant mode, we show that it is also possible to map the surface-potential distribution. Using a sphere-plane model for the tip-sample system we calculate the distribution of electric potential, field and polarization charge, and find good agreement with the experimental values. We also discuss the effects of surface contaminants on domain formation.
TL;DR: An experimental method is described for the measurement of charge transfer during bacterial adhesion in situ to a transparent, semiconducting indium tin oxide (ITO) coated glass plate in a parallel plate flow chamber.
TL;DR: A systematic study of flow in T-shaped intersecting channels showed that the hydrodynamic effect is an important factor that influences fluid leakage out of a channel where the electric potential is left floating.
TL;DR: In this paper, the authors investigated nodal sets of magnetic Schrodinger operators with zero magnetic field acting on a non-simplified domain in ℝ2 and obtained a characterisation of the nodal set, and used this to obtain bounds on the multiplicity of the groundstate.
Abstract: We investigate nodal sets of magnetic Schrodinger operators with zero magnetic field, acting on a non simply connected domain in ℝ2. For the case of circulation 1/2 of the magnetic vector potential around each hole in the region, we obtain a characterisation of the nodal set, and use this to obtain bounds on the multiplicity of the groundstate. For the case of one hole and a fixed electric potential, we show that the first eigenvalue takes its highest value for circulation 1/2.
TL;DR: In this article, the Poisson equation together with the drift-diffusion equations have been used to simulate both forward and reverse I-V and C-V characteristics of inhomogeneous Schottky diodes.
Abstract: The Poisson equation together with the drift-diffusion equations have been used to simulate both forward and reverse I–V and C–V characteristics of inhomogeneous Schottky diodes. The barrier height distribution has been modeled by a single Gaussian. It is shown that the I–V and C–V curves and consequently extracted apparent Schottky diode parameters depend only slightly, if at all, on a lateral correlation between the single barrier patches in the structure for larger dimension of patches. The apparent barrier height of ordered structures differ only in several thousandths of volt from that of uncorrelated barrier patches. Very small differences were also found between the currents through the diodes with large inhomogeneities and nanosize inhomogeneities. The numerical results show that there is almost no dependence of the current on a pinch-off effect of electric potential. The diminishing of a drift part of the total current in the area of pinched-off potential is probably compensated by a greater diffusion current in the region. Consequently, very small and not unambiguous differences were found between the so called interacting and noninteracting diodes and this division is, according to the above results, questionable.
TL;DR: In this paper, hybrid variational principles are employed for piezoelectric finite element formulation, starting from eight-node hexahedral elements with displacement and electric potential as the nodal d.o.f.s, hybrid models with assumed stress and electric displacement are devised.
TL;DR: In this article, the high-latitude, ionospheric electric potential have been derived for two groups, with and without the occurrence of magnetospheric substorms, and for all orientations of the interplanetary magnetic field.
Abstract: Characteristic patterns of the high-latitude, ionospheric electric potential have been derived for two groups, with and without the occurrence of magnetospheric substorms, and for all orientations of the interplanetary magnetic field (IMF). These maps were derived from all available, simultaneous Dynamics Explorer 2 and solar wind data, using a least error fit technique. There are distinctive patterns for each orientation of the IMF, both with and without substorms in progress. In comparison to the nonsubstorm electric potential patterns, the substorm group tends to have a more pronounced Harang discontinuity near midnight. The averages of the AE indices that were measured simultaneously with the electric potentials have also been analyzed. The AU index is found to be linearly proportional to the electric potential in the dusk cell, while the |AL| index compared with the dawn cell's potential has a nonlinear trend. The |AL| index is distinctively greater for the substorm group, as expected, while the electric potential and AU index remain relatively unchanged. The measured electric potential patterns have been combined with a conductivity model in order to derive ionospheric and field-aligned currents. The Harang discontinuity is prominent in the horizontal ionospheric currents, particularly for the substorm group. Model calculations of |AL| indicate that some of the substorm increase can be accounted for by an enhanced auroral conductivity, while the changes in the electric field's magnitude and orientation near midnight, in distortions that do not significantly increase the overall potential drop, also contribute to the substorm electrojet. The field-aligned currents show a systematic evolution of the region 1 and region 2 current belts as the IMF changes from a +Y to −Y orientation. For negative BY the upward currents form a continuous oval, linking the region 2 current on the dawn side with the region 1 current on the dusk side, through both noon and midnight. For positive BY the upward currents are no longer continuous through noon and are divided by downward current linking the region 2 current on the duskside with the region 1 current on the dawnside. The “region 0” or cusp currents, which move from prenoon to postnoon as the IMF BY changes from positive to negative, appear to be continuations of the post/prenoon region 1 current belts.
TL;DR: A new intermolecular force field of the (exp-6-1) type was derived from observed hydrocarbon crystal structures selected from a comprehensive set of 134 molecules with 5−16 carbon atoms, and eight observed heats of sublimation as discussed by the authors.
TL;DR: In this paper, a monotone scheme for finite volume simulation of magnetohydrodynamic internal flows at high Hartmann number is presented, where the numerical stability is analyzed with respect to the electromagnetic force.
TL;DR: In this article, the essential features of a full potential electronic structure method using Linear Muffin-Tin Orbitals (LMTOs) are presented, and the electron density and potential in the this method are represented with no inherent geometrical approximation.
Abstract: The essential features of a full potential electronic structure method using Linear Muffin-Tin Orbitals (LMTOs) are presented. The electron density and potential in the this method are represented with no inherent geometrical approximation. This method allows the calculation of total energies and forces with arbitrary accuracy while sacrificing much of the efficiency and physical content of approximate methods such as the LMTO-ASA method.
TL;DR: In this paper, the generalized first law of thermodynamics for an irreversible thermodynamic system was derived from the triphasic model for mechano-electrochemical mixtures, and a new biphasic mixture theory including the electrochemical effects including the deformation of a charged hydrated soft tissue was derived.
Abstract: From the generalized first law of thermodynamics for an irreversible thermodynamical system, a new set of governing equations for the mixture theory is derived based on the triphasic model for mechano-electrochemical mixtures. It is shown that, in the case of electroneutral solution, a new biphasic mixture theory including the electrochemical effects can be derived from the new governing equations. The chemical-expansion stress representing both the influences of deformation on the fixed charge density and the electric potential of fixed charge field is given. For comparison and verification purposes, the numerical solution for a confined compression problem of a charged hydrated soft tissue is computed using the multiquadric method.
TL;DR: In this paper, the Galerkin finite-element method is applied uniformly to all the equations in the mathematical system and the Newton iteration method is utilized to obtain quadratically converged steady-state solutions in a few steps.
TL;DR: In this article, the authors present an analysis of crack problems in homogeneous piezoelectrics or on the interfaces between two dissimilar bimaterial materials based on the continuity of normal electric displacement and electric potential across the crack faces.
Abstract: This paper presents an analysis of crack problems in homogeneous piezoelectrics or on the interfaces between two dissimilar piezoelectric materials based on the continuity of normal electric displacement and electric potential across the crack faces. The explicit analytic solutions are obtained for a single crack in an infinite piezoelectric or on the interface of piezoelectric bimaterials. For homogeneous materials it is found that the normal electric displacement D-2, induced by the crack, is constant along the crack faces which depends only on the remote applied stress fields. Within the crack slit, the perturbed electric fields induced by the crack are also constant and not affected by the applied electric displacement fields. For bimaterials, generally speaking, an interface crack exhibits oscillatory behavior and the normal electric displacement D-2 is a complex function along the crack faces. However, for bimaterials, having certain symmetry, in which an interface crack displays no oscillatory behavior, it is observed that the normal electric displacement D-2 is also constant along the crack faces and the electric field E-2 has the singularity ahead of the crack tip and has a jump across the interface. Energy release rates are established for homogeneous materials and bimaterials having certain symmetry. Both the crack front parallel to the poling axis and perpendicular to the poling axis are discussed. It is revealed that the energy release rates are always positive for stable materials and the applied electric displacements have no contribution to the energy release rates.
TL;DR: In this article, a functional relationship between the electric and gravitational potentials has been studied and the Majumdar condition is shown to hold for a bounded perfect fluid only if the matterpressure vanishes (that is, charged dust).
Abstract: Static solutions of the electro-gravitationalfield equations exhibiting a functional relationshipbetween the electric and gravitational potentials arestudied. General results for these metrics are presented which extend previous work of Majumdar. Inparticular it is shown that for any solution of thefield equations exhibiting such a Weyl-typerelationship, there exists a relationship between thematter density, the electric field density and the chargedensity. It is also found that the Majumdar conditioncan hold for a bounded perfect fluid only if the matterpressure vanishes (that is, charged dust). Byrestricting to spherically symmetric distributions ofcharged matter a number of exact solutions are presentedin closed form which generalise the Schwarzschildinterior solution. Some of these solutions exhibitfunctional relations between the electric andgravitational potentials different to the quadratic oneof Weyl. All the non-dust solutions are well-behavedand, by matching them to the Reissner-Nordstromsolution, all of the constants of integration areidentified in terms of the total mass, total charge andradius of the source. This is done in detail for anumber of specific examples. These are also shown tosatisfy the weak and strong energy conditions and manyother regularity and energy conditions that may berequired of any physically reasonable matterdistribution.
TL;DR: In this article, a numerical model of the electric and magnetic fields associated with fluid flow variations at the Nankai Trough is presented which gives a numerical solution of the coupled system of electric convection currents and conduction currents that directly determines the magnetic anomaly itself.
Abstract: Detection of changes in the flow rate of expelled fluids in accretionary prisms by monitoring of electric and magnetic fields is discussed. A numerical model of the electric and magnetic fields associated with fluid flow variations at the Nankai Trough is presented which gives a numerical solution of the coupled system of electric convection currents and conduction currents that directly determines the magnetic anomaly itself. Measurements in a borehole located between two vents are shown to be well adapted to detection of fluid flow variations using the vertical gradient of the electric potential and the horizontal magnetic field. The vertical electric field is about 10 mV/km up to 500 m depth where there is a lithologic reflector and about 50 mV/km below this reflector. The horizontal gradient of the magnetic field is 2 nT/km at the seafloor. Modelization with a lower fault conductivity and a larger decollement thickness has also been modeled. The vertical gradient of the horizontal magnetic field is ~5 to 15 nT/km. A variation of 3 mV and 1.5 to 3 nT at 600 m depth in a borehole could reveal a fluid flow rate variation of 20%, which is a reasonable fluid flow change based on some observations at short-scale time. Since a 1.5 to 3 nT anomaly seems easier to detect than a 3 mV anomaly, it is likely that the variation of the magnetic field would more sensitively reveal fluid flow variations. When monitoring the magnetic field at the seafloor, a change of 0.4 nT/km in the horizontal gradient could reveal a fluid flow rate variation of 20%.
Patent•
30 Jul 1999
TL;DR: In this paper, a micro-system with multiple points for chemical or biological analysis consisting of a structure provided with micro-cups (7), each microcup designed to receive a reagent (14a, 15a, 16a) coupled with a conductor polymer, each micro-cup having a receiving electrode (9a) whereon is fixed the reagent via of the polymer conductor with which it is coupled.
Abstract: The invention concerns a micro-system with multiple points for chemical or biological analysis consisting of a structure provided with micro-cups (7), each micro-cup designed to receive a reagent (14a, 15a, 16a) coupled with a conductor polymer, each micro-cup having a receiving electrode (9a) whereon is fixed the reagent via of the polymer conductor with which it is coupled, each micro-cup having a counter-electrode (9b) arranged so as to apply, in a volume of the micro-cup, an electric field between its counter-electrode and its receiving electrode, the structure having means for simultaneously connecting all the receiving electrodes to a first electric potential and means for simultaneously connecting all the counter-electrodes to a second electric potential for generating said electric field.
TL;DR: In this paper, a particle-in-cell simulation is used to study the time-dependent evolution of the potential and the electrical field surrounding two-dimensional objects during a high voltage pulse in the context of plasma immersion ion implantation.
Abstract: A particle-in-cell simulation is used to study the time-dependent evolution of the potential and the electrical field surrounding two-dimensional objects during a high voltage pulse in the context of plasma immersion ion implantation. The numerical procedure is based on the solution of Poisson’s equation on a grid and the determination of the movement of the particles through the grid. Ion current density, implanted concentration, average impact energy, and impact angle of the ions were calculated using this method for two geometrical shapes, a square and an L-shaped object. The nonuniformity of the sheath potential near convex and concave corners is shown. The divergence of the electrical field in the vicinity of corners leads to dramatically reduced concentration of the incident ions. The simulation also shows that a large ion flux hits the surface during the rise time of the pulse. Directly after the rise time, more than 40% of the whole concentration is implanted. Hence, the average impact energy of t...
TL;DR: In this paper, a method for the determination of velocity fields in conducting fluids is presented, where applying a magnetic field from outside, electric and magnetic fields are induced by the fluid motion.
Abstract: A possibility for the determination of velocity fields in conducting fluids is presented. Applying a magnetic field from outside, electric and magnetic fields are induced by the fluid motion. These fields can be measured at the walls and outside the fluid volume, respectively. The inverse problem of reconstructing the velocity from the measured electric and magnetic fields is solved using Tikhonov regularization.
TL;DR: In this article, the potential difference between two surfaces of zirconia is reported, when a normal stress is applied to one surface, leaving the other surface stress free, and the potential differences are proportional to the applied stress over a wide range.