Electric Polarization Effects Research Articles

Quantum chemical study of the HCl molecule and its binary complexes with CO, C 2H 2, C 2H 4, PH 3, H 2S, HCN, H 2O and NH 3: Hydrogen bonding and its effect on the 35Cl nuclear quadrupole coupling constant

The results of ab initio quantum chemical calculations are reported on the HCl molecule and the hydrogen bonded complexes B…HCl, where BCO, C 2H 2, C 2H 4, PH 3, H 2S, HCN, H 2O and NH 3. The main emphasis of this work is the accurate calc of the 35Cl nuclear quadrupole coupling constants, using SCF and averaged coupled pair functional methods, accounting for the electrical and geometrical polarization effects as well as librational averaging. Other quantities of interest that were calculated and compared with experiment include a range of one-electron properties for the HCl molecule such as its dipole and quadrupole moments, polarizability, the chlorine electric field gradient response tensors as well as derivatives of the field gradient. For the complexes the binding energies, dipole moment shifts, changes in the HCl bond length as well as in its stretching frequency and intensity are also reported. The overall agreement between theory and experiment, where comparison is possible, is very good. The hydrogen bonding and its effects on the dipole moment and the Cl field gradient are also analysed into electrostatic, exchange, polarization and charge transfer contributions using the Morokuma method and the constrained spatial orbital variation approach; these calculations convincingly demonstrate the importance of intermolecular exchange, especially with regard to the Cl field gradient.

Effects of electrical polarization on inner hair cell receptor potentials

Ac and dc receptor potential components in response to tone-burst stimuli were measured from inner hair cells in the third cochlear turn of the guinea pig. Comparisons were sought between conditions when constant polarizing current was injected into the cell through the recording electrode and when there was no extrinsic current. Hyperpolarization of the cell increased all responses, while depolarization decreased them. The input-output functions were vertically translated by current injection. The extent of translation was a function of current level. In addition, the amount of current-induced change was frequency dependent. Largest changes were seen at low frequencies and the current-induced change tended toward a constant high-frequency asymptote between 1-2 kHz. Changes in the dc response component were considerably in excess of those for the fundamental ac response. The frequency-dependent effects are quantified with the aid of a hair cell circuit model [P. Dallos, Hear. Res. 14, 281-291 (1984)]. It is assumed that the quantity altered by polarizing current (actually by the transmembrane voltage) is the resistance of the cell's basolateral membrane.

Heat induced polarization in molecular fluids

In this paper we discuss the interaction of electric polarization and the flow of heat. We show that in polar fluids, the flow of heat causes a spontaneous alignment of molecules generating an electric polarization. For the system studied the reciprocal effect of electric polarization upon the thermal conductivity appears to be weak.

Observation of quantum well polarization effects in the photocurrent of multilayer diodes

Large electrical polarization effects in the time photoresponse of multilayer heterostructure diodes have been observed. This phenomenon manifests itself in a displacement current spike synchronous to a dark–light transition and in an opposite spike in the light–dark one. The effect is associated with the pileup and spatial separation of photogenerated electrons and holes in the wells in the space-charge region of the diode. At a particular forward bias voltage, the conduction photocurrent is eliminated, allowing accurate measurements of this phenomenon.

A model of the effect of outer hair cell motility on cochlear vibrations.

A model of cochlear function is presented in which deformation forces within outer hair cells are assumed to occur in synchronized response to generator potentials. Assuming a 90 degree phase lag between the generator potentials and the deformation forces, it is shown that the forces act to reduce cochlear-partition damping and thus increase frequency selectivity. A number of other experimentally observed phenomena, such as the effects of efferent-fiber stimulation and electrical polarization, can also be accounted for with this model.

Estimation of applicability of the electrostatic model to calculate the crystal field parameters in garnets

The electrostatic model is used to calculate the electric field gradient (efg) at the cation sites for a number of garnets, such as RAlG ( R = Lu, Yb, Y, Dy, Gd), YFeG, YGaG and Na 3Sc 2V 3O 12, as well as the optical crystal field parameters (cfp) - Dq, v, v′, for Cr 3+ ions in YAlG in the octahedral sites. The calculations include the effects of electrical polarization of the oxygen sublattices (self-consistent dipole and quadrupole moments) and the local deformation of the lattice due to substitution of Al 3+ and Cr 3+. It is shown that the calculated efg correctly reflects the main properties of the experimental data. In the case of cfp for YAlG:Cr 3+, it is shown that this model provides a fairly good estimation of the twofold cfp whereas the fourfold cfp require a different analytical approach.

POSITRON ANNIHILATION STUDY OF ELECTRIC POLARIZA-TION EFFECT IN PIEZOELECTRIC CERAMICS OF PbZrO3-PbTiO3 SYSTEM

The electric polarization effect in piezoelectric ceramics of PbZrO3-PbTiO3 system (PZT) was examined by positron lifetime measurements. It was found that the mean lifetime τm increases with the increase of the electric field E. The micromechanism of the increase of τm was discussed, it may be mainly attributed to that the increase of the inner electric field would be energetically in favour of the positrons to form in qPs state. The measurements of the coupling factor K_p, the piezoelectric constant d33, and the dielectric constant ε33T/ε0 were also carried out and the results were compared with that of positron lifetime measurements. It is suggested that there is a possibility to take positrons as a tool for studying the extent of the domain turning and the changes of the energe situation of the electrons during the polarization.A special single sample method was used in the present work. Finally, our method of date analyzing was discussed.

On an axisymmetric boundary value problem for an elastic dielectric half-space

Hankel transforms are used to construct a closed-form solution for the axisymmetric boundary value problem of a point charge forced normal to the surface of an isotropic elastic dielectric semi-space. Exact closed form expressions are obtained for the components of displacement and polarization vectors in terms of the Bessel functions and the fundamental solutions (1/R), (e−mR/R), R being the distance from the source point. The electric potential fields are determined both inside and outside the elastic dielectric semi-space. In the absence of electric polarization effects, the problem reduces to the classical axisymmetric Boussinesq problem of a point force applied normal to the surface of an isotropic elastic semi-space. The expressions of the components of displacements derived from this particular case are found to agree with known results.

Cochlear frequency sharpening-a new synthesis.

Recent evidence indicates a substantial difference in sharpness of tuning between basilar membrane mechanics and primary neuron responses in mammals. This paper describes a new qualitative model for a sharpening mechanism. It is suggested that the inner hair cells are sensitive to d.c. potential changes in scala media that are induced by sound stimuli, and that these d.c. potentials can suppress neuron activity in a frequency-dependent way. The model explains sharpening of both sides of neural tuning curves, the shape of the low-frequency part of the tuning curves and is also compatible with other phenomena such as two-tone inhibition and the effects of electrical polarization of the basilar membrane.

Raman scattering in uniaxially oriented samples of planar zigzag poly(vinylidiene fluoride)

AbstractBand assignments of phase‐I PVF2 have been Revised by using additional data obtained by laser Raman spectra of oriented samples. A set of least‐squares refined force constants was obtained which reproduce the experimental data to an average error in frequencies of 1.3 cm−1. In order to determine the effect of electrical polarization on the spectra, a Gaussian distribution of the dipole axis was assumed. The calculation shows that polarizations of less than 60% will not significantly affect the Raman spectra.

Analytical model for a polarizable medium at radio and lower frequencies

The Maxwell equations are written and discussed in the frequency domain for a medium exhibiting electrical polarization at radio and lower frequencies, in the range of linearity between current density and electric-field intensity. A complex function of frequency is proposed for the conductivity, which is able to describe all the families of available experimental curves for rock samples in the natural state, showing the effect of polarization. Such a function is a constitutive relation for the polarizable medium in the frequency domain. The concept of ‘abnormal’ dielectric constant for rocks is discussed in the context of the physical mechanisms responsible for the effect of electrical polarization at radio frequencies and below. Such a concept, always possible theoretically, only introduces confusion in the understanding of the basic physical mechanisms involved. As an alternative the extensive use of the concept of a total current complex conductivity is suggested.

Effects of electrical current applied to cochlear partition on discharges in individual auditory-nerve fibers. I. Prolonged direct-current polarization.

This study is designed to reveal the effects of electrical polarization applied to the cochlear partition on discharges in individual auditory-nerve fibers in guinea pigs. Direct current is introduced in the basal turn across the organ of Corti. Its effects on the impulse discharges of the primary auditory fibers are measured during systematic variation of electrical and acoustic parameters. Data, recorded on tape, are analyzed by computing latency and interval histograms. With external current flowing from scala vestibuli to scala tympani, the spontaneous activity and sound-evoked responses increase in most of the auditory-nerve fibers. Current in the opposite direction causes decrease of impulse discharges. These nerve impulses show adaptation during application of the current and an aftereffect following its offset. It appears that electrical polarization modifies the resting current through the hair cells and also the excitability of the initial segment of the afferent auditory fibers.

Space-Charge Polarization in Glass Films

It is shown that electrical polarization effects in glass films can be conveniently studied using a metal-glass-silicon dioxide-silicon double-layer capacitor. The buildup of a polarization in the glass layer under the application of a voltage at elevated temperatures can be detected from the resulting shift ΔV in the capacitance-voltage characteristic. Equations are derived on the basis of a simple model which gives ΔV as a function of time, temperature, applied voltage, and the glass and oxide thicknesses. Experimental data for a lead borosilicate glass are presented and shown to be in excellent agreement with this model. The time constant for polarization of the glass has an activation energy of 1.05 eV and is of the order of weeks at room temperature and minutes at 100°C. The diffusion coefficient calculated from this time constant is in agreement with that for lead in glasses of similar composition and hence it is concluded that in this glass the major mobile ion is Pb++. Additional long-term polarization effects are observed when the metal is biased positively and these are related to the diffusion of sodium contaminant out of the glass layer into the underlying silicon dioxide.

Rapid Annihilations of Positrons in Polyatomic Gases

Experimental values are presented for the andnihilation rates in gases of slow positrons that have failed to form positronium. The observed values for argon, methane, ethane, propane, n-butane, isobutane, and carbon tetrachloride are found to exceed the values derived from Dirac theory by factors of 3 to 700. A Na/sup 22/ positron source was used in a cylinder where the sample gases were at up to 10 atm. and a constant (25 plus or minus 5) deg C. The effects of molecular electric polarization are discussed. (R.E.U.)

The effect of electrical polarization of the motor nerve endings on the transmission through them of single impulses

A frog nerve-muscle preparation was used to study the effects of depolarization and hyperpolarization of the transmission of single impulses at nerve endings. The efficacy of synaptic transmission was determined by the value of the end-plate potential led off intracellularly from the muscle fiber. Depolarization of the nerve endings produced a rapid reduction of up to 10–20% in the trans-synaptic action of the ending. Hyperpolarization of the endings caused the efficacy of trans-synaptic action to increase slowly for three minutes. In such cases the end-plate potential rose to 3 or 4 times the control level. These changes were observed only with a local polarization of the region of the nerve endings, and were absent when the preterminal branches of the nerve were polarized.

The effect of electric polarization of the spinal cord on central afferent fibres and on their excitatory synaptic action.

The Journal of PhysiologyVolume 162, Issue 1 p. 138-150 ArticleFree Access The effect of electric polarization of the spinal cord on central afferent fibres and on their excitatory synaptic action J. C. Eccles, J. C. EcclesSearch for more papers by this authorP. G. Kostyuk, P. G. KostyukSearch for more papers by this authorR. F. Schmidt, R. F. SchmidtSearch for more papers by this author J. C. Eccles, J. C. EcclesSearch for more papers by this authorP. G. Kostyuk, P. G. KostyukSearch for more papers by this authorR. F. Schmidt, R. F. SchmidtSearch for more papers by this author First published: 01 June 1962 https://doi.org/10.1113/jphysiol.1962.sp006920Citations: 80AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Citing Literature Volume162, Issue1June 1, 1962Pages 138-150 RelatedInformation

On adsorption at the oil/water interface and the calculation of electrical potentials in the aqueous surface phase. II. The effects of ionic size

An equation is derived similar to the Gouy equation for a flat diffuse double layer but which takes into acount the finite sizes of the adsorbed and counter ions. The corresponding equation giving the variation of potential with the distance from the plane of charge is derived for systems where the potential exceeds ca . 50 mV. A relation between specific surface charge and surface pressure (equation of state) is deduced on this basis for completely ionized adsorbed films. These equations are tested for films of sodium alkyl sulphates and dodecyltrimethylammonium bromide adsorbed at the petroleum-ether/water interface, allowance being made for the presence of counter-ions above the plane of the film ions. The modified equations predict the electrical potentials in the region of the interface much more completely than the simple Gouy equation. An estimate of the number of counter ions present in the region above the head groups is given and the possible effects of their presence there on surface viscosity and electrophoretic phenomena briefly considered. Other possible corrections to simple diffuse double-layer theory are discussed; it is concluded (in agreement with other recent authors) that electrical polarization and dielectric saturation effects tend to cancel out over the experimental range of electric field strengths. Fluctuation phenomena (‘self atmosphere * effects) may become important at high values of kx and in this region may cancel out the ionic size effect, so that the potential-distance relation derived from the standard Gouy-Chapman treatment should be obeyed in the outer regions of the diffuse double layer. Deviations occur from the modified Gouy equation for the shorter chain surface active agents in absence of any added electrolyte. The causes suggested are: (1) the inadequacy of the simple geometrical model used for determining the film ion size correction; (2) the inapplicability of the expression used to calculate bulk phase activity coefficients for detergents at high concentrations.

Effects of azide and electrical polarization on refractory period in frog nerve.

Effects of azide and electrical polarization on refractory period in frog nerve.

The Reaction of Hydrogen and Oxygen on Submerged Platinum Electrode Catalysts. I. Effect of Stirring, Temperature and Electric Polarization

The Reaction of Hydrogen and Oxygen on Submerged Platinum Electrode Catalysts. I. Effect of Stirring, Temperature and Electric Polarization

Course of spontaneous, rhythmic excitations on parabiotic nerve foci and the effect of electric polarization

Die einzelnen, denselben Muskel versorgenden motorischen Nervenfasern verhalten sich bei spontaner rhythmischer Tatigkeit, ausgehend von einer Parabiosestelle, nicht unabhangig voneinander, sondern unterliegen in ihrer Aktion einem gemeinsamen Steuervorgang.