Nonlinear Electrical Properties Research Articles

Study of the electrical field inside biological structures

A method to compute accurately the electric field behaviour inside spherical and cylindrical structures is presented. These structures model a living cell and a nerve axon, respectively, taking into account the non-linear electric properties of the lipidic bi-layer surrounding membrane. It is shown that, for most of the cases of practical interest, the linearisation of the membrane characteristic is correct, since the threshold for non-linear effects is very high. When large-size biological structures, such as squid giant axons, are considered, non-linear effects also arise in the case of relatively small applied fields.

Non-linear electrical properties of skin in the low frequency range.

This paper describes the non-linear electrical properties of the skin during the passage of a sinusoidal current from the standpoint of the constant-current method. The non-linearity occurs in the current dependency of the skin impedance and in Lissajous figures. It exhibits both rapid and slow variations. The concept of a non-linear impedance and its equivalent circuit are introduced for a sinusoidal voltage. With regard to the current dependency of the impedance it can be said that both the starting point and the degree of the dependency vary with frequency and impedance. The nonlinearity is more apparent with a larger current, a lower frequency, and a higher impedance. with an increasing current, the ionic conductance increases and the polarisation admittance decreases. Lissajous figures are formed when the voltage is distorted notably from the sinusoidal wave form. Detailed investigations are undertaken for the elliptic figures, third harmonics, rectification, and breakdown of the skin appearing with a decrease of the frequency and increase of the current. Finally, the special mechanism of the ionic conduction in the keratin layer is indicated as one of the causes for non-linearity.

Cation effects on the nonlinear electrical properties of DNA solutions.

AbstractThe nonlinear electrical properties of DNA solutions were measured when different monovalent cations were added to DNA. The influence of different parameters has been examined: fundamental frequency, field strength, and concentration. A linear relationship between the harmonic current Ih and the DNA concentration is shown, even for higher concentration values (400 mg/l.). The frequency dispersion of Ih has the same shape for all the cations and the low‐frequency amplitude of Ih increases in the following order: Li+ < Na+ < K+ < NH < Cs+. The nonlinear polarizability values are compared with the linear ones determined using the very low field electric birefringence technique. Both linear and nonlinear values are of the same order of magnitude. It is thought that the nonlinear electrical property of high‐molecular‐weight DNA mainly results from the deformation of the DNA coils by the electric field.

Dielectric nonlinearity and parametric interactions in strontium titanate and potassium tantalate single crystals at low temperature

Abstract Nonlinear and linear electric properties of SrTiO3 and KTaO3 single crystals were measured at microwaves in the temperature range 4.2–300 K. Nonlinear interactions (parametric amplification and subharmonic generation) were observed at 4.2 K in ferroelectric microwave resonators made of SrTiO3 single crystal.

Nonlinear electric properties of DNA solutions.

AbstractDNA solutions are shown to present a nonlinear electric behavior. This property is measured through the third harmonic current intensity, which appears when the solution is placed in a sinusoidal electric field of moderately high strength (about 100 V·cm−1).The influence of different parameters has been examined: fundamental frequency, field strength, concentration, molecular weight, and conformation. By progressive sonication, it is shown that the harmonic current is linearly proportional to the DNA molecular weight, but under an Mr of approximately 106, the nonlinear electrical property decreases sharply and its spectrum shows a drastic change.It is thought that the harmonic current is not related to an orientational phenomenon; an explanation based on the electrical deformation of the molecule is suggested.

Harmonic Bridge for Measurement of Nonlinear Electric and Electrooptic Properties of Crystals

A harmonic bridge circuit has been developed for measuring linear and nonlinear electric coefficients and quadratic electrooptic coefficients in high dielectric perovskite crystals. Third and fifth harmonic components are added to the fundamental audio-frequency driving voltage. The bridge is balanced when the charge or displacement of the crystal is sinusoidal. The harmonic content of the driving voltage may then be measured on a harmonic analyzer, from which measurements the electric coefficients of the crystal may be calculated. The same sinusoidal displacement may be used to display the electrically induced phase retardation intensity pattern on the oscilloscope. The effective electrooptic coefficients are readily determined from the oscillographs. The advantages of the harmonic bridge method are illustrated by measurements of the electric and electrooptic coefficients of a crystal of potassium tantalate niobate (KTN).

An electroluminescent digital indicator with a silicon carbide coding matrix

A digital indicator is described using an electroluminescent panel having its back electrode shaped as an array of lines, from combinations of which the digits are formed. Also described is a coding matrix which greatly simplifies the electrical switching needed for the indicator. The coding matrix utilizes the non-linear electrical properties of silicon carbide powder to discriminate between the voltage applied to wanted elements and unwanted elements, and allows a single-pole ten-way switch to be used for selecting the required digit.

The distribution of membrane current in nerve with longitudinal linearly increasing applied current

The distribution of membrane current in three models of nerve, when a longitudinal, linearly increasing current is applied, is derived. For the simple core conductor model it is shown that, if the region over which such a current is applied is large compared to the space constant of the model, the membrane current in the mid-portion of the region is a constant, independent of the distance, the time following the application of the current, and the impedance of the membrane. The effect of nonlinear membrane electrical properties is discussed. It is further shown that these conclusions apply equally to the case in which the simple model is surrounded by another concentric sheath (the double cable model). In this case the impedance of the sheath does not influence the membrane current in the mid-polar region. Finally, it is shown that the form of the solution for the saltatory model, for this type of applied current, is identical with that for the simple model.