Direct Current Flow Research Articles

THE EFFECT OF AN ELECTRICAL FIELD ON GERMINATION AND GROWTH OF SEEDLINGS

A weak electrical field has a stimulatory effect on germination of seeds and the early growth of young plants. Waldo bean seeds were placed in a chamber with moistened filter paper. Oppositely charged aluminum plates were used to stimulate growth. The top plate was,suspended above the filter paper to eliminate the possibility of a direct current flow through the paper. Each set of samples was examined after 5 days. The average root length of the test groups was significantly greater than that of the control groups. Additional experiments suggested that the rate of growth of the plants in soil was enhanced by applying a weak electric field to the soil. Using electricity to stimulate better germination has many practical applications. A current agricultural practice is to germinate seeds in dissolving tubes for planting as individual plants. Results of these experiments suggest that applying an electric current to the germinating seeds would stimulate them to grow more vigorously for more successful growth in the field, The use of electricity may have important applications as art adjunct to organic farming practices. Experiments are under way to apply the use of electricity to hydroponic systems. Foster, K.R. and H.P. Schwann. 1986. In: C. Polk and E. Postrow (eds.). CRC handbook of biological effects of electromagnetic fields. CRC Press, Inc., Boca Raton, Fla. Weaver, J.C. and R.D. Astumian. 1990. The response of living cells to very weak electric fields: The thermal noise limit. Science 247:459-462.

“Laminar” AND “turbulent” direct current flow in thin metal plates

Nonlinear and nonstationary effects in the do resistance of thin metal plates are studied experimentally. The bending of the electron trajectories in the self magnetic field of the current causes the resistance R to depend on the current. Current instability, in the form of periodic or random (parameter-dependind) self-oscillations of the voltage, was observed when current exceeds a certain value depending on the temperature and the width of the sample. The transition from monochromatic to random oscillations usually proceeds in accordance with the model proposed for arbitrary non-linear system by Ruelle and Takens. The possible physical origin of the observed effect is the inhom ogeneity of the current distribution over the sample cross section.

“Laminar” and “turbulent” direct current flow in thin metal plates

Nonlinear and nonstationary effects in the do resistance of thin metal plates are studied experimentally. The bending of the electron trajectories in the self magnetic field of the current causes the resistance R to depend on the current. Current instability, in the form of periodic or random (parameter-dependind) self-oscillations of the voltage, was observed when current exceeds a certain value depending on the temperature and the width of the sample. The transition from monochromatic to random oscillations usually proceeds in accordance with the model proposed for arbitrary non-linear system by Ruelle and Takens. The possible physical origin of the observed effect is the inhom ogeneity of the current distribution over the sample cross section.

Magnetic field of a direct current in a cylindrical-shaped conductor imbedded in a resistive half-space beneath a conductive surface layer

New applications of Fourier series and integral equation methods have yielded results of significance for electrical prospecting. This paper presents the first model calculation in three dimensions of the magnetic field due to a direct current flow in a conductor imbedded in a half-space beneath a conductive surface layer. The conductor is in the shape of a cylinder of semi-infinite length, and the current flow is from a point source in the surface layer. The vertical component of the magnetic field is given here by a Fourier series integral over a function which satisfies a Cauchy singular integral equation. For the two special cases, namely, an outcropping cylinder with no surface layer and a nearly invisible (in the sense of negligible conductivity contrast with its surrounding) cylinder, this integral equation can be solved exactly to yield closed-form expressions for the vertical component of the magnetic field. The exact solution in the first special case is based on a new generalization of the Hankel integral transform (published separately), and it extends the class of exactly solvable singular integral equations. This exact solution has also yielded as useful byproducts two new standard integrals involving Bessel functions. The integral equation approach used here, in contrast to the well-established surface integral equation approach, is suitable for numerical calculations, and typical magnetic field profiles are presented. The magnetic field results given here would be valuable for interpretation in electrical prospecting (based on the measurement of magnetic fields of direct currents), and the mathematical techniques used here would be useful for future calculations in electromagnetism.

Mechanisms responsible for decline in transthoracic impedance after DC shocks.

To test the hypothesis that tissue hyperemia and edema in the current pathway cause a decrease in transthoracic impedance (TTI) following direct current (DC) shock, the thoracic-skin and skeletal blood flow and blood volume were measured in anesthetized dogs after three 100-J shocks. TTI declined 11% (P less than 0.01) after DC shocks. Blood flow increased 10-fold in skeletal muscle from 0.9 +/- 0.2 to 11.3 +/- 2.6 (SE) ml.100 g-1.min-1 (P less than 0.05). Blood flow did not change outside the current pathway. Blood volume increased in skin in the current pathway from 7.6 +/- 1.5 ml/100 g preshock to 17.5 +/- 2.0 ml/100 g (P less than 0.01) at 60 min after shock; skeletal muscle blood volume did not change. We also determined postshock tissue weight before and after 72 h of drying at 70 degrees C. The percentage decline from wet weight after drying was 68.4 +/- 3.4% in the current pathway vs. 64 +/- 3.8% outside the pathway (P less than 0.05), indicating the tissue in the current pathway was more edematous. Finally, hindlimb edema was induced by deliberate overperfusion. As hindlimb circumference (edema) increased, impedance declined. We conclude that increases in tissue blood flow or tissue blood volume or tissue edema contribute to the decline in transthoracic impedance after DC shock.

Magnetic fields of direct currents in horizontally stratified conductors

A new proof is given of the result that, for direct current flow (from a constant current source) in a horizontally stratified conductor, the magnetic field outside the conductor is independent of its electrical conductivity. The original proof is based on symmetry considerations and the application of Ampére’s law to a contrived current circuit linking the horizontally stratified conductor. The new proof, however, does not rely on the use of any contrived current circuits, but is based on a rigorous analysis of the boundary value problem for the direct current flow in the horizontally stratified conductor. The mathematical techniques employed in this proof would be useful for future calculations in electromagnetism.

Formative mechanisms of current concentration and breakdown phenomena dependent on direct current flow through the skin by a dry electrode.

Direct current flow into the skin by dry electrode is useful in the fields of the electrocutaneous stimulation in sensory substitution systems and the probing of acupuncture points by means of electric resistance. During such. use, both the occurrences of a pain sensation and the electric breakdown of the skin become a hindrance to application. Equations describing these phenomena have been derived and the formative mechanisms of three phenomena, namely the current concentration in a minutely localized region, the occurrence of pain sensation as a result of heat generation, and the electric breakdown of the skin, have been made clear. The impottant values from which the key to solutions for these problems can be concretely obtained using equations are discussed in detail.

Reduction of Casing Leaks By Using Cathodic Protection-East Texas Field

Summary Our company has used cathodic protection successfully to reduce casing leaks as much as 75 % in the East Texas field, which produces oil from the Woodbine sand at approximately 3,600 ft (1181 m). Field operation information has been detailed for the casing cathodic protection system that began on an experimental basis in 1958 with 104 wells and was expanded to 1,034 wells by 1981. Introduction The company currently is operating 1,186 wells in the East Texas field. The East Texas field has been producing for 45 to 50 years, and some leases have a remaining estimated life of 50 years. Average well density is approximately 4 acres (1.6 × 10 to the 4th m2) per well (Table 1). Generally, cathodic protection can be justified in long-life fields and where casing leaks would cause a catastrophe, such as in sour gas fields. The East Texas field qualifies as long-lived. The majority of casing leaks in the field result from electrolytic corrosion from depths of 200 to 3,000 ft (65.6 to 984 m). The cathodic protection method of reducing casing leaks was installed first on 230 wells by other operators in 1956. We installed our first cathodic protection on 104 wells on an experimental basis in 1958. These wells were selected at random from various leases throughout the field and not necessarily from the high-leak-frequency areas. The need for cathodic protection was not critical in 1958 because we were experiencing only five leaks per year, but the predicted increase in casing leaks as the wells became older made cathodic protection more economical. This paper covers the trends of casing leaks from 1958 to the present. It gives company history of cathodic protection, details increasing costs of casing repair and cathodic protection installation and maintenance, and chronicles results of cathodic protection effectiveness over 9 years. Theory Cathodic protection can be defined as reduction or prevention of corrosion of a metal surface by making it cathodic with impressed currents. For well casing, this can be accomplished with direct current (DC) electricity from an external source to oppose the discharge of current from anodic areas of casing immersed in soil or salt water. Corrosion caused by DC flow from anodic to cathodic areas on the same structure through an electrolyte is electrochemical in nature.Cathodic protection does not eliminate corrosion but transfers it from the structure under protection and concentrates the corrosion at another known location where the current-discharging anode(s) can be designed for maximum life and ease of replacement.Cathodic protection is of value only to the surface of the metal exposed to the same electrolyte as the anode. For example, only the external surface of the oil string of casing between the surface pipe and the top of the cement circulated around the oil string from the bottom is protected in the East Texas field wells discussed in this paper. Fortunately, this casing is exposed to native soil from about 100 to 3,200 ft (33 to 1050 m) below the surface, which is the area needing protection. Problem Identification After the field had been operated for 20 to 25 years, casing leaks began to increase with 80% of the leaks occurring in the upper 500 ft (164 m) of casing. The majority of the leaks were external, resulting from electrolyte corrosion. In 1957, a cumulative 85 casing leaks had occurred on our 1,500 wells. JPT P. 1437^

Influence of direct current on the electrical activity of the heart and on its susceptibility to ventricular fibrillation.

Isolated perfused guinea pig hearts (Langendorff preparation) were used to study the influence of direct current (DC) on the shape of the electrogram and to determine the thresholds for extrasystoles and for fibrillation. DC impulse durations ranged between 30 ms and 5 s. During DC flow through the heart, marked deformations of the electrogram occur mainly concerning the repolarization phase and increasing with growing current strength. At an intensity of twice the diastolic threshold for stimulation, constant DC induces extrasystoles, which are suggested to result from an enhancement of the intrinsic automatic activity by cathodal polarization. Compared with the diastolic threshold for stimulation, the threshold for fibrillation is higher by a factor of about 15. The curve relating the threshold for fibrillation to the impulse duration shows a marked decline between 30 ms and 60 ms, followed by a slight increase and adjustment to a constant level beyond about 80 ms. In the used setup, the threshold for fibrillation is independent on the reversal of polarity of the electrodes. Long-lasting DC pulses are able to induce fibrillation even if they are switched on in the absolute refractory period of a normal beat. Application of 50-Hz alternating current revealed a higher threshold for stimulation and a three times lower fibrillation threshold compared with the effects of DC in the same heart.

Horizontal transmission of the polar electric field to the equator

A mode which makes possible the instantaneous transmission of the polar ionospheric electric field to the equator is obtained. The problem is solved analytically as an initial-boundary value problem by assuming a plane Earth-ionosphere waveguide system composed of the metallic ionosphere with vertical static magnetic field and the perfectly conducting Earth, The TM 0 (zeroth-order transverse magnetic) waveguide mode excited by the polar electric field propagates instantaneously to the low-latitude accompanying the electric field with the same direction as the polar field. The simultaneous occurrence of the PRI (preliminary reverse impulse) of the SC∗ and the DP-2 geomagnetic variations in the high-latitude and equatorial regions are interpreted in terms of the polar originated electric field associated with the TM 0 mode. The geometrical attenuation of the transmitted electric field due to the finite scale of the polar field causes the disappearance of the PRI at low-latitudes, but the PRI appears again in the dayside equatorial region because of the enhanced ionospheric conductivity. The twin current vortices for the high-latitude PRI are interpreted as the Hall current caused by the polar electric field with finite scale. It is suggested that the direct current flows between the magnetosphere and the equatorial ionosphere via the polar ionosphere, when a large scale electric field is generated in the magnetosphere. From the mid-latitude ionospheric part of this current, the electric field may be mapped upward along the magnetic lines of force into the low L-value hydromagnetic region and as a result the penetration of the magnetospheric electric field into the plasmasphere is achieved by way of the Earth-ionosphere waveguide.

Analysis of the complex impedance data for ?-PbF2

Previously published complex impedance plots for the ionic conductor β-PbF2 show the familiar depressed circular arcs with an angle 0.7 π/2 and an activation energy for the volume conductivity Wv=0.45 eV. A detailed analysis of this behaviour in terms of the recently developed “non-Debye” model shows the real part of the relative dielectric permittivity to have a frequency dependence ω0.7−1, with a high frequency limit of 50 Hz and with only weak dependence on temperature. The low-frequency “spurs” on the impedance plots are shown to indicate an interfacial barrier at each electrode having a similar “non-Debye” frequency characteristic to the bulk but showing a strong temperature dependence with an activation energy equal to Wv/2. This suggests the presence of low Debye-screened barriers of about k T height, resulting from depletion and accumulation of ionic carriers at incompletely transmitting electrodes. There is no visible effect of inter-grain boundaries on the flow of direct current.

Theory of noise investigations on conductors with the four-probe method

A general relation is derived for the spectral noise density of the ac open-circuit voltage fluctuations between two point electrodes in a homogeneous conductor with conductivity fluctuations. The conductor is assumed to extend to infinity and a noiseless direct current flows through the conductor via two current electrodes. Besides, the spectral noise density between two point electrodes is calculated for a number of conductors with specified dimensions and specified current electrodes. These theoretical results are compared with experimental results.

Effect of calcium on the differentiating operation of the ampullary electroreceptor inIctalurus nebulosus

1. Nerve impulses from the afferent fibre of the ampullary electroreceptor inIctalurus were recorded and changes of the response characteristics induced by calcium ions in the medium surrounding the fish were examined. 2. Under normal calcium concentration (2 mM/1) set and break of long lasting electrical stimuli lead to frequency changes, which are equal in size (and have opposite direction) for anodal and cathodal currents, respectively. With calcium deficiency only anodal currents evoke a response (Fig. 1). 3. Also in the case of low calcium, responses to intensity steps depend on direct current flow, but are largely unaffected by the d.c.-level under normal and high calcium (Fig. 3). 4. The decline of the frequency response does not alter the height of a succeeding response, and the off-response is fullsized already at the beginning of frequency decline. The response to the second current-step is only influenced by a preceding current onset, if the interval is shorter than 50–90 ms. For longer delays the frequency response is the same as a reaction unaffected by a prestimulus (Figs. 4–6). This time dependent decrease of the prestimulus effect is not seen with low calcium: there is a permanent (sensitivity enhancing) effect of direct current flow (Fig. 7). 5. From these results it has become evident that the differentiating operation mode of the ampullary electroreceptor is based on two different processes: (1) a calcium dependent mechanism, which makes the receptor independent of direct current and (2) the decline of the frequency response during continuous current flow which is not affected by calcium ions.

Skin impulses and locomotion in Oikopleura (tunicata: larvacea).

The skin covering the tail and hinder trunk region of Oikopleura propagates impulses at 15-21 cm/sec. Spread is non-decremental and unpolarized. The impulses are of short duration (8-12 msec) and in general resemble skin impulses in hydromedusae more than those of amphibian and tunicate tadpole larvae.The skin was examined by optical and electron microscopy. The cells are connected by gap junctions. Impulses are assumed to spread by direct current flow from cell to cell.Electromyograms of tail activity during three behavior patterns (pumping, swimming, and house rudiment expansion) are analyzed in relation to neuromuscular histology. There appear to be at least two classes of pacemakers, both located in the caudal ganglion. There is no evidence that proprioceptive feedback is required for maintenance of rhythmic activity; and isolation of the tail from the trunk, which contains the cerebral ganglion, does not affect rhythmicity. The system differs fundamentally from the locomotory systems of Amphioxus and...

Non-Nervous Conduction in Invertebrates and Embryos

Propagated electrical events in epithelial tissues have been recorded from a number of invertebrates and from vertebrate embryos. Those groups in which such events have been recorded are the Cnidaria, Ctenophora, Echinodermata, Urochordata, and Amphibia. In several cases these non-nervous action potentials mediate escape or protective responses. In other cases they cause ciliary reversal or arrest of ciliary beat. Propagation appears to occur via low resistance intercellular pathways involving direct current flow. The ontogeny of such epithelial impulses is described in an amphibian.

Mean Pore Sizes from Flow Measurements

A method is described in this note for determining the mean pore size of a porous plug from direct current measurements and hydraulic flows. This study deals with fitted glass disks having properties similar to a spectrum of soils ranging from a fine sand to a silty clay whose mean pore size can be determined by combining current characteristics with hydraulic permeability. The technique also appears promising for inactive clay.

The properties and propagation of a cardiac-like impulse in the skin of young tadpoles

The contact relationships of skin cells in late embryos and young larvae of Xenopus laevis are described. Superficial cells are joined by ‘tight’ or ‘gap’ junctions at their outer periphery but elsewhere ‘simple appositions’ are found. All-or-none impulses are evoked in the skin by electrical or mechanical stimuli (Fig. 3). Evidence is presented in favour of the view that these impulses are generated by the majority of skin cells and not by some neuronal element in the skin. The impulse propagates throughout the skin from any stimulated point (at average speed of 7.7 cm/sec) even when the animal is in distilled water. However, removal of Na+ from solutions bathing the inner skin surface or treatment with Tetrodotoxin abolishes the impulse indicating that it is Na+ dependent. Current injected into skin cells spreads to others so it is suggested that the impulse propagates by direct current flow from cell to cell. The ‘neuroid’ conduction system in the skin of Xenopus tadpoles is compared to similar systems in coelenterates and to the propagation of the vertebrate cardiac impulse.

Electrical transmission among neurons in the buccal ganglion of a mollusc, Navanax inermis.

The opisthobranch mollusc, Navanax, is carnivorous and cannibalistic. Prey are swallowed whole by way of a sudden expansion of the pharynx. The buccal ganglion which controls this sucking action was isolated and bathed in seawater. Attention was focused upon 10 identifiable cells visible on the ganglion's rostral side. Two cells were observed simultaneously, and each was penetrated with two glass microelectrodes, one for polarizing the membrane and the other for recording membrane potential variations. The coupling coefficients for direct current flow and action potentials of several identified cells were tabulated. Attenuation was essentially independent of the direction of current flow, but depended upon the relative size of the directly and indirectly polarized cells. The attenuation of subthreshold sinusoidally varying voltages increased with frequency above about 1 Hz. The coupling coefficient for spikes was lower than for DC due to greater high frequency attenuation. There is considerable similarity in the spontaneous PSP's of all cells, which is not due to the electrical coupling but to input from a common source. The 10 cells were not chemically interconnected but some were electrically connected to interneurons which fed back chemically mediated PSP's. The feedback can be negative or positive depending upon the membrane potential of the postsynaptic cell. We conclude that electrical coupling among the 10 cells plays a minor role in sudden pharyngeal contractions but that the dual electrical-chemical coupling with interneurons may be important in this respect.

Dc flow considerations for crossed-field acoustic amplifiers and other solid-state traveling-wave devices

The direct Current flow in two simple device structures used for crossed-field, traveling-wave devices is analyzed, and some properties of the flow which can affect the RF performance are studied in detail. The results show nonuniform flow to be significant only in localized regions, which can be made small by a proper choice of electrode and sample geometry. Approximate formulas are derived for estimating the important flow parameters of interest in specific applications. As an example, the effect of nonuniform flow on the acoustic amplifier is estimated. The deflection and refraction of a shear-wave acoustic beam in InSb at 77°K is found to be negligible, but the gain is reduced appreciably for large µB <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</inf> . Considerations entering into device design, such as heat sinking and the provision of an RF circuit, are also discussed with regard to an optimum choice of electrode configuration for a rectangular device.

LIGHT ENERGY CONVERSION IN NEURONAL MEMBRANES*

Summary Photocurrents and decrease in membrane resistance have been shown by illuminating pigmented nerve cells, and vitally stained nerve fibers.Any photocurrent, of threshold value, can elicit repetitive electrical activity as an extrinsic outward current dose. In pigmented nerve cells, photocurrents are additive to pre‐existing dark currents, thus modifying the frequency of the spontaneous activity.Light effects on electrogenic membrane were compared to those of infra red. Both radiations decrease, with different yields, the membrane resistance. However, the initiated membrane currents are generally of opposite directions.Similarly, opposite direction photocurrents are elicited by specific illuminations of two intracellular pigments (haemoprotein or carotenoid) in some nerve cells.From spectrographic, respirometric and oscillographic evidences, the molecular mechanisms implied in the light energy conversion into membrane photocurrent can be considered as follows:1. Release of electrons and hydrogen ions from dyes or natural pigments in molecular association with lipoproteins; secondary reactions of e and H+ with acceptors (dyes, or oxygen).2. Secondary changes in adsorption bonds between dyes or pigments and associated lipoproteins resulting in changes in molecular orientations.3. Directional fluxes of e, H+, and other ions, imitating fluxes elicited under a cathode during direct current flow.