Measurement Of Current Flow Research Articles

Current-influenced depositional provinces, continental margin off Cape Hatteras, identified by petrologic method

Analyses of DSRV “Alvin” core samples on the Cape Hatteras margin indicate major textural and compositional changes at depths of about 1000 and well below 2500 m. The distribution patterns of petrologic parameters correlate well with water mass flow and suspended-sediment plumes measured on this margin by other workers. Our study also shows: (a) vigorous erosion and sediment transport at depths of less than 400 m resulting from the NE-trending Gulf Stream flow; (b) deposition, largely planktonic-rich sediment released from the Gulf Stream, on the upper- to mid-slope, to depths of about 800–1200 m; (c) winnowing, resuspension and deposition induced by periodically intensified slope currents on the mid-slope to uppermost rise, between about 1000 and 2500 m; and (d) prevailing deposition on the upper rise proper (below 2500 m), from transport by the SW-trending Western Boundary Undercurrent. Sediments moved by bottom currents have altered the composition and distribution patterns of material transported downslope by offshelf spillover; this mixing of gravity-emplaced and bottom-current-transported sediment obscures depositional boundaries. Moreover, reworking of the seafloor by benthic organisms alters physical properties and changes erodability of surficial sediments by bottom currents. Measurement of current flow above the seafloor and direct observation of the bottom are insufficient to delineate surficial sediment boundaries. Detailed petrologic analyses are needed to recognize the long-term signature of processes and define depositional provinces.

Measurement of current flow through the rat under signaled and unsignaled grid-shock conditions

The present experiment was run to test the hypothesis that, when shock was signaled, rats would develop effective coping responses so as to reduce the current flow through them. A 1-sec shock was delivered through a grid floor by a fixed impedance ac shock source. The current-flow measure was taken over the last 30 of 90 trials given over 3 days and indexed by “gross skin conductance” or GSC (shock). The rat under the signaled shock condition (n=15) showed higher GSC (shock) than did the rats under the unsignaled shock condition (n=14). Thus, the result contradicted the hypothesis. There was no indication that the rats developed any preparatory response during the 5-sec signal, in terms of either GSC (signal) or posture. The results were discussed with reference to the preparatory-response hypothesis and various other possibilities.

Angiotensin II increases electrical coupling in mammalian ventricular myocardium.

Electrical measurements of current flow in ventricular myocardium immersed in silicone oil showed that angiotensin II increases the cell-to-cell spread of current within seconds. The increases in current spread and conduction velocity occur without any changes in resting membrane potential or maximum rate of rise of the action potential. The concentration range was 10 nM to 10 microM, with an ED50 of 100 nM for angiotensin exposures lasting about 10 seconds. The larges effects were an apparent decrease in resistance through the cellular pathway to 50% of control and a 40% increase in conduction velocity, which returned to control in about 15 minutes. Continuous or repeated exposure to angiotensin caused desensitization to appear. These effects were found with or without denervation by 6-hydroxydopamine and beta-adrenergic blockade by 1 microM propranolol in calf, pig, sheep, and rabbit ventricular myocardium. Therefore, angiotensin appears to increase electrical conduction rapidly and directly in cardiac muscle by decreasing resistance through the cellular pathway.

A COMPARISON OF METHODS FOR THE MEASUREMENT OF CARDIAC OUTPUT AND BLOOD OXYGEN CONTENT

A comparison has been made between the recently introduced thermal dilution method for measurement of cardiac output and the standard dye dilution technique. Two relatively new methods of measurement of blood oxygen content, one involving the measurement of oxygen tension after release of oxygen by carbon monoxide, and the other the measurement of current flow upon reduction of oxygen in a galvanic cell, have been compared with a standard indirect method of measurement of blood oxygen content. All three new methods fulfilled the criteria of accuracy and simplicity and compared favourably with the standard methods. Of the two new methods for measurement of oxygen content, that involving reduction of oxygen in a galvanic cell was superior by virtue of compactness and speed of operation.

Electrochemical Oxidation of Hydrogen on A Raised Horizontal Wire Electrode

ABSTRACT A horizontal platinum resistance thermometer, which supported a meniscus above a pool of electrolyte, was used as an electrode. The unique design allows the simultaneous measurement of electrode potential, current, temperature, and heat flow. Results that demonstrate some of the advantages of this experimental electrode design are presented.

The Simultaneous Measurement of Electrode Potential, Current, Temperature, and Heat Flow

ABSTRACT A horizontal platinum resistance thermometer, which supported a meniscus above a pool of electrolyte, was used as an electrode. The unique design allowed the simultaneous measurement of electrode potential, current, temperature, and heat flow. Initial results are presented.

Theory and operation of the split langmuir probe

An instrument, the split Langmuir probe, has been developed to make in situ measurements of current density and plasma bulk flow. The split Langmuir probe consists of two conducting elements that are separated by a thin insulator that shield each other over a 2π solid angle, and that are simultaneously swept from negative to positive potentials with respect to the plasma. By measuring the current to each plate and the difference current between plates, information can be obtained on the plasma's current density, bulk flow, electron temperature, and density. The instrument was successfully test flown from Fort Churchill on 2 August 1968, with results in reasonable agreement with those from another experiment on the same rocket. Sources of error indicated by these results include plate area differences, plate work function differences, input resistor differences, and probe wake effects. The error signal in the difference current data due to plate work function differences rose to a sharp maximum at plasma potential, which served the useful purpose of precisely marking plasma potential. Possible changes in probe geometry, sweep rate, and telemetry designed to reduce these errors are discussed.

Prebreakdown current and charge flow in long positive point-plane gaps with impulse-voltage waves having times to crest in the range 15–1200 μs

Measurements of prebreakdown current and charge flow in long positive point-plane gaps have shown a critical charge injection which is a function of time to peak of the voltage wave. With increasing time to peak, the pattern of current flow changes from a single large-amplitude pulse to a series of discrete pulses of lower amplitude but of similar duration.

Anomalous Tunneling in Normal Metal Junctions using Ferromagnetic Films

Measurements of tunnel current flow through normal metal junctions made with the ferromagnetic metals Fe, Ni, and Co have been carried out in the range 1°–300°K. The insulating layer has been an oxide of the above metals or aluminum oxide and the second metal either aluminum or silver. In the case of Fe-FeOx-Al a giant zero-bias anomaly corresponding to a resistance maximum has been observed at helium temperatures and this persists up to room temperature. Co-CoOx-Al also shows a similar but smaller anomaly while Ni-NiOx-Al shows an anomalous behavior of reverse sign. Data on the dynamic resistance as a function of voltage and temperature are presented in this paper. The effects of magnetic fields up to 50 kOe have also been studied.

The injection of tenuous plasma into a magnetic guide field in the absence of wall-shorting

A burst of plasma from a thetatron gun is allowed to expand freely as it passes along a drift tube; an aperture limiter selects a central beam of plasma which then flows axially into the field of a solenoid. The ion energy is centred about 800 eV and the maximum ion density is about 3 × 1011 cm-3. The solenoid is suspended in a large vacuum chamber so that the wall-shorting effect, described in connexion with a similar experiment, is inhibited. A removable conducting cylinder at the solenoid entrance enables a direct comparison to be made between the case when a radial space charge field exists in the plasma stream and when it is short-circuited. Measurements of azimuthal ion flux, electric field and current flow at the solenoid entrance, show that shorting can be prevented. The radius of the plasma stream is always comparable to twice the ion gyro-diameter 2Rci; it is not reduced to 2Rci(m/M)1/2, as simple theory predicts, when `shorting' is prevented.

ELECTRO-OSMOSIS IN NITELLA

Simultaneous measurements of minute electrical current and water flow through single living cells of Nitella translucens have shown that there is an electro-osmotic transport of the order of 100 moles of water per Faraday in the direction of the positive ion flow. This implies the existence of water-filled charged pores through the plasmalemma and tonoplast of the Nitella cell. The pores available for ion movement are far too few to account for the high water permeability of the cell membranes, and the possible extra turgor pressures which might be produced by an electro-osmotic flow through these pores could not be more than 10−4 atmosphere.

Electrode spacing in disc-seal triodes

Four different methods have been investigated for determining the working cathode-grid clearance in disc-seal triodes. The methods involved (a) direct observation with a microscope, (b) capacitance measurements, (c) measurement of current flow and (d) determination of magnetron cut-off conditions. Methods (a), (c) and (d) gave reasonably consistent results. The range of clearances involved was 0.1 to 0.5 mm. Methods (a) and (d) were also used to find the cathode-anode spacing in the same triodes. The capacitance method, though of little use for determining the clearances directly, has been applied to the extension and checking of the clearances determined by the other methods.

アミン類を主剤とする防食剤の研究 (第13報)

Current flow measurements have been carried out on the copper-mild steel and mild steel-aluminum couples in 3% NaCl solution at 30°C. Electrodes were separated by a diaphragm, and corrosion inhibitor which was hexadecyl compound of each series, such as amine, acid amide, acid and mercaptan, was added in each chamber or in both, respectively. Almost inhibitors were adsorbed on both electrodes, but amine and mercaptan were found to be adsorbed chiefly by copper. The corrosion-inhibition of high molecular weight polar organic compounds took place because of general adsorption which interfered with both anodic and cathodic processes.

Some Observations on Cathodic Protection Criteria—A Contribution to the Work of NACE Technical Unit Committee T-2C On Minimum Current Requirements

Abstract A comparison of cathodic protection criteria has been made on a 240-foot length of bare 6-inch pipe (steel) buried in 16,100—55,900 ohm. cm. soil. Anodic areas of representative size and position were established on the pipe by coupling high purity zinc plates through measuring circuits. Some of the cathodic protection criteria observed simultaneously on the pipeline include: 1. Measurement of the closure circuit current flow between the zinc plates and the pipe. 2. The McCollum Earth Current Meter. 3. Pipe-to-reference electrode potential, (a. electrode remote, b. electrode on ground over pipe. c. electrode close to pipe.) 4. The “apparent” break in the pot.-log c.d. relation. Further tests were conducted with a buried copper-iron ball corrosion system—to eliminate edge effects. Evaluation of the test data and fundamental considerations show: 1. Short lines of corrosion current continue to flow at the anode-cathode boundary even though the net closure circuit current flow is made zero. 2. Short ...

Galvanic Corrosion: I . Current Flow and Polarization Characteristics of the Aluminum‐Steel and Zinc‐Steel Couples in Sodium Chloride Solution

Current flow, weight loss, and polarization measurements have been carried out on the aluminum‐mild steel and zinc‐mild steel couples in normal solution at 25°C. Under a wide variety of experimental conditions both aluminum and zinc are anodic to mild steel and completely protect it against corrosion. In both galvanic couples the current flow and weight losses of the anodes are proportional to the area of the steel cathode and are much less dependent on the anode area. Galvanic corrosion rates of both couples appear to be controlled by oxygen depolarization and are thus markedly increased by stirring. At high stirring rates, the aluminum‐steel couple delivers a much higher galvanic current than the zinc‐steel couple.

Testing Methods and Corrosion Control Measures For Buried Telephone Cable

Abstract Most of the thousands of miles of buried telephone cable installed by the Bell System have been placed within the past 10 to 15 years. Although relatively few serious corrosion troubles have been experienced on these cables to date, investigations have indicated that damage due to corrosion on this type of plant may be expected to increase unless special mitigative measures are employed. The number of miles of cable involved has made desirable the development of special layout records which will serve as a base for recording such field data as potential of cable to reference electrodes, sheath current flow measurements, location of corrosion troubles, etc. One such record developed by the author is described. The difficulty involved in obtaining access to buried cable at the frequent intervals desirable for measurement of current flow on the cable sheath has led to consideration of other means of testing to more precisely locate areas of current loss and the amount of current discharged to the so...