The effect of some growth-regulating compounds upon electroosmotic measurements, transcellular water flow, and Na, K, and Cl influx in Nitella flexilis

1973 ◽  
Vol 51 (5) ◽  
pp. 1055-1070 ◽  
Author(s):  
I. R. Wanless ◽  
Nancy Bryniak ◽  
D. S. Fensom
Keyword(s):  
Water Flow ◽  
Pond Water ◽  
Basic Flow ◽  
Constant Current ◽  
Naphthaleneacetic Acid ◽  
Applied Current ◽  
Osmotic Effect ◽  
Membrane Complex ◽  
Small Constant ◽  
A Cell

By using a small, constant, applied current on a cell of Nitella in artificial pond water, it was possible to compare the effect of different growth-regulating compounds on the apparent electroosmotic water coupling in the cell wall – membrane complex. Indoleacetic acid (IAA) at first enhanced the electro-osmotic effect and then ceased to alter it, but began to change the asymmetric transcellular water flow. Gibberellic acid (GA), when added to IAA, increased this effect, while abscissic acid (ABA) added to IAA decreased it. Some compounds like naphthaleneacetic acid (NAA), alar-83, skatol, or ABA alone, had no effect on the electroosmotic (eo.) coefficient; but NAA, skatol, ABA (alone) changed the asymmetric water flow (basic flow) and some ion influxes. Light-degraded IAA acted in a manner very similar to skatol, which suggests that IAA is quickly converted to skatol in the cell in the presence of light. With light–dark transitions or with IAA, the electroosmotic coefficient changed in a manner parallel to passive ion (Na+ and K+) influx, but was not related to basic flow or Cl− influx changes.Under controlled conditions of low constant current applied to a test cell, it has been shown that a change in apparent eo. coefficient upon auxin addition is largely a reflection of change in the true electroosmotic properties of the cell membrane at the positive end of the cell.

A transcellular water flux induced by light in Nitella

1973 ◽  
Vol 51 (5) ◽  
pp. 1045-1053 ◽  
Author(s):  
D. S. Fensom ◽  
S. L. Barclay ◽  
Sophie Law ◽  
R. G. Thompson
Keyword(s):  
Water Flow ◽  
Plasma Membranes ◽  
Water Flux ◽  
Pond Water ◽  
Basic Flow ◽  
Membrane Properties ◽  
Light Change ◽  
Hydraulic Permeability ◽  
Closed Chamber ◽  
Current Flows

When Nitella cells in artificial pond water (APW) are illuminated in an electroosmometer, water appears to move into the closed chamber of the instrument. This has been termed the "basic flow" of the instrument. A part of this basic flow is thermal expansion but an appreciable part is a water flow through the living cell. This transcellular water flow is increased by illumination of any part of the cell and is mostly removed by 10−3 mM N-dichlorophenyl-N′,N′-dimethylurea (DCMU). It is readily altered by conditioners which alter the membrane properties at one end of the cell compared with the other: carbonyl cyanide m-chlorophenyl-hydrazone (CCCP) at 5 × 10−3 mM, dinitrophenol (DNP), 10−1 mM ouabain, and particularly pH. Asymmetrical changes in the hydraulic permeability of the membrane are indicated as the most probable cause of this water flow.An electric current flows between the two ends of the cell when the cell is differentially illuminated, particularly at the beginning or end of the light change. The current is thought to indicate the presence of some electrogenic pumps on the plasma membranes.

Antidiuretic hormone-dependent membrane capacitance and water permeability in the toad urinary bladder

1983 ◽  
Vol 244 (2) ◽  
pp. F195-F204
Author(s):  
L. G. Palmer ◽  
M. Lorenzen
Keyword(s):  
Antidiuretic Hormone ◽  
Water Flow ◽  
Time Course ◽  
Apical Membrane ◽  
Constant Current ◽  
Apical Plasma Membrane ◽  
Voltage Response ◽  
Toad Urinary Bladder ◽  
Osmotic Gradient ◽  
Capacitance Change

Antidiuretic hormone (ADH) increased the electrical capacitance of apical membrane of the toad bladder; this effect was modulated by the osmotic gradient across the tissue. Capacitance was measured from the transepithelial voltage response to constant-current pulses using bladders depolarized with KCl-sucrose serosal solution to reduce basolateral resistance and with Na-free mucosal solution to increase apical membrane resistance. Addition of ADH (20 mU/ml) increased capacitance by 28 +/- 9% (mean +/- SD) in the absence and by 8 +/- 3% in the presence of an osmotic gradient (200 mosM, mucosal side hypotonic). With bladders stimulated in the absence of an osmotic gradient, rapidly imposing a gradient resulted in a peak rate of water flow that declined to 40% of the peak value after 15-20 min. ADH-dependent capacitance also decreased with a similar time course. Removal of ADH reversed the capacitance change (t1/2 = 10-15 min), but the reversal was slower than the decline in water flow to basal levels (t1/2 less than 5 min). Colchicine and cytochalasin B also inhibited the ADH-induced capacitance increase. The capacitance change was also inhibited when the mucosal solution was made hypertonic with raffinose. The results are interpreted within the framework of a previously proposed model of ADH-stimulated water transport in which cytoplasmic vesicular structures fuse with the apical plasma membrane.

scholarly journals Estimating Time-Varying Applied Current in the Hodgkin-Huxley Model

2020 ◽  
Vol 10 (2) ◽  
pp. 550
Author(s):  
Kayleigh Campbell ◽  
Laura Staugler ◽  
Andrea Arnold
Keyword(s):  
Kalman Filter ◽  
Standard Deviation ◽  
Ensemble Kalman Filter ◽  
Single Neuron ◽  
Constant Current ◽  
Time Varying ◽  
Applied Current ◽  
Parameter Tracking ◽  
Voltage Spike ◽  
Low Amplitude

The classic Hodgkin-Huxley model is widely used for understanding the electrophysiological dynamics of a single neuron. While applying a low-amplitude constant current to the system results in a single voltage spike, it is possible to produce multiple voltage spikes by applying time-varying currents, which may not be experimentally measurable. The aim of this work is to estimate time-varying applied currents of different deterministic forms given noisy voltage data. In particular, we utilize an augmented ensemble Kalman filter with parameter tracking to estimate four different time-varying applied current parameters and associated Hodgkin-Huxley model states, along with uncertainty bounds in each case. We test the efficiency of the parameter tracking algorithm in this setting by analyzing the effects of changing the standard deviation of the parameter drift and the frequency of data available on the resulting time-varying applied current estimates and related uncertainty.

scholarly journals Removal of isopropyl alcohol by electrical discharge from an aqueous solution with microbubbles

2021 ◽  
pp. 32-37
Author(s):  
Vladislav Panov ◽  
Vladimir Pecherkin ◽  
Leonid Vasilyak ◽  
Yurii Kulikov ◽  
Sergei Vetchinin ◽  
...  
Keyword(s):  
Water Flow ◽  
Electric Discharge ◽  
Isopropyl Alcohol ◽  
Electrode System ◽  
Solution Flow Rate ◽  
Air Bubbles ◽  
Solution Flow ◽  
A Cell ◽  
Discharge Cell ◽  
Industrial Frequency

The removal of isopropyl alcohol impurities with an initial volume concentration of 20 % in a cell with a working area volume of 831 cm 3 in a water flow with fine air bubbles with a solution flow rate of 2 m 3/h by a quasi-volume electric discharge obtained using a multi-electrode system of sectioned needle electrodes has been experimentally investigated. At an alternating voltage of an industrial frequency of 50 Hz, the creation of a finely dispersed phase with air bubbles in an electric discharge cell increases the efficiency of isopropyl alcohol removal from the water flow by 6 %.

THE DESTRUCTION OF SUPERCONDUCTIVITY IN TANTALUM WIRES BY A CURRENT

1959 ◽  
Vol 37 (4) ◽  
pp. 485-495
Author(s):  
H. J. Fink
Keyword(s):  
Transition Temperature ◽  
Critical Current ◽  
Normal State ◽  
Constant Current ◽  
Small Constant ◽  
Large Hysteresis ◽  
Normal Resistance ◽  
Zero Resistance ◽  
The Wire ◽  
A Current

The transition from the superconducting to the normal state of various pre-stretched tantalum wires carrying current was investigated. When the resistance of the wire jumps discontinuously from the superconducting to the normal or intermediate state as a current is passed through it, then this current is defined as the critical current Ic. For temperatures T < (Tc−5 millidegrees K) the resistance of the wire jumps directly from zero resistance to its normal value at the critical current, such that the total cross section of the wire goes effectively into the normal state. Between (Tc−5 millidegrees K) and Tc the resistance of the wire jumps at Ic to any fraction of the normal resistance between approximately zero and one. For constant temperatures the resistance–current plots show a large hysteresis effect. The transition temperature, Tc, of the various samples is strongly dependent upon their normal resistivity at helium temperatures. If the wires with a small constant current (4.2 ma) flowing in them are cooled from above the transition temperature, the resistance decreases above Tc and approaches zero at approximately Tc, where Tc is defined by the extrapolation of the Ic–T curve to Ic = 0. If the wires are heated from below Tc the same resistance–temperature curves are reproduced.

Elektrochemische Untersuchung der chemischen Diffusion in Wüstit mit Hilfe eines oxidischen Festelektrolyten/ Electrochemical Investigation of Chemical Diffusion in Wüstite Using a Solid Oxide Electrolyte

1974 ◽  
Vol 29 (12) ◽  
pp. 1849-1859 ◽  
Author(s):  
H. Rickert ◽  
W. Weppner
Keyword(s):  
Diffusion Coefficient ◽  
Chemical Potential ◽  
Coulometric Titration ◽  
Chemical Diffusion ◽  
Tracer Diffusion ◽  
Correlation Factor ◽  
Galvanic Cell ◽  
Constant Current ◽  
Chemical Diffusion Coefficient ◽  
Small Constant

Chemical diffusion measurements in wüstite were carried out with the help of the solid state galvanic cell pO₂, Ptl |ZrO2(+Y2O3)| Fe1 - δ(ϰ)O| Pt2, N2 with doped ZrO2 as a solid electrolyte which exhibits practically pure conduction for oxygen ions. Starting from an initial homogeneous stoichiometry as given by δ, the voltage E of the cell, i. e. the chemical potential of oxygen (or δ) in Fe1 - δO at the phase boundary with the electrolyte, was changed in small steps, corresponding to 3,5 - 15% of the whole stoichiometric range. The re-equilibration of the compound was observed by the current as a function of time. Alternatively, a small constant current was applied to the galvanic cell and the voltage between the wüstite and a reference electrode was measured. From the relaxation behaviour the chemical diffusion coefficient can be determined in several ways. The values are consistent with those calculated from tracer diffusion coefficients, the thermodynamic factor, which could be estimated from coulometric titration measurements, and a correlation factor of the order of 1. In contradiction to previous results with thermogravimetric methods the chemical diffusion coefficient increases with growing deviation from the ideal stoichiometry.

Determination of EDTA by catalytic amperometric and catalytic potentiometric titration at a small constant current

1977 ◽  
Vol 286 (3-4) ◽  
pp. 222-225 ◽  
Author(s):  
Ferenc F. Gaál ◽  
Biljana F. Abramović ◽  
Ferenc B. Szebenyi ◽  
Velimir D. Canić
Keyword(s):  
Potentiometric Titration ◽  
Constant Current ◽  
Small Constant

scholarly journals Design Considerations for Fast Charging Lithium Ion Cells for NMC/MCMB Electrode Pairs

Batteries ◽  
2021 ◽  
Vol 7 (1) ◽  
pp. 4
Author(s):  
William Yourey ◽  
Yanbao Fu ◽  
Ning Li ◽  
Vincent Battaglia ◽  
Wei Tong
Keyword(s):  
Specific Capacity ◽  
Negative Electrode ◽  
Lithium Ion ◽  
N:P Ratio ◽  
Time Frame ◽  
Department Of Energy ◽  
Constant Current ◽  
Lithium Ion Cells ◽  
Fast Charging ◽  
A Cell

Lithium ion cells that can be quickly charged are of critical importance for the continued and accelerated penetration of electric vehicles (EV) into the consumer market. Considering this, the U.S. Department of Energy (DOE) has set a cell recharge time goal of 10–15 min. The following study provides an investigation into the effect of cell design, specifically negative to positive matching ratio (1.2:1 vs. 1.7:1) on fast charging performance. By using specific charging procedures based on negative electrode performance, as opposed to the industrial standard constant current constant voltage procedures, we show that the cells with a higher N:P ratio can be charged to ~16% higher capacity in the ten-minute time frame. Cells with a higher N:P ratio also show similar cycle life performance to those with a conventional N:P ratio, despite the fact that these cells experience a much higher irreversible capacity loss, leading to a lower reversible specific capacity.

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