Showing papers on "Conductance published in 1982"
TL;DR: Adding membrane vesicles prepared from transverse tubule (T-tubule) membranes of rabbit skeletal muscle to the aqueous phase of a planar lipid bilayer induces a stepwise increase in conductance that is both voltage and Ca2+ dependent.
Abstract: Addition of membrane vesicles prepared from transverse tubule (T-tubule) membranes of rabbit skeletal muscle to the aqueous phase of a planar lipid bilayer induces a stepwise increase in conductance. This conductance is both voltage and Ca2+ dependent. At 1 mM Ca2+, the steady-state conductance is maximal at voltages higher than +20 mV and decreases for more negative voltages. (Voltages refer to the side to which the vesicles are added, cis) Decreasing the Ca2+ concentration reversibly shifts the conductance-voltage curve toward the right along the voltage axis. Furthermore, Ca2+ can activate the conductance only if added to the cis compartment. Neither Mg2+, Ba2+, nor Cd2+ can activate the conductance induced by T-tubule vesicles. Addition of 5 mM tetraethylammonium ion to the trans, but not the cis, side abolishes the T-tubule-induced conductance. The Ca2+-dependent conductance appears as a consequence of ionic channel formation. Single-channel activity appears in bursts followed by periods of time in which the channel remains "silent". The conductance of the open channel averages 226 pS in 0.1 M KC1 and is voltage and Ca2+ independent. However, the fraction of time that the channel remains in the open state is voltage and Ca2+ dependent in a manner that parallels the voltage and Ca2+ dependence of the multichannel membrane. The channel is 6.6 times more permeable to K+ than to Na+ and is impermeable to C1-.
295 citations
TL;DR: In this paper, the authors observed threshold switching in n+−i−n+ sandwich structures of hydrogenated amorphous silicon after an initial forming process, and suggested that filamentary conduction occurs in a permanent altered region created during the forming process.
Abstract: Threshold switching is observed in n+‐i‐n+ sandwich structures of hydrogenated amorphous silicon after an initial forming process. At the threshold voltage the device switches from a low conductance to a high conductance state. The devices remain stable after more than 109 switching operations at a pulse frequency of 10 kHz. It is suggested that in the high conductance state filamentary conduction occurs in a permanent altered region created during the forming process.
212 citations
TL;DR: In this article, a heuristic model is constructed by combining some fundamental experimental observations with kinetic predictions of the barrier layer theory of adsorption, which results in identification of the physical mechanisms responsible for the complex kinetics and long time constants.
156 citations
TL;DR: The results suggest that junctional conductance can be modulated by changes in H ion concentration near physiological pH, but that unphysiologically high concentrations of Ca ion, such as would be reached only on cell death, are required for comparable changes in junctional Conductance.
Abstract: One cytoplasmic aspect of the junctional membrane between coupled pairs of Fundulus blastomeres was perfused with solutions of known H and Ca ion concentrations. Conductance of junctional membrane was decreased by either ion. The sensitivity to H ions was about 10,000 times greater than that to Ca ions. The results suggest that junctional conductance can be modulated by changes in H ion concentration near physiological pH, but that unphysiologically high concentrations of Ca ion, such as would be reached only on cell death, are required for comparable changes in junctional conductance.
151 citations
TL;DR: In this article, it was shown that the conductance of an interacting one-dimensional system may be expressed in the form of a Landauer formula and that an insulator-ideal-conductor transition is found as the interaction is varied at zero temperature.
Abstract: It is shown that the conductance of an interacting one-dimensional system may be expressed in the form of a Landauer formula. An insulator-ideal-conductor transition is found as the interaction is varied at zero temperature.
123 citations
TL;DR: In this article, the functional coupling between photosynthesis and stomatal conductance in the leaf was investigated in gas exchange experiments using monochromatic light provided by lasers, and it was shown that the PAR-dependent system in the guard cells may function as a specific light sensor.
Abstract: The photocontrol of the functional coupling between photosynthesis and stomatal conductance in the leaf was investigated in gas exchange experiments using monochromatic light provided by lasers. Net photosynthesis and stomatal conductance were measured in attached leaves of Malva parviflora L. as a function of photon irradiance at 457.9 and 640.0 nanometers. Photosynthetic rates and quantum yields of photosynthesis were higher under red light than under blue, on an absorbed or incident basis. Stomatal conductance was higher under blue than under red light at all intensities. Based on a calculated apparent photon efficiency of conductance, blue and red light had similar effects on conductance at intensities higher than 0.02 millimoles per square meter per second, but blue light was several-fold more efficient at very low photon irradiances. Red light had no effect on conductance at photon irradiances below 0.02 millimoles per square meter per second. These observations support the hypothesis that stomatal conductance is modulated by two photosystems: a blue light-dependent one, driving stomatal opening at low light intensities and a photosynthetically active radiation (PAR)-dependent one operating at higher irradiances. When low intensity blue light was used to illuminate a leaf already irradiated with high intensity, 640 nanometers light, the leaf exhibited substantial increases in stomatal conductance. Net photosynthesis changed only slightly. Additional far-red light increased net photosynthesis without affecting stomatal conductance. These observations indicate that under conditions where the PAR-dependent system is driven by high intensity red light, the blue light-dependent system has an additive effect on stomatal conductance. The wavelength dependence of photosynthesis and stomatal conductance demonstrates that these processes are not obligatorily coupled and can be controlled by light, independent of prevailing levels of intercellular CO 2 . The blue light-dependent system in the guard cells may function as a specific light sensor while the PAR-dependent system supplies a CO 2 -modulated energy source providing functional coupling between the guard cells and the photosynthesizing mesophyll.
94 citations
TL;DR: In this article, the effect of a progressive annealing up to 670°C was studied by electron spectroscopy, sheet conductance and CPD measurements, where four temperature regions were identified whereafter the surface structure is (i) amorphous (25−250°C), (ii) p(4 × 1 + c(1 × 1) (250−370°C) and (iii) (1× 1) + p(1× 2) (above 470°C).
72 citations
TL;DR: In this article, an improved Bjerrum theory obtained by combining the mean spherical approximation with the mass action law (MSA&MAL) is used to calculate the fraction of ions unpaired over the full range of states of a primitive model electrolyte.
Abstract: An improved Bjerrum theory obtained by combining the mean spherical approximation with the mass action law (MSA&MAL) is used to calculate the fraction of ions unpaired over the full range of states of a primitive model electrolyte It is combined with a new theory for the electrical conductance of the primitive model under the MSA to yield the conductance of an electrolyte over a wide range of concentrations and Bjerrum parameters with only two parameters Ao and R, the distance of closest approach, adjusted to fit the conductivity data The theory fits the data for aqueous alkali halides over a wide concentration range with Ao values in good agreement with those deduced by more conventional theories and with reasonable small ion pairing constants deduced from the data It fits the data for LiBr in octanol without the need for invoking triple ion formation It leads to reasonable predictions for the conductance curves for 1:1 electrolytes even up to the molar region for solvents with dielectric constant from 10 to 80
68 citations
TL;DR: The spontaneous activity and the membrane conductances to Na+, Ca2+ and K+ ions of the bursting pace‐maker neurone R‐15 and the repetitively discharging L‐11 in the abdominal ganglion of the marine mollusc, Aplysia californica, were compared.
Abstract: 1. The spontaneous activity and the membrane conductances to Na(+), Ca(2+) and K(+) ions of the bursting pace-maker neurone R-15 and the repetitively discharging (beating) pace-maker neurone L-11 in the abdominal ganglion of the marine mollusc, Aplysia californica, were compared.2. The bursting pace-maker R-15 can be converted to a beating pace-maker neurone by the removal of external Ca(2+) or by the injection of EGTA intracellularly. Bursting pace-maker activity is not restored by changes in the resting potential.3. Spontaneous action potentials of cell R-15 are reduced, but not abolished, by the addition of tetrodotoxin (TTX) to block Na(+) currents or by the removal of external Ca(2+) to abolish Ca(2+) currents, whereas the spontaneous action potentials of cell L-11 are abolished by external TTX, but are unaffected by external Ca(2+) removal.4. The membranes of both cells contain Na(+) and Ca(2+) inward currents. The specific Na(+) conductance of both cells is of similar magnitude, whereas the specific Ca(2+) conductance is about half the Na(+) conductance in R-15 cells and an order of magnitude smaller in L-11 cells.5. The delayed K(+) conductance of cell L-11 is about 1.2 times greater than this conductance in cell R-15. The transient K(+) currents of the two cells are about the same magnitude.6. The Ca(2+)-activated K(+) conductance of cell R-15 and cell L-11 was estimated using two methods. The Ca(2+)-activated K(+) conductance of cell R-15 estimated from the difference in the total outward current in normal external solution and the delayed K(+) current in Ca(2+)-free solution (to preclude Ca(2+) influx) or after internal EGTA injection (to prevent Ca(2+) accumulation) is about 23 times greater than this conductance in cell L-11. The Ca(2+)-activated K(+) conductance of cell R-15, estimated from local internal Ca(2+) injections in Ca(2+)-free solution, is about 3 times greater than this conductance in cell L-11.7. The leakage conductance of cell L-11 is about 1.3 times greater than this conductance in cell R-15. This conductance increases by a factor of about 2 in both cells in Ca(2+)-free external solutions containing 1 mM-EGTA, but is unchanged or is decreased slightly by injection of EGTA internally.8. It is concluded that the Ca(2+) conductance and the Ca(2+)-activated K(+) conductance are appreciably greater in the bursting pace-maker neurone R-15 than in the beating pace-maker neurone L-11, whereas other voltage-dependent conductances to Na(+) and K(+) ions as well as the leakage conductance are quite similar. These quantitative differences provide a basis for understanding the different spontaneous activities of the two cells.
62 citations
01 Jan 1982
57 citations
TL;DR: In sheep cardiac Purkinje fibres superfused with K‐free, Na‐free medium, the membrane potential can be stable either at a low negative level (‐50 mV) or at a high negative levels (‐100 mV).
Abstract: 1. In sheep cardiac Purkinje fibres superfused with K-free, Na-free medium, the membrane potential can be stable either at a low negative level (-50 mV) or at a high negative level (-100 mV). The mechanism underlying the existence of these two stable potential levels was investigated using the two-micro-electrode voltage-clamp technique.
2. By applying a voltage clamp of a certain duration at an appropriate level the membrane potential could be shifted from one stable level to the other. The shift was observed in Cl-free medium, excluding a redistribution of Cl as a possible explanation.
3. Currents during and following a voltage step and their change with amplitude and duration of the voltage step could not be explained on the basis of depletion or accumulation of K ions in the narrow extracellular clefts.
4. Instantaneous currents determined from the high negative resting level showed a high conductance and a pronounced inward rectification, while measurements from the low negative resting level indicated a low conductance and absence of inward rectification. The steady-state current—voltage relation was dependent on the holding potential and showed memory or hysteresis.
5. Estimation of the conductance by superimposed short voltage-clamp pulses showed an increase in conductance during a hyperpolarizing clamp from the low negative level and a decrease in conductance during a depolarizing clamp from the high negative level. The time-dependent current during a hyperpolarizing clamp from the low negative level reversed direction at a potential level corresponding to EK, assuming a cleft K concentration of about 1 mM. In the presence of 0·1 mM-Ba the time-dependent current was abolished.
6. The results suggest that the shift between the two stable levels is due to a time-dependent conductance change in the K inward rectifier channel, iK1. The existence of memory excludes activation or de-activation only depending on the voltage gradient. Interaction of extracellular K ions with a site in the membrane is proposed as the activating mechanism.
TL;DR: In this paper, the authors measured the field effect conductance of α-Si:H and its dependence on annealing to 180°C and illumination with white light, and found that illumination produces changes in the Fermi level with respect to the conduction band mobility edge.
Abstract: We have measured the field effect conductance of α‐Si:H and its dependence on annealing to 180 °C and illumination with white light. We find that illumination produces changes in the field effect conductance which are completely reversed by annealing. Illumination produces a decrease in the off conductance between a factor of 5 and 30 times, together with a shift of the threshold voltage. We interpret the effect of illumination as a modification of the density or occupancy of deep states in such a way that the bulk Fermi level is moved with respect to the conduction band mobility edge. Space‐charge regions can exist at either or both interfaces of the α‐Si:H film and these are very sensitive to interface conditions. The magnitude of the surface band bending is modified by electron trapping in the gate insulator (SiN), which is brought about by bias‐ temperature stressing. Annealing to 180 °C causes the detrapping of excess electrons in the SiN layer, reversing the effect of positive bias‐temperature stres...
TL;DR: It is concluded that variations in the Na and K conductance of the apical cell membrane and the Cl conductances of the tight junction and basolateral cell membrane predominantly account for the variations inThe electrophysiological properties of the rabbit isolated cortical collecting tubule.
Abstract: The Na, K, and Cl conductive properties and the electrophysiological variability of the rabbit isolated cortical collecting tubule were assessed by evaluating the effect of single-ion substitutions on the transepithelial potential difference, Vte, and the transepithelial conductance, Gte. The Na permeability (and conductance) of the tight junction and basolateral cell membrane appeared to be low. However, a significant but variable amiloride-sensitive Na conductance was identified at the apical cell membrane. Although this Na conductance accounts for less than 10% of the Gte, variations in this conductance caused major alterations in the active transepithelial Na current and the Vte. A highly variable K permeability (and conductance) was also identified at the apical cell border and may account for some of the variability in Vte and Gte. This probably provides a pathway for K secretion from cell to lumen. The K permeability of the tight junction and basolateral cell membrane appeared to be relatively low. In contrast, the Cl permeability (and conductance) of the tight junction, and perhaps of the basolateral cell membrane, appeared to be high but variable and to account for the major fraction of the Gte and its variability. It is concluded that variations in the Na and K conductance of the apical cell membrane and the Cl conductance of the tight junction and basolateral cell membrane predominantly account for the variations in the electrophysiological properties of the cortical collecting tubule.
TL;DR: In this paper, the axial diffusion of a passive scalar field (eg temperature) in Poiseuille flow through a duct is considered, taking account of leakage of heat through the duct boundary.
Abstract: SUMMARY The axial diffusion of a passive scalar field (eg temperature) in Poiseuille flow through a duct is considered, taking account of leakage of heat through the duct boundary The cases of the two-dimensional channel and the pipe of circular cross-section are considered in detail, and it is shown that (i) the centroid of the scalar field moves (asymptotically) with a velocity intermediate between the mean and the maximum flow rates and increases with increasing wall conductance, and (ii) the effective diffusivity in the flow direction is a decreasing function of wall conductance The temperature field downstream of a maintained heat source is determined as a function of wall conductance
TL;DR: The calculated value of the dipole moment was found to be larger than the value of direct measurements, indicating that several alamethicin molecules are required to form a conducting pore and that their dipole moments are oriented parallel to each other.
TL;DR: This article characterize the behavior of the individual conductance events observed when adding small amounts of monazomycin to one side of a lipid bilayer, and finds that there are several apparent channel types with one or sometimes two amplitudes predominating.
Abstract: Monazomycin (a positively charged, polyene-like antibiotic) induces voltage-dependent conductance changes in lipid bilayer membranes when added to one of the bathing solutions. These conductance changes have generally been attributed to the existence of channels spanning the membrane. In this article we characterize the behavior of the individual conductance events observed when adding small amounts of monazomycin to one side of a lipid bilayer. We find that there are several apparent channel types with one or sometimes two amplitudes predominating. We find further that these fairly similar amplitudes represent two different states of the same fundamental channel entity, presumed to be the monazomycin channel. The current-voltage characteristics of these channels are weakly hyperbolic functions of applied potential. The average lifetimes are essentially voltage independent (between 50 and 400 mV). The average channel intervals, on the other hand, can be strongly voltage dependent, and we can show that the time-averaged conductance of a membrane is proportional to the average channel frequency.
TL;DR: If the activities of two-state (open-closed) ion channels underlie the electrical behaviour of the membrane at the resting potential and at more depolarized levels, then the results suggest the presence of K+ ion channels whose activation depends both on potential and Ca2+ ions.
TL;DR: Small fluctuations in external glucose levels, such as occur in diabetes, thus cause marked changes in membrane permeability and these changes are likely to impose an additional strain on lens volume regulation.
TL;DR: This property of the inhibitory channel may be functionally important in preventing intracellular Cl− accumulation during periods of intense synaptic activity when inhibition might otherwise convert progressively to excitation as the Cl− equilibrium potential became more and more positive.
Abstract: Glycine increases Cl− conductance in neurones of the lamprey central nervous system and mimics the natural inhibitory transmitter pharmacologically1,2. We have used current noise produced by glycine to examine in more detail the characteristics of inhibitory channels in Muller cells in the brain stem reticular formation. The channels have large conductances and mean open times consistent with large amplitudes and long durations of spontaneously occurring inhibitory synaptic currents3. We now show that, unlike any post-junctional channels reported so far, their conductance decreases rapidly with increasing intracellular concentration of the permeant ion. This surprising behaviour is inconsistent with constant field theory4,5 and also with a single-site pore model such as proposed for cationic channels at the motor endplate6, both of which predict an increase in conductance with concentration. In addition, the decrease in conductance cannot be explained quantitatively by a two-site, single-file pore model such as proposed for K+ channels7 and Na+ channels8 in nerve and for gramicidin channels9. This property of the inhibitory channel may be functionally important in preventing intracellular Cl− accumulation during periods of intense synaptic activity when inhibition might otherwise convert progressively to excitation as the Cl− equilibrium potential became more and more positive.
TL;DR: The conductance and kinetics of the Ca2+ activated K+ channels were studied in voltage clampedHelix neurones by using noise and relaxation techniques to suggest that the effective open time of the ion channel is prolonged by a decrease in the backward rateconstants determining the transition to the closed state.
Abstract: 1.
The conductance and kinetics of the Ca2+ activated K+ channels were studied in voltage clampedHelix neurones by using noise and relaxation techniques.
2.
The increase of outward current activated by the injection of Ca2+ ions into the cells is associated with an increase of membrane current fluctuations. The spectral density of the K+ current fluctuations decays at high frequency quency with an overall slope of aboutf−1.5. Most of the spectra can be fitted by double Lorentzian curves. The single channel conductance derived from integrated powder spectra is 12–16 pS.
3.
Voltage jump experiments show that the gating of the Ca2+ activated K+ current follows first order kinetics provided that the currents are small. The time constant is voltage dependent and increases about e-fold per 85 mV membrane depolarization. Its magnitude isindependent of the previous membrane potential.
4.
The instantaneous current-voltage relation of the Ca2+ activated K+ current is non-linear and can be fitted by the constant field relation. The steady-state current-voltage relation exhibits stronger rectification than the instantaneous current-voltage relation and follows the constant field relation with voltage dependent permeability coefficient. The voltage dependence of the permeability coefficient is the same as that of the relaxation time constant.
5.
The voltage dependent increase of the K+ conductance together with the voltage dependent increase of the time constant suggests that the effective open time of the ion channel is prolonged by a decrease in the backward rateconstants determining the transition to the closed state, i.e. either the channel life-time or the unbinding rate-constant of Ca2+. The opening rate-constant appears to be voltage independent.
TL;DR: The conductance increase during depolarizing voltage-clamp pulses was analyzed assuming that two separate potassium channels exist in these axons and that these two postulated channels are blocked by internal application of caesium, tetraethylammonium and sodium ions.
Abstract: Measurements were made of the kinetics and steady-state properties of the sodium conductance changes in the giant axon of the crabCarcinus maenas. The conductance measurements were made in the presence of small concentrations of tetrodotoxin and as much electrical compensation as possible in order to minimize errors caused by the series resistance. After an initial delay of 10–150 μsec, the conductance increase during depolarizing voltage clamp pulses followed the Hodgkin-Huxley kinetics. Values of the time constant for the activation of the sodium conductance lay on a bell-shaped curve with a maximum under 180 μsec at −40 mV (at 18°C). Values of the time constant for the inactivation of the sodium conductance were also fitted using a bell-shaped curve with a maximum under 7 msec at −70 mV. The effects of membrane potential on the fraction of Na channels available for activation studied using double pulse protocols suggest that hyperpolarizing potentials more negative than −100 mV lock a fraction of the Na channels in a closed conformation.
TL;DR: In this paper, the effect of uranyl ions on the background conductance, capacitance, viscoelastic properties, surface tension and surface potentials of bilayer lipid membranes (BLM) is studied.
TL;DR: In this article, a conductance in any dimensionality is reduced to a one-dimensional (1D) conductance and a mobility edge appears at 2D in an infinite system.
Abstract: A conductance in any dimensionality is reduced to a one-dimensional (1D) conductance. In an infinite system a true mobility edge appears at 2D. In a finite system a continuous change (with the Fermi energy) in the conductance dependence on the system length is determined.
TL;DR: In this paper, the properties of two purified alamethicin fractions, Fraction 4 and Fraction 6, have been studied in PE and PS membranes and they have been shown to have a lower dipole moment than those of fraction 4.
TL;DR: In this paper, the authors used the Fuoss-Onsager equation of conductance to obtain the limiting molar conductance (Λ0) for dilute (10−3−10−2 M) aqueous solutions of KCl at low temperatures of −5, −10, −15, and −20 C at pressure intervals of 250 bar up to 2 kbar.
Abstract: Conductance measurements have been carried out on dilute (10−3–10−2 M) aqueous solutions of KCl at low temperatures of −5, −10, −15, and −20 °C at pressure intervals of 250 bar up to 2 kbar. The limiting molar conductance (Λ0) obtained with the aid of the Fuoss–Onsager equation of conductance has a maximum against pressure at each temperature, and the pressure of the maximum conductance increases very slightly with decreasing temperature. The low‐temperature conductances fit well an empirical equation of the critical law form over the pressure range studied; Λ0=A(T/TS−1)γ. The parameter TS decreases with a rise in pressure below 1.5 kbar, but above that TS is almost constant. The pressure dependence of the drag coefficient (Δζ) subtracted by that due to Stokes’ law for perfect slip (4πηR) is obtained for the K+ ion over a wide range of temperature (−10–45 °C) and compared with that predicted by the Hubbard–Onsager (HO) dielectric friction theory. The observed slight decrease in Δζ with pressure at 45 °C c...
TL;DR: In this paper, it was shown that the inversion layer of the Si MOSFET exhibits conductance oscillations that arise from an oscillating activation energy which is due to either an oscillation interaction contribution to the activation energy, or a negative effective density of states at certain values of carrier concentration.
Abstract: The authors show that on changing the nature of the background random potential the inversion layer of the Si MOSFET exhibits the conductance oscillations previously observed in both GaAs, the source and drain regions of Si MOSFETS and MOSFETS with a very high concentration of Na+ ions at the Si-SiO2 interface. Measurements of the temperature dependence of conductance show that oscillations are found when conductance is by an excitation process as well as hopping. The oscillations arise from an oscillating activation energy which is due to either an oscillating interaction contribution to the activation energy, or a negative effective density of states at certain values of carrier concentration. This appears due to electron ordering in a small current limiting region and is contrasted with the case where the oscillations are absent, although localisation is due to both background disorder and the random field of localised electrons. It is shown that near the transition, localisation is due almost entirely to the random field of the localised electrons, and the system is a strongly interacting Fermi glass (or Wigner glass), even though the oscillations are not apparent.
TL;DR: In this article, it is shown that it is possible to fit conductance data in solvents of low dielectric constant without the additional assumption of triple ion formation, and two new conductance equations, which incoporate in different ways a mass action law for ion pairing but not for ion triplets, can account for the conductivity data for the systems LiBr in octanol and NaI in butanol.
Abstract: It is shown that it is possible to fit conductance data in solvents of low dielectric constant without the additional assumption of triple ion formation. With the aid of two new conductance equations, which incoporate in different ways a mass action law for ion pairing but not for ion triplets, we can account for the conductivity data for the systems LiBr in octanol and NaI in butanol. One of the equations incorporates the mean spherical approximation.
TL;DR: Incorporation of Megatura crenulata hemocyanin into phosphatidylcholine black lipid membranes results in the formation of ion channels, and steady-state voltage-conductance relations are nonlinear for both signs but show slight saturation with ionic strength.
TL;DR: In this paper, the electrical conductivity of SnO2 samples was studied in several mixtures of oxygen and nitrogen and the apparent activation energy ranges from 25.3 to 11.0 kcal/mol in the temperature range 100-450°C.
Abstract: The electrical conductivity of SnO2 samples was studied in several mixtures of oxygen and nitrogen. The conductivity decreases strongly with increasing oxygen content and with decreasing temperature. The apparent activation energy ranges from 25.3 to 11.0 kcal/mol in the temperature range 100-450°C. Ionosorption of O2- is proposed to account for a conductivity maximum at 150°C.
TL;DR: The measurement of conductance provides a non-destructive and continuous method for studying the hydration of plaster of Paris and improved dental stone.
Abstract: The measurement of conductance provides a non-destructive and continuous method for studying the hydration of plaster of Paris and improved dental stone. The kinetics can be described by two parameters: an induction period, to and a first order reaction constant, k, for the decrease of conductance. The influence of additives on both parameters has been studied.