Potential Generated Research Articles

Modeling the extracellular potential generated by a muscle fiber as the output signal of a convolutional system.

A central topic in Bioelectricity is the generation of the extracellular potential that results from the propagation of a transmembrane action potential along the muscle fiber. However, the way in which the extracellular potential is determined by the propagating action potential is difficult to describe, conceptualize, and visualize. Moreover, traditional quantitative approaches aimed at modeling extracellular potentials involve complex mathematical formulations, which do not allow students to visualize how the extracellular potential is generated around the active fiber. The present study is aimed at presenting a novel pedagogical approach to teaching the generation of extracellular potentials produced by muscle fibers based on the convolution operation. The effectiveness of this convolutional model was tested using a written exam and a satisfaction survey. Most students reported that a great advantage of this model was that it simplifies the problem by dividing it into three distinct components: 1) the input signal (associated with the action potential), 2) the impulse response (linked to the system formed by the fiber and the recording electrode), and 3) the output signal (the extracellular potential). Another key aspect of the present approach was that the input signal was represented by a sequence of electric dipoles, which allowed students to visualize the individual contribution of each dipole to the resulting extracellular potential. The results of the survey indicate that the combination of basic principles of electrical fields and intuitive graphical representations largely improves students' understanding of Bioelectricity concepts and enhances their motivation to complete their studies of biomedical engineering.NEW & NOTEWORTHY We presented a new pedagogical method to describe the extracellular potential generated by a muscle fiber as the output signal of the convolution between an input signal and an impulse response. The input signal represents the action potential traveling along the fiber, and the impulse response represents the system formed by the fiber and the recording electrode. The output signal is the summation of the contributions from all individual dipoles that formed the input signal.

Differential behavior of magnetic field and magnetic vector potential in an optically pumped Rb atomic magnetometer

Although vector potentials are more intrinsic physical quantities than magnetic and electric fields, measuring them macroscopically is difficult. A double-nested Helmholtz-type vector potential coil, consisting of an elongated solenoid coil wound around a cylinder, and producing a uniform magnetic vector potential, was developed in this study. The coil is carefully designed to reduce the influence of the leakage magnetic field and the scalar potential generated by the coil’s electrical resistance on the measurement. It has the ability to toggle between vector potential and magnetic field generation. We adapted the coil for use in an optically pumped atomic magnetometer. We also developed an optically pumping Rb atomic magnetometer that can calibrate in a zero magnetic field and applied a time-varying magnetic vector potential. We found that the output signal changed with the vector potential even when there was virtually no magnetic field. With increasing frequency, the output voltage decreases for the magnetic signal and increases for the magnetic vector potential signal. The results revealed that the atomic magnetometer is influenced not only by the magnetic field but also by the magnetic vector potential and that the frequency responses are opposite.

Anomalous potentials on bilayer lipid membranes in the presence of usnic acid: Markin-Sokolov versus Nernst-Donnan equilibrium

To gain insight into the mechanisms of ionophoric activity of usnic acid (UA), we examined the UA-induced generation of potentials on a planar bilayer lipid membrane (BLM) in the presence of concentration gradients of hydrogen and magnesium or calcium ions under open-circuit conditions. Remarkably, the BLM potential generated by UA at the proton concentration gradient of 1 pH unit was approximately twice the Nernst equilibrium level. With a concentration gradient of magnesium or calcium ions, the BLM potential generated by UA had the opposite sign. The observed anomalies in the membrane potentials were consistent with a theory developed by Markin and Sokolov (Bioelectrochem. Bioenerg. 1990) for the case of ionophore-mediated coupled fluxes of several ions across a membrane.

The Mechanisms of Electrogenic Reactions in Bacterial Photosynthetic Reaction Centers: Studies in Collaboration with Alexander Konstantinov.

In this review, we discuss our studies conducted in 1985-1988 in collaboration with A. A. Konstantinov, one of the top scientists in the field of membrane bioenergetics. Studying fast kinetics of membrane potential generation in photosynthetic reaction centers (RCs) of purple bacteria in response to a laser flash has made it possible to examine in detail the mechanisms of electrogenic reactions at the donor and acceptor sides of RCs. Electrogenesis associated with the intraprotein electron transfer from the exogenous secondary donors, redox dyes, and soluble cytochrome (cyt) c to the photooxidized dimer of bacteriochlorophyll P870 was studied using proteoliposomes containing RCs from the non-sulfur purple bacterium Rhodospirillum rubrum. It was found that reduction of the secondary quinone electron acceptor QB accompanied by its protonation in the chromatophores from R. rubrum in response to every second light flash was electrogenic. Spectral characteristics and redox potentials of the four hemes in the tightly bound cyt c in the RC of Blastochloris viridis and electrogenic reactions associated with the electron transfer within the RC complex were identified. For the first time, relative amplitudes of the membrane potential generated in the course of individual electrogenic reactions were compared with the distances between the redox cofactors determined based on the three-dimensional structure of the Bl. viridis RC.

Electrogenesis in Plasma Membrane Fraction of Halotolerant Microalga Dunaliella maritima and Effects of N,N′-Dicyclohexylcarbodiimide

The effects of N,N'-dicyclohexylcarbodiimide (DCCD), non-specific inhibitor of various transport systems functioning in biological membranes, on Na+-transporting P-type ATPase of the green halotolerant microalga Dunaliella maritima were studied in the experiments with vesicular plasma membranes isolated from the alga cells. The effects of DCCD on electrogenic/ion transport function of the enzyme and its ATP hydrolase activity were investigated. Electrogenic/ion transport function of the enzyme was recorded as a Na+-dependent generation of electric potential on the vesicle membranes with the help of the potential-sensitive probe oxonol VI. It was found that unlike many other ion-transporting ATPases, the Na+-ATPase of D. maritima is insensitive to DCCD. This agent did not inhibit either ATP hydrolysis catalyzed by this enzyme or its transport activity. At the same time DCCD affected the ability of the vesicle membranes to maintain electric potential generated by the D. maritima Na+-ATPase. The observed effects can be explained based on the assumption that DCCD interacts with the Na+/H+ antiporter in the plasma membrane of D. maritima.

A Novel Method to Improve the Accuracy of Heart Disease Identification Using K-NN Method

The ECG represents a graph of variations in electrical potential generated by the heart and recorded at the body surface. The contraction and relaxation of the cardiac muscles repression in generation of electrical potential which could be used to diagnose different disorders of the heart. In this paper we implement a Novel method to improve the accuracy of heart disease identification using K-NN method. The visual identification of different wavelet features in the ECG signal is done to compare it with respect to the normal values for finding the novelties in it so that physician can make brief move against any issue.

Potential Generation Using Salinity Gradients

Salinity Gradient Power (SGP) is one such power, which is environmentally sound as well as sustainable, that can be generated from reversible mixing of two kinds of water with different salt concentrations. This Reverse Electrodialysis (RED) technology uses a concentration gradient to derive a potential. The salinity gradient is created using a fuel cell type cell with a micro-porous ion exchange membrane, both anionic (AEM) and cationic (CEM). The study was performed for various gradients. Salt : Fresh, from 100 : 0 to 16000 : 0 was established using NaCl solution, in the electrode chambers. A potential of 25mV/cm was realized at ambient temperatures and pressures for a bipolar AEM/CEM cell. The achievable potential is still below theoretical values. The higher the salinity gradient the larger is the potential generated. This is limited by the membrane characteristics. This process is a unique technology for potential generation.

Generation of the Outer Membrane Potential in Mitochondria by VDAC-Kinase Complexes: Thermodynamic Estimations

The voltage-dependent anion channels (VDACs) of the mitochondrial outer membrane have been reported as targets for various kinases (hexokinase, glucokinase, creatine kinase and glycerol kinase). The formation of VDAC-hexokinase, VDAC-creatine kinase or of other VDAC-kinase complexes has been assumed to facilitate the selective use of mitochondrial ATP for corresponding cytosolic processes. Such selective use of mitochondrial ATP might result not only due to the energy channeling mediated by a specific kinase, but also due to the recently described VDAC-kinase mediated generation of the outer membrane potential, up to the values sufficiently high to induce the closure of free (unbound) VDACs, thus restricting or even preventing the use of mitochondrial ATP by other cytosolic users. Such metabolically dependent generation of the outer membrane potential by the VDAC-hexokinase complexes, for example, might explain the Warburg effect in cancer cells, as we have suggested earlier. In the cardiac cells, the VDAC-creatine kinase mediated generation of the outer membrane potential at the systolic phase might prevent the use of mitochondrial ATP by the cytosolic users that do not participate directly in the cardiac contraction. The thermodynamic estimations of the outer membrane potential generated by various VDAC-kinase complexes demonstrate the dependence of its value on the free energy of corresponding kinase reaction, on the percentage of VDACs forming the VDAC-kinase complexes and the presence of other proteins or peptides influencing the conductance of free VDACs.

Energy Conversion using electrolytic concentration gradients

ABSTRACTSalinity gradient is an enormous source of clean energy. A process for potential generation from an ionic concentration gradient produced in single and multicell assembly is presented. The ionic gradient is created using a fuel cell type cell with a micro-porous ion exchange membrane, both anionic (AEM) and cationic (CEM). Various salinity gradients, Salt : Fresh, from 100 : 0 to 16000 : 0 was established using NaCl solution, in the electrode chambers. A potential of 20 mV/cm to 25 mV/cm can be realized at ambient temperatures and pressures for a bipolar AEM/CEM cell. The performance was optimized for various static and dynamic flow rates of the saline and fresh water. The cell performance can further be optimized for Membrane Electrode System (MES) morphology. A multicell unit was assembled and the results presented for various conditions like concentration gradients, flow rates and pressure. The thermodynamic and electrical efficiency needs to be evaluated for various gradients and flow rates. The relation with number of valance electrons/ ion and the potential generated changes for various dynamic condition of salinity. The higher the salinity gradient the larger is the potential generated. This is limited by the membrane characteristics. There exists a monotonic relation between the number of valence electron/ion/unit time and the potential generated up to about 16000 concentration. The membrane characteristics have been studied for optimal ion crossover for various gradients and flow. The graph between ln (gradient) versus Voltage provides insights into this process. This presents a very cost effective and clean process of energy conversion.

Membrane potential generated by ion adsorption.

It has been widely acknowledged that the Goldman-Hodgkin-Katz (GHK) equation fully explains membrane potential behavior. The fundamental facet of the GHK equation lies in its consideration of permeability of membrane to ions, when the membrane serves as a separator for separating two electrolytic solutions. The GHK equation describes that: variation of membrane permeability to ion in accordance with ion species results in the variation of the membrane potential. However, nonzero potential was observed even across the impermeable membrane (or separator) separating two electrolytic solutions. It gave rise to a question concerning the validity of the GHK equation for explaining the membrane potential generation. In this work, an alternative theory was proposed. It is the adsorption theory. The adsorption theory attributes the membrane potential generation to the ion adsorption onto the membrane (or separator) surface not to the ion passage through the membrane (or separator). The computationally obtained potential behavior based on the adsorption theory was in good agreement with the experimentally observed potential whether the membrane (or separator) was permeable to ions or not. It was strongly speculated that the membrane potential origin could lie primarily in the ion adsorption on the membrane (or separator) rather than the membrane permeability to ions. It might be necessary to reconsider the origin of membrane potential which has been so far believed explicable by the GHK equation.

Gravity Effect on Electrical Field Generation and Charge Carriers Transfer During Combustion Synthesis of Sulfides

The effect of gravity on the electric potential generated by the combustion synthesis of zinc sulfide is analyzed using the numerical simulation. Recent experimental studies on generation of electric voltage during combustion synthesis of zinc sulfide (ZnS) have revealed high voltage signals (4 V) with duration about 1 s, which are much higher than those produced by the gas-solid and solid-solid combustion reactions studied previously. These data have raised the question about mechanism of such a phenomenon. In our previous work we developed a novel (distributed) model describing the electric potential generation during combustion synthesis of sulfides (CSS) that didn't count the effect of gravity. In this paper the simulations of heat - mass transfer, charge carriers motion, and voltage profiles taking into account the Earth gravity effect. The simulations confirms that the gravitation force strongly affects the emission of negatively charged sulfur ions as well as electrons and has a significant impact on the amplitude and temporal evolution of the combustion induced voltage. The voltage reduction up to four times has been observed numerically in the case when gravity acts in the direction coincident to that of the propagating combustion wave. Vice versa, the significant acceleration of the combustion and the voltage amplification due to the advection is simulated when gravity acts in the direction opposite to that of the propagating combustion wave.

Measurement of liquid flow rate by self-generated electrokinetic potential on the microchannel surface of a solid

A model to describe the interactions between the electrokinetic potential and the liquid ion slip is proposed. The model assumes that the electric charge at the liquid and solid interface causes an attraction force, whereas the fluid shear force at the wall induces a frictional force. Using the proposed model, the condition underlying liquid ion slip is described by analyzing the generation of the surface electric potential when the shear force of flow is above 0.1mN. Once liquid ion slip occurs, the electric charges at the interface move in the direction of the flow but are retarded by electric resistance. Thus, there is a difference in the surface electric potential generated at the solid wall in the direction of the flow. In the water flowing through the microchannel, the velocity of the liquid ion slip was 5.09×10−5 to 2.19×10−3m/s, whereas the generated surface electric potential varied from 0 to 64μV. The proposed model and the experimental analyses provide the groundwork for precise flow sensors, which could easily be integrated into microfluidic systems.

ELECTROPHYSIOLOGICAL MARKERS OF MIDDLE CEREBRAL ARTERY BLOOD FLOW VELOCITY IN HEALTHY SUBJECTS

to determine electrophysiological markers of middle cerebral artery blood flow velocity (BFV). transcranial Doppler registration of middle cerebral artery BFV and direct current (DC) potentials recording from surface of head were performed in 30 healthy volunteers. Analysis of correlation between the BFV and DC potentials was used. significant correlation between BFV and DC potential characteristics was observed. The highest correlation was found between BFV in middle cerebral artery and the difference of DC potentials between central and temporal areas of head (r = 0,55; p = 0,003). These areas coincide with the location of middle cerebral artery and the correlation observed may be connected with streaming potential generated by the blood flow in middle cerebral artery. If electrode placement did not coincide with blood current, DC potentials and BFV were not correlated. it is assumed that electrical field created BFV in middle cerebral artery may contribute to the generation of DC potentials registered from the head.

Evidence that the compound action potential (CAP) from the auditory nerve is a stationary potential generated across dura mater

We have investigated the generation of the compound action potential (CAP) from the auditory nerve of guinea pigs. Responses to acoustic tone-bursts were recorded from the round window (RW), throughout the cochlear fluids, from the surface of the cochlear nucleus, from the central end of the auditory nerve after removal of the cochlear nucleus, from the scalp vertex, and from the contralateral ear. Responses were compared before, during and after experimental manipulations including pharmacological blockade of the auditory nerve, section of the auditory nerve, section of the efferent nerves, removal of the cochlear nucleus, and focal cooling of the cochlear nerve and/or cochlear nucleus. Regardless of the waveform changes occurring with these manipulations, the responses were similar in waveform but inverted polarity across the internal auditory meatus. The CAP waveforms were very similar before and after removal of the cochlear nucleus, apart from transient changes that could last many minutes. This suggests that the main CAP components are generated entirely by the eighth nerve. Based on previous studies and a clear understanding of the generation of extracellular potentials, we suggest that the early components in the responses recorded from the round window, from the cochlear fluids, from the surface of the cochlear nucleus, or from the scalp are a far-field or stationary potential, generated when the circulating action currents associated with each auditory neurone encounters a high extracellular resistance as it passes through the dura mater.

Laboratory simulation of field aligned currents in an experiment on laser-produced plasma interacting with a magnetic dipole

In an experiment on a magnetic dipole interacting with a laser-produced plasma the generation of an intense field aligned current (FAC) system was observed for the first time in a laboratory. The detailed measurements of the total value and local current density, of the magnetic field at the poles and in the equatorial magnetopause, and particular features of electron motion in the current channels revealed its similarity to the Region-1 current system in the Earth magnetosphere. Such currents were found to exist only if they can close via conductive cover of the dipole. Comparison of conductive and dielectric cases revealed specific magnetic features produced by FAC and their connection with electric potential generated in the equatorial part of the magnetopause. To interpret the data we consider a model of electric potential generation in the boundary layer which agrees with experiment and with measurements of the Earth's transpolar potential in the absence of an interplanetary magnetic field as well. The results could be of importance for the investigation of Mercury as a magnetic disturbance due to FAC could be especially large because of the small size of the Hermean magnetosphere.

대지전위와 통신회선 잡음.발생에 대한 고찰

본 논문에서는 전기철도에서 발생하는 대지전위와 통신회선의 잡음에 대한 실험적 증명에 관한 것이다. 대지전 위차가 발생하는 곳에서 전력유도잡음전압과 케이블 평형도 등을 측정할 경우 계측 오차가 심각하게 발생되는 것으로 나타났다. 측정결과, 고속철도 인접한 곳의 통신케이블은 시스층에 지전류가 많이 흐르는 차폐 케이블보다 일반 케이블을 그대로 사용하는 것이 잡음피해를 보다 줄일 수 있음이 실험 결과로 확인 되었다.

Na+-transporting ATPase in the plasma membrane of halotolerant microalga Dunaliella maritima operates as a Na+ uniporter

A fraction of inside-out membrane vesicles enriched in plasma membranes (PM) was isolated from Dunaliella maritima cells. Attempts were made to reveal ATP-driven Na+-dependent H+ efflux from the PM vesicles to external medium, as detected by alkalization of the vesicle lumen. In parallel experiments, ATP-dependent Na+ uptake and electric potential generation in PM vesicles were investigated. The alkalization of the vesicle lumen was monitored with an impermeant pH-sensitive optical probe pyranine (8-hydroxy-1,3,6-pyrenetrisulfonic acid), which was loaded into vesicles during the isolation procedure. Sodium uptake was measured with 22Na+ radioactive label. The generation of electric potential in PM vesicles (positive inside) was recorded with a voltage-sensitive probe oxonol VI. Appreciable Na+-and ATP-dependent alkalization of vesicle lumen was only observed in the presence of a protonophore CCCP (carbonyl cyanide-chlorophenylhydrazone). In parallel experiments, CCCP accelerated the ATP-dependent 22Na+ uptake and abolished the electric potential generated by the Na+-ATPase at the vesicle membrane. A permeant anion NO− 3 accelerated ATP-dependent 22Na+ uptake and promoted dissipation of the electric potential like CCCP did. At the same time, NO− 3 inhibited the ATP-and Na+-dependent alkalization of the vesicle lumen. The results clearly show that the ATP-and Na+-dependent H+ efflux from PM vesicles of D. maritima is driven by the electric potential generated at the vesicle membrane by the Na+-ATPase. Hence, the Na+-transporting ATPase of D. maritima carries only one ion species, i.e., Na+. Proton is not involved as a counter-ion in the catalytic cycle of this enzyme.

Flow-Induced Transverse Electrical Potential across an Assembly of Gold Nanoparticles

We report the generation of a potential difference, of the order of tens of millivolts, induced by the flow of polar liquids over an assembly of gold nanoparticles. The device consisted of two conducting glass plates, one of which contained the gold nanoparticle multilayer assembly. The potential generated is in transverse direction to the flow and is dependent on the nature of the flowing liquid. We propose a simple theoretical model to account qualitatively for the generation of the flow-induced transverse potential.

The Different Effects of Phenothiazines on Cardiac Action Potential Duration

The Different Effects of Phenothiazines on Cardiac Action Potential Duration

Mixed potential sensors using lanthanum manganate and terbium yttrium zirconium oxide electrodes

We have demonstrated a mixed potential, zirconia electrolyte-based sensor that utilizes dense, thin films of LaMnO 3 and Y 0.16Tb 0.30Zr 0.54O 2 − as electrodes to generate an EMF that is proportional to the oxidizable gas species (CO, C 3H 6, and C 3H 8) concentration in a gas stream containing oxygen. The devices reported in this work were tested at 600 and 700 °C and in gas mixtures with O 2 concentrations between 0.86 and 1.75%. An Au/LaMnO 3/YSZ/Y 0.16Tb 0.30Zr 0.54O 2 −/Au device was tested for a total of 3000 h at 600 and 700 °C and was subject to periodic excursions to 10 −10 atm PO 2 to simulate reducing conditions. SEM analysis indicated that the aging effects measured in the device response over the course of this experiment may be linked to the sintering of the Au pad used for current collection on the metal oxide electrode. Three-terminal devices were fabricated so that the magnitude of the mixed potential generated from CO and C 3H 6 exposure on the Au/Y 0.16Tb 0.30Zr 0.54O 2 −, Pt/Y 0.16Tb 0.30Zr 0.54O 2 −, Au/LaMnO 3, and Pt/LaMnO 3 metal/metal oxide electrode combinations could be studied at 600 °C and in 1% O 2. It was found that the catalytic properties of the Au or Pt used for current collection played a significant role in the generation of the mixed potential for both metal oxides tested. The combination of Pt on LaMnO 3 gave an equilibrium response whereas a significant mixed potential was generated on both Au/Y 0.16Tb 0.30Zr 0.54O 2 − and Au/LaMnO 3 electrodes at 600 °C.