The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Kylie A Beattie - One of the best experts on this subject based on the ideXlab platform.
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Sinusoidal Voltage protocols for rapid characterisation of ion channel kinetics
The Journal of Physiology, 2018Co-Authors: Kylie A Beattie, Adam P Hill, Remi Bardenet, Yi Cui, Jamie I Vandenberg, David J Gavaghan, Teun P De BoerAbstract:Understanding the roles of ion currents is crucial to predict the action of pharmaceuticals and mutations in different scenarios, and thereby to guide clinical interventions in the heart, brain and other electrophysiological systems. Our ability to predict how ion currents contribute to cellular electrophysiology is in turn critically dependent on our characterisation of ion channel kinetics - the Voltage-dependent rates of transition between open, closed and inactivated channel states. We present a new method for rapidly exploring and characterising ion channel kinetics, applying it to the hERG potassium channel as an example, with the aim of generating a quantitatively predictive representation of the ion current. We fit a mathematical model to currents evoked by a novel 8 second Sinusoidal Voltage clamp in CHO cells over-expressing hERG1a. The model is then used to predict over 5 minutes of recordings in the same cell in response to further protocols: a series of traditional square step Voltage clamps, and also a novel Voltage clamp comprised of a collection of physiologically-relevant action potentials. We demonstrate that we can make predictive cell-specific models that outperform the use of averaged data from a number of different cells, and thereby examine which changes in gating are responsible for cell-cell variability in current kinetics. Our technique allows rapid collection of consistent and high quality data, from single cells, and produces more predictive mathematical ion channel models than traditional approaches.
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Sinusoidal Voltage protocols for rapid characterization of ion channel kinetics
bioRxiv, 2017Co-Authors: Kylie A Beattie, Adam P Hill, Remi Bardenet, Yi Cui, Jamie I Vandenberg, David J Gavaghan, Teun P De Boer, Gary R MiramsAbstract:Understanding the roles of ion currents is crucial to predict the action of pharmaceuticals and also to guide clinical interventions in the heart, brain and other electrophysiological systems. Our ability to predict how ion currents contribute to cellular electrophysiology is in turn critically dependent on the characterization of ion channel kinetics. We present a method for rapidly exploring and characterizing ion channel kinetics, using the hERG channel, responsible for cardiac I Kr current, as an example. We fit a mathematical model to currents evoked by a novel 8-second Sinusoidal Voltage clamp. The model is then used to predict over 5 minutes of recordings in the same cell in response to further Voltage clamp protocols, including a new collection of physiological action potentials. Our technique allows rapid collection of data from single cells, produces more predictive ion current models than traditional approaches, and will be widely applicable to many ion currents.
Sergey Macheret - One of the best experts on this subject based on the ideXlab platform.
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surface charge in dielectric barrier discharge plasma actuators
Physics of Plasmas, 2008Co-Authors: Dmitry Opaits, Mikhail N Shneider, Richard B Miles, Alexandre Likhanskii, Sergey MacheretAbstract:Direct measurements of the dielectric surface potential and its dynamics in asymmetric dielectric barrier discharge (DBD) plasma actuators show that the charge builds up at the dielectric surface and extends far downstream of the plasma. The surface charge persists for a long time (tens of minutes) after the driving Voltage has been turned off. For a Sinusoidal Voltage waveform, the dielectric surface charges positively. With the Voltage waveform consisting of nanosecond pulses superimposed on a dc bias, the sign of the dielectric surface charge is the same as the sign (polarity) of the bias Voltage. The surface charging significantly affects DBD plasma actuator performance.
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modeling of interaction between weakly ionized near surface plasmas and gas flow
44th AIAA Aerospace Sciences Meeting and Exhibit, 2006Co-Authors: Alexander Likhanskii, Mikhail N Shneider, Sergey Macheret, Richard B MilesAbstract:Detailed physical model for asymmetric dielectric barrier discharge (DBD) in air is developed. Modeling of DBD with applied Sinusoidal Voltage is carried out. The leading role of charging the dielectric surface by electrons in the cathode phase is shown to be critical, acting as a harpoon that pulls positive ions forward and accelerates the gas in the anode phase. The positive ion motion back towards the exposed electrode is shown to be a major source of inefficiency in the Sinusoidal or near-Sinusoidal Voltage cases. Based on understanding of the DBD physics, an optimal Voltage waveform is proposed, consisting in high repetition rate short (a few nanoseconds in duration) negative pulses combined with positive dc bias applied to the exposed electrode. The velocity of near-surface gas jet produced by the DBD actuator thus optimized is shown to be considerably (potentially – by 1-2 orders of magnitude) greater than that for a Sinusoidal signal with similar parameters.
L C Pitchford - One of the best experts on this subject based on the ideXlab platform.
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contribution of positive and negative ions to the electrohydrodynamic force in a dielectric barrier discharge plasma actuator operating in air
Journal of Applied Physics, 2009Co-Authors: J P Boeuf, Y Lagmich, L C PitchfordAbstract:We present a parametric study of the electrohydrodynamic force generated by surface dielectric barrier discharge plasma actuators in air for Sinusoidal Voltage waveforms. The simulation results confirm that momentum is transferred from the charged particles to the neutral species in the same direction during both positive and negative parts of the cycle. The momentum transfer is due to positive ions during the positive part of the cycle (electrode above the dielectric layer is the anode), and to negative ions during the negative part of the cycle. The relative contribution of the positive and negative parts of the cycle depends on the Voltage amplitude and frequency. The model predicts that the contribution of negative ions tends to be dominant at low Voltage frequencies and high Voltage amplitudes.
Teun P De Boer - One of the best experts on this subject based on the ideXlab platform.
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Sinusoidal Voltage protocols for rapid characterisation of ion channel kinetics
The Journal of Physiology, 2018Co-Authors: Kylie A Beattie, Adam P Hill, Remi Bardenet, Yi Cui, Jamie I Vandenberg, David J Gavaghan, Teun P De BoerAbstract:Understanding the roles of ion currents is crucial to predict the action of pharmaceuticals and mutations in different scenarios, and thereby to guide clinical interventions in the heart, brain and other electrophysiological systems. Our ability to predict how ion currents contribute to cellular electrophysiology is in turn critically dependent on our characterisation of ion channel kinetics - the Voltage-dependent rates of transition between open, closed and inactivated channel states. We present a new method for rapidly exploring and characterising ion channel kinetics, applying it to the hERG potassium channel as an example, with the aim of generating a quantitatively predictive representation of the ion current. We fit a mathematical model to currents evoked by a novel 8 second Sinusoidal Voltage clamp in CHO cells over-expressing hERG1a. The model is then used to predict over 5 minutes of recordings in the same cell in response to further protocols: a series of traditional square step Voltage clamps, and also a novel Voltage clamp comprised of a collection of physiologically-relevant action potentials. We demonstrate that we can make predictive cell-specific models that outperform the use of averaged data from a number of different cells, and thereby examine which changes in gating are responsible for cell-cell variability in current kinetics. Our technique allows rapid collection of consistent and high quality data, from single cells, and produces more predictive mathematical ion channel models than traditional approaches.
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Sinusoidal Voltage protocols for rapid characterization of ion channel kinetics
bioRxiv, 2017Co-Authors: Kylie A Beattie, Adam P Hill, Remi Bardenet, Yi Cui, Jamie I Vandenberg, David J Gavaghan, Teun P De Boer, Gary R MiramsAbstract:Understanding the roles of ion currents is crucial to predict the action of pharmaceuticals and also to guide clinical interventions in the heart, brain and other electrophysiological systems. Our ability to predict how ion currents contribute to cellular electrophysiology is in turn critically dependent on the characterization of ion channel kinetics. We present a method for rapidly exploring and characterizing ion channel kinetics, using the hERG channel, responsible for cardiac I Kr current, as an example. We fit a mathematical model to currents evoked by a novel 8-second Sinusoidal Voltage clamp. The model is then used to predict over 5 minutes of recordings in the same cell in response to further Voltage clamp protocols, including a new collection of physiological action potentials. Our technique allows rapid collection of data from single cells, produces more predictive ion current models than traditional approaches, and will be widely applicable to many ion currents.
Jean-paul Booth - One of the best experts on this subject based on the ideXlab platform.
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Control of the ion flux and ion energy in CCP discharges using non-Sinusoidal Voltage waveforms
Journal of Physics D: Applied Physics, 2012Co-Authors: Trevor Lafleur, Jean-paul BoothAbstract:Using particle-in-cell simulations we perform a characterization of the ion flux and ion energy in a capacitively coupled rf plasma reactor excited with non-Sinusoidal Voltage waveforms. The waveforms used are positive Gaussian type pulses (with a repetition frequency of 13.56 MHz), and as the pulse width is decreased, three main effects are identified that are not present in typical symmetric Sinusoidal discharges: (1) the ion flux (and plasma density) rapidly increases, (2) as the pressure increases a significant asymmetry in the ion fluxes to the powered and grounded electrodes develops and (3) the average ion energy on the grounded electrode cannot be made arbitrarily small, but in fact remains essentially constant (together with the bias Voltage) for the pressures investigated (20500 mTorr). Effects (1) and (3) potentially offer a new form of control in these types of rf discharges, where the ion flux can be increased while keeping the average ion energy on the grounded electrode constant. This is in contrast with the opposite control mechanism recently identified in Donkó et al (2009 J. Phys. D: Appl. Phys. 42 025205), where by changing the phase angle between applied Voltage harmonics the ion flux can be kept constant while the ion energy (and bias Voltage) varies.
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Enhanced sheath heating in capacitively coupled discharges due to non-Sinusoidal Voltage waveforms
Applied Physics Letters, 2012Co-Authors: Trevor Lafleur, R.w. Boswell, Jean-paul BoothAbstract:Through the use of particle-in-cell simulations, we demonstrate that the power deposition in capacitively coupled discharges (in argon) can be increased by replacing Sinusoidal waveforms with Gaussian-shaped Voltage pulses (with a repetition frequency of 13.56 MHz). By changing the Gaussian pulse width, electron heating can be directly controlled, allowing for an increased plasma density and ion flux for the same gas pressure and geometrical operating conditions. Analysis of the power deposition profiles and electron distribution functions shows that enhanced electron-sheath heating is responsible for the increased power absorption.
