Ramp Pulse Research Articles

Transient performance of a Peltier super cooler under varied electric pulse conditions with phase change material

In this work, a novel technique to improve the performance of Peltier cooler under varying electric pulse conditions has been studied with the use of phase change material (PCM). The 2D heat transfer model of Peltier cooler along with heat sink has been developed and studied numerically. The results show that the cold side temperature of Peltier cooler with PCM has been reduced significantly from −14.5 °C to −17.5 °C under pulse operation as compared to the Peltier cooler without PCM under pulse operation. It is also found that, there is no significant reduction in COP of the Peltier cooler under pulse operation with PCM as compared to pulse operation without PCM. These studies have been carried out by varying the hot side heat transfer coefficient, fill volume of PCM in heat sink and the shape of the electric pulse. It has been observed that the super cooling of Peltier cooler increases with increase in fill volume of PCM. Furthermore, it has been found that the super cooling performance of the Peltier cooler is more predominant with the square pulse as compared to ramp and triangular pulses.

High-Power Nanosecond Pulse Generators With Improved Reliability by Adopting Auxiliary Triggering Topology

Marx bank circuits (MBCs) based on avalanche transistors are widely used to generate nanosecond pulses with high power, high repetition rate, and low jitter. However, it was observed that avalanche transistors in the first and second stages of traditional M × N -stage MBCs have high failure rates. This paper proposes an auxiliary triggering topology (ATT) for improving the reliability of high-power MBCs based on avalanche transistors. The operation principles of ATT and failure mechanisms of traditional MBCs are analyzed. By adopting ATT, the auxiliary triggering pulse is generated between the base and emitter of the transistor, and the switching mode is changed from “overvoltage switching- on ” to “triggering switching- on . ” The combined effect of overvoltage ramp and auxiliary triggering pulse significantly reduces the failure rate and prolongs the lifetime of easily damaged transistors. Two high-power nanosecond pulse generators, 3 × 12-stage and 6 × 10-stage MBCs adopting ATT, are developed to verify the feasibility of the proposed configuration. The output amplitude and the rising time are 8.5 kV/6 ns and 17 kV/6 ns at the open end of coaxial cable with 75-Ω impedance, respectively. Both generators are tested continuously at the repetition rate of 2 kHz for 60 min and no failure occurs, which shows much better performance in repetition rate and reliability than traditional M × N -stage MBCs.

Time-of-flight angiography at 7T using TONE double spokes with parallel transmission

PurposeTo demonstrate that fast-kz spokes can be used in parallel transmission to homogenize flip angle ramp profiles (known as TONE) in slab selections, and thereby improve Time-Of-Flight angiography of the whole human brain at 7T. MethodsB1+ and B0 maps were measured on seven human brains with a z-segmented coil connected to an 8-channel pTx system. Tailored two-spoke pulses were designed under strict hardware and SAR constraints for uniform slab profile before transforming their subpulse waveforms for linearly-increasing flip-angle ramps. Increasing angulations along the feet-head direction were prescribed in 2-slab and 3-slab TOF acquisitions. Excitation patterns were simulated and compared with RF-shimmed (single spoke) ramp pulses. Excitation performances were assessed in ~10-min TOF acquisitions by visually inspecting Maximal Intensity Projections angiograms. ResultsThe flip-angle ramp fidelity achieved by double spokes inside slabs of interest was improved by 30–40% compared to RF-shimmed ramps. This allowed better homogenizing signal along arteries, and depicting small vessels in distal areas of the brain, in comparison with RF-shimmed ramp pulses or double-spoke uniform excitation. ConclusionRamp double spokes used in conjunction with parallel transmission yield better blood saturation compensation and more finely resolved TOF angiograms than mere double spokes or ramp single spokes at 7T.

Evidence for Effective Multiple K+-Current Inhibitions by Tolvaptan, a Non-peptide Antagonist of Vasopressin V2 Receptor.

Tolvaptan (TLV), an oral non-peptide antagonist of vasopressin V2 receptor, has been increasingly used for managements in patients with hyponatremia and/or syndrome of inappropriate antidiuretic hormone secretion. However, none of the studies have thus far been investigated with regard to its possible perturbations on membrane ion currents in endocrine or neuroendocrine cells. In our electrophysiological study, the whole-cell current recordings showed that the presence of TLV effectively and differentially suppressed the amplitude of delayed rectifier K+ (IK(DR)) and M-type K+ current (IK(M)) in pituitary GH3 cells with an IC50 value of 6.42 and 1.91 μM, respectively. This compound was also capable of shifting the steady-state activation curve of IK(M) to less depolarized potential without any appreciable change in the gating charge of this current. TLV at a concentration greater than 10 μM also suppressed the amplitude of erg-mediated K+ current or the activity of large-conductance Ca2+-activated K+ channels; however, this compound failed to alter the amplitude of hyperpolarization-activated cation current in GH3 cells. In vasopressin-preincubated GH3 cells, TLV-mediated suppression of IK(M) remained little altered. Under current-clamp condition, we also observed that addition of TLV increased the firing of spontaneous action potentials in GH3 cells and further addition of flupirtine could reverse TLV-mediated elevation of the firing. In Madin-Darby canine kidney (MDCK) cells, the K+ current elicited by long ramp pulse was also effectively subject to inhibition by this compound. Findings from the present study were thus stated as saying that the suppression by TLV of multiple type K+ currents could be direct and independent of its antagonism of vasopressin V2 receptors. Our study also reveals an important aspect that should be considered when assessing aquaretic effect of TLV or its structurally similar compounds.

Role of temperature in valence change memory devices

The I-V curve of forming, switching between SET and RESET and memory are evaluated theoretically. The key features of the model are: a) drift diffusion of ions and of electrons, b) stoichiometry changes by exchange of oxygen with the ambient, c) temperature changes with current, d) Mott transitions in forming the filament and e) switching by changes in tunneling through a thin insulating layer. Forming, SET and RESET are induced by stoichiometry changes. Both voltage ramp and voltage pulses are considered. For pulses the interplay between pulse duration and pulse voltage is evaluated.

Triggering of the breakdown in a discharge tube by visible-spectrum light pulses

The influence of the pulses of visible-spectrum light on the breakdown in a discharge tube was studied experimentally. The tube of 80 cm length and 1.5 cm inner diameter contained neon at a pressure of 0.6 Torr. High-voltage rectangular or ramp pulses were applied to the anode. The light pulses of 0.1–100 µs duration were produced by the light-emitting diode or laser diode at a wavelength of 460 and 407 nm, respectively. A small area of the tube wall near the anode was illuminated at different moments after or before the voltage pulse onset.It has been found that the light pulse exerts the strongest influence on the breakdown. In the case of rectangular pulse, it drastically decreases the statistical delay time of the breakdown. As a result, all the breakdowns, which did not happen before the light pulse, occur during several microseconds after its onset. The light pulse influences the breakdown delay time even if it terminates before the voltage pulse onset. This can be explained by the finite lifetime of the secondary electrons produced by the light. In the case of the ramp voltage pulse, an essential decrease in the breakdown voltage scatter is observed under illumination. The effect is especially pronounced if the light pulse is applied at the moment when the anode voltage is equal to or somewhat lower than the minimum breakdown voltage. For later moments, the breakdown voltages are strictly bounded by both sides. The average breakdown voltage decreases noticeably.As for the mechanism responsible for the observed effect, electron photodesorption from the tube wall is suggested. This process presumably occurs in dielectric barrier discharge at atmospheric pressure where it can influence the breakdown voltage and provide synchronous breakdown of micro discharges, thus causing the formation of multiple filaments.

Controlled generation of a single Trichel pulse and a series of single Trichel pulses in air

In this paper, a simple method for the controlled generation of a single Trichel pulse or a series of single Trichel pulses of a regulated repetition frequency in air is proposed. The concept of triggering a single Trichel pulse or a series of such pulses is based on the precise controlling the voltage inception of the negative corona, which can be accomplished through the use of a ramp voltage pulse or a series of such pulses with properly chosen ramp voltage pulse parameters (rise and fall times, and ramp voltage pulse repetition frequency). The proposal has been tested in experiments using a needle-to-plate electrode arrangement in air, and reproducible Trichel pulses (single or in a series) were obtained by triggering them with an appropriately designed voltage waveform. The proposed method and results obtained have been qualitatively analysed. The analysis provides guidance for designing the voltage ramp pulse in respect of the generation of a single Trichel pulse or a series of single Trichel pulses. The controlled generation of a single Trichel pulse or a series of such pulses would be a helpful research tool for the refined studies of the fundamental processes in a negative corona discharge in a single- (air is an example) and multi-phase gaseous fluids. The controlled generation of a single Trichel pulse or a series of Trichel pulses can also be attractive for those corona treatments which need manipulation of the electric charge and heat portions delivered by the Trichel pulses to the object.

Coupled thermoelastic analysis of an FG multilayer graphene platelets-reinforced nanocomposite cylinder using meshless GFD method: A modified micromechanical model

The coupled thermoelasticity analysis based on the Green–Naghdi theory with energy dissipation is carried out to assess the thermoelastic wave propagations in an FG multilayer graphene platelets-reinforced nanocomposite cylinder. The cylinder is assumed to be made of multi-layers (sub-cylinders), and each layer is reinforced by a uniform distribution of graphene platelets (GPLs). A modified micromechanical model is used to calculate the thermal and mechanical properties considering nonlinear grading patterns of the GPLs along the radial direction of the cylinder. Using a proper arrangement of the layers, the nonlinear grading patterns of the GPLs are created along the radial direction of the whole cylinder. To solve the obtained governing partial differential equations (PDEs), the meshless generalized finite-difference (GFD) method and the Newmark method are employed. The inner surface of the cylinder is excited by three types of the thermal shock loading including the suddenly temperature increase described by the Heaviside step function, as well as sinusoidal and ramp pulses. The effects of the key parameters such as the weight fraction of the GPLs and volume fraction index on the thermoelastic wave propagations and dynamic behaviors of the field variables are studied in details. Also, the effects of the key parameters on the thermoelastic damping in the temperature field are illustrated using the presented modified micromechanical model. The accuracy and stability of the presented meshless method and the numerical results are verified by the published reference data.

Full-Bridge Modular Multilevel Submodule-Based High-Voltage Bipolar Pulse Generator With Low-Voltage DC, Input for Pulsed Electric Field Applications

High-voltage (HV) pulse generators (PGs) are the core of pulsed electric field applications. Applying HV pulses produces electrical pores in a biological cell membrane, in which if the size of the pores increases beyond a critical size, the cell will not survive. This paper proposes a new HV-PG based on the modular multilevel converter with full-bridge submodules (FB-SMs). In order to alleviate the need of complicated sensorless or sensor-based voltage balancing techniques for the FB-SM capacitors, a dedicated self-regulating charging circuit is connected across each FB-SM capacitor. The individual capacitor charging voltage level is obtained from three successive stages, namely, convert the low-voltage dc input voltage to a high-frequency square ac voltage, increase the ac voltage level via a nanocrystalline step-up transformer, and rectify the secondary transformer ac voltage via a diode FB rectifier. The HV bipolar pulses are formed across the load in a fourth stage through series connected FB-SMs. The flexibility of inserting and bypassing the FB-SM capacitors allows the proposed topology to generate different pulse-waveform shapes, including rectangular waveforms with specifically reduced ${dv/dt}$ and ramp pulses. The practical results, from a scaled-down experimental rig with five FB-SMs and a 1-kV peak-to-peak pulse output, validate the proposed topology.

Modified pulse operation of thermoelectric coolers for building cooling applications

This paper presents a modified pulse operation of the thermoelectric cooler (TEC) for building space cooling application. In the normal pulse operation of a thermoelectric cooler, a current pulse is given as the input, but in the modified pulse operation, along with the pulse current, the hot side heat transfer coefficient is also pulsed. A numerical model for the thermoelectric cooling system is developed assuming one-dimensional unsteady state heat transfer having convective heat transfer boundary condition at its hot side and constant heat flux boundary condition at its cold side. Then the thermoelectric cooling system is studied with variable pulse current ratio, cooling load, variable pulse width and with dissimilar pulse shapes. The result shows that, for a typical operating condition with the modified pulse operation, the thermoelectric cooling system can provide an average cooling power of 600W with the COP of 1.01, which are 23.3% and 2.12% higher than the normal mode of operation (i.e. without current pulse) respectively. This study also found that the rectangular-shaped pulse can provide higher average cooling power and COP when compared with the ramp and exponential pulse.

Influence of Charge Transport and Defects on the Performance of Planar and Mesostructured Perovskite Solar Cells

Photoinduced charge selective carrier extraction by linearly increasing voltage technique allows straightforward assessment of charge transport properties within planar and mesostructured perovskite solar cells with respect to light intensity and signal delay time. Charge sensitive device architecture is realized through implementation of insulating layer between the anode or cathode to prevent extraction of unwanted type of carriers. Resulting behavior of comparatively efficient mesoporous and planar solar cells exhibits well balanced charge transport with slight dependence of charge mobility on applied laser pulse fluence, for given pulse delay times. Very similar charge carrier mobilities are present within mesoporous devices, whereas holes trail approximately half an order of magnitude behind electrons in planar structured specimens. Moreover, dispersive transport is identified in the electron selective devices with titanium oxide electron transporter, suggesting considerable presence of trapping states at the perovskite interface, whereas no such behavior characterizes planar samples. Variation in delay time between laser pulse and extraction ramp only affects initial charge concentration present within the device, while transient outlay remains unchanged, indicating absence of film charging effect.

Block of Na+/Ca2+ exchanger by SEA0400 in human right atrial preparations from patients in sinus rhythm and in atrial fibrillation

The Na+/Ca2+ exchanger (NCX) plays a major role in myocardial Ca2+ homoeostasis, but is also considered to contribute to the electrical instability and contractile dysfunction in chronic atrial fibrillation (AF). Here we have investigated the effects of the selective NCX blocker SEA0400 in human right atrial cardiomyocytes from patients in sinus rhythm (SR) and AF in order to obtain electrophysiological evidence for putative antiarrhythmic activity of this new class of drugs. Action potentials were measured in right atrial trabeculae using conventional microelectrodes. Human myocytes were enzymatically isolated. Rat atrial and ventricular cardiomyocytes were used for comparison. Using perforated-patch, NCX was measured as Ni2+-sensitive current during ramp pulses. In ruptured-patch experiments, NCX current was activated by changing the extracellular Ca2+ concentration from 0 to 1mM in Na+-free bath solution (100mM Na+ intracellular, “Hilgemann protocol”). Although SEA0400 was effective in rat cardiomyocytes, 10µM did not influence action potentials and contractility, neither in SR nor AF. SEA0400 (10μM) also failed to affect human atrial NCX current measured with perforated patch. With the “Hilgemann protocol” SEA0400 concentration-dependently suppressed human atrial NCX current, and its amplitude was larger in AF than in SR cardiomyocytes. Our results confirm higher NCX activity in AF than SR. SEA0400 fails to block Ni2+-sensitive current in human atrial cells unless unphysiological conditions are used. We speculate that block of NCX with SEA0400 depends on intracellular Na+ concentration.

CriSAA: A Simulation Code for Evaluation of Criticality Transients Involving Low Source Start-Up

A code called CriSAA used for criticality excursion evaluation and analysis is developed by coupling a two-dimensional thermal-hydraulic code and a zero-dimensional neutron kinetics code. The generalized semi-Markov process simulation method is improved in the neutron kinetics code, which makes it suitable for the transient cases of both stochastic and intense neutron fields. Pulse withdrawal experiments and ramp feed experiments performed on the Transient Experiment Critical Facility (TRACY) are simulated with CriSAA. The transient characteristics of isolated and open criticality excursions on TRACY are studied. The simulation fits well with the experiments. Stochastic phenomena of the criticality excursions under a weak source case are studied. The statistics characteristics, including time and energy to first peak, power of first peak, and total energy, are shown. This work provides an advanced approach for criticality excursion evaluation and analysis.

Study of temporal pulse shape effects on W using simulations and laser heating

Transient heat pulses with triangular, square, and ELM-like temporal shapes are investigated in order to further understand how transient plasma instabilities will affect plasma facing components in tokamaks. A solution to the 1D heat equation for triangular pulses allows the peak surface temperature to be written analytically for arbitrary rise times. The solution as well as ANSYS simulations reveal that a positive ramp (maximum rise time) triangular pulse has a higher peak surface temperature by a factor of compared to that from a negative ramp (rise time = 0) pulse shape with equal energy density, peak power, and pulse width. Translating the results to ITER, an ELM or disruption pulse with the shortest rise time is the most benign compared to other pulse shapes with the same peak heat flux and same energy density.

Reducing Current Spread by Use of a Novel Pulse Shape for Electrical Stimulation of the Auditory Nerve.

Improving the electrode-neuron interface to reduce current spread between individual electrodes has been identified as one of the main objectives in the search for future improvements in cochlear-implant performance. Here, we address this problem by presenting a novel stimulation strategy that takes account of the biophysical properties of the auditory neurons (spiral ganglion neurons, SGNs) stimulated in electrical hearing. This new strategy employs a ramped pulse shape, where the maximum amplitude is achieved through a linear slope in the injected current. We present the theoretical framework that supports this new strategy and that suggests it will improve the modulation of SGNs’ activity by exploiting their sensitivity to the rising slope of current pulses. The theoretical consequence of this sensitivity to the slope is a reduction in the spread of excitation within the cochlea and, consequently, an increase in the neural dynamic range. To explore the impact of the novel stimulation method on neural activity, we performed in vitro recordings of SGNs in culture. We show that the stimulus efficacy required to evoke action potentials in SGNs falls as the stimulus slope decreases. This work lays the foundation for a novel, and more biomimetic, stimulation strategy with considerable potential for implementation in cochlear-implant technology.

Generation of resonance-dependent oscillation by mGluR-I activation switches single spiking to bursting in mesencephalic trigeminal sensory neurons.

The primary sensory neurons supplying muscle spindles of jaw-closing muscles are unique in that they have their somata in the mesencephalic trigeminal nucleus (MTN) in the brainstem, thereby receiving various synaptic inputs. MTN neurons display bursting upon activation of glutamatergic synaptic inputs while they faithfully relay respective impulses arising from peripheral sensory organs. The persistent sodium current (IN aP ) is reported to be responsible for both the generation of bursts and the relay of impulses. We addressed how IN aP is controlled either to trigger bursts or to relay respective impulses as single spikes in MTN neurons. Protein kinase C (PKC) activation enhanced IN aP only at low voltages. Spike generation was facilitated by PKC activation at membrane potentials more depolarized than the resting potential. By injection of a ramp current pulse, a burst of spikes was triggered from a depolarized membrane potential whereas its instantaneous spike frequency remained almost constant despite the ramp increases in the current intensity beyond the threshold. A puff application of glutamate preceding the ramp pulse lowered the threshold for evoking bursts by ramp pulses while chelerythrine abolished such effects of glutamate. Dihydroxyphenylglycine, an agonist of mGluR1/5, also caused similar effects, and increased both the frequency and impedance of membrane resonance. Immunohistochemistry revealed that glutamatergic synapses are made onto the stem axons, and that mGluR1/5 and Nav1.6 are co-localized in the stem axon. Taken together, glutamatergic synaptic inputs onto the stem axon may be able to switch the relaying to the bursting mode.

Inhibitory actions by ibandronate sodium, a nitrogen-containing bisphosphonate, on calcium-activated potassium channels in Madin-Darby canine kidney cells.

The nitrogen-containing bisphosphonates used for management of the patients with osteoporosis were reported to influence the function of renal tubular cells. However, how nitrogen-containing bisphosphates exert any effects on ion currents remains controversial. The effects of ibandronate (Iban), a nitrogen-containing bisphosphonate, on ionic channels, including two types of Ca2+-activated K+ (KCa) channels, namely, large-conductance KCa (BKCa) and intermediate-conductance KCa (IKCa) channels, were investigated in Madin–Darby canine kidney (MDCK) cells. In whole-cell current recordings, Iban suppressed the amplitude of voltage-gated K+ current elicited by long ramp pulse. Addition of Iban caused a reduction of BKCa channels accompanied by a right shift in the activation curve of BKCa channels, despite no change in single-channel conductance. Ca2+ sensitivity of these channels was modified in the presence of this compound; however, the magnitude of Iban-mediated decrease in BKCa-channel activity under membrane stretch with different negative pressure remained unchanged. Iban suppressed the probability of BKCa-channel openings linked primarily to a shortening in the slow component of mean open time in these channels. The dissociation constant needed for Iban-mediated suppression of mean open time in MDCK cells was 12.2 μM. Additionally, cell exposure to Iban suppressed the activity of IKCa channels, and DC-EBIO or 9-phenanthrol effectively reversed its suppression. Under current-clamp configuration, Iban depolarized the cells and DC-EBIO or PF573228 reversed its depolarizing effect. Taken together, the inhibitory action of Iban on KCa-channel activity may contribute to the underlying mechanism of pharmacological or toxicological actions of Iban and its structurally similar bisphosphonates on renal tubular cells occurring in vivo.

Influence of heat flux loading patterns on the surface cracking features of tungsten armor under ELM-like thermal shocks

In this work, the influence of different high heat flux (HHF) loading patterns on the surface cracking of tungsten was investigated under edge-localized mode (ELM)-like thermal loads. Two numerical approaches were employed, namely, the extended finite element method (XFEM) and the virtual crack tip extension (VCE) method. Comparative assessment of initial cracking and crack growth was conducted for six HHF loading patterns (combinations of three spatial and two temporal variants) assuming the same deposited energy for all cases. A ramp pulse with a longer duration leads to slightly lower temperatures and stresses in comparison to a constant pulse with a shorter duration, and no significant difference in cracking appears for these two temporal loading scenarios. In the central part of the loading area, cracks propagate perpendicularly to the surface and the final length of these cracks is dependent on the applied power density. For both triangular and uniformly distributed HHF loadings, cracks initiated near the position, where the peak stress occurred at the surface, tend to kink from the initial vertical paths and then grow parallel to the surface. The driving force for this type of crack propagation is larger under uniform than triangular loading.

Generation of isentropic compression by use of multi-layer composite flyer and its influence on system thermodynamics: A simulation study

Recently the possibility of achieving quasi-isentropic compression using functionally graded materials, in both gas gun and explosive driven systems was explored by hydro-dynamic simulations. In the current paper, we show that multi-layered composite flyer with progressively increasing shock impedances, referred to as graded density impactor (GDI), has the potential to enable increased flexibility in suitably tailoring the applied-pressure profiles, further relaxing constraints on the thermodynamic path of compressed material. Present simulation study pertaining to constant velocity impact of GDI reveals that linear ramp pulses of different pressure rise times, with comparable peak values can be realized only by changing the layer thicknesses of a particular GDI. We report generation of three different slope ramp pulses by five layer GDI made of PMMA, Al, Ti, Cu and Ta with different set of thicknesses obtained by genetic algorithm based optimization technique. Generation of long duration (μs) isentropic pressures using discrete GDI is a significant step, since it is devoid of fabrication difficulties of ultra-thin lamellae of FGM. Signatures of isentropic compression of a thin Cu target under different slope ramp loadings are identified from basic thermodynamic aspects in terms of temperature rise and entropy production. It is shown that that extent of entropy increase is closely related to the slope of ramping pulse. Further, a physical model has been constructed to determine approximate time profile of pressure pulse generated by equal layer-width GDI.

Abstract 161: TRPC6 Activator Hyperforin Facilitates Arrhythmias Via Activating Store-operated Calcium Entry

Hyperforin, a major antidepressant constituent of St. John’s wort ( Hypericum perforatum ), exhibits high selectivity in activating the canonical transient potential channel 6 (TRPC6). Our previous studies have shown that TRPC6 may modulate Ca 2+ handling via store-operated Ca 2+ entry (SOCE) in adult ventricular myocytes. In the present study, we aim to test whether hyperforin is arrhythmogenic by facilitating Ca 2+ waves. Intracellular Ca 2+ fluorescence (F/F 0 ) was imaged in Fluo-4-AM loaded ventricular myocytes isolated from adult mice (2-4 month old). SOCE was evaluated by increasing the external Ca 2+ concentration ([Ca 2+ ] o ) from 0 to 1 mM after caffeine (10 mM) and thapsigargin (10 µM) were used to completely deplete SR Ca 2+ . Hyperforin (0.1-10 µM) perfusion increased SOCE up to 3.7 folds (F/F 0 = 3.73 ± 0.42, n = 7, compared to the control F/F 0 = 1.69 ± 0.37, n = 9, p < 0.05), in a concentration dependent fashion. Whole-cell currents were recorded using ramp pulses from -110 mV to +50 mV, while K + , Na + , L-type Ca 2+ , and Na + -Ca 2+ exchange currents were pre-blocked. Hyperforin at a lower concentration (0.1 µM) induced a significant increase of inward current (from -1.44 ± 0.23 pA/pF to -2.56 ± 0.36 pA/pF, n = 8, p < 0.05), which was then inhibited by the SOCE blocker Gd 3+ (1 mM) (-0.43 ± 0.22 pA/pF, n = 8, p < 0.05). Hyperforin promotes spontaneous CaWs ([Ca 2+ ] o 4 mM) by increasing the frequency to 180± 14 % (n = 11. p < 0.05), which can be attenuated by Gd 3+ (1 mM), or SKF-96265 (10 μM). In addition, both the amplitudes of Ca 2+ transients (F/F 0 =1.92 ± 0.09 to 2.09 ± 0.10, n = 12, p < 0.05) and calcium content (control: F/F 0 = 2.03 ± 0.11, n=16 to 2.12 ± 0.13, n = 11, p < 0.05) were enhanced by acute hyperforin perfusion (0.1 µM), when the cells were paced at a pacing cycle length of 2 seconds. The proarrhythmic effect of hyperforin was also confirmed in Langendorff-perfused hearts, from which optical membrane voltage mapping and EKG were simultaneously recorded. In conclusion, the TRPC6 activator hyperforin exhibits an arrhythmogenic effect in the heart. Its action is likely to be mediated by generating an inward current and increasing the calcium load in cardiac myocytes through the SOCE pathway. Caution should be taken when prescribing this drug to patients with heart disease.