Ramp Pulse Research Articles

Experiment for measurements of the gas breakdown statistics by ramp voltage pulses

In the first part of this article the electronic automatic system for the measurements of dynamic breakdown voltages Ub with linearly rising (ramp) pulses is presented. It generates the sequence of ramp pulses with subvoltage level Usub≈0 during the relaxation time τ of the tube, and the ramp pulses start from the static breakdown voltage Us, thus enabling the correct study of electrical breakdowns and relaxation in gases. In the second part the measurements in argon with and without a voltage during the off period of the pulse are analyzed. The influence of the subvoltage on the mean value of the breakdown voltage Ub¯ as a function of the rise rate k, on the statistical Ub distributions and on the afterglow kinetics is also discussed.

Post-breakdown leakage resistance and its dependence on device area

Sub-nanosecond pulses were used to stress gate capacitors and the post-breakdown leakage resistance is analyzed. Post-breakdown leakage resistance obtained using sub-nanosecond pulse stress and ramp voltage stress are compared, and a power-law relationship between the inverse of the post-breakdown leakage resistance and device area is observed.

Effects of Linear Falling Ramp Reset Pulse on Addressing Operation in AC PDP

The effects of linear falling ramp reset pulse related to addressing operation in an alternating current plasma display panel (AC PDP) were studied. The wall charge waveforms were measured by the electrode balance method in a 12-inch coplanar AC PDP. The wall charge waveforms show the relationship between the slope ratio of the falling ramp reset pulse and the wall charges at the end of the falling ramp reset pulse which influences the addressing stability. Then the effects of the slope ratio of the linear falling ramp reset pulse on the addressing voltage and addressing time were investigated. The experimental results show that the minimum addressing voltage increases with the increase of the slope ratio of the falling ramp reset pulse, and so does the minimum addressing time. Based on the experimental results, the optimization of the addressing time and the slope ratio of the falling ramp pulse is discussed.

Pulse line ion accelerator concept

April 3, 2006 LBNL-59492 The pulse line ion accelerator concept Richard J. Briggs Science Applications International Corporation, Alamo, California, 94507 The Pulse Line Ion Accelerator concept was motivated by the desire for an inexpensive way to accelerate intense short pulse heavy ion beams to regimes of interest for studies of High Energy Density Physics and Warm Dense Matter. A pulse power driver applied at one end of a helical pulse line creates a traveling wave pulse that accelerates and axially confines the heavy ion beam pulse. Acceleration scenarios with constant parameter helical lines are described which result in output energies of a single stage much larger than the several hundred kilovolt peak voltages on the line, with a goal of 3-5 MeV/meter acceleration gradients. The concept might be described crudely as an “air core” induction linac where the PFN is integrated into the beam line so the accelerating voltage pulse can move along with the ions to get voltage multiplication. 1. Introduction In the “Pulse Line Ion Accelerator” (PLIA) concept described in this paper a ramped high voltage pulse is applied at the input end of a helical pulse line structure. The resulting traveling wave pulse on the line can accelerate an ion bunch to energies much greater than the peak voltage applied to the line. It should also be possible to achieve an axial acceleration gradient of several MeV per meter with realistic helix parameters. The development of this concept was originally motivated by a proposal to use moderate energy intense ion beams to heat matter to regimes of interest for studies of High Energy Density Physics (HEDP) and Warm Dense Matter (WDM) [ 1 ] . In this approach, very short pulses (~ a nanosecond or less) of “medium mass” ions with energies slightly above the Bragg peak are focused to mm scale spot sizes onto thin target “foils”, which may in fact be foams with mean densities of order 10% solid density or less. The high degree of uniformity and efficiency with volumetric and shock-less heating of the target to temperatures of order 1 to 10 eV are attractive features in this approach. The concept presented in this paper is an excellent fit to the accelerator requirements for this HEDP/WDM application. A helical pulse line inserted into a large bore 5 - 10T superconducting solenoid can transport and accelerate a singly charged Ne or Na ion bunch with a total charge of order 0.1 to 1 micro-coulombs, an axial bunch length of 10’s of cm, and a radius of a few cm. The required axial compression to bunch lengths of order one cm in a neutralized drift compression region following the accelerator is then only a factor of 10-30, which greatly eases the requirements on longitudinal emittance, velocity tilt, and drift distance.

P-110: A New Reset Waveform for a Large-Sustain-Gap Structure in AC PDPs

In this paper, we present a new reset waveform for a large-sustain-gap structure in ac PDPs. In the driving of the large-sustain-gap structure with a conventional ramp reset waveform, we cannot avoid the condition of an address being a cathode, which causes lots of trouble in stabilizing a reset discharge. To solve these problems, we use the square pulse instead of the conventional rising ramp pulse. Before making a strong discharge between the address (cathode) and scan (anode) electrodes, we make a priming discharge between the address (anode) and the scan (cathode) electrodes to stabilize the strong discharge in which the address electrodes are the cathode. With this scheme, we obtained 60V minimum address voltage and 145V maximum address voltage in 250μm and 350μm gap structures.

Genetic Demonstration That the Plasma Membrane Maxianion Channel and Voltage-dependent Anion Channels Are Unrelated Proteins

The maxianion channel is widely expressed in many cell types, where it fulfills a general physiological function as an ATP-conductive gate for cell-to-cell purinergic signaling. Establishing the molecular identity of this channel is crucial to understanding the mechanisms of regulated ATP release. A mitochondrial porin (voltage-dependent anion channel (VDAC)) located in the plasma membrane has long been considered as the molecule underlying the maxianion channel activity, based upon similarities in the biophysical properties of these two channels and the purported presence of VDAC protein in the plasma membrane. We have deleted each of the three genes encoding the VDAC isoforms individually and collectively and demonstrate that maxianion channel (approximately 400 picosiemens) activity in VDAC-deficient mouse fibroblasts is unaltered. The channel activity is similar in VDAC1/VDAC3-double-deficient cells and in double-deficient cells with the VDAC2 protein depleted by RNA interference. VDAC deletion slightly down-regulated, but never abolished, the swelling-induced ATP release. The lack of correlation between VDAC protein expression and maxianion channel activity strongly argues against the long held hypothesis of plasmalemmal VDAC being the maxianion channel.

Dependence of a Wall Voltage Variation on Priming Effects During a Reset Discharge in AC Plasma Display Panels

The characteristics of a wall voltage driven by ramp pulses have been investigated in terms of priming effects in an ac plasma display panel. The effective firing voltage is decreased due to the priming effects of ramp discharges, and the resultant wall voltage is relatively larger compared to the conventional prediction.

Stochastic and Relaxation Processes in Argon by Measurements of Dynamic Breakdown Voltages

AbstractStatistically based measurements of breakdown voltages U b and breakdown delay times td and their variations in transient regimes of establishment and relaxation of discharges are a convenient method to study stochastic processes of electrical breakdown of gases, as well as relaxation kinetics in afterglow. In this paper the measurements and statistical analysis of the dynamic breakdown voltages U b for linearly rising (ramp) pulses in argon at 1.33 mbar and the rates of voltage rise k up to 800 V s –1 are presented. It was found that electrical breakdowns by linearly rising (ramp) pulses is an inhomogeneous Poisson process caused by primary and secondary ionization coefficients α , γ and electron yield Y variations on the voltage (time). The experimental breakdown voltage distributions were fitted by theoretical distributions by applying approximate analytical and numerical models. The afterglow kinetics in argon was studied based on the dependence of the initial electron yield on the relaxation time Y 0 (τ ) derived from fitting of distributions. The space charge decay was explained by the surface recombination of nitrogen atoms present as impurities. The afterglow kinetics and the surface recombination coefficients on the gas tube and cathode were determined from a gas‐phase model. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

The effect of prostaglandin E 1 on ion currents of NG108-15 cells

The aim of this study was to elucidate the mechanism by which prostaglandin E 1 (PGE 1) acts on ion currents of whole-cell voltage-clamped NG108-15 neuroblastoma × glioma hybrid cells. Ruptured and perforated patch were used. The holding current at −70 mV, the current–voltage curve produced by ramp pulses from −70 to 0 mV and the T-type and hva (high-voltage-activated) Ca 2+ currents associated with rectangular pulses were recorded. Bath application of PGE 1 (0.2 or 3 μM) reversibly increased the holding current, an effect mimicked by the prostanoid agonist iloprost (5–50 nM). The PGE 1 effect was totally blocked by the cAMP-antagonist Rp-cAMPS whereas H-89, an inhibitor of protein kinase A (PKA), failed to inhibit it, even when applied in the fairly high bath concentration of 30 μM. PGE 1 and iloprost also inhibited the T-type and hva Ca 2+ currents and this effect of PGE 1 was likewise not prevented by H-89. In some of the cells, the PGE 1 effect on holding current could be mimicked by 8-pCPT-2Me-cAMP (100–300 μM), a selective agonist of Epac (exchange protein activated by cAMP), but unlike the PGE 1 effect its action was not abolished by Rp-cAMPS. The effect of PGE 1 on the the holding current and on the T-type Ca 2+ current was diminished when EGTA in the pipette solution was replaced by BAPTA, suggesting that Ca 2+ ions are involved in the PGE 1 effect. It is concluded that the PGE 1 effect is mediated by cAMP and Ca 2+ ions but not by PKA or Epac.

AC-PDP에서 프라이밍 효과를 이용한 대조비 향상에 관한 연구

Recently, Plasma Display Panel(PDP) has been in the spotlight as one of the next generation flat-panel-display device. However, it has several drawbacks like the low contrast ratio and the low luminance. In this study, a new address waveform is suggested to improve the priming effect and contrast ratio at the address period in the Address Display period Separated(ADS) method. We modified waveform, instead of a conventional waveform, to an address period, for operating on the Plasma Display Panels, which used the conventional gas [He-Ne-Xe〕. When the ramp pulse is added to the address period at the sustain electrode, it is improved on the priming effect and contrast ratio.

Effects of amiodarone on mutant Na +/Ca 2+ exchangers expressed in CCL 39 cells

Using the whole cell voltage clamp, we reported previously that amiodarone acutely inhibits Na +/Ca 2+ exchange current ( I NCX) in guinea pig cardiac ventricular myocytes. Intracellular application of trypsin via the patch pipette attenuated the blocking effect of amiodarone, suggesting that amiodarone affects the Na +/Ca 2+ exchanger (NCX) from the cytoplasmic side. Here, we attempted to detect the site of amiodarone inhibition using wild type NCX1, mutants, and NCX3 expressed in CCL39 fibroblasts. I NCX was recorded by ramp pulses. Amiodarone at 30 μM inhibited I NCX by 80% in cells expressing wild type NCX1. However, 30 μM amiodarone inhibited I NCX by about 55% in cells expressing mutant NCX1 with amino acids 217-671 (ΔXIP) or 247-671 (Δ247-671) deleted in the long intracellular loop between the transmembrane segments (TM) 5 and 6. I NCXs from NCX mutants deleted of cytoplasmic TM1-2, TM3-4 or the C-terminus were inhibited by amiodarone to a similar extent as the wild type. Amiodarone also inhibited I NCX of NCX3 by 76%. These results suggest that a long intracellular loop may be involved in the inhibition of NCX1 by amiodarone, but that other intracellular loops, XIP region or C terminus are not involved in the amiodarone inhibition of NCX1.

P‐74: A Study of the Addressing Discharge Change for the Ramp Pulse in ac Plasma Display Panels

AbstractIn this study, a new driving method is suggested to improve the luminance efficiency and the luminance. We applied a ramp pulse, instead of a square pulse, to an address period in Address Display period Separated, for operating on the Plasma Display Panels, which used the conventional gas [He‐Ne‐Xe]. When the ramp pulse is applied to the address period, improvement of the luminance and the luminance efficiency, and discharge response time was decreased. Additionally, infra red ray emission and discharge current were almost constant irrespective of the slopes of ramp pulse.

8.3: New Bipolar Ramp Waveform for Enhancing Low‐Gray‐Level Expression in ACPDPs

AbstractA new bipolar ramp waveform that can reduce the minimum luminance level considerably is proposed to improve the low gray level expression in AC‐PDP. In the new bipolar ramp waveform, the conventional first subfield with a sustain‐period is replaced by the new first subfield that consists of the first negative square pulse and second positive ramp pulse during a scan‐period. The weak discharge produced by the second positive ramp pulse is used to generate and control the low luminance level stably.

Evidence for a persistent Na-conductance in identified command neurones of the snail, Helix pomatia

Neurones RPa3 and LPa3 were identified as ‘command’ neurones in the Helix parietal ganglia. The physiological role of these cells is the integration of sensory information before triggering withdrawal behaviour. Properties of the Na-channels are poorly understood in these neurones which produce Na +-dependent action potentials in Ca 2+-free solution. Our aim was to describe the kinetic properties and TTX-sensitivity of the Na-channels of these cells, and to provide evidence for the existence of a persistent inward sodium current ( I NaP) in them. Two-microelectrode voltage- and patch-clamp techniques were used on isolated or semi-isolated neurones. The kinetics and potential dependence of the transient inward sodium current ( I NaT) agreed well with those obtained on other molluscan neurones. We concluded that I NaT present in these neurones is slow and TTX-resistant ( k D=8 μM of TTX) and has two components with different rates of inactivation. In addition, the presence of an I NaP component was revealed. We showed that I NaP is neither an artifact nor the contribution of a Ca-channel or a ‘window’ current. With slow voltage ramp pulses I NaP could be activated and separated from I NaT. Like I NaT it appeared to be TTX-resistant and Na-dependent. I NaP was upregulated by increased pH (8.0) and decreased by elevated extracellular Mg 2+ concentration parallel with the I NaT. Our results suggest that I NaP originates from the same set of sodium channels that underlie I NaT.

Decreased ATP-sensitive K + current density during chronic human atrial fibrillation

Chronic atrial fibrillation (AF) is associated with shortening of action potential duration (APD), which involves modified activity of atrial ion currents. However, little is known about the activity of ATP-sensitive K + channels ( I K,ATP) during chronic AF. An AF-related increase in the activity of I K,ATP would reduce APD and could contribute to initiation and/or perpetuation of AF. Here, we studied the activity of I K,ATP in atrial myocytes from patients with sinus rhythm (SR) and chronic AF. Human atrial myocytes were isolated from atrial tissue obtained from patients undergoing open-heart surgery. Inward rectifier currents were measured with the whole-cell patch-clamp technique by applying a depolarizing ramp pulse (1245 ms) from –100 to +40 mV (0.5 Hz). I K,ATP was activated with the I K,ATP channel opener rilmakalim. The inward rectifier I K1 and I K,ATP were identified by their sensitivity to 1 mM Ba 2+. Density of I K1 did not differ between cells from patients with AF (at –100 mV: –14.8 ± 1.3 pA/pF, n = 38/10 (cells/patients)) and SR (–13.8 ± 1.5 pA/pF, n = 33/16). In both types of cells, rilmakalim stimulated I K,ATP (defined as rilmakalim-inducible current) in a concentration-dependent manner (0.3–10 μM). However, maximum activation of I K,ATP with 10 μM rilmakalim was smaller in AF than in SR cells (at –100 mV: –5.3 ± 0.8 pA/pF, n = 22/7 vs. –11.2 ± 2.9 pA/pF, n = 19/9; at +40 mV: +9.6 ± 2.1 pA/pF, n = 22/7 vs. +23.7 ± 3.4 pA/pF, n = 19/9 for AF and SR, respectively; P < 0.05). Only aortic valve disease and pulmonary hypertension were found to be independent contributors to I K,ATP current density. We provide evidence that chronic AF is associated with a downregulation of ATP-sensitive K + currents. These changes may provide an additional molecular mechanism for electrical remodeling in chronic AF.

Prostaglandin E 1 induces an inward current in voltage-clamped NG108-15 cells

The aim of this study was to explore the effect of prostaglandin E 1 (PGE 1) on the membrane current of whole-cell voltage-clamped NG108-15 neuroblastoma×glioma hybrid cells. Perforated patch was used. The membrane current at −70 mV (leakage current) and the current–voltage curve produced by ramp pulses from −70 to 0 mV were recorded; from the I– V curve, the conductance of the leakage current and its reversal potential were determined. Bath application of PGE 1 (22 nM–3 μM) produced an inward current accompanied by a reversible conductance increase. The PGE 1 effect varied greatly from cell to cell. In a group of 11 differentiated cells, the inward current induced by 0.2 μM PGE 1 was on average 171.1±49.8 pA, the conductance increased 2.66±0.50-fold and the reversal potential shifted by +13.2±4.0 mV. The average values observed with 22 nM and 3 μM PGE 1 were similar. The cell-permeable cAMP analog CPT-cAMP (0.5 mM) acted like PGE 1. In 9 out of 16 cells, the PGE 1 effect did not disappear and was not even noticeably reduced when the NaCl in the bath was replaced by N-methyl- d-glucamine (NMDG). The PGE 1 effect was also seen in Ca 2+-free NMDG bath but vanished when NMDG was replaced by glucose. It is concluded that PGE 1, probably acting via intracellular cAMP, opens non-selective cation channels with large pore diameters which allow the passage of big organic cations.

An accumulative x-ray streak camera with sub-600-fs temporal resolution and 50-fs timing jitter

We demonstrated that the shot-to-shot timing jitter of an x-ray streak camera was reduced to close to 50 fs when it was triggered by a standard kilohertz laser with 1.2% rms pulse energy fluctuation. This was achieved by improving the response time of deflection plates and the rise time of the ramp pulse generated by a photoconductive switch, and by operating the photoconductive switch at optimum conditions. Furthermore, after reducing the angular distribution of electron bunch, the temporal resolution of the x-ray streak camera operating in accumulation mode was measured to be better than 600 fs.

P‐60: Reset Waveform for Dark‐Room Contrast‐Ratio Improvement

AbstractIn this paper, we propose the new reset waveform which shows high dark‐room contrast‐ratio and robustness for cross talk. We apply a ramp pulse to the address electrode after the erase X ramp pulse. And a constant bias voltage is applied to X electrode during the Y rising‐falling ramp and the address period. Using this method, we achieved a great dark‐room contrastratio 2750:1. However, the address minimum voltage was increased about 17∼37V compared with the conventional ramp reset method. We could reduce the minimum address voltage through the waveform optimizing. As a result, when VSB is −30V, we could reduce the address minimum voltage about 14∼28V and improve the dark‐room contrast‐ratio3000:1.

Angiotensin II-induced ionic currents and signalling pathways in submandibular ganglion neurons

Angiotensin II (Ang II) is one of the most important vasoconstrictive hormones but is also known to act as a neuromodulator and a neurotransmitter in the central and peripheral nervous system. The submandibular ganglion (SMG) neuron is a parasympathetic ganglion which receives inputs from preganglionic cholinergic neurons, and innervates the submandibular salivary gland to control saliva secretion. In this study, the effects of Ang II on SMG neurons were investigated using the whole-cell patch clamp technique. Membrane currents evoked by a ramp pulse from +50 to −100 mV (−150 mV/500 ms) were compared in both the absence and presence of Ang II. In eight neurons tested, 1 μM Ang II increased inward currents by 42.0±8.2%. The reversal potentials of the Ang II-induced current were 0.2±0.6 mV. These increase of inward currents by Ang II were antagonized by losartan, a selective antagonist of AT 1 receptors. Intracellular dialysis with 0.1 mM guanosin 5′- O-(2-thiodiphosphate) (GDP-β-S), a G-proteins blocker, and anti-G q/11 antibody attenuated Ang II-induced ionic current. In addition, pretreatment of neurons with 10 μM staurosporine (stauro), a protein kinase C (PKC) inhibitor, 0.5 μM PMA, a PKC activator, and 10 μM KN-93, a Ca 2+/calmodulin-dependent protein kinase II (CaM K II) inhibitor, attenuated Ang II-induced ionic current in SMG neurons. The data presented here demonstrated that Ang II-induced ionic current via G q/11-proteins involving both PKC and CaM K II pathways in SMG neurons.

Bifurcation Buckling Analysis of Conical Roof Shell Subjected to Dynamic Internal Pressure by the Finite Element Method

Cylindrical tanks with conical roof shells are utilized as oil storage tanks and for some containment vessels. It is known that conical roof shells and torispherical shells subjected to static internal pressure buckle into a displaced shape with circumferential waves caused by an instability condition commonly called bifurcation buckling. It can be important to obtain the dynamic bifurcation buckling load in designing conical roof shells. In this paper, the bifurcation buckling pressure is calculated for dynamic pressure during accident conditions as characterized by step pressure loading, ramp pressure loading and pulse pressure loading. The minimum bifurcation buckling pressure is shown to be a linear function of radius-to-thickness ratio R/h of the shell in a linear fashion on a logarithmic scale. The minimum bifurcation buckling pressure is minimum for conical roof shells subjected to the step loading. The minimum dynamic bifurcation buckling pressure for step loading is about half of the static bifurcation buckling pressure.