Mechanism of Auricular Flutter and Fibrillation

Scherf, David; Terranova, Rosario

doi:10.1152/ajplegacy.1949.159.1.137

Cited by 63 publications

(21 citation statements)

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“…Both Cell A and Cell B experienced a huge increase in the ohmic resistance and this did not seem to level off after several hundred hours of testing, which in turn will be detrimental to the cells. This is much in line with observations reported previously for electrolysis testing at high current densities [6,7,38]. Cell C, on the other hand, have an ohmic resistance development that was significantly different even though these three cells are tested at nominally the same electrolysis test conditions.…”

Section: Sem Imagingsupporting

confidence: 91%

“…The results presented here also emphasize the importance of long-term testing and illustrate how structural optimization of the well-known Ni/YSZ electrode can lead to technological relevant low long-term degradation rates. Figure 10 -inspired by Schefold and co-workes [38] -illustrates the importance in decreasing the long-term degradation rate from e.g. around 2 %/kh as reported by Schefold and co-workes [38] and Corre and Brisse [45] to the long-term degradation rate of 0.3-0.4 %/kh reported here for Cell C at similar test conditions.…”

Section: Microstructures Of Soec Long-term Tested At 125 A/cmsupporting

confidence: 69%

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Ni/YSZ electrodes structures optimized for increased electrolysis performance and durability

et al. 2016

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Cermet Ni/YSZ electrodes are the most commonly applied fuel electrode for solid oxide cells (SOC) both when targeting solid oxide fuel cell (SOFC) applications and when used as solid oxide electrolysis cell (SOEC). In this work we report on the correlation between initial Ni/YSZ microstructure and the resulting electrochemical performance both initially and during long-term electrolysis testing at high current density and high p(H2O) inlet. Especially, this work focuses on microstructure optimization to hinder Ni mobility and migration during long-term operation and illustrates the key-role of electrode over-potential on the degradation of the Ni/YSZ electrodes in SOEC. We find that for long-term stability for electrolysis at high current densities and high p(H2O) the as-produced NiO/YSZ precursor electrode should be: 1) As dense as possible, 2) as fine particle and pore sized as possible and 3) the three phases (Ni, YSZ and pore phase) shall be size-matched and welldispersed. Applying such microstructure optimized Ni/YSZ electrode we show SOEC test results with long-term degradation rate as low as 0.3-0.4 %/kh at 1 A/cm 2 , 800 C and inlet gas mixture of p(H2O)/p(H2):90/10. This enables SOEC operation of such cell for more than 5 years below thermo-neutral potential at these operating conditions.

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Section: Sem Imagingsupporting

confidence: 91%

Section: Microstructures Of Soec Long-term Tested At 125 A/cmsupporting

confidence: 69%

Ni/YSZ electrodes structures optimized for increased electrolysis performance and durability

et al. 2016

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“…After ∼20,000 h, the ohmic resistances of both layers were more than triple the starting values. Possible explanations of the continuous increase in the ohmic resistance include grain growth in the electrolyte, pore formation near the 8YSZ/GDC (gadolinium doped ceria) interface, as reported by Schefold et al 17 and Tietz et al, 18 and depletion of nickel near the boundary of the electrolyte and fuel electrode as observed by different groups. [19][20][21][22] The effective ionic conductivity of the composite electrodes is usually below 10% of that of the bulk electrolyte depending on the porosity and volume fraction of the composites according to Zheng et al 23 Therefore, the increase of ohmic resistance can be one of the consequences of Ni depletion in Ni/YSZ electrode, which shifts the working electrode area outwards and increases the electrolyte thickness.…”

Section: Resultsmentioning

confidence: 79%

Electrochemical Performance and Preliminary Post-Mortem Analysis of a Solid Oxide Cell Stack with 20,000 h of Operation

Fang

Frey

Menzler

et al. 2018

J. Electrochem. Soc.

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A long-term test with a two-layer solid oxide cell stack was carried out for more than 20,000 hours. The stack was mainly characterized in a furnace environment in electrolysis mode, with 50% humidification of H 2 at 800 • C. The endothermic operation was carried out with a current density of −0.5 Acm −2 and steam conversion rate of 50%. Electrolysis at lower temperatures (i.e., 700 • C and 750 • C) and fuel cell operation (with 0.5 Acm −2 and fuel utilization of 50%) at 800 • C were also carried out (<2000 h each) for comparison. The voltage and area specific resistance degradation rates were ∼0.6%/kh and 8.2%/kh after ∼18,460 hours of operation. In total, the stack was operated above 700 • C for more than 20,000 hours. Impedance measurement and analysis showed that the increase of ohmic resistance was the main degradation phenomenon, while electrode polarizations were kept nearly constant before a severe burning took place in one layer. Ni-depletion in fuel electrodes was confirmed during post-mortem analysis, which was assumed to be the major degradation mechanism observed. The stack performance and degradation analysis under different working conditions, as well as the results of preliminary post-mortem analysis will be presented. One of the critical challenges to the application and commercialization of solid oxide cell (SOC) technology is the long-term stability of complete systems, stacks and single components. Despite the fact that accelerating methods have long been under discussion, the time-consuming and costly endurance tests of stacks and cells under relevant conditions are still necessary for reliable degradation analyses and lifetime prediction. Compared to the tests with single cell or other stack and system component, the results of long-term degradation tests with stacks are quite limited. [1][2][3][4][5] Previous results have shown stable performance of stacks working in the temperature range of 700-800• C in SOFC mode. [6][7][8][9] Recently, a short stack achieved a 10 years lifetime, and remains in operation. 10 With proper protective coating, a voltage degradation rate of less than 0.3%/kh and lifetime of more than 40,000 h at 700• C is possible with current stack design and components. In contrast to the low degradation rate in SOFC mode, higher degradation rates of ∼0.6-1.5%/kh were observed with similar types of cells in the same stack design in SOEC mode, as described by Nguyen et al. 11 Therefore, the functionality and optimization potential of the cells and stacks, as well as their long-term degradation behavior and mechanisms in SOEC mode, needs to be further investigated. Amongst the stacks operated in SOEC mode, a two-layer stack was operated under different stationary conditions for more than 20,000 h. The stack performance was regularly monitored by open circuit voltage, voltage-current curves and impedance measurements. After cooling down, one third of the stack was embedded in resin for cross-section preparation, and the rest was disassembled for visual inspection. The prelim...

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“…The ventricular complexes have a pattern which suggests injury, presumably because ouabain leaked into the ventricular myocardium. There was in addition alternation in cycle length, a phenomenon previously observed in atrial arrhythmia elicited by aconitine and in ventricular tachycardia precipitated by ouabain (Scherf, 1944;Scherf & Terranova, 1949). Stimulation of the carotid sinus nerve abruptly suppressed the ectopic arrhythmia and a slow sinus rhythm appeared.…”

Section: Resultsmentioning

confidence: 65%

“…Many years earlier the same vagal response was obtained during atrial flutter produced by faradization (Rothberger & Winterberg, 1914). Suppression of the atrial arrhythmia by vagus stimulation in the two conditions was only infrequently obtained (Lewis, Drury & Bulger, 1921 ;Scherf & Terranova, 1949;Scherf, Blumenfeld, Mueller & Beinfield, 1953). It was on the basis of these observations that the aconitine-induced arrhythmia was classified as atrial flutter as distinct from paroxysmal tachycardia.…”

Section: Discussionmentioning

confidence: 82%

Suppression of Ouabain‐induced Atrial Arrhythmias by Carotid Sinus Stimulation

Schott

1961

British Journal of Pharmacology and Chemotherapy

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In dogs anaesthetized with chloralose ectopic atrial arrhythmias were produced by subepicardial injection of ouabain. Stimulation of the right carotid sinus abruptly suppressed the ectopic arrhythmias. They returned on cessation of stimulation and sometimes already during the period of stimulation. It is suggested that in view of its response to carotid sinus stimulation the ouabain-induced arrhythmia resembles paroxysmal atrial tachycardia and that it is distinct from the aconitine-induced arrhythmia which on account of its response to vagal stimulation has been classified as atrial flutter.It is well known to clinicians that attacks of atrial paroxysmal tachycardia can often be terminated by carotid sinus pressure whereas this procedure is ineffective in atrial flutter. It is equally well known that different types of atrial arrhythmias can be produced in animals by local application of various drugs to the epicardial surface of the heart (Scherf, 1944(Scherf, , 1947Kisch, 1944;Scherf & Chick, 1951;Prinzmetal, Corday, Brill, Oblath & Kruger, 1952;Scherf, Blumenfeld, Taner & Yildiz, 1960), but it has never been shown that any of these resemble paroxysmal atrial tachycardia in man by the crucial test of being consistently suppressible by means of carotid sinus stimulation. It has now been found that the arrhythmia produced by subepicardial injection of ouabain is regularly susceptible to carotid sinus stimulation. METHODSDogs weighing between 9 and 14 kg were premedicated with morphine, 1 mg/kg injected subcutaneously, and anaesthetized with chloralose, 0.1 g/kg injected intravenously. The blood pressure was recorded from a femoral artery and a cannula was inserted into the trachea.In all experiments stimulation of the carotid sinus was carried out on the right side with both sinus and aortic nerves intact in order to approximate the effects obtained in man, where pressure on the right carotid sinus is more frequently effective in terminating attacks of atrial paroxysmal tachycardia (Scherf & Schott, 1953). The right carotid sinus was exposed, and stimulating shielded platinum electrodes were applied to the dissected sinus nerve and connected to a transistor stimulator (Joslin, 1959). Stimulation was carried out with impulses of 15 V, 1 msec, 100/sec. In a few experiments the innervated right carotid sinus was isolated, according to the method of Moissejeff (1927), making possible its distension by introducing liquid into it, and at the same time recording the intrasinusal pressure.After dissection of the carotid sinus, the sternum was split, the chest opened in the midline to expose the heart, while artificial respiration was given with a Starling (" Ideal ") pump.

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Mechanism of Auricular Flutter and Fibrillation

Cited by 63 publications

References 0 publications

Ni/YSZ electrodes structures optimized for increased electrolysis performance and durability

Ni/YSZ electrodes structures optimized for increased electrolysis performance and durability

Electrochemical Performance and Preliminary Post-Mortem Analysis of a Solid Oxide Cell Stack with 20,000 h of Operation

Suppression of Ouabain‐induced Atrial Arrhythmias by Carotid Sinus Stimulation

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