MODELING EXCITATION AND PROPAGATION OF ACTION POTENTIALS ACROSS INHOMOGENEOUS VENTRICULAR TISSUE

2003 ◽  
Vol 13 (12) ◽  
pp. 3845-3863 ◽  
Author(s):  
Z. LI ◽  
A. V. HOLDEN ◽  
C. H. ORCHARD ◽  
H. ZHANG
Keyword(s):  
Action Potentials ◽  
Computational Models ◽  
Ionic Current ◽  
Cell Models ◽  
Intercellular Coupling ◽  
Ventricular Tissue ◽  
Current Densities ◽  
Myocardial Membrane ◽  
Transmural Heterogeneity ◽  
Kinetics Of

Heterogeneity in the electrical activity across the ventricular wall might result from transmural differences in myocardial membrane ionic current densities. Computational models of endo- and epi-cardial action potentials of guinea-pig myocytes were developed, assuming transmural differences in the ionic current densities and kinetics of i Kr and i Ks . The cell models were able to reproduce the characteristics of action potentials of endo and epi cells. One- and two-dimensional models of ventricular tissue were also developed to study the effects of transmural heterogeneity on the propagation of excitation waves across the ventricle wall. It was shown that intercellular coupling reduces the transmural heterogeneity across the ventricle wall.

scholarly journals Transmural heterogeneity of repolarization and Ca2+ handling in a model of mouse ventricular tissue

2010 ◽  
Vol 299 (2) ◽  
pp. H454-H469 ◽  
Author(s):  
Vladimir E. Bondarenko ◽  
Randall L. Rasmusson
Keyword(s):  
Action Potentials ◽  
Cardiac Cells ◽  
Two Dimensional ◽  
Epicardial Cells ◽  
Irregular Structures ◽  
Ventricular Tissue ◽  
Intracellular Ca ◽  
Heterogeneous Tissue ◽  
Transmural Heterogeneity ◽  
Epicardial Myocytes

Mouse hearts have a diversity of action potentials (APs) generated by the cardiac myocytes from different regions. Recent evidence shows that cells from the epicardial and endocardial regions of the mouse ventricle have a diversity in Ca2+ handling properties as well as K+ current expression. To examine the mechanisms of AP generation, propagation, and stability in transmurally heterogeneous tissue, we developed a comprehensive model of the mouse cardiac cells from the epicardial and endocardial regions of the heart. Our computer model simulates the following differences between epicardial and endocardial myocytes: 1) AP duration is longer in endocardial and shorter in epicardial myocytes, 2) diastolic and systolic intracellular Ca2+ concentration and intracellular Ca2+ concentration transients are higher in paced endocardial and lower in epicardial myocytes, 3) Ca2+ release rate is about two times larger in endocardial than in epicardial myocytes, and 4) Na+/Ca2+ exchanger rate is greater in epicardial than in endocardial myocytes. Isolated epicardial cells showed a higher threshold for stability of AP generation but more complex patterns of AP duration at fast pacing rates. AP propagation velocities in the model of two-dimensional tissue are close to those measured experimentally. Simulations show that heterogeneity of repolarization and Ca2+ handling are sustained across the mouse ventricular wall. Stability analysis of AP propagation in the two-dimensional model showed the generation of Ca2+ alternans and more complex transmurally heterogeneous irregular structures of repolarization and intracellular Ca2+ transients at fast pacing rates.

scholarly journals Growth Kinetics of Anodic Oxide Films Formed on Zircaloy-2 in Various Electrolytes

2009 ◽  
Vol 6 (3) ◽  
pp. 880-886
Author(s):  
V. Jeevana Jyothi ◽  
CH. Anjaneyulu
Keyword(s):  
Current Density ◽  
Formation Rate ◽  
Ionic Current ◽  
Anodic Oxide ◽  
Anodic Films ◽  
Differential Field ◽  
Increase With Increase ◽  
Jump Distance ◽  
Current Densities ◽  
Kinetics Of

The Kinetics of anodic oxidation of zircaloy-2 have been studied at current densities ranging from 4 to 12 mA cm-2at room temperature in order to investigate the dependence of ionic current density on the field across the oxide film. Thickness of the anodic films was estimated from capacitance data. The formation rate, current efficiency and differential field were found to increase with increase in the ionic current density for zircaloy-2. Plots of logarithm of formation ratevs. logarithm of current density is fairly linear. From linear plots of logarithm of ionic current densityvs. differential field and applying the Cabrera - Mott theory, the half - jump distance (a) and height of energy barrier (W) were deduced.

scholarly journals Effect of Current Density on the Anodic Behavior of Zircaloy - 2 and Titanium-A Comparative Study

2009 ◽  
Vol 6 (s1) ◽  
pp. S12-S16
Author(s):  
N. N. S. Aparna ◽  
Ch. Anjaneyulu
Keyword(s):  
Current Density ◽  
Formation Rate ◽  
Ionic Current ◽  
Anodic Films ◽  
Differential Field ◽  
Oxide Film Thickness ◽  
Increase With Increase ◽  
Jump Distance ◽  
Current Densities ◽  
Kinetics Of

The kinetics of anodic oxidation of zircaloy-2 and titanium have been studied at current densities ranging from 2 to 12 mAcm-2at room temperature in order to investigate the dependence of ionic current density on the field across the oxide film. Thickness of the anodic films were estimated from capacitance data. The formation rate, current efficiency and differential field were found to increase with increase in the ionic current density for both zircaloy-2 and Titanium. Plots of the logarithm of formation ratevslogarithm of the current density are fairly linear. From linear plots of logarithm of ionic current densityvsdifferential field and applying the Cabrera-Mott theory, the half-jump distance and the height of the energy barrier are deduced and compared.

scholarly journals Fundamental Mechanisms of Copper CMP – Passivation Kinetics of Copper in CMP Slurry Constituents

2009 ◽  
Vol 1157 ◽  
Author(s):  
Shantanu Tripathi ◽  
Fiona M. Doyle ◽  
David A. Dornfeld
Keyword(s):  
Electrochemical Impedance ◽  
Protective Film ◽  
Current Decay ◽  
Glycine Solution ◽  
Current Densities ◽  
Circuit Elements ◽  
Copper Cmp ◽  
Cu Cmp ◽  
Kinetics Of ◽  
Capacitive Charging

AbstractDuring copper CMP, abrasives and asperities interact with the copper at the nano-scale, partially removing protective films. The local Cu oxidation rate increases, then decays with time as the protective film reforms. In order to estimate the copper removal rate and other Cu-CMP output parameters with a mechanistic model, the passivation kinetics of Cu, i.e. the decay of the oxidation current with time after an abrasive/copper interaction, are needed. For the first time in studying Cu-CMP, microelectrodes were used to reduce interference from capacitive charging, IR drops and low diffusion limited currents, problems typical with traditional macroelectrodes. Electrochemical impedance spectroscopy (EIS) was used to obtain the equivalent circuit elements associated with different electrochemical phenomena (capacitive, kinetics, diffusion etc.) at different polarization potentials. These circuit elements were used to interpret potential-step chronoamperometry results in inhibiting and passivating solutions, notably to distinguish between capacitive charging and Faradaic currents.Chronoamperometry of Cu in acidic aqueous glycine solution containing the corrosion inhibitor benzotriazole (BTA) displayed a very consistent current decay behavior at all potentials, indicating that the rate of current decay was controlled by diffusion of BTA to the surface. In basic aqueous glycine solution, Cu (which undergoes passivation by a mechanism similar to that operating in weakly acidic hydrogen peroxide slurries) displayed similar chronoamperometric behavior for the first second or so at all anodic potentials. Thereafter, the current densities at active potentials settled to values around those expected from polarization curves, whereas the current densities at passive potentials continued to decline. Oxidized Cu species typically formed at ‘active’ potentials were found to cause significant current decay at active potentials and at passive potentials before more protective passive films form. This was established from galvanostatic experiments.

Thermal Breakdown Kinetics of 1-Ethyl-3-Methylimidazolium Ethylsulfate Measured Using Quantitative Infrared Spectroscopy

2017 ◽  
Vol 71 (12) ◽  
pp. 2626-2631 ◽  
Author(s):  
Jeffrey L. Wheeler ◽  
McKinley Pugh ◽  
S. Jake Atkins ◽  
Jason M. Porter
Keyword(s):  
Thermal Stability ◽  
Room Temperature ◽  
Computational Models ◽  
Elevated Temperatures ◽  
Molar Absorptivity ◽  
Ir Absorption ◽  
Optical Cell ◽  
Multiple Samples ◽  
Kinetics Of ◽  
Thermal Stability Of

In this work, the thermal stability of the room temperature ionic liquid (RTIL) 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO4]) is investigated using infrared (IR) spectroscopy. Quantitative IR absorption spectral data are measured for heated [EMIM][EtSO4]. Spectra have been collected between 25 ℃ and 100 ℃ using a heated optical cell. Multiple samples and cell pathlengths are used to determine quantitative values for the molar absorptivity of [EMIM][EtSO4]. These results are compared to previous computational models of the ion pair. These quantitative spectra are used to measure the rate of thermal decomposition of [EMIM][EtSO4] at elevated temperatures. The spectroscopic measurements of the rate of decomposition show that thermogravimetric methods overestimate the thermal stability of [EMIM][EtSO4].

scholarly journals Electrophysiology of Syncytial Smooth Muscle

2019 ◽  
Vol 13 ◽  
pp. 117906951882191 ◽  
Author(s):  
Rohit Manchanda ◽  
Shailesh Appukuttan ◽  
Mithun Padmakumar
Keyword(s):  
Smooth Muscle ◽  
Action Potentials ◽  
Signal Analysis ◽  
Computational Models ◽  
Vas Deferens ◽  
Contractile Activity ◽  
Smooth Muscles ◽  
Biophysical Analysis ◽  
Recent Developments ◽  
The Many

As in other excitable tissues, two classes of electrical signals are of fundamental importance to the functioning of smooth muscles: junction potentials, which arise from neurotransmission and represent the initiation of excitation (or in some instances inhibition) of the tissue, and spikes or action potentials, which represent the accomplishment of excitation and lead on to contractile activity. Unlike the case in skeletal muscle and in neurons, junction potentials and spikes in smooth muscle have been poorly understood in relation to the electrical properties of the tissue and in terms of their spatiotemporal spread within it. This owes principally to the experimental difficulties involved in making precise electrical recordings from smooth muscles and also to two inherent features of this class of muscle, ie, the syncytial organization of its cells and the distributed innervation they receive, which renders their biophysical analysis problematic. In this review, we outline the development of hypotheses and knowledge on junction potentials and spikes in syncytial smooth muscle, showing how our concepts have frequently undergone radical changes and how recent developments hold promise in unraveling some of the many puzzles that remain. We focus especially on computational models and signal analysis approaches. We take as illustrative examples the smooth muscles of two organs with distinct functional characteristics, the vas deferens and urinary bladder, while also touching on features of electrical functioning in the smooth muscles of other organs.

Ionic current abnormalities associated with prolonged action potentials in cardiomyocytes from diseased human right ventricles

Heart Rhythm ◽  
2004 ◽  
Vol 1 (4) ◽  
pp. 460-468 ◽  
Author(s):  
Gui-Rong Li ◽  
Chu-Pak Lau ◽  
Tack-Ki Leung ◽  
Stanley Nattel
Keyword(s):  
Action Potentials ◽  
Ionic Current ◽  
Prolonged Action ◽  
Human Right

scholarly journals Development of a Fluorine-Free Polymer-Assisted-Deposition Route for YBa2Cu3O7−x Superconducting Films

Coatings ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 966
Author(s):  
Mircea Nasui ◽  
Ramona Bianca Sonher ◽  
Traian Petrisor ◽  
Sorin Varodi ◽  
Cornelia Pop ◽  
...  
Keyword(s):  
Superconducting Films ◽  
Single Step ◽  
Precursor Powder ◽  
Superconducting Properties ◽  
Epitaxial Relationship ◽  
Ybco Films ◽  
Out Of Plane ◽  
Growth Method ◽  
Current Densities ◽  
Kinetics Of

Polymer assisted deposition (PAD) was used as an environmentally friendly, non-fluorine, growth method for superconducting YBa2Cu3O7−x (YBCO) films. The kinetics of the thermal decomposition of the precursor powder was studied by thermogravimetry coupled with mass spectrometry (TG-QMS). YBCO films were spin coated on (100) SrTiO3 (STO) single crystalline substrates, followed by a single step thermal treatment under wet and dry O2 and O2/N2 mixture. The as-obtained films were epitaxially grown having a [001]YBCO||[001]STO out-of-plane epitaxial relationship and exhibited good superconducting properties with Tc (R = 0) > 88 K, transition widths, ΔT ≈ 2 K and critical current densities as high as 2.3 MA/cm2 at 77 K and self magnetic field.

scholarly journals Computational modeling of pitting corrosion

2019 ◽  
Vol 37 (5) ◽  
pp. 419-439 ◽  
Author(s):  
Siavash Jafarzadeh ◽  
Ziguang Chen ◽  
Florin Bobaru
Keyword(s):  
Pitting Corrosion ◽  
Computational Models ◽  
Dissolution Kinetics ◽  
Corrosion Damage ◽  
Material Strength ◽  
Unified Framework ◽  
Advantages And Disadvantages ◽  
Phase Field Models ◽  
Classical Transport ◽  
Kinetics Of

AbstractPitting corrosion damage is a major problem affecting material strength and may result in difficult to predict catastrophic failure of metallic material systems and structures. Computational models have been developed to study and predict the evolution of pitting corrosion with the goal of, in conjunction with experiments, providing insight into pitting processes and their consequences in terms of material reliability. This paper presents a critical review of the computational models for pitting corrosion. Based on the anodic reaction (dissolution) kinetics at the corrosion front, transport kinetics of ions in the electrolyte inside the pits, and time evolution of the damage (pit growth), these models can be classified into two categories: (1) non-autonomous models that solve a classical transport equation and, separately, solve for the evolution of the pit boundary; and (2) autonomous models like cellular automata, peridynamics, and phase-field models which address the transport, dissolution, and autonomous pit growth in a unified framework. We compare these models with one another and comment on the advantages and disadvantages of each of them. We especially focus on peridynamic and phase-filed models of pitting corrosion. We conclude the paper with a discussion of open areas for future developments.

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