scholarly journals Chronotropic Modulation of the Source-Sink Relationship of Sinoatrial-Atrial Impulse Conduction and Its Significance to Initiation of AF: A One-Dimensional Model Study

2015 ◽  
Vol 2015 ◽  
pp. 1-18 ◽  
Author(s):  
Francesca Cacciani ◽  
Massimiliano Zaniboni
Keyword(s):  
Sinoatrial Node ◽  
Calcium Handling ◽  
Conduction Delay ◽  
Antiarrhythmic Agents ◽  
Class Iii ◽  
One Dimensional ◽  
Model Study ◽  
Source Sink ◽  
Relationship Of ◽  
Junctional Resistance

Initiation and maintenance of atrial fibrillation (AF) is often associated with pharmacologically or pathologically induced bradycardic states. Even drugs specifically developed in order to counteract cardiac arrhythmias often combine their action with bradycardia and, in turn, with development of AF, via still largely unknown mechanisms. This study aims to simulate action potential (AP) conduction between sinoatrial node (SAN) and atrial cells, either arranged in cell pairs or in a one-dimensional strand, where the relative amount of SAN membrane is made varying, in turn, with junctional resistance. The source-sink relationship between the two membrane types is studied in control conditions and under different simulated chronotropic interventions, in order to define a safety factor for pacemaker-to-atrial AP conduction (SASF) for each treatment. Whereas antiarrhythmic-like interventions which involve downregulation of calcium channels or of calcium handling decrease SASF, the simulation of Ivabradine administration does so to a lesser extent. Particularly interesting is the increase of SASF observed when downregulationGKr, which simulates the administration of class III antiarrhythmic agents and is likely sustained by an increase inICaL. Also, the increase in SASF is accompanied by a decreased conduction delay and a better entrainment of repolarization, which is significant to anti-AF strategies.

scholarly journals One-Dimensional Vacuum Steady Seepage Model of Unsaturated Soil and Finite Difference Solution

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Feng Huang ◽  
Jianguo Lyu ◽  
Guihe Wang ◽  
Hongyan Liu
Keyword(s):  
Finite Difference ◽  
Unsaturated Soil ◽  
Vacuum Pressure ◽  
Vacuum Field ◽  
One Dimensional ◽  
Steady Seepage ◽  
Basic Equations ◽  
The One ◽  
Seepage Law ◽  
Relationship Of

Vacuum tube dewatering method and light well point method have been widely used in engineering dewatering and foundation treatment. However, there is little research on the calculation method of unsaturated seepage under the effect of vacuum pressure which is generated by the vacuum well. In view of this, the one-dimensional (1D) steady seepage law of unsaturated soil in vacuum field has been analyzed based on Darcy’s law, basic equations, and finite difference method. First, the gravity drainage ability is analyzed. The analysis presents that much unsaturated water can not be drained off only by gravity effect because of surface tension. Second, the unsaturated vacuum seepage equations are built up in conditions of flux boundary and waterhead boundary. Finally, two examples are analyzed based on the relationship of matric suction and permeability coefficient after boundary conditions are determined. The results show that vacuum pressure will significantly enhance the drainage ability of unsaturated water by improving the hydraulic gradient of unsaturated water.

scholarly journals Two components of cardiac delayed rectifier K+ current. Differential sensitivity to block by class III antiarrhythmic agents.

1990 ◽  
Vol 96 (1) ◽  
pp. 195-215 ◽  
Author(s):  
M C Sanguinetti ◽  
N K Jurkiewicz
Keyword(s):  
Antiarrhythmic Agent ◽  
Reversal Potential ◽  
Differential Sensitivity ◽  
Inward Rectification ◽  
Delayed Rectifier ◽  
Antiarrhythmic Agents ◽  
Class Iii ◽  
Activation Curve ◽  
Voltage Range ◽  
K Current

An envelope of tails test was used to show that the delayed rectifier K+ current (IK) of guinea pig ventricular myocytes results from the activation of two outward K+ currents. One current was specifically blocked by the benzenesulfonamide antiarrhythmic agent, E-4031 (IC50 = 397 nM). The drug-sensitive current, "IKr" exhibits prominent rectification and activates very rapidly relative to the slowly activating drug-insensitive current, "IKs." IKs was characterized by a delayed onset of activation that occurs over a voltage range typical of the classically described cardiac IK. Fully activated IKs, measured as tail current after 7.5-s test pulses, was 11.4 times larger than the fully activated IKr. IKr was also blocked by d-sotalol (100 microM), a less potent benzenesulfonamide Class III antiarrhythmic agent. The activation curve of IKr had a steep slope (+7.5 mV) and a negative half-point (-21.5 mV) relative to the activation curve of IKs (slope = +12.7 mV, half-point = +15.7 mV). The reversal potential (Erev) of IKr (-93 mV) was similar to EK (-94 mV for [K+]o = 4 mM), whereas Erev of IKs was -77 mV. The time constants for activation and deactivation of IKr made up a bell-shaped function of membrane potential, peaking between -30 and -40 mV (170 ms). The slope conductance of the linear portion of the fully activated IKr-V relation was 22.5 S/F. Inward rectification of this relation occurred at potentials greater than -50 mV, resulting in a voltage-dependent decrease in peak IKr at test potentials greater than 0 mV. Peak IKr at 0 mV averaged 0.8 pA/pF (n = 21). Although the magnitude of IKr was small relative to fully activated IKs, the two currents were of similar magnitude when measured during a relatively short pulse protocol (225 ms) at membrane potentials (-20 to +20 mV) typical of the plateau phase of cardiac action potentials.

scholarly journals Estimation for Two-Dimensional Nonsymmetric Coherently Distributed Source in L-Shaped Arrays

2018 ◽  
Vol 2018 ◽  
pp. 1-16
Author(s):  
Tao Wu ◽  
Zhenghong Deng ◽  
Qingyue Gu ◽  
Jiwei Xu
Keyword(s):  
Expectation Maximization ◽  
Two Dimensional ◽  
Signal Distribution ◽  
Distributed Source ◽  
One Dimensional ◽  
Least Squares Estimators ◽  
Iterative Calculation ◽  
Symmetric Source ◽  
Relationship Of ◽  
The Relationship

We explore the estimation of a two-dimensional (2D) nonsymmetric coherently distributed (CD) source using L-shaped arrays. Compared with a symmetric source, the modeling and estimation of a nonsymmetric source are more practical. A nonsymmetric CD source is established through modeling the deterministic angular signal distribution function as a summation of Gaussian probability density functions. Parameter estimation of the nonsymmetric distributed source is proposed under an expectation maximization (EM) framework. The proposed EM iterative calculation contains three steps in each cycle. Firstly, the nominal azimuth angles and nominal elevation angles of Gaussian components in the nonsymmetric source are obtained from the relationship of rotational invariance matrices. Then, angular spreads can be solved through one-dimensional (1D) searching based on nominal angles. Finally, the powers of Gaussian components are obtained by solving least-squares estimators. Simulations are conducted to verify the effectiveness of the nonsymmetric CD model and estimation technique.

Calculation and Analysis on the Soft Soil Foundation Settlement with Elastic-Visco-Plasticity (EVP) Model

2018 ◽  
Vol 1145 ◽  
pp. 8-16 ◽  
Author(s):  
Jing Rui Guo ◽  
Xian Chang Zheng ◽  
Ji Qing Zhang ◽  
Zhi Meng Zhao
Keyword(s):  
Soft Soil ◽  
Soil Consolidation ◽  
One Dimensional ◽  
Model Study ◽  
Long Time ◽  
Soft Soil Area ◽  
Soil Foundation ◽  
Soft Soil Foundation ◽  
Soil Area ◽  
Engineering Monitoring

The EVP model is an available method to apply to the vertical settlement of soft soil consolidation calculation and analysis. Compared with Visco-Plasticity model, it shows more consistent with the actual stress conditions of the soil. In this paper, We have extracted soil samples in BinHai garden for assay. Then through the comparison with calculating results and a long-time engineering monitoring in BinHai garden soft soil area, a feasibility EVP model study on the vertical settlement in soft soil area is peoposed. Further a consequent sedimentation forecast was made according with the EVP model calculation. In the end, the settlement influence from creep was analyzed through one-dimensional consolidation theory.

Abstract MP44: Biomarker Measures of Fish-Derived Omega-3 Fatty Acids and J-Point Elevation in the Atherosclerosis Risk in Communities (ARIC) Study

Circulation ◽  
2013 ◽  
Vol 127 (suppl_12) ◽  
Author(s):  
Noelle N Gronroos ◽  
Pamela J Schreiner ◽  
Elsayed Z Soliman ◽  
Lisa Harnack ◽  
Richard F MacLehose ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Fatty Acid ◽  
Linear Trend ◽  
Antiarrhythmic Agents ◽  
Omega 3 ◽  
Class Iii ◽  
Atherosclerosis Risk In Communities ◽  
Surface Ecg ◽  
Atherosclerosis Risk ◽  
Aric Study

Background: Higher intake of fish-derived omega-3 polyunsaturated fatty acids (PUFAs) has been associated with lower incidence of Sudden Cardiac Death (SCD), but the exact mechanisms underlying this association are unconfirmed. Early ventricular repolarization characterized by an elevation of the QRS-ST junction (J-Point) in the surface ECG has been associated with idiopathic ventricular fibrillation, the most common cause of SCD. We aimed to study the association of fish-derived PUFAs in plasma with the prevalence of J-Point elevation. Methods: We conducted a cross-sectional analysis of participants aged 45-64 (45.7% male, 100% whites) from the Minnesota Field Center of the Atherosclerosis Risk in Communities (ARIC) Study. Participants were excluded if they did not have an ECG, had a QRS duration ≥ 120 ms, were taking Class I or Class III antiarrhythmic agents, or had prevalent cardiovascular disease. Fish-derived PUFAs were measured in plasma phospholipids as a percentage of total fatty acids, categorized into quartiles, and logistic regression was used to estimate the odds of J-Point Elevation, defined as elevation of greater than 100 microvolts in at least two contiguous leads. Models were adjusted for potential confounders and tests of linear trend were conducted by assigning the median values for each exposure category and modeling as a continuous variable. Results: Among 3,330 eligible individuals, 126 presented J-Point elevation. Median fish-derived fatty acid percentage was 3.2% (range: 0.7-12.2). Using multivariable analyses, plasma measures of fish-derived omega-3 PUFAs were linearly associated with the log odds of J-Point elevation with increasing fatty acid percentages associated with lower odds of J-Point elevation (see Table). Conclusions: In this population, higher plasma levels of fish-derived PUFAs were inversely associated with J-Point elevation. Fish-derived PUFAs could reduce risk of SCD through decreased prevalence of early repolarization.

scholarly journals The prevalence of malocclusion among 7–15-year-old Lithuanian schoolchildren

Medicina ◽  
2009 ◽  
Vol 45 (2) ◽  
pp. 147 ◽  
Author(s):  
Antanas Šidlauskas ◽  
Kristina Lopatienė
Keyword(s):  
Important Determinant ◽  
Age Groups ◽  
Epidemiological Data ◽  
Dental Arch ◽  
Class Iii ◽  
Posterior Crossbite ◽  
Normal Occlusion ◽  
Dental Crowding ◽  
Relationship Of ◽  
The Relationship

The epidemiological data on the prevalence of malocclusion is an important determinant in planning appropriate levels of orthodontic services. The occurrence of occlusal anomalies varies between different countries, ethnic and age groups. The aim of this study was to describe the prevalence of malocclusion among Lithuanian schoolchildren in the 7–9-, 10– 12-, and 13–15-year age groups assessing occlusal morphology. The study included 1681 schoolchildren aged 7–15 years. The crowding, spacing, overbite, overjet, the relationship of the first upper and lower molars according Angle’s classification, and posterior crossbite were assessed. The study demonstrated that only 257 children had normal occlusion, and 44 had undergone orthodontic treatment among them. The greatest overjet in the studied contingent was 11 mm, and the negative overjet – 3 mm. The overbite ranged between 0 and 6 mm with a mean of 2.29±1.23 mm. Posterior crossbite was recorded in 148 children (8.8%). This study showed that the prevalence of malocclusion among 7–15-year-old Lithuanian schoolchildren is 84.6%. The most common malocclusion was dental crowding. The upper dental arch crowding was registered for 44.1% and lower for 40.3% of all schoolchildren. The class I molar relationship was detected in 68.4% of the subjects, class II – in 27.7%, and class III – in 2.8%.

Sign in / Sign up

Export Citation Format

Share Document