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Related Concept Videos

Modes of Standing Waves: II01:04

Modes of Standing Waves: II

The starting point for expressing the modes of standing waves is understanding the boundary conditions that the waves must follow. The boundary conditions are derived from the physical understanding of how the standing waves are sustained, that is, how the vibrating particles of the medium behave at the boundaries imposed on them.
For a tube open at one end and closed at the other filled with air, the modes are such that there is always an antinode at the open end and a node at the closed end.
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When a wave propagates from one medium to another, part of it may get reflected in the first medium, and part of it may get transmitted to the second medium. In such a case, the interface of the two mediums can be considered as a boundary that is neither fixed nor free.
Consider a scenario where a wave propagates from a string of low linear mass density to a string of high linear mass density. In such a case, the reflected wave is out of phase with respect to the incident wave, however the...
Sound Waves: Interference00:53

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Sound waves can be modeled either as longitudinal waves, wherein the molecules of the medium oscillate around an equilibrium position, or as pressure waves. When two identical waves from the same source superimpose on each other, the combination of two crests or two troughs results in amplitude reinforcement known as constructive interference. If two identical waves, that are initially in phase, become out of phase because of different path lengths, the combination of crests with troughs...
Modes of Standing Waves - I01:03

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A close look at earthquakes provides evidence for the conditions appropriate for resonance, standing waves, and constructive and destructive interference. A building may vibrate for several seconds with a driving frequency matching the building's natural frequency of vibration; this produces a resonance that results in one building collapsing while the neighboring buildings do not. Often, buildings of a certain height are devastated, while other taller buildings remain intact. This phenomenon...
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Microparticle Manipulation by Standing Surface Acoustic Waves with Dual-frequency Excitations
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Published on: August 21, 2018

Computer-simulated alternative modes of U-wave genesis.

Matjaz Depolli1, Viktor Avbelj, Roman Trobec

  • 1Department of Communication Systems, Jozef Stefan Institute, Ljubljana, Slovenia. matjaz.depolli@ijs.si

Journal of Cardiovascular Electrophysiology
|October 6, 2007
PubMed
Summary

Computer simulations reveal that U waves in electrocardiograms (ECGs) can arise from various action potential combinations within the ventricular wall, even with minor repolarization differences.

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Area of Science:

  • Cardiovascular Physiology
  • Computational Biology
  • Biophysics

Background:

  • The origin of the U wave in electrocardiograms (ECGs) remains incompletely understood, with several hypotheses proposed.
  • Investigating U-wave genesis is crucial for a comprehensive understanding of cardiac electrical activity.

Purpose of the Study:

  • To explore and test alternative modes of U-wave genesis using advanced computer simulations.
  • To elucidate the underlying mechanisms responsible for U-wave generation in ECGs.

Main Methods:

  • Construction of a detailed spatial model of the left ventricle using 12 layers of cubic cells.
  • Assignment of time-dependent action potentials to each cell, contributing to electrical potential at measured ECG points.
  • Generation of simulated ECGs to analyze U-wave formation under various conditions.

Main Results:

  • Simulated ECGs demonstrate that U waves can be generated through diverse combinations of action potentials across ventricular wall layers.
  • A novel mode of U-wave genesis is identified, occurring even with subtle differences in cellular repolarization.
  • The study highlights the potential for U waves to form without the necessity of specific myocardial layers like M cells with prolonged action potentials.

Conclusions:

  • The U wave can be generated in the presence of robust intercellular coupling within the heart.
  • Specific myocardial layers, such as M cells known for prolonged action potentials, are not essential for U-wave genesis.
  • These findings offer new insights into the electrophysiological basis of U-wave generation.