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Interference and Superposition of Waves01:07

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When two waves of the same nature occur in the same region simultaneously, they result in interference. Interference of waves implies that the net effect of the waves is the sum of the individual waves' effects. However, it does not imply that the individual waves affect the propagation of other waves.
Interference occurs in mechanical waves, such as sound waves, waves on a string, and surface water waves. Mechanical waves correspond to the physical displacement of particles. Hence,...
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Electrocardiogram Fundamentals01:28

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Introduction
An electrocardiogram (ECG) is a diagnostic tool for identifying cardiac conditions such as arrhythmias, conduction abnormalities, and myocardial ischemia.
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An electrocardiogram (ECG) visualizes the heart's electrical activity by tracing the electrical movement associated with each heartbeat on a graph or monitor. As the heart beats, an electrical wave passes through it, correlating with the cardiac cycle events.
Parts of an ECG
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Brain Waves01:23

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Brain waves are electrical signals generated by the neurons in the brain, which are regularly monitored to measure mental activities. Brain waves and their frequency ranges can be measured using an electroencephalogram or EEG. There are four main types of brain waves, each with distinct characteristics:
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Correlation between ECG and Cardiac Cycle01:25

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The electrical signals recorded on an electrocardiogram (ECG) occur before the mechanical processes of contraction and relaxation during the cardiac cycle.
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NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences01:17

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A pulse is a short burst of radio waves distributed over a range of frequencies that simultaneously excites all the nuclei in the sample. Upon passing a radio frequency pulse along the x-axis, the nuclei absorb energy corresponding to their Larmor frequencies and achieve resonance. This shifts the net magnetization vector from the z-axis toward the transverse plane. This angle of rotation of the magnetization vector, or the flip angle, is proportional to the duration and intensity of the pulse.
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The de Broglie Wavelength02:32

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In the macroscopic world, objects that are large enough to be seen by the naked eye follow the rules of classical physics. A billiard ball moving on a table will behave like a particle; it will continue traveling in a straight line unless it collides with another ball, or it is acted on by some other force, such as friction. The ball has a well-defined position and velocity or well-defined momentum, p = mv, which is defined by mass m and velocity v at any given moment. This is the typical...
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Related Experiment Video

Updated: Jun 29, 2025

Quantifying Infra-slow Dynamics of Spectral Power and Heart Rate in Sleeping Mice
10:56

Quantifying Infra-slow Dynamics of Spectral Power and Heart Rate in Sleeping Mice

Published on: August 2, 2017

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What are those intermittent "S" waves?

Laszlo Littmann1

  • 1Department Internal Medicine, Atrium Health Carolinas Medical Center, Charlotte, NC, USA.

Journal of Electrocardiology
|April 6, 2024
PubMed
Summary

A 69-year-old woman experienced fainting due to severe bradycardia. Analysis of electrocardiograms and telemetry data guided pacemaker programming to manage her heart rhythm.

Area of Science:

  • Cardiology
  • Electrophysiology

Background:

  • Syncope, or fainting, can be caused by various cardiac conditions.
  • Bradycardia, characterized by a slow heart rate, is a significant risk factor for syncope.

Observation:

  • A 69-year-old female experienced recurrent syncope during air travel.
  • Initial electrocardiograms (ECGs) revealed profoundly slow ventricular rates (in the 30s).
  • ECGs showed both narrow and wide QRS complexes with unusual negative deflections.

Findings:

  • Telemetry recordings were crucial in identifying the underlying cardiac mechanism.
  • The specific ECG findings, including wide negative deflections, aided in diagnosis.
  • Pacemaker programming was successfully adjusted based on the electrophysiological analysis.
Keywords:
Pacemaker-mediated tachycardiaSyncopeThird-degree AV blockUnidirectional block

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Last Updated: Jun 29, 2025

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Implications:

  • This case highlights the importance of detailed ECG and telemetry analysis in diagnosing syncope.
  • Appropriate pacemaker management can effectively treat bradycardia-induced syncope.
  • Understanding complex ECG patterns is vital for effective cardiac rhythm management.