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Related Concept Videos

Pulse01:16

Pulse

2.2K
When the heart pumps blood out, arterial elastic fibers play a crucial role in sustaining a high-pressure gradient. They expand to accommodate the received blood and then recoil - a process known as the pulse that can be either manually palpated or electronically quantified. Despite a reduction in its effect with increased distance from the heart, elements of the pulse's systolic and diastolic components persist, observable even at the arteriole level.
The pulse serves as a clinical...
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Pulse01:05

Pulse

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The pulse is one of the most fundamental physiological indicators of the body's cardiovascular health. It is the rhythmic expansion and contraction of the arterial walls in response to the pressure generated by the heart's pumping action.
Pulse Rate and its Significance
Pulse rate, often measured in beats per minute (bpm), reflects the heart rate (HR), which is influenced by numerous factors such as stress, physical activity, and hormonal changes. A normal resting adult pulse rate falls...
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Phase Diagrams02:39

Phase Diagrams

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A phase diagram combines plots of pressure versus temperature for the liquid-gas, solid-liquid, and solid-gas phase-transition equilibria of a substance. These diagrams indicate the physical states that exist under specific conditions of pressure and temperature and also provide the pressure dependence of the phase-transition temperatures (melting points, sublimation points, boiling points). Regions or areas labeled solid, liquid, and gas represent single phases, while lines or curves represent...
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NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences01:17

NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences

1.8K
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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Phase Transitions02:31

Phase Transitions

23.2K
Whether solid, liquid, or gas, a substance's state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the solid pack closely together, generally in a pattern. The particles vibrate about their fixed positions but do not move or squeeze past their neighbors. In liquids, although the particles are closely spaced, they are randomly arranged. The position of the particles are not fixed—that is, they are free to move past their neighbors to...
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Pulse Oximetry01:24

Pulse Oximetry

1.4K
Pulse oximetry, or SpO2, is a non-invasive method for continuously monitoring arterial oxygen saturation (SaO2). This procedure involves attaching a probe or sensor to the patient's fingertip, forehead, earlobe, or nose bridge. The sensor works by detecting changes in oxygen saturation levels through light signals generated by the oximeter and reflected by the pulsing blood under the probe.
Purpose
Average SpO2 values are greater than 95%. If the readings fall below 90%, it indicates that...
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High-speed Continuous-wave Stimulated Brillouin Scattering Spectrometer for Material Analysis
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Enhanced phase-sensitive OTDR system with pulse width modulation Brillouin amplification.

Haijun He, Bin Luo, Xihua Zou

    Optics Express
    |September 7, 2018
    PubMed
    Summary
    This summary is machine-generated.

    Pulse width modulation (PWM) Brillouin amplification enhances phase-sensitive optical time domain reflectometry (Ф-OTDR) systems. This technique improves signal-to-noise ratio and sensitivity, especially in long fiber optic sensing applications.

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    Area of Science:

    • Optoelectronics
    • Fiber Optic Sensing
    • Signal Processing

    Background:

    • Phase-sensitive optical time domain reflectometry (Ф-OTDR) systems face challenges with signal-to-noise ratio (SNR) and sensitivity, particularly at the far end of sensing fibers.
    • Conventional Brillouin amplification methods may not offer sufficient gain control for uniform sensitivity across the entire fiber length.

    Purpose of the Study:

    • To propose and demonstrate a novel pulse width modulation (PWM) Brillouin amplification technique for Ф-OTDR.
    • To achieve arbitrary and adjustable gain distribution along the sensing fiber.
    • To enhance SNR, sensitivity, and overcome transmission attenuation in Ф-OTDR systems.

    Main Methods:

    • Utilized a customizable PWM function to control Brillouin gain distribution.
    • Experimentally demonstrated three gain profiles: up-ramp sawtooth, sine, and triangle.
    • Employed linear PWM pump light to amplify backscattering Rayleigh light.
    • Incorporated a preamplifier and acoustic-optic modulator (AOM) to suppress noise and improve extinction ratio (ER).

    Main Results:

    • Achieved significant signal enhancement at the leading end (approx. 11.5 dB).
    • Successfully compensated for 9 dB of transmission attenuation over 25 km of single-mode fiber (SMF).
    • Accurately recovered vibrations at 100 Hz and 300 Hz at the trailing end.
    • Observed lower relative intensity noise (RIN) compared to conventional Brillouin amplification.

    Conclusions:

    • PWM Brillouin amplification effectively improves SNR and equalizes sensitivity along the entire sensing fiber.
    • The technique offers adjustable gain, compensating for attenuation and enhancing detection at the far end.
    • This universal scheme has the potential to improve other distributed fiber optic sensing techniques, reducing calibration complexity and false alarms.