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  • 1
    Publication Date: 2019-06-27
    Description: Blood flow velocity measurements, using Doppler velocimeter, are described. The ability to measure blood velocity using ultrasound is derived from the Doppler effect; the change in frequency which occurs when sound is reflected or transmitted from a moving target. When ultrasound of the appropriate frequency is transmitted through a moving blood stream, the blood cells act as point scatterers of ultrasonic energy. If this scattered ultrasonic energy is detected, it is found to be shifted in frequency according to the velocity of the blood cells, nu, the frequency of the incident sound, f sub o, the speed of sound in the medium, c, and the angle between the sound beam and the velocity vector, o. The relation describing this effect is known as the Doppler equation. Delta f = 2 f sub o x nu x cos alpha/c. The theoretical and experimental methods are evaluated.
    Keywords: AEROSPACE MEDICINE
    Type: NASA-CR-155233
    Format: application/pdf
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  • 2
    Publication Date: 2019-06-27
    Description: A pulsed ultrasonic Doppler velocity meter which can be used (by modifying transducers) as a flowmeter for blood circulation was experimentally studied. Calculations and profiles of turbulent and laminar flow within blood vessels are shown. Graphs and charts of transducers are included.
    Keywords: AEROSPACE MEDICINE
    Type: NASA-CR-143458
    Format: application/pdf
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  • 3
    Publication Date: 2019-06-27
    Description: Rankings of relative toxicity can be markedly affected by changes in test variables. Revision of the USF/NASA toxicity screening test procedure to eliminate the connecting tube and supporting floor and incorporate a 1.0 g sample weight, 200 C starting temperature, and 800 C upper limit temperature for pyrolysis, reversed the rankings of flexible polyurethane and polychloroprene foams, not only in relation to each other, but also in relation to cotton and red oak. Much of the change is attributed to reduction of the distance between the sample and the test animals, and reduction of the sample weight charged. Elimination of the connecting tube increased the relative toxicity of the polyurethane foams. The materials tested were flexible polyurethane foam, without and with fire retardant; rigid polyurethane foam with fire retardant; flexible polychloroprene foam; cotton, Douglas fir, red oak, hemlock, hardboard, particle board, polystyrene, and polymethyl methacrylate.
    Keywords: AEROSPACE MEDICINE
    Type: Journal of Combustion Toxicology; 3; Aug. 197
    Format: text
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  • 4
    Publication Date: 2019-06-27
    Description: A transcutanous method to measure instantaneous mean blood flow in peripheral arteries of the human body was defined. Transcutanous and implanted cuff ultrasound velocity measurements were evaluated, and the accuracies of velocity, flow, and diameter measurements were assessed for steady flow. Performance criteria were established for the pulsed Doppler velocity meter (PUDVM), and performance tests were conducted. Several improvements are suggested.
    Keywords: AEROSPACE MEDICINE
    Type: NASA-CR-141235
    Format: application/pdf
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