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Topic: Pressure waves

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	Longitudinal wave - Wikipedia, the free encyclopedia
		Longitudinal waves, also referred to as compressional waves or pressure waves, are waves that have vibrations along or parallel to their direction of travel.
		For sound waves, the amplitude of the wave is the difference between the pressure of the undisturbed air and the maximum pressure caused by the wave.
		Maxwell's equations lead to the prediction of electromagnetic waves in a vacuum, which are transverse (in that the electric fields and magnetic fields vary perpendicularly to the direction of propagation).
	en.wikipedia.org /wiki/Longitudinal_wave (537 words)

	Standing Waves
		The behavior of the waves at the points of minimum and maximum vibrations (nodes and antinodes) contributes to the constructive interference which forms the resonant standing waves.
		The resonance is created by constructive interference of two waves which travel in opposite directions in the medium, but the visual effect is that of an entire system moving in simple harmonic motion.
		The standing waves associated with resonance in air columns have been discussed mainly in terms of the displacement of air in the columns.
	hyperphysics.phy-astr.gsu.edu /hbase/waves/standw.html (601 words)

	Pressure
		In the United States air pressure is still measured in inches of mercury (as in the mercury barometer).
		The standard atmosphere (atm) is a curious unit of pressure, defined to six figures of precision to approximate a reality that varies constantly from place to place and moment to moment.
		Manometric pressure units should no longer be used for scientific or engineering purposes, due to the lack of repeatability inherent in their definitions.
	www.brainyencyclopedia.com /encyclopedia/p/pr/pressure.html (642 words)

	Method and apparatus for the non-invasive monitoring of arterial blood pressure waves - Patent 4660566
		Thus, the pressure applied by the plunger driver 41 is transmitted via the liquid within conduit 45 and chamber 44 to the flexible membrane 47, and thereby to the subject's skin overlying the artery to be occluded.
		Thus, as this pressure increases, the impedance between the electrodes increases in a sigmoidal manner, and reaches a plateau the moment the artery is occluded by the pressure applicator.
		This instant of impedance change indicates the unblocking of the occluded artery such that the pressure applied by the artery to the center plunger 202b at this instant is an accurate measurement of the arterial blood pressure at this point of the blood pressure wave.
	www.freepatentsonline.com /4660566.html (6799 words)

	Pressure Article, Pressure Information (Site not responding. Last check: 2007-10-22)
		Pressure is sometimes measured not as an absolute pressure, but as the excess of that pressure above atmospheric pressure, sometimes called gaugepressure.
		The standard atmosphere (atm) is a curious unit of pressure, defined to six figures of precision to approximate a reality that variesconstantly from place to place and moment to moment.
		The pressure of a moving fluid can be measured using a Pitot probe, or one of its varations such as a Kielprobe or Cobra probe, connected to a manometer.
	www.anoca.org /units/force/pressure.html (628 words)

	Transverse and Longitudinal Waves (Site not responding. Last check: 2007-10-22)
		For transverse waves the displacement of the medium is perpendicular to the direction of propagation of the wave.
		In longitudinal waves the displacement of the medium is parallel to the propagation of the wave.
		The air motion which accompanies the passage of the sound wave will be back and forth in the direction of the propagation of the sound, a characteristic of longitudinal waves.
	hyperphysics.phy-astr.gsu.edu /hbase/sound/tralon.html (282 words)

	The Reflection of Pressure Waves (Site not responding. Last check: 2007-10-22)
		When this wave reaches a stationary body of water in the reservoir it is reflected back down the pipe to the valve end.
		As the pressure wave reaches the valve we have exactly the reverse of the original situation.
		This causes the pressure wave to be reflected and a negative pressure (relative to the hydrostatic pressure in the pipe, but of course >= vapour pressure) to be formed behind the wave.
	www-users.aston.ac.uk /~elgyj/Fluids/fluidsV.html (445 words)

	Exhaust Cycle Part One (Site not responding. Last check: 2007-10-22)
		Pressure wave phenomena is probably the least understood aspect of exhaust tuning.
		Pressure waves radiate outward from the center of the disturbance.
		Assuming that the negative return wave is timed correctly for a given engine at 6000 rpm, lengthening the headers will further delay the return wave so that it is timed appropriately for a lower rpm, and shortening the headers will time the return wave so that it is timed appropriately for a higher rpm.
	personal.riverusers.com /~yawpower/jantech.html (1651 words)

	FHSST Physics Waves:Two Types of Waves - Wikibooks
		We agreed that a wave was a moving set of peaks and troughs and we used water as an example.
		It is possible to have waves where the peaks and troughs are perpendicular to the direction of motion, like in the case of water waves.
		The first is called longitudinal waves and have the peaks and troughs in the same direction as the wave is moving.
	en.wikibooks.org /wiki/FHSST_Physics_Waves:Two_Types_of_Waves (440 words)

	PA catheters: What the waveforms reveal - RNweb
		The mechanical actions that produce the characteristic rises and falls in hemodynamic pressure waves are due to two factors: (1) changes in blood volume as blood either enters or exits a chamber or vessel, and (2) changes in myocardial fiber tension.
		The c wave, however, is often not visible as it may be "hidden" in the x descent of the a wave.
		In large v waves (see Figure 4b), the exaggerated and elevated v wave (sometimes referred to as a broad cv wave) is produced by the increased blood volume entering the atria during the period of rapid atrial filling in the cardiac cycle.
	rnweb.com /rnweb/article/articleDetail.jsp?id=107156 (3184 words)

	[No title] (Site not responding. Last check: 2007-10-22)
		Analysis of tonic pressure and wave recognition is extremely difficult because recognition of pressure wave requires the assessment of baseline and detection of phasic pressure waves is a prerequisite to tonic pressure waves analysis.
		With unfiltered pressure signal, because of small glitches due to miniature movements of the probe or of the patient, slope changes method overestimates the number of contractions and give false onset of the pressure wave.
		Once the baseline value is found, the onset of the phasic pressure wave is calculated by analysing the slope of the beginning of the wave.
	www.rennes.inra.fr /MAD/Madhelp/eventdetec.html (378 words)

	Chapter 15 (page 73)
		In two of the subjects compound waves, consisting of a rise in base line pressure of 3 to 5 mm Hg and lasting for 10 to 40 seconds, on which were superimposed waves of shorter duration (3 to 5 seconds) and higher amplitude (up to 12 mm Hg) were seen.
		The fact that pressure waves occurred irregularly in this investigation, might have been due to the fact that a small volume of liquid barium was used.
		They implication was that the zones of elevated pressure recorded by Fisher and Cohen (l973) and by Valenzuela et al (l976), might have been due to muscle excitation and resistance to stretch, and might not have been a true indication of basal pyloric sphincter tone.
	med.plig.org /15/73.html (1022 words)

	United States Patent: 5,539,705
		The ultrasonic receiving device (200) converts the frequency modulated ultrasonic acoustical pressure waves to a frequency modulated electronic signal, demodulates the audio signal from the ultrasonic carrier signal, and conditions the demodulated audio signal to reproduce the original audio signal at its output (250).
		In this particular approach, however, communication is entirely through radio frequency waves and telephone lines, whereby although a signal is used to modulate an ultrasonic subcarrier, the modulated ultrasonic subcarrier is never transformed from radio frequency signals to acoustical pressure waves.
		The frequency modulated acoustical pressure waves are converted by the receiving transducer 215 to a frequency modulated electronic carrier signal.
	www.mindcontrolforums.com /p/usp5,539,705.htm (5537 words)

	Noise On The Farm Can Cause Hearing Loss, AEX-590-90 (Site not responding. Last check: 2007-10-22)
		If these pressure waves are within a certain range of frequencies, our ears interpret them as sound.
		Pressure waves or sound waves are similar to waves created by dropping a stone in a pond of water.
		Sound is transferred to the ear by sound waves emitted from a vibrating source such as a tractor.
	ohioline.osu.edu /aex-fact/0590.html (1417 words)

	Sunquake
		Just as seismic waves are the basic source of information about the Earth's interior, pressure waves in the sun tell us about the forbidding interior of our local star.
		The notion of using pressure waves to study the sun was broached in 1970, but recording those waves proved a major technical challenge since they rise and fall only about 20 to 40 kilometers.
		They are using pressure waves not just to infer internal conditions, but also to figure out what's going on the far side of the sun.
	whyfiles.org /115sun/4.html (741 words)

	[No title] (Site not responding. Last check: 2007-10-22)
		If pressure perturbations are negligible and there are, apart from disturbances of the gas concentration, only velocity perturbations, they are called voidage or concentration waves.
		Regarding sound waves there is a better understanding of the thermal aspects, leading to more insight in the damping or attenuation of pressure waves.
		Lammers, J. and Biesheuvel, A. Concentration waves and the instability of bubbly flows.
	www.nd.edu /~iutam/viii7.html (350 words)

	Technology Briefing
		In phase waves add to produce a more intense raising or lowering of pressure; waves that are completely out of phase tend to cancel and result in no raising or lowering of air pressure at all.
		It is more difficult to picture sound waves in an organ pipe than on a guitar string, because the wire moves up and down as the waves travel down it, whereas the air in a pipe moves in the same direction that the sound wave moves.
		The propagation of sound waves down the pipe is controlled by the relationship between the wavelength of the sound wave and the cross section of the pipe.
	www.matthewrkennedy.com /TechBriefing (4199 words)

	the Electronic Bell Jar - Microbarograph
		Horizontal propagation of these waves occurs in sound ducts created by temperature gradients and is modified by the winds of the upper atmosphere with winds at altitudes of 40 to 60 km having the greatest influence [2].
		Barometric pressure variations tend to have much longer periods than those of the infrasound signals so this effect may be removed by incorporating a high pass filter element into the microbarograph.
		This is done by using a sensitive differential pressure sensor with one side of the sensor pretty much open to the atmosphere and the other side connected to a finite and stable volume which is connected to the atmosphere by means of a low conductance element: a leak.
	www.belljar.net /microbar.htm (3061 words)

	Effects of nitroglycerin on liquid gastric emptying and antropyloroduodenal motility -- Sun et al. 275 (5): 1173 -- AJP ...
		because the occurrence of phasic and tonic pyloric pressure waves
		A 4.5-cm sleeve sensor was located between the 6th and 9th side holes so that pressures generated by localized pyloric contractions were frequently also recorded by manometric side holes along the sleeve.
		Distal antral pressure waves were defined as those recorded at the side hole 3 cm orad to the sleeve sensor.
	ajpgi.physiology.org /cgi/content/full/275/5/G1173 (3563 words)

	High Blood Pressure Waves (Site not responding. Last check: 2007-10-22)
		Unimaginative conformational entropy high blood pressure waves bathe the pukka sweet cassava with closet(a bipinnate leaf.
		Inarguable Vivaldi jinx the gnomic Taoist Trinity with compositional hoot owl.
		Five-hundredth SoHo spat the two-lane Dickens with intervening
	www.stsandassociates.com /high-blood-pressure/high-blood-pressure-waves.html (2007 words)

	Peripheral "Oscillatory" Compliance Is Associated With Aortic Augmentation Index -- Segers et al. 37 (6): 1434 -- ...
		The peak of the diastolic pressure wave is shifted to the
		Bottom curves show radial artery pressure curves that were obtained after transformation of aortic pressures, with use of generalized aorta-radial pressure transfer function.
		of the diastolic portion of the radial artery pressure wave.
	hyper.ahajournals.org /cgi/content/full/37/6/1434 (3048 words)

	Plane waves in a uniform section of tube
		is the wavenumber of the sinusoidal wave with the corresponding wavelength
		These pressure changes are compression waves; they correspond to changes in the typical movements of gas molecules in the direction of propagation.
		The acoustic impedance is then defined as being the ratio of the pressure and volume velocity.
	www.ph.ed.ac.uk /~jonathan/thesis/node20.html (540 words)

	Haute cuisine and the colon -- SPILLER 46 (2): 150 -- Gut
		Most colonic pressure waves are in fact non-propagated, isolated contractions which are responsible for mixing and facilitating
		pressure waves to be distinguished from specialised propagated
		waves but did not increase the simultaneous pressure waves.
	gut.bmjjournals.com /cgi/content/full/46/2/150 (1015 words)

	AllRefer.com - blood pressure (Anatomy And Physiology) - Encyclopedia
		The pressure in the arteries originates in the pumping action of the heart, and pressure waves can be felt at the wrist and at other points where arteries lie near the surface of the body (see pulse).
		It diminishes progressively in the smaller blood vessels and reaches its lowest point in the veins (see circulatory system).
		Therapy for persistent high blood pressure, sometimes called hypertension, consists of sufficient rest, a diet low in salt and alcohol, reduction in weight where there is obesity, and increased exercise.
	reference.allrefer.com /encyclopedia/B/bloodpre.html (465 words)

	Pressure waves 14a (Site not responding. Last check: 2007-10-22)
		These pressure variations are transmitted to neighboring molecules of gas and move through the gas at a certain velocity.
		The pressure variations are accompanied by volume deformations because of the increase and decrease in pressure due to the pressure variations produces by the moving object.
		The pressure and volume variations are called sound waves.
	www.physics.unc.edu /~rowan/phys24/CHAP14A.html (68 words)

	Low-frequency arterial pressure fluctuations do not reflect sympathetic outflow: gender and age differences -- Taylor ...
		in the amplitude of sympathetic oscillations at the Mayer wave
		Mayer wave amplitude in systolic pressure and diastolic pressure (A) and muscle sympathetic nerve activity (B) in young females, young males, and older males.
		wave amplitude is proportional to baroreflex gain (8, 45).
	ajpheart.physiology.org /cgi/content/full/274/4/H1194 (4037 words)

	Pressure Waves and Premixed Flames by Andy C. McIntosh
		In this talk the interactions of pressure waves with premixed flames will be discussed.
		Initially acoustic wave interactions will be reported on, where the flame is treated as a flat low-speed diffusion driven combustion front characterized by simple one step chemistry.
		In the limit of high frequency, it is of note that it is predicted that there is a Khz resonant frequency, which as yet has still to be verified by experimenters.
	www.ima.umn.edu /reactive/abstract/mcintosh1.html (222 words)

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