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Ultrasound speed

Rennie. J. Ultrasound Speeds the Release of Dings from Medical Implants, Sci. Amer., 30 (April 1990). [Pg.1639]

Structural changes in aqueous micellar solutions can also be seen from conductivity and ultrasound speed measurements as shown in figure 3. The relative viscosity, the conductivity, and the speed of sound have all been plotted in the same figure. The speed of sound and the conductivity curves exhibit a break at the same hexanol molality as the viscosity starts increasing. It is thus possible to use any of these methods to investigate shape transitions. [Pg.36]

The compressibihties of RTILs are available via two routes high pressure density measurements, leading to the isothermal compressibilities Xj and ultrasound speed measurements with ambient pressure densities, leading to the adiabatic compressibilities xs, which with some further data lead to the isothermal ones. The first route yields ... [Pg.160]

The coefficients Cj and Cp were obtained through a separate study in which the ultrasound speed in the polymer melt were measured imdCT various temperatures and pressmes and when the melt was in a static state. [Pg.2045]

Abstract Acoustic cavitation is the formation and collapse of bubbles in liquid irradiated by intense ultrasound. The speed of the bubble collapse sometimes reaches the sound velocity in the liquid. Accordingly, the bubble collapse becomes a quasi-adiabatic process. The temperature and pressure inside a bubble increase to thousands of Kelvin and thousands of bars, respectively. As a result, water vapor and oxygen, if present, are dissociated inside a bubble and oxidants such as OH, O, and H2O2 are produced, which is called sonochemical reactions. The pulsation of active bubbles is intrinsically nonlinear. In the present review, fundamentals of acoustic cavitation, sonochemistry, and acoustic fields in sonochemical reactors have been discussed. [Pg.1]

In the literature we can now find several papers which establish a widely accepted scenario of the benefits and effects of an ultrasound field in an electrochemical process [13-15]. Most of this work has been focused on low frequency and high power ultrasound fields. Its propagation in a fluid such as water is quite complex, where the acoustic streaming and especially the cavitation are the two most important phenomena. In addition, other effects derived from the cavitation such as microjetting and shock waves have been related with other benefits reported for this coupling. For example, shock waves induced in the liquid cause not only an enhanced convective movement of material but also a possible surface damage. Micro jets of liquid, with speeds of up to 100 ms-1, result from the asymmetric collapse of cavitation bubbles at the solid surface [16] and contribute to the enhancement of the mass transport of material to the solid surface of the electrode. Therefore, depassivation [17], reaction mechanism modification [18], surface activation [19], adsorption phenomena decrease [20] and the mass transport enhancement [21] are effects derived from the presence of an ultrasound field on electrode processes. We have only listed the main phenomena referring to the reader to the specific reviews [22, 23] and reference therein. [Pg.108]

De Morais NLPA, Brett CMA (2002) Influence of power ultrasound on the corrosion of aluminium and high speed steel. J Appl Electrochem 32 653-660... [Pg.269]

When a liquid-solid interface is subjected to ultrasound, transient cavitation still occurs, but with major changes in the nature of the bubble collapse. No longer do cavities implode spherically. Instead, a markedly asymmetric collapse occurs, which generates a jet of liquid directed at the surface, as seen in high speed micro-cinematography by Ellis (9) and Lauterborn (K)) (shown... [Pg.196]

Industrially, the silver is recovered from either the wash water, or the bleach fix separately or from a mixture of the two using electrolysis employing a stainless steel cathode cylinder and an anode of stainless steel mesh. A typical wash solution composition contains silver (4 g L ), sodium thiosulphate (220 g L ), sodium bisulphite (22 g L ) and sodium ferric EDTA (4 g L ). At Coventry we have used a scaled down version of the industrial process employing 250 mL samples [46]. Electrolysis experiments were performed at ambient temperature with both wash and bleach fix solutions and in which the potential applied to the cathode and the speed of rotation of the cathode were varied. The sonic energy (30 W) was supplied by a 38 kHz bath. The results are given in Tab. 6.9. The table shows that the recovery of silver on sonication of the wash or bleach fix solutions is much improved especially if the electrode is rotated while ultrasound is applied. Yields with bleach fix (which contains ferric ions) are less since Fe and Ag compete for discharge (Eqs. 6.13 and 6.14). [Pg.246]

Lipid microparticles and nanopellets for oral use were first described by Speiser [11]. Nanopellets are prepared by dispersing melted lipids with high-speed mixers or via ultrasound techniques. Lipospheres developed by Domb are also prepared from dispersed lipids by stirring and sonication [12]. These preparations may contain a high degree of microparticles, which thus excludes an intravenous injection. For other routes of application (e.g., peroral administration), these microparticles might not be a serious problem. Furthermore, the dispersions may be contaminated by metal shed. With optimized conditions, however, mean particles sizes of 1(X) to 200 nm are possible [13]. [Pg.3]

It is possible that microbubble shell may be shattered during the interaction with an ultrasound pulse. Indeed, drastic variation of microbubble size, up to several-fold in less than a microsecond, has been reported [33], with linear speeds of the wall motion of microbubble approaching hundreds of meters per second in certain conditions. At these rates, it is easy to shatter the materials that would otherwise flow under slow deformation conditions. In some cases (e.g., lipid monolayer shells, which are held together solely by the hydrophobic interaction of the adjacent molecules), after such shattering the re-formation of the shell maybe possible in other cases - e.g., with a solid crosslinked polymer or a denatured protein shells - the detached iceberg-like pieces of the microbubble shell coat would probably not re-form and anneal, and the acoustic response of microbubbles to the subsequent ultrasound pulses would be different [34]. [Pg.84]

Ultrasound activation accelerates the synthesis, probably by maintaining a clean surface on the sodium particles. This allows the Wurtz synthesis to be carried out at much lower temperature, in benzene, tetrahydrofuran (THF) or diethyl ether.14 The synthesis is also speeded by the addition of additives which complex alkali metal cations, that is 15-crown-5 ether.15... [Pg.204]

Perez-Cid, B., Lavilla, I. and Bendicho, C. (1998) Speeding up of a three-stage sequential extraction method for metal speciation using focused ultrasound. Anal. Chim. Acta, 360, 35-41. [Pg.294]

This technique appears particularly attractive because the high frame rate allows the dynamics of fast changing liquid flows to be studied and the spatial resolution is significantly reduced using a high ultrasound frequency (Manneville et al., 2005). This technique can be adapted to small-scale, high-speed gas-liquid two-phase flows that are not presently subject to ultrasound-based techniques. [Pg.4]


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See also in sourсe #XX -- [ Pg.194 , Pg.205 ]




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