Use of Ultrasound

Mason T J and Lorimer J P 1998 Sonochemistry Theory, Applications and Uses of Ultrasound In Chemistry (Chichester Ellis Florwood)... 

Implantable valves, particularly mechanical valves which continue to encroach on tissue valves, are unique. Methods such as valvuloplasty, mitral valve repair, or use of ultrasound are unlikely to reduce the number of valve replacements into the twenty-first century. Valve selection remains in the hands of the surgeon because of the critical nature of the procedure. If anything goes wrong, the result can be catastrophic to the patient. Cost of a valve, from 3000— 4000, is a relatively small part of the cost of open-heart surgery which can mn as high as 30,000. Growth of the cardiovascular valve market has slowed in the United States with the decline of the threat of rheumatic fever. 

In addition to sodium, other metals have found application for the Wurtz coupling reaction, e.g. zinc, iron, copper, lithium, magnesium. The use of ultrasound can have positive effect on reactivity as well as rate and yield of this two-phase reaction aryl halides can then even undergo an aryl-aryl coupling reaction to yield biaryls. ... 

Mason TJ, Lorimer JP (1989) Sonochemistry Theory, applications and uses of ultrasound in chemistry, Ellis Horwood Limited, Chichester, chap 2... 

T.J. Mason, ed., "Sonochemistry the Uses of Ultrasound in Chemistry , Royal Society of Chemistry, London, (1990). 

The most common method to extract xylan is the alkaline extraction. Several pretreatment methods can be used in association in order to break the covalent bonds that exist between xylan and other carbohydrates during the extraction (Wang Zhang, 2006). A number of articles studied the use of ultrasound on the xylan extraction. Hromadkova and coworkers reported that 36.1% of xylan was extracted from corn cobs with 5% NaOH solution at 60°C for 10 min of ultrasonication in comparison with 31.5% of xylan in the classical extraction. Both extractive methods yielded xylan with immunogenic properties (Hromadkova et al., 1999). 

Sonochemistry started in 1927 when Richards and Loomis [173] first described chemical reactions brought about by ultrasonic waves, but rapid development of ultrasound in chemistry really only began in the 1980s. Over the past decades there has been a remarkable expansion in the use of ultrasound as an energy source to produce bond scission and to promote or modify chemical reactivity. Although acoustic cavitation plays... 

Use of ultrasounds in catalyst preparation leads to higher penetration of the active metal inside the pores of the support and greatly increases the metal dispersion on the support [185]. Major advances in ultrasonic technology have increased the acoustic power and sensitivity of transducers. 

Mason TJ, Joyce E, Phull SS, Lorimer JP (2003) Potential uses of ultrasound in the biological decontamination of water. Ultrason Sonochem 10 319-323... 

Zirconia nanopowders have attracted much attention recently due to their specific optical and electrical properties [38] and as catalysts [39]. Liang et al. [40] have synthesized pure Zr02 nanopowders via sonochemical method. In this study, the use of ultrasound has dramatically reduced the temperature of reaction and made the reaction conditions very easy to maintain. 

Swamy KM, Sukla LB, Narayana KL, Kar KN, Panchanadikar VV (1995) Use of ultrasound in microbial leaching of nickel from laterites. Ultrason Sonochem 2(1) S5-S9... 

Cains PW, Martin PD, Price CJ (1998) The use of ultrasound in industrial chemical synthesis and crystallization. Parti. Applications to synthetic chemistry. Org Process Res Dev 2 34... 

The synthesis [33] of magnesium ferrite (MgFe2C>4) from Fe203 and MgO for catalytic applications has been reported by the use of ultrasound of 20 kHz and power 100 W/cm2. Short range ordering of the alloy of Ni-(0.2-10.3) atomic percent in Cr solid could be affected by 17.5 Hz sound wave at liquid helium temperature (40 K) [34]. 

Abstract Hazardous effects of various amines, produced in the environment from the partial degradation of azo dyes and amino acids, adversely affect the quality of human life through water, soil and air pollution and therefore needed to be degraded. A number of such studies are already available in the literature, with or without the use of ultrasound, which have been summarized briefly. The sono-chemical degradation of amines and in the combination with a photocatalyst, TiC>2 has also been discussed. Similar such degradation studies for ethylamine (EA), aniline (A), diphenylamine (DPA) and naphthylamine (NA) in the presence of ultrasound, Ti02 and rare earths (REs) La, Pr, Nd, Sm and Gd, in aqueous solutions at 20 kHz and 250 W power have been carried out and reported, to examine the combinatorial efficacy of ultrasound in the presence of a photocatalyst and rare earth ions with reactive f-electrons. 

The use of ultrasound in both the synthesis and crystallisation of a broad array of both organic and inorganic materials has been intensively researched and is well documented [61-64]. An application of ultrasound that has received relatively less attention however, is in the dissolution of colloidal particles. Prakash and Ghosh [65] reported on the dissolution of silver colloids under 1 MHz ultrasound irradiation, proposing that the silver is oxidised by sonochemically produced hydroxyl radicals. Sostaric et al. [66] investigated the dissolution of MnC>2 colloids in the presence of aliphatic alcohols at a lower frequency of 20 kHz. They found that... 

I began my research into Sonochemistry over 30 years ago now and at that time it was for me an exploration of the unknown. In 1988 with my colleague Phil Lorimer we wrote the first book to carry in its title the word Sonochemistry with a subtitle Theory applications and uses of ultrasound in chemistry . In recent years,... 

The effect of ultrasound on liquid-liquid interfaces between immiscible fluids is emulsification. This is one of the major industrial uses of ultrasound (74-76) and a variety of apparatus have been devised which will generate micrometer-sized emulsions (9). The mechanism of ultrasonic emulsification lies in the shearing stresses and deformations created by the sound field of larger droplets. When these stresses become greater than the interfacial surface tension, the droplet will burst (77,78). The chemical effects of emulsification lie principally in the greatly increased surface area of contact between the two immiscible liquids. Results not unlike phase transfer catalysis may be expected. 

Sonochemistry is strongly affected by a variety of external parameters, including acoustic frequency, acoustic intensity, bulk temperature, static pressure, choice of ambient gas, and choice of solvent. These are important considerations in the effective use of ultrasound to influence chemical reactivity, and are also easily understandable in terms of the cavitational hot-spot mechanism. A summary of these effects is given in Table II. 

In organometallic chemistry, the use of ultrasound in liquid-liquid heterogeneous systems has been limited to Hg. The emulsification of Hg with various liquids dates to the very first reports on sonochemistry (3,203,204). The use of such emulsions for chemical purposes, however, was delineated by the extensive investigations of Fry and co-workers (205-212), who have reported the sonochemical reaction of various nucleophiles with a,a -dibromoketones and mercury. The versatility of this reagent is summarized in Eqs. (30)-(36). 

Extensions of the use of ultrasound in lithiation reactions have been profitable for a variety of reactions. The Bouveault reaction for the synthesis of aldehydes [Eq. (40)] suffers from side reactions and low yields. 

The sonochemistry of the other alkali metals is less explored. The use of ultrasound to produce colloidal Na has early origins and was found to greatly facilitate the production of the radical anion salt of 5,6-benzo-quinoline (225) and to give higher yields with greater control in the synthesis of phenylsodium (226). In addition, the use of an ultrasonic cleaning bath to promote the formation of other aromatic radical anions from chunk Na in undried solvents has been reported (227). Luche has recently studied the ultrasonic dispersion of potassium in toluene or xylene and its use for the cyclization of a, o-difunctionalized alkanes and for other reactions (228). 

Finally, an improved synthesis of (rj6-l, 3,5-cyclooctatriene)-(i74-l,5-cyclooctadiene)ruthenium(0) has been reported which utilizes a cleaning bath to hasten the Zn reduction of RuCl3 in the presence of 1,5-cyclooctadiene (240). The use of ultrasound in simple reductions using Zn are a likely area for further development. 

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