Ultrasound ultrasonic treatment

One impediment of universally applying PET in the area of packaging is its gas-barrier properties. These can be slightly improved by measures to increase the density (crystallinity) during blow molding, for example, by treatment with ultrasound. Ultrasonic treatment during injection reduces the gas permeability to a certain extent [34],... 

Application of a high ionic strength media on the skin after ultrasonic treatment was also found to be effective in extracting glucose.9 In the SonoPrep device, the electrical impedance of the skin is continuously monitored, so application of the ultrasound can continue until a fixed permeability is achieved (see Figure 7.6). Generally, about 10 s is required to reduce the impedance below 10 k 2. The ultrasonic... 

Contrasting with the microwaves, ultrasound is applied much more in synthetic coordination and organometallic chemistry, and has now become a classic conventional synthetic tool. This approach is used, in particular, for the activation of elemental metals in organic synthesis. A recent monograph [708] and previously published books [709-711] contain a complete description of the possibilities of ultrasonic treatment for obtaining metal complexes, so, in the present monograph, we give only selected applications. 

A combination of different techniques can frequently improve yields of final compounds or synthetic conditions, for example a reunion of direct electrochemical synthesis and simultaneous ultrasonic treatment of the reaction system [715]. Reunion of microwave and ultrasonic treatment was an aim to construct an original microwave-ultrasound reactor suitable for organic synthesis (pyrolysis and esterification) (Fig. 3.7) [716], The US system is a cup horn type the emission of ultrasound waves occurs at the bottom of the reactor. The US probe is not in direct contact with the reactive mixture. It is placed a distance from the electromagnetic field in order to avoid interactions and short circuits. The propagation of the US waves into the reactor occurs by means of decalin introduced into the double jacket. This liquid was chosen by the authors of Ref. 716 because of its low viscosity that induces good propagation of ultrasonic waves and inertia towards microwaves. 

A simultaneous ultrasonic treatment of the reaction phase (with ultrasonic cleaner Bransonic 12 was carried out in all experiments using a weak source of ultrasound in order to eliminate formed products from the metal surface and thus stabilize the current in the process. Stronger sources of ultrasound have not been used to avoid turbulent processes and the uncontrolled superheating of the reaction zone. 

Both starch-g-PAN and starch-g-polyacrylamide were prepared by cobalt-60 initiation, since acrylamide does not graft efficiently in the presence of ceric ammonium nitrate (16). Both graft copolymers were irradiated with ultrasound to give totally soluble products the ultrasonic treatment of starch-g-PAN was carried out in DMSO, while that of starch-g-polyacrylamide was run in water. 

Photocatalysis can be associated not only with a biological treatment, but also with other processes whose properties differ in some aspects from photocatalytic treatment. For instance, an initial ultrasonic treatment can allow one to destroy the CF3 group (124,125), which withstands most oxidation reactions. Ultrasound can also be more appropriate to start the destruction of hydrophobic compounds with long hydrocarbon chains, which interact poorly with Ti02 in water (125). 

Ultrasonic treatment can also disrupt milk fat globules, probably through cavitation and other shear and shock effects (Villamiel, 1999). Wu et al. (2001) reported that high amplitude ultrasound homogenization of milk for yogurt manufacture achieved similar effects as conventional homogenization. 

Successful acceleration by sonication has also been reported in the field of organic biocatalysis, employing whole cell and immobilized enzymes. The improved yields and retained stereoselectivities obtained under ultrasound irradiation emphasize the broad range of chemical transformations that benefits from ultrasonic treatment. 

The pulse-pause mode, which is used to maintain the temperature within a specific range. Ultrasound is applied to the sample while keeping the sample temperature between the limits of this range. This mode allows the sample temperature to be kept within the range while continuing the ultrasonic treatment during the process time. 

Industry uses special devices similar to ultrasonic baths and probes but appropriately scaled up in size and ultrasound irradiation power. The UIP16000 model from Hielscher Ultrasound Technology is by far the most powerful ultrasonic processor available worldwide the apparatus is capable of delivering a continuous power of 16000 W at efficiency above 80%. Such powerful systems have been developed in response to the demand for the ultrasonic treatment of liquids on a large scale in fact, the ultrasound power required usually increases in proportion to the amount of liquid to be treated within a certain time. 

Exfoliation is also facilitated by mechanical methods such as the application of high-intensity ultrasound. High-intensity ultrasound is known to increase the rate of intercalation reactions. However, in recent studies on the exfoliation of the misfit layer compounds PbNb2S5 and SmNb2S5, some degree of dispersion was obtained by ultrasonic treatment in specific solvents such as ethanol and isopropanol. ° The solvents were not intercalated, but acted to stabilize the dispersions. The dispersions contained a substantial fraction of particles with fewer than 10 layers, but only a small fraction was exfoliated. Along with the ion exchange reaction under relatively severe conditions compared with other layered... 

An interesting set of investigations on an effect of ultrasound with pulsed and continuous initiation of cavitation on solidification of low-melting metals and alloys has been performed by Buxmann [15] in Switzerland. The results of studies on the ultrasonic treatment of melts of aluminum and its alloys have been published... 

The wide industrial use of the ultrasonic treatment of melts requires further development of ultrasonic technique and equipment. Most of industrial sources of ultrasound work with automatic adjustment of frequency. Expansion of fields of application of the ultrasonic treatment requires the development of automatic control systems with automatic adjustment of amplitude, which may require generators and transducers of increased power. 

Dobatkin, V.I. and Eskin, G.I. Ultrasonic treatment of melts of nonferrous metals and alloys. In Action of Powerful Ultrasound on Metal Interfaces. Nauka, Moscow, 1986 pp. 6-51 (in Russian). 

A remarkable influence of ultrasound on fish egg hatching has been reported [20]. The eggs were exposed to ultrasound of frequency 1 MHz for 35 min, 3 times a day and this led to a reduction in hatch time to 6 days compared to the normal 7 days. This, in itself, is of considerable industrial importance for fish-farming, but there are also two other benefits of ultrasonic treatment. It was also found that the ultrasound increased the fraction of the eggs which hatched and further that, once hatched, the fish demonstrated a higher survival rate. 

Power ultrasound has also been found to be effective in the extraction of protein from meat [58]. Ultrasound disrupts the meat myofibrils and this releases a sticky exudate which binds the meat together. The binding strength, water holding capacity, product color, and yields were examined after treatment either with salt tumbling, sonication, or both. Samples which received both salt treatment and sonication were superior in all qualities. Similar results were obtained from a study of the effect of sonication on cured rolled ham [59]. Ultrasonic treatment enhanced the extraction of myofibrillar proteins leading to an increase in the strength of the reformed meat. 

In the third experiment the (CD)ex was added in a calculated amoimt prior to the treatment with ultrasound. In this experiment the ee value was constant but was opposite in sign, i.e., during the ultrasonic treatment full exchange between the two forms of the alkaloid took place (see Figure 4). The phenomenon appeared to be fully reproducible. Further studies reviled that this exchange is strongly influenced by the concentration of acetic acid, too [18]. 

The use of ultrasounds to aid the extraction is another possibility. Phthalates (Abb et al. 2009) and perfluorinated alkanoic acid (PEA) (Kato et al. 2009) determinations have been reported. Ethyl acetate (phthalates) or formic acid with methanol (perfluoroalkyl chemicals) was added to the dust sample, and extraction was performed in an ultrasonic bath at room temperature for 10 min. In the case of phthalates an enrichment step was not carried out to avoid the risk of contamination. Pyrethroids and their metabolites can also been extracted from indoor dust samples by adding methylene chloride followed by sonication for 10 min (Starr et al. 2008). Another option is the combination of Soxhlet extraction with an ultrasonic treatment (Schecter et al. 2009). 

The gelation time is taken as the time interval between the end of the ultrasonic treatment and the transition from a viscous fluid to an elastic solid. The first outstanding effect of ultrasound on the gelation process is the drastic decrease of this time in comparison... 

The composition of microcapsule shell also affects the ultrasonic sensitivity of microcapsules. The increase of common number of polyelectrolyte layers in microcapsule shell, i.e. the increase of shell thickness, demands more prolonged sonication time. So, the sensitivity of microcapsules to the ultrasound falls with the growth of the number of polyelectrolyte layers. The presence of inorganic nanoparticles essentially raises microcapsule sensitivity to the ultrasonic treatment. Thus, ul-... 

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