Ultrasonic degradation of cellulose is expected to give oligomers, which are valuable reagents in the biological field. In this work, we examine the ultrasonic degradation of cellulose in solutions and discuss the production of the oligo-cellulose. Cellulose (Avicel-PH101) was dissolved in lithium chloride (LiCl)/dimethylacetamide (DMAc) solvent. The concentration of LiCl was 8wt%. The ultrasonic homogenizer (BRANSON SONIFIER 450D) was used and its working frequency was 20kHz. Sonication was carried out at 25℃. The viscosity-averaged molecular (M_v) weight was estimated for the cellulose after the sonication. The M_v value of the sonicated sample deceased from 2×10^5 with increasing the ultrasonic intensity to around 1×10^5. The ethanol was added to the sonicated solutions as the precipitating agent and the precipitation was filtered and dried. After that it was dissolved in water and was fractionated into the water-insoluble component and soluble one. The water-soluble component was characterized by the GPC measurements and ^1H NMR spectroscopy. From the GPC and ^1H NMR analysis, the production of the oligo-cellulose was suggested.

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Various phenolic compounds and polyphenols were produced using ultrasonication in the hydroxylation reaction. In the aqueous solution, ultrasonication was useful for producing hydroxyl radical from water. Hydroxylation was also known in the production via epoxy compound. In the method via epoxy compounds high pressure or strong acidic conditions are necessary. Various monophenols substituted with alkyl and methoxy groups were reacted with hydroxyl radicals producing under ultrasonic irradiation(Sus-4005C, 50W, 40kHz and Kaijo, 200kHz) for 12-24h to give the corresponding polyphenolic compounds. When no irradiation of ultrasound was done in this reaction, no reaction was found. The effect of irradiation of ultrasound accelerated the hydroxylation of phenolic compounds. In the case of using cupric acetate in acetic acid, acetoxylation was also accelerated under ultrasonication. When catechols were reacted under oxygen and ultrasound irradiation in aqueous solution, pyrogallols were produced exceptionally. When resorcinols were reacted under the same condition, pyrogallols were also obtained. In the case of 2-t-butyl-4-methoxyphenol with cupric acetate under irradiation of ultrasound in acetic acid, 6-acetoxy-2-t-butyl-4-methoxyphenol was produced in good yield to give 3-t-butyl-5-methoxycatechol quantitatively.

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Biodiesel (fatty acid alkyl esters) is a cleaner burning diesel replacement fuel made from natural, renewable sources such as new and used vegetable oils and animal fats. Just like petroleum diesel, biodiesel operates in combustion-ignition engines. The influence of low frequency ultrasound (28 and 40 kHz) versus mechanical stirring on the trans-esterification of neat vegetable oil under base catalyst was studied. The results of investigation of trans-esterification of with short-chain alcohols (C1〜C4) in the presence of ultrasound to give alkyl esters of fatty acids are presented. Reaction conditions that affect the yield include the type and concentration of the catalyst, the ratio of alcohol to vegetable oil, reaction time and ultrasound frequency. Methanol, ethanol and n-propanol give the best yields in isolated bio-diesel product (>90 %), while the other alcohols give small amounts of esters or do not react at all. A set of experiments was carried out to see the effect of alcohol type to triglycerides. Table 1. The influence of alcohol on the transesterification time [table] When the catalyst was added in a ratio of 0.5% and 1.0% to the vegetable oil (wt./wt.) the yield of isolated product was 90-95% and there were no notable differences in the time to complete the reaction. Low frequency ultrasounds can be a valuable tool for the trans-esterification of fatty acids, aiming to prepare the bio-diesel fuel.

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Similarity between sonochemical and mechanochemical processes is much further than the general concept of applying non-thermal energy to the chemical reaction. Mechanisms are still to be elucidated, particularly for the process where these two effects are exerted simultaneously, i.e., sono-mechanochemical effects (SME). Two phenomenological examples are given to stimulate mechanistic discussion. Equipment with agitation bead milling and ultrasonication simultaneously is shown in Fig. 1. We applied SME to two reaction systems, i.e., for the preparation of composite perovskite, PMN-PZN, and hydroxy apatite - silk fibroin nanocomposites. [figure] Fig. 1 Mechanochemical reactor equipped with agitation mill and ultrasonic bath SME brought about decrease in the complex perovskite by an order of magnitude, as shown in Fig. 2. As we examined the surface structure of the reaction mixture, we observed the formation of well-developed surface layers comprising hydrated composite gel, assisted by SME. [figure] Fig. 2 SEM image of PMN-PZN after firing the precursor prepared (a) without US, (b) by SME, at 850 C for 1h Above-mentioned examples demonstrate two common aspects, i.e., dispersion of particulates or fibrils and promotion of nucleation. Enhanced nucleation might be attributed to the local activation of the substrate surface, associated polarization of surface species or radical formation at the solid / liquid boundary. We do not, however, have convincing evidences yet. In the case of PMN-PZN, enhanced dissolution - precipitation should be taken into account. Redeposited surface layer comprises hydrated gel with the composition close to the product. Enhanced nucleation in the surface layer, as illustrated in Fig. 3, results in the formation of finer products as shown in Fig. 2. [figure] Fig. 3 Schematic diagram of SEM on the nucleation in the surface hydrated gel layer The author thanks coworkers in his lab and appreciates financial support from NIMS.

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Sol-gel process in the ternary system of tetraethylorthosilicate (TEOS)-H_2O-ethanol was subjected to a power ultrasound of 20kHz-15W/cm^2. Sonication abruptly reduced the gelling time, and enhanced polycondensation to form Si-O-Si bonds. The ultrasonic effect increased with the increasing time up to 〜2 hours, and decreased with the increasing temperature. The latter is due to the "sonochemical effect" which prefers lower pressure of solvent vapor in the bubbles at lower temperature. On the other hand, argon-substituted atmospehre which should have higher effect of sonochemistry did have a lower effect than unsubstituted atmosphere (air). Comparing the sol-gel processes in N_2, O_2, Ar, and air, we found that oxygen has a positive effect on emulsification between TEOS and water. Ultrasonic-derived xerogels have higher density and specific surface area, and smaller pore size than normal ones. Incorporation of ammonia in the ternary causes the catalytic enhancement of polycondensation, resulting in the formation of spherical particles at a certain concentration condition. Ultrasonication to the system induced the polymerization at the surface of particles. The spherical shape was preserved when the particle size is as large as 300nm, while it was not when as small as 50nm. Ultrasonic effect on the sol-gel process might involve different mechanisms for homogeneous and heterogeneou systems.

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Ultrasonic fields were applied to the electropolymerization of pyrrole as a novel technique to control the properties of the conducting polymer. The p-toluenesulfonate-doped polypyrrole films prepared in the ultrasonic fields exhibited a more negative cathodic peak than those prepared in the silent conditions in the cyclic voltammograms. This voltammetric change at the reduction process was explained as change from the anion undoping to the cation doping, and attributed to formation of a highly dense film. Hence, a polypyrrole ClO_4^- -selective electrode has been prepared successfully by polymerizing pyrrole in ClO_4^- solution on a platinum-wire with and without ultrasonication. Both electrodes give Nernstian potentiometric responses in the range of the 10^<-1> - 10^<-4> M ClO_4^-. In the presence of various interfering ions, the selectivity for ClO_4^- of the electrode prepared under ultrasonication is higher than that prepared without ultrasonication. Thus, the polypyrrole films prepared under ultrasonication exhibit unique electrochemical properties in a doping/undoping process and excellent properties as the ClO_4^- -selective electrode.

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Influence of surfactants on instability of a sonoluminescing single bubble (SB) is studied through stroboscopic observation of the bubble. A rectangular quartz glass cell of 56×56×70 mm^3 internal dimensions was used as the SB cell. The bottom of the cell was attached to a bolted Langevin-type transducer, which was driven by a function generator through an amplifier at 24.5105 kHz. Direct observation of bubble behavior was performed with a stroboscopic lamp of 90 ns full width pulse at half maximum. The results show that the surfactant additives of sodium dodecyl sulfate (SDS) promote a distortion of the spherical bubble surface. Therefore, upper stable bubble region with sonoluminescence (SL) became narrower as the concentration of SDS increased. Instead, the dancing bubble region became broader, where a bubble ejects tiny bubbles due to the evolution of surface distortion and dances by counteraction. Since the instability of bubble collapse is a key parameter for sonochemistry in bulk liquids, surfactant additives have potential for promoting sonochemical reactions in bulk liquids.

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Bubble dynamics in acoustic cavitation bubble fields is monitored by high speed stereoscopic digital videography and compared with bubble motion models containing interaction forces. Single bubble dynamics studies via molecular dynamics calculations are presented.

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It is known that nano-size metal particles have different functions from bulk-size metal. Sonochemically prepared metal particles such as Pd, Au, and Pt are of nanometer size with a fairly narrow distribution. For example, Pd particles obtained from a 1.0mM Pd(II) in polyethylene glycol monostearate(PEG-MS) solution were about 5 nm sizes. We have suggested three different reduction pathways of metal ions under sonication: (i)reduction by H atoms, (ii)reduction by secondary reducing radicals formed by hydrogen abstraction from organic additives with OH radicals and H atoms, (iii)reduction by radicals formed from pyrolysis of the additives at the interfacial region between cavitation bubbles and the bulk solution. With these processes, the solution composed of PdCl_2・2NaCl(1.0mM), CuSO_4(3.0mM), and PEG-MS(0.4mM) was sonicated for 24 hours. Products were Cu-Pd bimetal particles. By X-rays analyses, it was found that the particles consisted of Cu-core and Pd-shell.

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Metal nanoparticles have been widely studied in recent years, as their physical and chemical propertiesto apply in various fields of industry are often quite different from those of the bulk materials. Various methods to prepare nanoparticles from metal ions in an aqueous solution have been proposed, and the sonochemical preparation is one of the unique methods because the organic additives such as alcohols and surfactants can be used as the reducing agents. The formation rate of gold nanoparticles was studied using an ultrasonic cleaning bath and it was found that the formation rate was controllable by selecting the type of the additives as well as the hydrogen ion concentration in the solution. When lower alcohols such as methanol or ethanol were used, the formation rate of gold nanoparticles in the neutral region of pH was rapid comparing with that in acid region or alkaline region. It was also observed that gold nanoparticles aggregated at low pH. On the other hand, the formation rate using higher alcohols such as pentanol or hexanol was higher than those using lower alcohols at low pH conditions. However, the formation rate became extremely slow at higher pH than 9.5, when butanol, pentanol or hexanol was used as an additive under the ultrasound field with 200 or 600 kHz frequencies. Moreover, formation rate with surfactant depends on the pH values

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We propose a method to fabricate a metal-coated fiber probe with a submicron-sized aperture for near-field optical microscopy based on size-dependent electroless plating under ultrasonic irradiation. The method consists of four steps: (A) chemically etching an optical fiber with a core diameter of 2μm and a refractive index difference of 2% in a buffered HF solution with a volume ratio of 40%NH_4F : 50%HF : H_2O= 10:1:1, (B, C) the surface activation by immersing in 1.0 g/dm^3-SnCl_2 and 5.0 mg/dm^3-PdCl_2 aqueous solutions, respectively, (D) electroless nickel plating under ultrasonic irradiation. We performed this method by using a 1MHz-ultrasonic generator (Honda Electronics, W-357HP) with the maximum input power of 600 W, and succeeded in obtaining a nickel-coated probe tip with submicron-sized aperture at an input power of 225W.

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Effects of ultrasound(US) irradiation, sonication, on the electroplating of platinum onto an indium tin oxide(ITO) electrode were examined in 0.1 mol dm^<-3> Na_2SO_4 solution with H_2PtCl_6. Electroplatings were carried out at constant currents and the electrode potentials were measured during the electroplatings. Applying the ultrasound (28 kHz, 150 W) during the plating decreased the electrode potential, which is one of the advantage of sonication in the electroplating. The deposition rate of platinum onto the ITO electrode under with US sonication was higher than that without US at the initial stage of the plating, then lowered with increasing the quantity of electricity. This fact suggests that the US sonication not only enhances the electrodeposition but also scrapes the deposited platinum of its surface parts, which may cause the more uniform deposition and leveling the surface of the electrode.

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Titanium is one of the prominent candidate for the material of an overpack for the geological disposal of high-level radioactive wastes. After being enclosed the radioactive wastes, the overpack is disposed of in deep ground, where it is to contact with a reducing groundwater, which will be irradiated by γ -ray from the inside of it. The cathodic polarization behavior of a material is a key factor in controlling its corrosion rate in a reducing solution, and the polarization behavior of pure -titanium was investigated under ultrasonic irradiation, because where the solution is dissociated to hydrogen and hydroxyl radicals as well as under the γ -irradiation. The cathodic current was increased with the irradiation intensity. This current increasing was supposed to be provided by the reduction of hydrogen peroxides, which were generated by the union of hydroxyl radicals that had be formed by the ultrasonic irradiation; H_2O → ・H + ・OH, ・OH + ・OH → H_2O_2, H_2O_2 + 2e^- → 2OH^-. To confirm the supposed mechanism, the H_2O_2 concentrations in the solution were measured before and after a constant cathodic potential being applied to the pure-titanium electrode, evaluating the change in the H_2O_2 reduction rate. The results, however, showed only the about half of the cathodic current was provided by the reduction of the H_2O_2. Accounting this difference, we considered the possibility of the direct discharging from the hydroxyl radicals; ・OH + 2e^- → 2OH^-. If this mechanism hold, the increasing of the cathodic current is not restricted by the reduction rate of the H_2O_2, but the generation rate of H_2 is increased because the hydrogen radicals that do not recombine with the hydroxyl radicals form H_2 gas as follows; ・H + ・H → H_2. To confirm the supposed model, the H_2 generation rates were measured before and after the electrode being polarized, however, the generation rates were not changed with the polarization, so that it was considered that the model could not hold.

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The effect of intense ultrasound on chemical processes is a field which is attracting much attention in both fundamental and applied researches in recent years. When a liquid is irradiated with ultrasound with high intensity, it may be rupture to form bubbles or cavities. This phenomenon is called acoustic cavitation which is accompanied by generating extreme local temperature (〜 5000 K) and pressure (〜 500 atm) on a sub-microsecond time scale. However, the cavitation generated by power ultrasound is very complex physical and chemical phenomenon. In this study, an alternative method was applied to investigate the cavitation phenomena using an ultramicroelectrode as an acoustic probe. It was demonstrated that that ultramicroelectrodes are essentially suited for the investigation of cavitation events at the solid/liquid interface because they are small enough on comparing with the cavitational bubbles. Hence, the lifetime of the cavitation, the activities of individual cavitational bubbles and their distribution in the vicinity of the electrode can be determined directly. Moreover, as the currents measured at ultramicroelectrodes are so small that the signals at noise level are easily recorded, and thus, might be used as a probe for the acoustic noise analysis. Microelectrodes are also ideally used for the fast sweep voltammetry because their inherently low capacitive current and low iR drop. They are facilitated for in situ monitoring the chemical reaction in ultrasonic field, and give a great deal of experimental flexibility in sonochemical methodology.

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Ultrasound is applied to recover valuable polyphenols, catechins from tea leaves that are used for producing tea beverages. More than 60% of catechins are remaining in leaves after the first infusion and the leaves can be a good cheap source of valuable compounds. The present study is focused on developing an effective method to recover catechins from tea leaves. An ultrasonic transducer is attached to bottom of a cylindrical vessel, and ultrasound of 404kHz is irradiated to a mixture of tea leaves and deionized water. For extraction of catechins, applying ultrasound enhances both its extraction ratio and rate. Since the liquid temperature increases during ultrasound irradiation, an experiment under simple heating is also carried out as control tests. Ultrasound irradiation gives much larger extraction ratio of catechins than simple heating. The extraction ratio and rate also depend on the power of ultrasound. Powerful ultrasound yields better extraction of catechins. Interestingly, for extraction of caffeine, no effect of ultrasonic power is observed. Since caffeine is undesirable species to extract for pharmaceutical compounds production, suppression of caffeine extraction is preferred. Time course of caffeine concentration suggests that the extraction slows down after 15 minutes operation. For catechins, the concentrations are kept increasing with increasing time. Since selective extraction is attained for catechins against caffeine, ultrasound irradiation is a promising method to recover valuable ingredients from tea leaves.

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We have investigated the inactivation of Saccharomyces cerevisiae and Cryptosporidium parvum by ultrasonic irradiation. Cryptosporidium parvum is one of the most serious poisonous protozoa that causes the waterborne disease and has high resistance to chlorine because of the hard oosyst. After ultrasonic irradiation, the viability of Saccharomyces cerevisiae was observed by the colony counting technique, and that of Cryptosporidium parvum was evaluated by the infectivity test using mice. In this study, the flow ultrasonic reactor with several frequencies (23.7, 44.6, 98.7, 144, 168 kHz) was used for the irradiation of ultrasound. The influence of the height of the reflector on the formation of OH radical and the inactivation of yeast cells was investigated at each frequency in batch system. The sonolytic inactivation of Cryptosporidium parvum was carried out with batch and flow systems at a sound frequency of 23.7 kHz. The addition of NaClO (1 ppm) to the suspension on the infectivity test was found to be effective, suggesting the oosyst might be damaged by the shock wave induced from the cavitation.

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Research into the use of ultrasound in environmental protection has received much attention with the investigations focusing on harnessing of cavitational effects for the destruction of biological and chemical pollutants in water. On the other hand, sonochemical synthesis has been applied for producing a wide variety of noble materials from aqueous solutions. In both applications, there are often encountered cases where the presence of particulate matters could play an important role. In this paper, the sonochemical degradation of methyl orange in suspensions of alumina powders was investigated (Fig.1). The system was selected as a model to understand the influence of particles on the chemical effects of ultrasounds in aqueous solution. The results showed that the addition of 0.5 - 5g/L of coarse alumina powders enhanced the rate of sonochemical degradation of methyl orange up to 50% (Fig.2). The enhancement was not obvious in suspensions of finer alumina powders having average diameters of a few micrometers. The addition of large amount of alumina powders exceeding 5g/L suppressed the degradation reaction due to the shielding and scattering of ultrasound radiation by the particles. The mechanism of the enhancement of sonochemical reaction in the suspension is not clear at this stage, but the possible explanations are as follows; i) increase in the number of cavitational bubbles at the rough surface of suspended particles, ii) mechanochemical activation of the particle surface by the frequent collisions between the particles, and iii) increase of effective reaction volume by the redistribution of ultrasonic radiation field by random movement of particles.

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Irradiation by high power ultrasound in a liquid leads to the formation of cavitation bubbles. It has been proposed that three different reaction site in the cavitation bubbles, i.e., the inside of the cavitation bubbles, the gas-liquid interfacial region of the cavitation bubbles, and the bulk solution are present during the ultrasonic irradiation. The surfactant was accumulated in a relatively high ratio in the interfacial region. The destruction of surfactants occurred by reaction with the hydroxyl radical and also by pyrolysis at high temperature. In this study, we have investigated the influence of pH in solution and the frequency on the sonolysis of surfactants.

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The decomposition performance of p-chlorophenol in aqueous solution by combination of ultrasound and ultraviolet light was examined. The decomposition of p-chlorophenol in aqueous solution was the pseudo-1st-order reaction. The decomposition rate constant increased with increasing ultrasonic intensity and became lower as the initial concentration increased. The p-chlorophenol in aqueous solution was decomposed by OH radicals and photolysis. The synergy effect between ultrasound and ultraviolet light was observed. It is considered that the amount of OH radicals increased due to the photolysis of H_2O_2, which formed from the sonolysis of water. The decomposition of p-chlorophenol was simply modeled and kinetic analysis was performed. The calculated results were agreed with the experimental data.

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To optimize sonochemical reactors and design a more efficient reactor, it is important to know the sonochemical effects under free surface. As a measure of the sonochemical effects, we measured the production yield of I_3^- in aqueous solution of 0.1M KI under sonication. The ultrasonic frequency used here was 132.2 kHz and the experimental temperature was 25 ℃. The surface rise was observed above the transducer on sonication. The concentration of I_3^- under the free surface condition was larger than that obtained by using a reflector. This means that the sonochemical effect for free surface is enhanced. The results are interpreted in terms of the piston effect, which is induced by the fluctuation of surface and aeration. We will discuss the influence of the flow rate on the sonochemical effect under free surface condition for a continuous flow ultrasonic reactor.

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The effect of liquid property on the concentration by ultrasonic atomization is examined. The concentration by ultrasonic atomization is simply modeled and the surface excess content under ultrasound irradiation is estimated. A cylindrical and transparent vessel (100 mm in diameter and 500 mm in height) was used. The carrier gas was air and flowed thorough the vessel to accompany droplets atomized. The samples to be atomized were Methanol, Ethanol and n - Propanol aqueous solutions. The initial content in liquid was changed. After the ultrasound irradiation, the liquid volume and the content in residual liquid were measured. For accompanied liquid, the flow rate and content were calculated from the material balance. The flow rate of accompanied liquid becomes lower as the liquid viscosity becomes higher. This is because the attenuation of ultrasonic energy increases with increasing liquid viscosity. The content in accompanied liquid is higher than that in liquid. At the same content in liquid, the content in accompanied liquid increases with increasing length of hydrophobic group. In the model of mechanism of concentration by ultrasonic atomization, it is assumed that the droplet has the alcohol film around its surface and that the content in film corresponds to the surface excess content (alcohol mole per surface area). The surface excess content is estimated from the content in accompanied liquid, content in liquid and droplet size. As the content in liquid becomes higher, the surface excess content increases. At the same content in liquid, the surface excess content is scarcely affected by the alcohol kind.

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The effects of acoustic cavitation on in vitro gene transfer by ultrasound were investigated. HeLa cells were exposed to 1 MHz continuous waves in culture medium containing the luciferase gene. Transfection efficiency was elevated when an echo contrast agent, Levovist was added or air was dissolved in the medium. When cells were sonicated in medium saturated with Ar, N_2, or N_2O which have different γ values (Cp/Cv), or were saturated with He, Ar, or Ne with different thermal conductivties, the effectiveness for the dissolved gases in the ultrasound mediated gene transfer was Ar > N_2 > N_2O or Ar > Ne > He, respectively. When free radical formation in water by ultrasound was monitored as a measure of inertial cavitation, it was similarly affected by dissolved gases. In addition, effects of hyperthermia and a local anesthetics, lidocaine, which increase the plasma membrane fluidity, on ultrasound mediated gene transfer in PC-3 cells were studied. Although both enhanced ultrasound mediated gene transfer, the enhancement of inertial cavitation was observed only under hyperthermic conditions. These results indicate that the efficiency of ultrasound mediated gene transfer was significantly affected either by occurrence of or by modification of inertial cavitation due to various gasses. These results also suggest that the membrane fluidity plays an important role in ultrasound mediated gene transfer.

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A method to observe sonoluminescing single-bubble motion has been studied experimentally. The measurement of the bubble size is performed using a light scattering method, but it is rather troublesome to arrange the optical axis precisely. This paper describes a method for the simultaneous observation of bubble shape and measurement of the bubble radius by the light scattering method. This optical system consists of a beam splitter inserted between a lens and the CCD camera, and a photomultiplier tube (PMT) is mounted at the beam splitter. Then, the optical sensing system is positioned easily by monitoring the bubble image. Moreover, when an optical filter is appended, it is possible to capture the bubble image even with the scattered laser light. The bubble radius is measured by light scattering at the interval of the successive flash lights. It is confirmed that this system is useful for the simultaneous observation of the bubble size, shape and its translational motion.

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Inside collapsing bubbles in liquid water irradiated by ultrasound, water vapor is dissociated because the bubble temperature increases dramatically. As a result, OH radicals are created inside bubbles and dispersed in the liquid. As OH radicals are strong oxidant, solutes are easily oxidized. On the other hand, volatile solutes enter bubbles and many kinds of chemical reactions take place inside collapsing bubbles. For the industrial application of sonochemistry, a detailed understanding of cavitation bubbles is required. In the present study, computer simulations of bubble oscillations are performed in order to study a life of cavitation bubbles. According to the present computer simulations, bubbles are classified into five categories by their ambient radii. They are dissolving bubbles, stable sonoluminescing bubbles, unstable sonoluminescing bubbles, unstable bubbles, and "degas" bubbles. The range of the ambient radius for each category depends on the frequency and amplitude of ultrasound. A bubble emits light immediately after its appearance when the ambient radius is in a certain range, while the previous theory predicts that a bubble emits light only when it grows to the resonance size by rectified diffusion. Now we discuss the previous classification of bubbles; transient cavitation bubbles and stable cavitation bubbles. As is understood from the terminology, a "transient cavitation bubble" exsists only a few acoustic cycles or less. It expands to many times of its ambient size and collapses violently, often disintegrating into a mass of smaller bubbles. They are filled mainly with vapor. A "stable cavitation bubble" exists for a long period of time. It repeats expansion and collapse many times. They contain mainly a permanent gas. According to the present study, the previous classification of bubbles covers only a fraction of bubbles. "Transient cavitation bubbles" correspond to the unstable SL bubbles at high acoustic amplitude at low ultrasonic frequency in the present classification. "Stable cavitation bubbles" correspond to the stable SL bubbles.

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Cans filled with beverages are generally sterilized by heating. In order to reduce damages to the content caused by the heat sterilization, experimental studies were performed to lighten the heat-sterilizing conditions by ultrasonic irradiation. In the study, effects of the ultrasonic irradiating condition, subject bacterial strain, and experimental temperature were studied, and the effect on heat-resistant bacteria was also studied. The sterilizing effect against mesophilic bacteria by ultrasonic frequency was more significant in the order of 500kHz > 45kHz > 130kHz > 90kHz. Also, it was found that the sterilizing effect is not found against heat-resistant bacteria. In order to obtain the effect of ultrasonic irradiation, water is required as a medium. Also, lower frequencies are desirable with respect to the better sound transmission. Therefore, in view of the present sterilizing facilities, the conversion of hot-shower type sterilizer to hot-bath type and addition of vibration equipment to heat exchanger in the treatment of compounded liquid are considered appropriate. Further, this method was found to be not applicable to the pressurized sterilizer of over 100℃ temperatures because it is not effective against heat-resistant bacteria.

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Cavitation derived from ultrasonic irradiation of a liquid is recently defined as an unusual and unique reaction site, attributing to a transient and small cavitation bubbles with extremely high temperature and high pressure. Reaction-pathways proceeded by the cavitation are, therefore, often different from those of the conventional thermal- and photochemical reactions. During the last decade, the application of the cavitation to an environmental preservation is one of the most important subjects. In the present study, we have performed the sonochemical decolorization and decomposition of low concentrations of azo dyes, such as C. I. Reactive Red 22 and methyl orange. It was confirmed that the color of dye solution smoothly faded by the irradiation, particularly at the experiment of lower initial concentration of dye. The rates of decomposition were also dependent on the irradiated atmosphere and pH of the solutions. A new kinetics model for the sonochemical decomposition of azo dye is proposed on the basis of a heterogeneous reaction model taking into account the local high concentration of OH radicals at the interface of cavitation bubbles.

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The aim of this study is the construction of photosynthesis-like system using sono-catalytical reaction. I consider that there are two steps of overall process of photosynthesis, those are oxygen generation from water for photo system II (PS II) and reduction of carbon dioxide for photo system I (PS I). As experiment, sono-catalytic reactions of water were performed under carbon dioxide-argon (CO_2-Ar) atmosphere using iron ammonium sulfate (iron alum, FeNH_4(SO_4)_2) homogeneous catalyst. As results, both reduction of carbon dioxide and production of oxygen were accomplished. The reactions in this system proceed through a two-step reaction, as follows. Step 1: Sono-catalytic process 2H_2O → 2H_2 + O_2 Step 2: Chemical process CO_2 + H_2 (from former equation) → CO + H_2O Step 1 and 2 are similar to PS II and PS I, respectively. Direct reduction of CO_2, however, is thought to be possible, as follows. 2CO_2 → 2CO + O_2 The possibility of construction of photosynthesis-like system should be discussed. Research in this area still continues to be conducted and efforts are being made to synthesize organic compounds.

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Heterogeneous photocatalysis over TiO_2 or ultrasonic irradiation have been reported to be a promising application for decomposition of the hazardous chemical substances. We observed the generation of ・OH in the aqueous solution during the irradiation of ultrasound on TiO_2. The purpose of this study was to verify the generation of ・OH by indicating (1) decomposition of methylene blue, (2) nucleophilic addition of ・OH to salicylic acid, which produce dihydroxybenzoic acid. The decomposition of bisphenol A (BPA) and pentachlorophenol (PCP) by the irradiation of ultrasound in presence of TiO_2 were further studied. The results are summarized as follows. Decomposition of methylene blue Experimentally it was observed that although the Al_2O_3 had no effect on the decomposition of methylene blue by ultrasonic irradiation, it was decomposed slightly by the presence of TiO_2. In addition H_2O_2 accelerated the decomposition of methylene blue for the TiO_2 containing system. But the addition of H_2O_2 had no effect on the methylene blue decomposition when the system containing Al_2O_3 only. The effect of radical scavengers on the decomposition of methylene blue was also investigated for the system with TiO_2. It was found that the scavengers such as methanol, DMSO, mannitol reduced the decomposition. Among them DMSO was the most significant. Effect of TiO_2 on the nucleophilic addition of ・OH to salicylic acid Ultrasonification of 10 μM salicylic acid (2 ml) was carried out in absence and presence of 0.4 g TiO_2 for exactly 10 minutes, and produced dihydroxybenzoic acid (DHBA) was measured by HPLC/ECD. In presence of TiO_2, significant amount of DHBA (34 pg/20μl) was produced, but almost no DHBA (2.2 pg/20μl) was found to produce without TiO_2. The effect of scavengers on the generation of DHBA was the same as it was observed in the case of methylene blue decomposition. This result inferred that the ultrasonic irradiation generated the ・OH, which is responsible for the hydroxylation of salicylic acid. Decomposition of BPA and PCP Ultrasonification of BPA and PCP, a representative endocrine disruptors, were carried out in the presence of TiO_2 (0.4 g) and the change in the concentration of BPA and PCP were measured by HPLC/ECD. The initial concentration of BPA (1 ppm) was gradually decreased with the irradiation time and was totally decomposed by 15 minute irradiation of ultrasound. The similar results were observed for PCP. It was concluded that the irradiation of ultrasound on TiO_2 in aqueous solution significantly generate hydroxyl radicals which is responsible for the decomposition of the endocrine disruptors such as BPA and PCP.

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It is very important to know the effective ultrasonic intensity in a reaction vessel to compare and reproduce the reported results carried out by the different laboratories. Last year, Japan Society of Sonochemistry has organized a working group for standardization of ultrasonic power for sonochemistry and examined the standardized method to calibrate for the sonochemical efficiency. In this paper, we report on the results of Fricke reaction, KI oxidation and decomposition of porphyrin derivatives by use of seven types of sonochemical apparatus in four different laboratories in the frequency range of 19.5kHz to 1.2 MHz. We found that there is the frequency dependence of the production yields of I_3^- and Fe^<3+> and the sonochemical efficiency of Fricke reaction and KI oxidation which was defined as the number of reacted molecule per unit ultrasonic energy. From these results, we propose the KI oxidation dosimetry using 0.1 mol・dm^<-3> KI solution as a standard method to calibrate the sonochemical efficiency of an individual reaction system.

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Recently, it will become to be an important theme to apply the sonodynamic therapy (SDT) for cancer treatment. We have applied the ceramic particles (Al_2O_3, SiO_2, TiO_2) as the catalyst for the SDT to search the best catalyst and to investigate the mechanism of sono-catalytic action. As the basic study, 0.1 M KI aqueous solution saturated with air for more than 30 min was used for analysis of OH radicals (OH^- + I^- → OH^- + I) in the sono-catalytic reaction under sonication (42 kHz, 70 W for 1 min) inside the centering grass tube (Iwaki Grass Ltd., 1 ml solution, 13 x 100 mm) in the bath (Branson Inc. Ltd., 1610J-MT type). The absorption of irradiated sample solution was analyzed at 355 nm (against I_3^-; ε = 26,303) by an absorption spectrophotometer (JASCO Ltd., Co.) with 10 min after irradiation. In the results, It was found those as follows: (1) The reaction rate constant was 76 nM/sec for the generation of I_3^- in the reaction of 2I + I^- → I_3^-. (2) The optimal size (Φ) of Al_2O_3 particles (170 mg/ml) was 20 μm for the catalytic reaction of SDT, which enhanced 63 % against the control KI solution without the particles. The optimal weight of the 20 μm Al_2O_3 particles was 40 mg/ml, which enhanced 75 % against the control. (3) In the case of TiO_2 particles, the concentration of I_3^- was enhanced 3 times and the Fe in TiO_2 particles enhanced 4 times against the control. From these results, it was considered that the nano-size particles treated with Fe ions more enhanced the catalytic reaction of SDT because the Fenton reaction was included.

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The possibility of double excitation of ultrasound and UV light is examined in a homogeneous reaction system, without the intervention of such physical effects as cleaning of the solid surface. We had already reported that simultaneous irradiation of ultrasound accelerated the rate of the photochemical disappearance of 4,4'-dihalogenated benzils depending on their substituents. In this work, photochemical reaction of iso-propanol was studied using low-pressure mercury lamp (Fig.1). When UV light and ultrasound were simultaneously irradiated into iso-propanol, the rate of photochemical production of pinacol were accelerated as shown in Fig.2. Since pinacol is known to be produced by dimerization of the radical, (CH_3)_2(OH)C・, the acceleration is ascribed to the increase of collision frequency between the radicals. Ultrasonic irradiation might enhance the collision frequency through the acceleration of mass transportation. This result suggests that simultaneous irradiation of ultrasound can substantially affect the other types of bimolecular photochemical reactions.

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Previous studies have shown that if a solution for cell suspension is saturated with CO_2, ultrasound-induced in vitro cell killing and free radical production are inhibited. However, the dose dependency of this observation has not been explored. Here, we used NaHCO_3 and HCl to produce a predictable concentration of CO_2 within the culture medium. Using 1 MHz continuous wave 4 W/cm^2 ultrasound, we sonicated U937 cells suspension for 1 min at 37℃ with CO_2 at different concentrations. At 2 mM, reduced cell killing was observed that further decreased with increasing CO_2 concentration until 100% protection was attained at 20 mM. Ultrasound-induced free radical production was significantly decreased at 1 mM and became undetectable at 2 mM CO_2. This finding shows that CO_2-mediated inhibition is concentration dependent and that the threshold for free radical production is one order of magnitude higher than the threshold for cell killing induced by ultrasound. In addition, it also cautions researchers when adding acids and acid-based agents to a culture medium, which almost always contains NaHCO_3, in experiments related to the chemical bioeffects of ultrasound.

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