We theoretically and experimentally study the dynamics of spherical gas bubbles in a viscoelastic material under ultrasound irradiation. First, we formulate a Rayleigh-Plesset-type nonlinear equation that describes the dynamics of spherical gas bubbles in the Voigt solid (with linear viscoelasticity). The model equation is linearized to derive the analytical solution for the case of small-amplitude oscillations. Then, we propose an experimental technique to observe ultrasound-forced dynamics of micron-sized gas bubbles in a gelatin gel. To trigger gas bubble nucleation, an infrared laser pulse is focused into gels of 3 wt % gelatin concentration that are supersaturated with ambient air. The nucleated gas bubble grows through the incoming mass flux of air dissolved beyond Henry’s limit, allowing us to control the radius of bubbles under mechanical equilibrium (with ultrasound irradiation turned off). Low-intensity ultrasound at 28 kHz is irradiated toward the gas bubble, while the equilibrium bubble radius is tuned through the gradual mass transfer. The linearized bubble dynamics are recorded by a high-speed camera; the observed dynamics are compared to the linearized Rayleigh-Plesset solutions. Through the comparisons, we calculate viscosity and rigidity of the gel at the given frequency.

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To confirm the O2- production in the ultrasonic fields, O2- was detected by a spectrofluorometric method using 2-(2-pyridyl)benzothiazoline as the fluorescent probe. The probe can selectively react with O2- by deleting hydrogen to yield 2-(2-pyridyl)benzothiazole (Scheme 1), which exhibits strong fluorescence at 528 nm. It is shown that the fluorescence (FL) spectra of 10 mM 2-(2-pyridyl)benzothiazoline obtained by sonication of the O2-saturated solution containing 1.0 mM of tri-n-ethylamine (TEA). Before ultrasound irradiation, 2-(2-pyridyl)benzothiazoline itself exhibited no fluorescence. The FL intensity at 528 nm increased with increasing ultrasonic irradiation time, which demonstrated that O2- was gradually produced in the solution. We suggest that TEA molecule in the interfacial region of a cavitation bubble reacts with a hydroxyl radical (•OH) to produce a TEA•+ which is deprotonated immediately in water to form TPA radical (TPA•), a strong reducing species. The TPA• can subsequently react with dissolved oxygen to generate O2-

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Influence of microbubbles on the free radical formation by the ultrasonic cavitation have been investigated using KI method as well as coumarin fluorescence probe methods. It was found that microbubbles enhanced the amount of OH radicals when the 45 kHz ultrasound were irradiated to the solution, on the other hand, the amount of OH radicals was reduced by the introduction of microbubbles when the 28 kHz or 100 kHz ultrasound were irradiated to the solution. Influence of microbubbles on the degradation rate of the organic dyes have been investigated by measuring the absorbance of dyes after the irradiation of ultrasound. Similar to the case of KI method as well as coumarin fluorescence probe methods, degradation rate was enhanced only when the 45 kHz ultrasound was irradiated to the microbubble solution. The pH of the dye solution was changed from pH=3 to 10, but similarly degradation rate was fastest when the 45 kHz ultrasound was irradiated to the dye solution with microbbules.

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The effect of types of alcohol, concentrations of alcohol, solution temperature, types of dissolved gases on the rate of Au(III) reduction and amount of gas products were investigated. At 1.0 mM alcohol concentration, a good relationship was observed between the rate of Au(III) reduction and log P_ow of alcohol used. By analyzing the amount of H₂O₂ formed in the presence and absence of alcohol, it was confirmed that alcohol molecules were accumulated at the interface region of bubbles. To discuss the effect of alcohol vapor pressure and amount of Ar gas in the solution, 1-hexanol was used as an alcohol additive at different solution temperature. The rate of Au(III) reduction and the amounts of the pyrolysis products were related to the amount of Ar gas in the solution. It was suggested that the number of bubbles reached high temperature was related to the amount of gas in the solution. We also investigated the effect of types of rare gases. The rate of Au(III) reduction, the amount of the formed H₂O₂, and the amount of the pyrolysis products were also reasonably related to the amount of rare gas in water. Furthermore, it was found that the chemical effects of each bubble would be different among the types of rare gas.

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This study introduces results of experiments concerning the effects of sonotrode tip shape on cavitation intensity and acoustic streaming in a water bath irradiated with high-intensity ultrasound.Sonotorode with plane, trapezium and cone tips, were used to conduct three kinds of experiments : 1 - PIV investigation of acoustic streaming underneath the sonotrode tip, 2 - measurements of cavitation efficiency using the Weissler reaction, 3 - measurements of perfect mixing time of a sonificated water bath. The sonotrode tip diameter was 48 mm, the vibration amplitude varied from 10 to 70 micro m (p-p). The results revealed that the acoustic streaming pattern is depended on the tip shape, being varied from a jet-like downward streaming for the plane tip to a distributed and relatively slow cone tip. Although the acoustic streaming velocity was varied with distance from the tip, the averaged values for cone tip was more than twice less than that for the plane tip at a constant vibration amplitude. These data were also confirmed by the perfect mixing time measurements. In contrary, cavitation efficiency was twice better for the cone tip as compared to the for the plane tip. Thus, the results indicate that controlling the flow pattern of acoustic streaming by changing the sonotrode tip shape is able to improve cavitation efficiency and lead to a better treatment performance in ultrasonic-assisted processes.

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Advanced oxidation process (AOP) is very effective technique for degradation and mineralization of organic pollutants. On the other hand, ultrasonic atomization is a very useful technique to produce ultrasonic mist which consists of submicron-scale droplets. Using these techniques, volatile organic compound (VOC) gas was decomposed on the mist surface by OH radicals generated by AOPs, and water-soluble decomposition intermediates were rapidly captured into the mist. As a result, the removal rate of toluene under UV/H₂O₂/mist condition was faster than that under UV/H₂O₂ condition. This result indicated that toluene gas could easily react with OH radicals on the mist surface using ultrasonic atomization because gas-liquid interfaces increased by the mist generation. Furthermore, we tried degradation experiments of toluene gas under conditions with ozone addition. Ozone also reacts with H₂O₂ to generate OH radicals (peroxone reaction) on the mist surface, and toluene gas was effectively decomposed there by OH radicals. Since this reaction process strongly affected the improvement of toluene gas removal and mineralization, it can be a useful air purification technique.

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Ultrasound (US) stimulated drug release was examined by using chitin hydrogel matrix loaded with gallic acid (GA), which was used as the drug for wound healing and anticancer agents. The GA-chitin hydrogels were prepared from chitin-dimethylacetamide (DMAc)/lithium chloride (LiCl) solution in the presence of GA by phase inversion method, when the solution was exposed to water vapor for 24 h. The GA release from the GA-chitin hydrogel was researched under different US powers of 0-30 W at 43 kHz. The effect of chitin concentrations (0.1, 0.5 and 1 wt%) on the release behavior was also studied under 43 kHz US exposure at 30 W, respectively. It was noted that the US accelerated release efficiencies for all the samples. Besides, the release efficiency increased as increasing of the US power and the decreasing of chitin concentration in the hydrogel matrix. The release rate of 0.73 μg/mL·min was obtained from the 0.54 mg/cm³ of GA loading hydrogel, which was fabricated from 0.1 wt% chitin mixture solution, when 43 kHz US exposure at 30 W was exposed. This efficiency was 9.1 times higher than the sample without US exposure.

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Polymer nanoparticles have received much attention because of their wide range of applications such as inks, cosmetics and so on. In this work, we have successfully synthesized size-controlled polymer nanoparticles by using the acoustic emulsification method. This synthetic method involves sequential ultrasonic irradiation (20 kHz → 500 kHz → 1.6 MHz → 2.4 MHz) for acoustic emulsification of a water-insoluble monomer(MMA) in an aqueous medium, followed by emulsion polymerization in the obtained solution without using any surfactants. We have also investigated the effect of experimental parameters for tandem acoustic emulsification on MMA droplets size in more detail. In addition, other monomers were used to check the versatility of this technique.

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LiFePO₄ has attracted attention as a promising cathode material for lithium ion battery, because it consists of iron which exists abundantly. However, its low electronic conductivity was a problem to use as a commercial product. The deposition of conductive carbon on the surface of LiFePO₄ (LiFePO₄/C) is the main method to improve the electronic conductivity of it. Furthermore, gold, which has higher electronic conductivity than carbon, has been studied to attach the surface of LFP to increase the electronic conductivity. However, direct attachment of Au on LFP surface leads to low battery performance because gold disturbed Li+ insertion/deinsertion. Therefore, we synthesized Au or Pd nanoparticles on LiFePO₄/C. 0.1mM Au[III] solution and 0.5 mM Pd[II] solution were irradiated with LiFePO₄/C by 200 kHz-ultrasound for 20 minutes in Ar atmosphere. 2-propanol was added into the solution before the ultrasound irradiation. As a result, the size of Au nanoparticles was ‹ 10 nm and Pd nanoparticles were agglomerated (the size of secondary particles was 20-30 nm). Especially, Au nanoparticles existed in the carbon layer. LiFePO4/C·Au and LiFePO₄/C·Pd showed good battery performances at high current density (10 C).

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In this study, the viscoelasticity of PVA/[BMI]Cl composites in the absence and presence of US was tested using a rheometer equipped with an ultrasonic system. PVA/[BMI]Cl composites were prepared by mixing PVAs with different molecular weights and [BMI]Cl synthesized from 1-methylimidazole and 1-chlorobutane. A constant frequency of 1Hz and a constant strain of 1% were applied in this experiment for the viscoelasticy. The samples of the PVA/[BMI]Cl composite were exposed to 43kHz of US with a power of 12.5W at 25℃ for 5min, and then US was stopped. By irradiating the US, storage moduli G′ and loss moduli G″ decreased in the whole composites. Moreover, the values of G′ and G″ were returned to the original value after US stopped. This behavior was seen in the second and third cycles. The value of tan δ = G″/G′ refracted the gelatinous property of the material and increased under US exposure. The increase in the value of tan δ indicated that these four composites behaved much more like liquid under US.

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Ultrasound/ HAp/ Contamination/ ICP/ Specific surface area Abstract: It is known that the outbreak of cavitation gives horn damage. This study reports effects of horn materials (titanium alloy, SiC, alumina) on contamination into product (hydroxyapatite, HAp). HAp was synthesized by Ca(OH)₂-H₃PO₄-H₂O system with horn type ultrasound apparatuses. The frequency of ultrasound apparatuses was 20 kHz at horn of titanium alloy and was 24 kHz at horn of ceramics. In initial this reaction, amorphous calcium phosphate (ACP) was formed, and then ACP was crystallized sequentially to HAp. The HAp with specific surface area of 290 m² ·g^-1 formed by irradiating ultrasound. The specific surface area of HAp decreased by prolonging reaction time. The optimum reaction time using horn of ceramics lengthened than that of titanium alloy for 4 min. The HAp obtained using horn of ceramics or titanium alloy were contaminated by Si or Ti and Al, respectively. Namely, the constituent of the horn just eluded in the HAp. The amount of contamination in the HAp was increased with extension of irradiating time. Furthermore, the amount of contamination was slightly enhanced with the increase of the amplitude.

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Emulsions composed of oil and water are typically stabilized by emulsifiers (e.g., surfactants and amphiphilic polymers) because oil and water are immiscible with each other. However, since the emulsions are thermodynamically unstable even upon the utilization of emulsifiers, the colloidal stabilization of emulsions remains a challenging task. To this end, we have investigated the colloidal stability of oil-in-water (O/W) emulsions in the absence of any emulsifiers such as surfactants and amphiphilic polymers (named as emulsifier-free or surfactant-free O/W emulsions) in order to evaluate the essential features of colloidal stabilization of O/W emulsions. Recently, we found that the paraffin-in-water emulsion was destabilized with the addition of L-menthol to paraffin. Then, we applied the polar oils for stabilization the L-menthol-containing paraffin-in-water emulsions because the polar oils are expected to homogenize L-menthol in paraffin droplets by the hydrogen bonding between L-menthol and polar oil. Indeed, L-menthol-containing paraffin-in-water emulsions were stabilized with the addition of polar oil to paraffin.

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To better understand the molecular mechanism underlying cellular responses to low-intensity pulsed ultrasound (LIPUS), we investigated gene expression profiles in mouse MC3T3-E1 preosteoblastic cells exposed to LIPUS using DNA microarray and bioinformatics analysis tools. Although treatment of the cells with a single 20-min LIPUS (1.5 MHz, 30 mW/cm2; SAFHS 4000J; Teijin Pharma, Ltd.) did not affect the cell growth or alkaline phosphatase activity (an osteoblast differentiation marker), the treatment significantly increased the mRNA level of BGLAP, an osteoblast differentiation marker protein. Microarray analysis demonstrated that 38 genes were up-regulated and 37 genes were down-regulated by 1.5-fold or more in the cells treated with LIPUS. Gene network analysis also demonstrated that the gene network U contained many up-regulated genes that were mainly associated with bone morphology in the category of biological functions of skeletal and muscular system development and function. The biological function of the gene network D, which contained down-regulated genes, was associated with gene expression, the cell cycle, and connective tissue development and function. These findings will provide a basis for understanding the detailed molecular mechanisms of the LIPUS response in osteoblasts.

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«Purpose» To develop a novel bubble formulation for ultrasound (US) imaging and therapy with small particle size and a good stability and test the formulation as US imaging contrast agent and for gene delivery in vitro and in vivo.
«Methods» Lipid-stabilized bubbles were prepared by homogenization of a lipid dispersion in the presence of perfluoropropane gas. After bubble formation the bubbles were freeze-dried so that a dry sample containing bubbles was formed. After re-constitution of the samples they were analyzed for size, gas content and US signal intensity. The bubbles were also evaluated as contrast agents in vivo, and for US activated gene delivery of luciferase pDNA in vitro on cell culture and in vivo in mice.
«Results and Discussion» Bubbles were in the size range 800-1100 nm and could be re-constituted by simple addition of water to the dry sample. In vivo imaging of B16BL6 tumours in mice, using the most stable bubbles showed circulation times longer than for the commercial bubble Sonazoid®. Also, the bubbles were well suited for visualization of tumour neovasculature. Bubbles together with pDNA and US exposure increased the luciferase activity by about 300 times in vitro and 2000 times in vivo, compared to only pDNA+US. We believe this new formulation shows great promise for both diagnostic and therapeutic applications thanks to its good stability, relatively small bubble size and the simplicity of handling.

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Poly (N-Isopropylacrylamide-co-2-hydroxyethyl methacrylate) (P(NIPAM-co-HEMA)) was synthesized using ultrasonic irradiation in a mixed solvent of water and ethanol without chemical initiator. The effects of monomer molar ratio and ultrasonic intensity on time courses of molar fraction of NIPAM and responsive temperature of synthesized polymers were investigated. In the early stage of the reaction, NIPAM fraction of copolymer was low, that is, the polymerization rate of HEMA is high. This is because the radical stability of HEMA is higher than that of NIPAM. The relationship between conversion and molar fraction of NIPAM did not depend on the ultrasound intensity. The lower the ratio of NIPAM, the lower the critical value (LCST) because HEMA is more hydrophobic than NIPAM. The higher polymerization rate resulted in the higher LCST. Those results suggested that the composition and responsive temperature of the copolymer can be controlled by changing the irradiation time and the ultrasound intensity.

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Sonochemical reaction in water with 10 mM tert-butanol as radical scavenger was investigated at various irradiation time. Sonochemical reaction was estimated from degradation rate of methylene blue in water. All experiments were carried out under the same acoustic power of 10 W measured by calorimetry at the ultrasonic frequency of 410 kHz. The degradation rates of methylene blue decreased with increasing irradiation time. In addition, multi-bubble sonoluminescence spectra from air-saturated water with 10 mM tert-butanol were measured in the range of 257-540 nm. The sonoluminescence intensity decreased with increasing irradiation time. The shape of the continuum of sonoluminescence spectra changed with increasing irradiation time. Some studies have reported that the sonolysis of alcohols yielded CO2 and other degradation products. The others reported that the sonochemical reaction and sonoluminescence in CO2-aerated solution were significantly suppressed as compared with air-aerated solution at high frequency ultrasound irradiation. In this study, the lower sonoluminescence intensities from water and the less sonochemical reactions in methylene blue solution were attributed to degradation products of tert-butanol.

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Recently, it has been reported that photocatalytic reaction drived using ultrasonic (US) irradiation even under dark condition, and this reaction has been known as sonocatalytic reaction. However, its reaction mechanism has not become clear in detail. In this study, we evaluated the removal ratio of organic compounds in water phase based on sonocatalytic activity with 50 kHz US irradiation under dark condition. In order to clarify the influences of TiO₂ crystal structure, physical properties of target compounds, and H₂O₂ addition on the removal ratio, three crystal types of TiO₂ and two different aldehydes, such as benzaldehyde (C₆H₅CHO) and formaldehyde (HCHO), were used for the degradation experiments. In case of TiO₂ (P25) suspension with US irradiation under dark condition (US/P25), removal ratios of both aldehydes increased 10 % approximately. On the other hand, the effects of crystal structure and particle size of TiO₂ were evaluated by comparing US/P25 with US/ST21 and US/ST21 with US/ST01, respectively. When smaller size TiO₂ particles including rutile type structure (P25) were used, the removal ratio of C₆H₅CHO improved slightly whereas the removal ratio of HCHO did not change in contrast. It was estimated that sonocatalytic reaction can be occurred in hydrophobic field near the cavitation bubble. Furthermore, it has been reported that OH radicals formation was influenced by H2O2 addition, and depended on TiO₂ structure. Therefore, we also investigated the effect of H₂O₂ addition on removal ratio by US/P25 and US/ST21. As a result, by H2O2 addition, removal ratio of HCHO was enhanced by US/P25 and reduced by US/ST21. However, removal ratio of C₆H₅CHO was reduced by both US/P25 and US/ST21. The different behavior in H₂O₂ addition means that TiO₂ characteristics contribute to sonocatalyst reaction.

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To investigate generation of ultrasonic cavitation in gel, sodium polyacrylate swollen in potassium iodide solution was used as a sample. After ultrasonic irradiation at 500 kHz, absorbance and viscosity of sample were measured. The absorbance and viscosity changes are originated from oxidation reaction of potassium iodide and decrease in the degree of polymerization of sodium polyacrylate, respectively. The absorbance started to increase after several minutes irradiation. On the other hand, viscosity decreases immediately after irradiation. This is because polymer is degraded due to shear stress of ultrasonic propagation in addition to cavitation. After sample viscosity fully decreased, it is able to generate ultrasonic cavitation and chemical reaction occurs. As sample temperature became lower, the viscosity decreased and the absorbance increased. To use this sample, detection of cavitation generation in gel is possible.

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Ethanol and organic material mixed aqueous solution were atomized using ultrasonic irradiation at 2.4 MHz. Atomized liquid was collected by refrigeration of liquid nitrogen. The concentrations in collected liquid and mist were experimentally investigated. Malic acid, lactic acid (organic acid), 1-propanol, methanol (alcohol), methyl ethyl ketone, diethyl ketone (ketone) were used as organic material. The ethanol concentration in collected liquid was little affected by addition of organic materials. Organic acid in ethanol aqueous solution was not separated. On the other hand, alcohol and ketone concentrations in collected liquid were higher than those in sample. The 1-propanol concentration in collected liquid was lower than that in mist. This is because it is difficult to collect nano-sized droplets which contain highly condensed alcohol.

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We synthesized graphene-Pd nanocomposites in one-pot by ultrasound, radiation and liquid phase plasma. Graphene dispersion containing Pd ions and 2-propanol was irradiated with ultrasound (200 kHz, 200 W) for 30 min and with gamma-ray (̴1 MeV) and electron beam (̴6 MeV). In radiochemical synthesis, the absorbed dose was 10 kGy. In these processes, the reduction of Pd ions and oxidation of graphene occurred simultaneously in one-pot. In the liquid plasma method, Pd nanoparticles generated directly from the electrodes were deposited onto carbonyl modified graphene. Based on the results, the formation mechanism of the nanocomposites was discussed.

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SL intensity varied with the concentration of glycerol, the frequency and power. Compared to pure water, the pulse width becomes larger with increasing the concentration. The increase in the SL pulse width may be associated with a viscous slowing of the bubble wall in the very last stages of the initial collapse. If the compressive heating is still strong enough to result in plasma formation, the lowered wall velocity might allow the plasma to remain intact and hot for a longer period of time than in pure water. For highly viscous solution and only at 28 kHz and 50 kHz, we observed large bubbles of 100-300 μm in diameter. The large bubbles are generated via the coalescence of 8-10 bubbles and keep stable because viscosity tends to stabilize the shape anisotropy of large bubbles. Beside this large cluster bubbles, a number of tiny bubbles were observed, the size of which is smaller than those in pure water. The multiple-peak pulses observed from NaCl solution of 80% glycerol at 28 kHz are caused by the superposition of SL from the large cluster bubbles which radiate Na emission.

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We have been studied about layered double hydroxide (LDH) as an arsenic absorbent. The structural formula of LDH used in this experiment is [Mg_0.67Al_0.33(OH)₂](NO₃)_0.33·mH2O. The layer of LDH is formed by Mg and Al, and the interlayer is formed by nitrate ion. LDH has an ion-exchange capacity, which is able to exchange the nitrate ion to other anions in the solution. Arsenic absorption capacity of LDH relates to the form of arsenic. In normally, absorption amount of As (V) is larger than that of As (III) when LDH is used as absorbent. In previous studies, we considered that As (III) should be oxidized to As (V) before addition of LDH. Thus, ultrasound was used to oxide As (III) to As (V). As a result, 50% of As (III) was oxidized for 2 h. Removal ratio of As (III) using ultrasound and LDH was larger than that using stirring and LDH. In this study, we investigated pH change of the solution and particles size and morphology of LDH irradiated by ultrasound. Ultrasound irradiation generates NO₃^-and NO₂^-, and these generated ions cause an acidity solution (low pH). LDH becomes pH buffer, therefore, we expect LDH to prevent the decrease in pH during ultrasound irradiation. Morphology of LDH is observed using TEM. The morphology of LDH irradiated by ultrasound seems to be changed from the original one.

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The coprecipitation of pentavalent arsenic with trivalent iron compounds such as iron hydroxide and ferric oxide has been used as one of the methods to remove arsenic in aqueous solution. The valence of arsenic in acid mine drainage (AMD) is normally trivalent, As(III). Adsorbent materials, trivalent iron compounds, are able to adsorb As(V). However, adsorption of As(III) is difficult using these trivalent iron materials. Therefore it is necessary to oxidize As(III) to As(V) in sulfuric acid solutions before the treatment using adsorbent materials. Ultrasound oxidation is effective to oxidize As(III) in the sulfuric acid solution. In this study, we performed the oxidation of As(III) in the sulfuric acid solution using ultrasound reaction and electrochemical reaction. We performed As(III) (10ppm) oxidation in sulfuric acid solutions (pH 2) by addition of H2O2 (200 ppm) under following 3 conditions: (1) ultrasound reaction by irradiation at 200 kHz, (2) electrochemical reaction by applied voltage of 1.5 V, (3)combination utilization of ultrasound reaction and electrochemical reaction. Each reaction time was 10 min. As the result, oxidized ratio of As(III) was 1.7 ppm (1), 6.5 ppm (2), 3.0 ppm (3), respectively.

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We investigated the effect of the ultrasound irradiation with CaCl₂ addition on desorption amount of CO₂ from MEA solution at low temperature. The desorption amount of CO₂ as gas is regulated by pH. To overcome the regulation of pH, CaCl₂ was added just before the ultrasound irradiation. As the results, CO₂(g) desorption ratio was improved. CaCl₂ was reacted with HCO₃^－ and pH of the solution decreased.

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In recent years, algae have attracted attention as non-exhaustible resources with the potential to be used as a substitute for nonrenewable fossil fuels. The source of within the algae cells is in the form of lipids. On the other hands, algae cause a significant water pollution. One of the more recent developments in inactivation technology of algae has been the use of ultrasound. A lot of studies to inactivate microorganisms such as algae in water by ultrasonic cavitation have been reported. Yet despite these reports, there remain many unanswered questions about the mechanisms of inactivation of microorganisms in water by ultrasound. In this study, the efficiency of ultrasonic disruption of Chaetoceros gracilis was investigated by applying ultrasonic waves of 0.02, 0.4, 1.0, 2.2, 3.4, and 4.4 MHz to degassed suspensions to confirm the necessity of cavitation bubbles.

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Green tea polyphenols, catechins attract a lot of attention due to the benefits of health improvement. Extraction of these polyphenols has been conducted with hot water, supercritical CO2 and organic solvent. To avoid heat degradation and prevent co-extraction of unwanted chemical species, water is preferred and the use at lower temperature is recommended. Ultrasound assisted extraction has been applied to various compounds contained in plants and the advantage is well proven. We set our target for extracting epigallocatechin gallate, EGCg and we tried to elucidate the difference of extraction behavior with another type of catechin, epicatechin, EC which is one of a free-type catechin. By irradiating 20 kHz, extraction of EGCg and EC was significantly improved. After 30 minutes irradiation, percent extraction reached more than 80 %, which is the double of 40 % reported on hot water extraction. Percent extraction of EC increased faster than EGCg, which suggests that EC dissolution was readily enhanced by ultrasound. The binding strength of EC on leaf tissues is probably weaker than that of EGCg. Otherwise EC locates near the leaf surface while EGCg locates inside of a leaf. The result proved that the ultrasound enabled extracting most of EGCg and EC in 30 minutes under a low temperature in the range of 293-303 K. Depending on the type of catechin, ultrasonic effect worked differently.

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The effects of inorganic salts or irradiation time on the yield of hydrogen peroxide formed in the sonolysis of water and bubble temperature were investigated under argon. It was confirmed that the yield of hydrogen peroxide decreased with increasing NaCl concentration. It was suggested that the number of bubbles reached high temperature was affected by the amount of argon gas in water. The bubble temperature estimated by the kinetic analysis of methyl radical recombination reactions also tended to decrease with increasing NaCl concentration. The behavior of t-butanol molecules during ultrasonic cavitation was suggested to be affected by the presence of NaCl.

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When water under air atmosphere is irradiated with high intensity ultrasound, cavitation is generated, and nitrogen is oxidized to form nitrite and nitrate ions. This is due to that the formation of thousand degrees or more of the high temperature of bubble occurred. In this study, analyses of nitrite and nitrate ions were performed to discuss the chemical effects of bubbles. In addition, the results were compared with the yield of hydrogen peroxide formed in the sonolysis of water. We examined the effects of the ultrasound power and the amount of solution on the formation of nitrite ions, nitrate ions and hydrogen peroxide by ultrasound cavitation. It was confirmed that the optimum volume and ultrasound power existed for the formation of nitrite and nitrate ions and hydrogen peroxide.

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Formaldehyde is released into water from factories and processing facilities, and its emission also occurs into gas phase. Formaldehyde is a very harmful substance, and it is difficult to be decomposed after mixing into water. It has a problem because degradation reaction rate is very slow in the conventional degradation method in water. In this study, we selected the ultrasound as a main degradation technique, and evaluated quantitatively its decomposition ability and combination effects of UV light and ultrasonic atomization under various experimental conditions. In order to investigate the influence of physical properties on the degradation rate, we used two different aldehydes, formaldehyde and benzaldehyde, as model substances. As a result, it was confirmed that benzaldehyde with high hydrophobicity was decomposed more effectively than formaldehyde because it could volatilize into inside or interface of cavities and decomposed there thermally. Also, in the case of combining the UV irradiation and the ultrasonic atomization, even formaldehyde with high hydrophilicity decomposed effectively in gas phase. This means that UV irradiation acts on decomposition of organic pollutants which exist in mists effectively.

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We have observed an extraordinary light emission during multi-bubbles sonoluminescence (MBSL) measurements in He saturated water at 1MHz. The light was orange, and its spectrum showed He line around 700 nm. The ground electrode of the transducer, which was exposed to sample liquid, was damaged by cavitation erosion. The electric field leaked from the transducer affected sonoluminescing bubbles near the ground electrode. In this study, we have experimentally investigated the effect of electric fields externally controlled on MBSL. We applied direct-current (DC) voltage (~250 V) or alternating-current (AC) (250V) voltage which synchronizing with the ultrasound frequency using platinum needle as electrode. MBSL was apparently changed when applying DC voltage. The MBSL intensity increased by applying +250 V compared with that with no voltage was applied.

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Silver Nanowires, Silver Carboxylates, Transparent Conductive Films, Low-Dimension Materials Abstract: Silver nanowires transparent conductive films are expected as a material to replace indium tin oxide films. Silver nanowires are mainly synthesized by the polyol method, which used protective agents to achieve an anisotropic crystal growth. However, protective agents decrease conductivity of the films because they cover the surface of nanowires. In this study, we have conveniently synthesized needle-shaped silver carboxylates by ultrasound irradiation, and then obtained silver nanowires transparent conductive films by spray coating them on substrates and exposing them to gas-phase hydrazine.
Silver carboxylates were synthesized by ultrasound irradiation to mixture that contains silver(I) oxide, acetic acid, propionic acid, and ethanol. These carboxylates were put onto a glass substrate, and then reduced by exposure to hydrazine gas (vaporized hydrazine monohydrate). The obtained samples were characterized by FE-SEM, XRD, TG-DTA, four-probe method, and UV-Vis.
Silver oxide completely reacted and silver carboxylates were produced after 1 h of ultrasound irradiation (22.32-44.13 kHz, 100 W). Raw materials were most homogeneity dispersed and consumed at 44.13 kHz. The study on coating conditions of the precursor, in case of short height of the spray, produced transparent conductive films showed low transmittance and very low resistance. And high transmittance and low resistance were achieved by adjusting the coating time and spray height.

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Ultrasonic atomization, Mist droplet, Ultrasonic frequency, Number concentration, Size distribution Abstract: Ultrasonic atomization is used to produce fine liquid mists with diameter ranges below 100 nm. We investigated the effect of the frequency on the size distribution of ultrasonic mist. A bimodal distribution was obtained for the mist generated by ultrasonic atomization with a wide-range particle spectrometer. The peak diameter decreased with increasing frequency, and the number concentration of the mist increased in the smaller range. We determined the relation between the size distribution of the mist and the ultrasonic frequency, and we proposed a generation mechanism for the ultrasonic nano-sized mist based on the amount of water vapor around the liquid column. Increasing the power intensity and density by changing the surface diameter of the ultrasonic oscillator affected the number concentration and size distribution of the nano-sized mist. Using this technique, the diameter of the mist can be controlled by changing the frequency of the ultrasonic transducer.

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In previous paper, we demonstrated the rate of sono-oxidation of 0.1 M KI increased with the introduction of a small amount of CO₂ and had a peak value. Because H radicals produced from water by sonication are quenched by CO₂ and OH radicals are expected to remain. However, after the maximum value, absorbance decreased with increasing CO₂. As you know, presence of CO₂ in the system is to suppress sonochemical reaction. In this presentation, we discussed rate control factors for sono-oxidation under a CO2-Ar atmosphere. Ultrasonic irradiation was performed using an ultrasonic atomizer (Honda Electric HM-303N, 2.4 MHz, 15W)for 10 min at 25°C. Before sonication, the reactor was filled with argon gas and certain amount of CO₂ was injected. The rate of sono-oxidation was evaluated by potassium iodide (0.01 M KI) dosimetry using UV-Vis spectrophotometer (JASCO V-650, measuring wavelength is 355 nm). We concluded that effect of reactant volume on the rate of sono-oxidation was clear and the best volume was 10 ml in our system. In that case, the absorbance was 4 times as high as one without CO₂. The effect of KI concentration, however, was not clear. Because of increasing pH value of solution, concentration of CO₂ in the solution might decrease during sonication.

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In the previous presentation, we concluded that dilute NaHCO₃-KI solution had more sono-oxidation rate compared with the KI solution without NaHCO₃ under Argon (Ar) atmosphere using 200 kHz ultrasonic generator. In this presentation, to confirm the previous results we carried out sonolysis of 0.1 M KI-NaHCO₃ solution under high frequency using by an ultrasonic generator (Honda Electronics HM-303, 2.4 MHz and maximum power 15 W). The rate of sono-oxidation was evaluated by potassium iodide (KI) dosimetry at 355 nm using UV-Vis spectrophotometer (JASCO V-650 and V-730). We also observed multi-bubble sonoluminescence (MBSL) of NaHCO₃ solution. The intensity of MBSL fell down with concentration of NaHCO₃. Namely, cavitation intensity decreases in the presence of NaHCO₃. As you know, NaHCO₃ reacts to CO₂ during sonication and the temperature in bubbles fall down by CO₂. The rate of sono-oxidation, however, increased in the solution with a small amount of NaHCO₃. It has been known that CO₂ quenches •H radicals, which are produced from solvent (H₂O). Remaining •OH radicals oxidize I^-. Therefore, increasing rate of sono-oxidation by adding NaHCO₃ in an aqueous solution was confirmed not only at 200 kHz but also at 2.4 MHz ultrasonic atomizer.

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Hollow nanocapsules of polymer materials are expected to be used as carriers for drug delivery systems in medical applications. In this work, we have developed a simple and novel method for the preparation of hollow nanocapsules composed of polyaniline (PANI) polymerized on finebubble soft templates formed by ultrasonic irradiation. The key features of the method are an effective finebubble generation by ultrasonication and its application for the template synthesis of nano-sized hollow particles. At first, 20 kHz ultrasonic irradiation (183 W cm^-2) was carried out in water. By this operation, a large number of finebubbles could be obtained. Next, we added anilinium chloride aqueous solution to the water. Subsequently, ammonium persulfate (APS) aqueous solution was added to the anilinium chloride solution to drive the oxidative polymerization on the surface of finebubbles, and finally PANI hollow nanocapsules in the size ranging from 200 to 300 nm were synthesized (finebubble template method). This method is regarded as an environmental-friendly process since it doesn’t require template removing process such as evaporation, thermolysis, and dissolution.

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In the sonochemical reduction method for metal nanoparticle synthesis, the reduction auxiliary such as alcohols and surfactants are generally required for metal ion reduction in solutions. On the other hand, we found that gold nanoparticles were synthesized through the reduction of gold chloride ions ([AuCl4]^-) in water by irradiation of high-frequency ultrasound (e.g., 200 kHz and 950 kHz) even in the absence of reduction auxiliary. The reduction rate of [AuCl4]- in solution by irradiation of 950 kHz ultrasound was 26.8 mM min^-1, which is consistent with the reduction rate of [AuCl4]^- in solution in the presence of ethanol as an auxiliary (the conventional sonochemical reduction method). In this work, we examine the mechanism on the reduction of [AuCl4]^- by irradiation of high-frequency ultrasound and the resulting formation of naked gold nanoparticles in water. In particular, we examine the effect of solution and gas volume in a vessel, area of gas-liquid interface and Argon purge on the reduction rate of [AuCl4]^- and the resulting gold nanoparticle formation in solutions. We found that the formation rate of gold nanoparticles in solutions decreased with increase in the solution volume in the vessel.

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The objective of the present study is to discuss the effect of ultrasound irradiation on the transformation ability of octacalcium phosphate (OCP) to hydroxyapatite (HAp) in simulated body fluid (SBF). OCP powders were prepared by a reaction of an aqueous suspension of dicalcium phosphate dehydrate and calcium carbonate at 60℃ for 12h. EDS analysis indicated that HAp converted in SBF is calcium-deficient bone-like apatite with a Ca/P ratio of 1.53. The results from SEM observation and XRD study demonstrated that the ultrasound irradiation exerts an influence on the OCP/HAp conversion process particularly in the initial stage of OCP dissolution and HAp nuclear generation process, and also suggested that the transformation rate will depend probably on the ultrasound frequency. Low-intensity pulsed ultrasound device recently used for bone healing promoting method was also applied to elucidate the effectiveness of ultrasound irradiation.

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The ultrasound (US) irradiation technique have efficacy to regulate the nucleation and growth of crystal. The effect of the US frequency on the crystal morphology in the cooling crystallization process of L-aspartic acid was tested using 26kHz, 78kHz and 130kHz US at 298K. Rod-like crystals were sufficiently formed under 130kHz US, where the mode of the breadth/length ratio was almost 0.1. Plate-like crystals were partially observed with 130kHz US. In spite of the high yield of rod-like crystals with US irradiation, XRD patterns of the crystals have remarkable peak of (200)-plane which is characteristic for the plate-like α type crystal of L-aspartic acid. This result suggests that rod-like crystals formed under US irradiation are the polysynthetic twin composed of small size plate-like crystals.

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A system for the determination of antioxidant activity has two components: 1) a generator of free radicals of Reactive oxygen species, ROS, and 2) a detector allowing quantification of the generated species and indicating changes in the measured signal in response to the presence of antioxidative compounds. It is well recognized that acoustic cavitation in liquids give rise to very intense local physicochemical effects that could lead to the hemolytic cleavage of covalent bonds between the oxygen and hydrogen atoms comprising the water molecules present. As a result, when liquid is irradiated by an ultrasonic wave, water and oxygen molecules inside the bubble are dissociated and reactive radical species are created in the bubble. Thus, ultrasonic irradiation is considered an effective source for ROS generation. It was indicated in our previous study^1,2) that the intensity of Luc²⁺ SCL is essentially due to the generation of O2•⁻in the ultrasonic fields. That is to say, the SCL system permits the quantification of antioxidant activity without using an enzyme for O2•⁻ production. The potential use of SCL in determining antioxidant activity has not been well investigated, and published literature in this area is very scarce. In this study, the SCL of the Luc²⁺/2-propanol system is proposed for the evaluation of antioxidant activity against O2•⁻ for the first time. The kinetic aspects of the SCL reactions are discussed.

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When an ultrasonic cavitation is produced, many different frequency components of sound pressure in water are generated. The sound pressure of fundamental frequency, subharmonics, and harmonics were compared with the cavitation threshold obtained from white noise. When the electric power which applied to the transducer was gradually raised, the harmonic component appeared first, the sound pressure of fundamental frequency became unstable near the cavitation threshold, after the cavitation was produced, subsequently followed by the generation of the subharmonic component. After average of sound pressure (AP) and average of broadband sound pressure (ABP) were defined, it was possible to compare the white noise with the subharmonic and harmonic components. The cavitation threshold values were measured in the frequency range from 22 kHz to 5 MHz. The threshold values of the erosion of aluminum foil, and I3 -generation of the KI method were measured. The threshold values of I3 -generation were almost the same as the cavitation threshold values at all frequency. Although the threshold values of erosion less than 100 kHz were close to the cavitation threshold values, above 100 kHz, the threshold values of erosion became larger than that of the cavitation.

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Amyloid fibrils form in supersaturated solutions via a nucleation and growth mechanism. We proposed that ultrasonication may be an effective agitation to trigger nucleation that would otherwise not occur under the persistent metastability of supersaturation1. However, the roles of supersaturation and effects of ultrasonication have not been elucidated in detail except for limited cases. Insulin is a typical amyloidogenic protein that is useful for investigating the mechanisms underlying amyloid fibrillation with biological relevance. We studied the alcohol-induced amyloid fibrillation of insulin using various concentrations of 2,2,2-trifluoroethanol, and 1,1,1,3,3,3-hexafluoro-2-propanol at pH 2.0 and 4.8. Ultrasonic irradiation effectively triggered fibrillation under conditions in which insulin retained persistent supersaturation. Structural analyses by circular dichroism, Fourier transform infrared spectroscopy, transmission electron microscopy and atomic force microscopy revealed that the dominant structures of fibrils varied between parallel and antiparallel β-sheets depending on the solvent conditions. pH- and alcohol-concentration-dependent phase diagrams showed a marked difference before and after the ultrasonic treatment, which indicated that the persistent metastability of supersaturation determined the conformations of insulin. These results indicate the importance of an alternative view of amyloid fibrils as supersaturation-limited crystal-like aggregates formed above the solubility limit2.

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Amyloid fibrils and amorphous aggregates are two types of aberrant protein aggregates. Amyloid fibrils have highly ordered structure called cross-β structure. On the other hand, amorphous aggregates have no ordered structure. It is known that these two types of aggregates are associated with many serious diseases (e.g. Alzheimer’s and Parkinson’s diseases, dialysis-related amyloidosis). Moreover, protein aggregates are important in industries. For an example, antibodies stored at high concentrations have been known to aggregate, reducing the quality of antibody drugs. Furthermore, the spider silk has ordered β-structure like amyloid fibrils, representing a type of functional amyloids. Thus, the study of the formation of protein aggregates will contribute not only to preventing various diseases and developing therapeutic strategies but also to creating functional amyloids. The aim of this work is to understand the comprehensive mechanism of amyloid fibrillation and amorphous aggregation. With β2-microglobulin (β2m) and ultrasonic irradiation, we investigated the competition between amyloid fibrillation and amorphous aggregation. The results confirmed that ultrasonic irradiation is an effective method for accelerating amyloid fibrillation. We show that the rate of amyloid fibrillation depends on the ultrasonic energy. Moreover, we found that fibril-like aggregates was generated by ultrasonic irradiation. Consequently, we propose a competitive mechanism of amyloid fibrillation, amorphous aggregation and fibril-like aggregation useful for comprehensive understanding of protein aggregation.

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Although proteins generally fold into a specific native structure, aberrant aggregates sometimes form. It is known that there are two types of aggregates, i.e. amyloid fibrils and amorphous aggregates. Amyloid fibrils have ordered cross β structure. On the other hand, amorphous aggregates have no or less ordered structure. These aggregates are associated with various diseases such as Alzheimer’s disease. Recently, the effects of additives on acceleration or inhibition of aggregation have been highlighted. However, the relation between the effects of additive and aggregation mechanisms is still unclear. In this study, we focused on the effects of heparin, used as an anticoagulant agent, on fibrillation of hen egg white lysozyme (HEWL). At first, amyloid fibrils were induced by adding a low concentratios of heparin under acidic conditions where no fibrillation occurred. However, exceeding a certain heparin concentration (1 mg/mL), amorphous aggregation occurred immediately. Interestingly, at a higher heparin concentration (37 mg/ml) under ultrasonication, amorphous aggregation did not occurr but amyloid fibrillation occurred again. These results, we suggest that heparin showed the concentration-dependent acceleration or inhibition of fibrillation. We propose a new viewpoint of the salt-dependent aggregation mechanism of proteins. This suggests that amyloid fibrils and amorphous aggregates form competitively depending on concentrations of additives. The interpretation that amyloid fibrils are in a close relationship with amorphous aggregates. These interpretation will be important to revealing the fibrillation mechanism.

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Porous metal materials have been widely employed as typical materials of catalysts for cleaning exhaust gas, manufacturing a reformed gas containing hydrogen and carbon monoxide from hydrocarbon compounds, and so on. The particle size, morphology and structure of the metal materials are significant factors for improving catalytic activity and adsorption capacity of the materials. In this study, Ni/Al particles were prepared by coprecipitation methods using surfactants or/and ultrasound techniques and the influence of surfactant, ultrasonication and temperature on the structure and morphology of the particles were investigated and their catalytic activities were evaluated via steam reforming of ethanol.

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A new Triazole compound 1H,1H`-5,5’-Bibenzotria zole was sonochemically synthesized from carcinogenic 3,3`-Diaminobenzidine (DAB) after exposure of 500 kHz 100 W ultrasound(US). The ultrasonicated samples were characterized by chemical analyses with FTIR, NMR and UV-Vis spectroscopy. Fluorescence spectroscopy measured every 30mins interval of the US exposure, the triazole comp ound fluorescence intensity changed at varied frequency and output power.

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