The intensity of MBSL excited by burst-type of ultrasonic waves were measured in air-saturated water at the frequency of 104kHz as a function of duty ratio for various pulse-on duration and ultrasonic powers. The MBSL intensity takes a maximum at the duty ratio of 5-10 depending on the power for the pulse-on duration of 250 cycle. The enhancement of MBSL intensity was 18 times compared to the intensity at continuous wave, at the power of 3.6W, and 5 times at the power of 10.5W. The results were explained by the change of initial bubble radius with pulse-off duration time.

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New type of supersonic washer-disinfector using ozone bubbling and silver electrolysis was developed in order to clean many devices and materials such as semiconductors, endoscopes and cut vegetables. This washer has fourteen supersonic oscillators of umbrella shape, which emit supersonic traveling waves along more than two directions and are driven independently by each supersonic transducer. The intensity of supersonic levitation wave in water was measured with a quartz-tube sensor and found to be even all over the aqueous container space. This supersonic levitation washer can evenly clean not only hard materials such as glasses, jewels and metals, but also soft materials such as clothes, plastics, rubbers and bodies. Neither detergent nor disinfectant is necessary, therefore the drainage does not cause any environmental pollution. Disinfection is easy and rapid using ozone oxidation and silver electrolysis. Ozone is produced by the irradiation of 185nm ultraviolet light against air and evolved as micro-bubbles. Electrolysis is carried out using direct current between the positive electrode of net-shape silver plate and the negative electrode of stainless-steel container. This apparatus meets the present demand of cleaning regarding the global environmental conservation.

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Generation of OH radicals by ultrasound irradiation in the presence of TiO_2 was studied. The effects of dissolved argon and xenon applied into the irradiating solutions were studied in the presence of TiO_2. Heat capacity ratio of argon and xenon is higher than that of nitrogen and oxygen. Higher heat capacity ratio of dissolved argon and xenon causes higher local temperature when cavitation bubble collapsed, and it results in the induced pyrolysis of H_2O and generation of OH radicals. Further, the effect of the photocatalysis of TiO_2 may be more intensified by high temperature and sonoluminescence.

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Potential clinical use of ultrasound in enhancing the effects of anticancer drugs in the treatment of cancers has been highlighted in previous reports. Increased uptake of drugs by the cancer cells due to ultrasound has been suggested as a mechanism. However, the precise mechanism of the enhancement has not yet been elucidated. Here, the combined effects of low-intensity pulsed ultrasound and doxorubicin (DOX) on killing (loss of viability and apoptosis) of U937 cells, and the involved mechanism were investigated. The synergistic enhancement in cell killing and additive enhancement in induction of apoptosis were observed above 0.3W/cm^2. No enhancement was observed at intensity of 0.2W/cm^2 in cell killing and induction of apoptosis. The mechanisms of the enhancement are 1) Increase in incorporation of the DOX by ultrasound involved with sonoporation. 2) Enhancement of the cavitation by DOX. 3) Cavitation is required for the enhancement of the DOX effects.

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To well characterize disinfection system and to investigate the mechanism of cell killing by TiO_2/US method, Escherichia coli (E. coli) was used as a model and target microorganism. At present, our research is going on developing disinfection system by using ultrasonic reactor in the presence of nonwoven TiO_2 fabric. It was found that the decrease in cell concentration was almost insignificant without ultrasonic irradiation although TiO_2 filter was present, and vice versa. In contrast, applying ultrasonic irradiation with TiO_2 filter reduces the E. coli cell concentration very rapidly which indicated very high disinfection power at this condition or system. However, the effect of new ultrasonic reactors on the disinfection rate, the characterization of affecting parameters of the ultrasonic reactors, as well as possible germicidal mechanism of disinfection remain to be studied. Given an opportunity to conduct these research will uncover above issues and will be benefited our scientific career to develop, in addition to enrich the bio-industrial field as well.

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Titanium dioxide (TiO_2), have high reactive potential by photoexcitation, had been investigated its medical use for anticancer therapy. However, TiO_2 has a pKa around 6.6, these particles are unstable at neutral pH, and it tends to aggregate. This problem makes it difficult to use for medical practically. We developed a very stable nanocomposites, it consist of the TiO_2 and the hydrophilic polymers (TiO_2 nanocomposites). It was synthesized by heat reaction in DMF, could disperse even in 10% protein containing aqueous solution. Previously, we reported the anticancer activity of the TiO_2 nanocomposites by UV irradiation. In this work, we investigated both the radical generation and the killing effect of the TiO_2 nanocomposites by ultrasonic irradiation especially at a high frequency, which is well used for medical diagnosis. The generation of reactive oxygen species and the killing effect are enhanced in the presence of TiO_2 nanocomposites by ultrasonic irradiation. On the other hand, in the presence of P25 particle or absence of TiO_2 particle neither enhancement of radical generation nor killing effect. Thus, it seemed that the radical generation and/or the killing effect are strongly related to properties of particles (ie., size, surface charge). In conclusion, TiO_2 nanocomposites has potential that is suited for this new anticancer therapy system.

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The sterilization of the microorganism by ultrasound is due to OH radical and shock wave caused by ultrasonic irradiation in water. In this work, the growth activity of the Saccharomyces cerevisiae (yeast) and Escherichia coli XL1-Blue (E.coli) and by sonication with various frequencies(24, 168, 200, 1500kHz) was investigated. In order to evaluate the growth activity of the sonicated yeast cells and E.coli, the formation of the nucleic acid during the growth in the culture medium and permeability of the cell membrane were analyzed by flow cytometry. As a result, the inactivation effect of ultrasound on yeast cells was the largest at 24kHz, where the yeast cell was inactivated mainly by shock wave. On the other hand, the effect of OH radicals is large at 168 and 200kHz.

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We have proposed a concept of 'Sonofunctional Molecules', which develop new functionalities by ultrasonic irradiation. As a first sonofunctional molecule, compound 1, which had the potential for cancer treatment, was prepared. By the ultrasonic irradiation, compound 1 can be expected to form irreversible binding with DNA, which may cause damages on DNA duplication. Previously, we reported ultrasound irradiation with DNA enhanced the solubility of 1 into water, although 1 had no solubility into water in the absence of DNA. This result indicates that the sonofunctional molecule 1 is bound to DNA by ultrasonic irradiation, and terminal thiol groups take an important function in the binding. In this study, the binding mechanism of 1 to DNA was examined mainly by means of electrophoresis. Figure 1 indicated that DNA was damaged and degraded into shorter fragments by ultrasonic irradiation. However, even after 24 hrs' irradiation, considerable amount of DNA fragments remained. UV spectra of recovered solution of DNA and 1 from agarose gel after 24 hrs' ultrasonic irradiation is shown in Figure 2. These spectra indicated that 1 was not contained in the solution, and this result suggested that the binding between DNA and 1 was being easily broken weak by recovery or electrophoresis.

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Influence of the ultrasound (US) on the formation of hydrogen bonds between the polymer and alumina was investigated in this research. It was expected that the positive/negative sound pressure changes of sonic wave led the weaking ability of the hydrogen bonds between alumina and polyacrylic acid under US exposune. The slurry solutions contained both alumina and polyacrylic acid(PAA) (molecular weight 250000) in 100ml water with weight ratio of 10:3, 20:3, and 30:3 was used. In the slurry solution, viscosity was measured when B type viscosity meter was used with 6, 12, 30, 60 rpm rotation after exposune of different frequency (28, 45, 100kHz) and the power of US (200, 250, and 300W/cm^2). It was found that hydrogen bonds were brooken by irradiating the US, because the viscosity of the solution decreases.

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