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Microbubble manipulation by acoustic radiation force may play an important role in future drug delivery systems, because the required bubble manipulations, such as bubble trapping at the desired position and payload release by bubble destruction using a high-intensity ultrasonic wave, are controlled by ultrasonic waves. In this paper, a novel method of microbubble trapping by bubble nonlinear oscillation is proposed. Two ultrasonic waves, which have a harmonic frequency relation, are used in order to generate the force for trapping bubbles. The first wave is a pumping wave, which has a relatively high sound pressure. This wave is used for inducing the nonlinear oscillation of bubbles. The second wave is a control wave, whose frequency is set to be the harmonic frequency of the nonlinear bubble oscillation. The pressure gradient of the control wave in conjunction with the harmonic component of nonlinear oscillation generates the Bjerknes force applied to bubbles. This force forms multiple traps with a narrow separation for bubbles, which flow into the cross area of the two ultrasonic waves.

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It is well known that evaluation of rebar corrosion is important for the maintenance of reinforced concrete structures, but, it is difficult to simply, quickly and quantitatively evaluate the amount of corrosion of rebars embedded in concrete by conventional non-destructive evaluation (NDE) methods such as electrical, electromagnetic and mechanical method. This paper proposes a vibro-Doppler radar (VDR) measurement method to quantitatively evaluate rebar corrosion by measuring the vibration ability of the rebar forcibly vibrated in concrete by an excitation coil. It is experimentally demonstrated in RC test pieces that the rebar vibration displacement obtained by developed VDR method is valid and is less affected by the moisture in the concrete. In addition, simultaneous monitoring of the rebar vibration displacement of the test pieces is performed through an electrolytic corrosion test and the measured vibration displacement is compared to the rebar corrosion loss evaluated. As the results, it is cleared that the rebar vibration displacement starts to increase from slightly before the occurrences of corrosion crack on the concrete surface as the corrosion loss increases. It is also shown that the rebar vibration displacement becomes 4 times higher than that in initial condition at the rebar corrosion loss of 250 mg/cm2. This implies that the VDR has potential to nondestructively and quantitatively evaluate rebar corrosion in concrete.

The chromodomain protein MRG-1 is an essential maternal factor for proper germline development that protects germ cells from cell death in C. elegans. Unlike germ granules, which are exclusively segregated to the germline blastomeres at each cell division from the first cleavage of the embryo, MRG-1 is abundant in all cells in early embryos and is then gradually restricted to the primordial germ cells (PGCs) by the morphogenesis stage. Here, we show that this characteristic spatiotemporal expression pattern is dictated by the mrg-1 3'UTR and is differentially regulated at the RNA level between germline and somatic cells. Asymmetric segregation of germ granules is not necessary to localize MRG-1 to the PGCs. We found that MES-4, an essential chromatin regulator in germ cells, also accumulates in the PGCs in a germ granuleindependent manner. We propose that C. elegans PGCs have a novel mechanism to accumulate at least some chromatin-associated proteins that are essential for germline immortality.

Sonoporation, which makes micropores through a cell membrane by bubble cavitation, improves the efficacy in ultrasonic wave drug delivery systems. However, the effects of bubble cavitation are affected largely by bubble condition, such as bubble density and bubble aggregation, just before the irradiation of a high-intensity ultrasonic wave. Aiming at preparing a specific bubble condition in bubble cavitation, a method which uses the frequency modulation of a pumping ultrasonic wave was proposed. In this paper, the effects of the ultrasonic wave irradiation sequence are evaluated under different flow velocities and bubble densities. The spatial correlation between microbubble clouds produced by the pumping ultrasonic wave and the microhollows produced by the bubble cloud cavitation is also discussed.