Evaluation of solvent property of air-water interface based on the fluorescence spectra of 1,2'-dinaphthylamine in the aqueous solution of ultrafine bubbles.

Solvent property of air-water interface was evaluated based on the fluorescence spectra of 1,2'-dinaphthylamine in water containing ultrafine bubbles (average diameter: 103 nm, standard deviation: 38 nm). Among naphthylamine derivatives whose fluorescence spectra were responsive to microscopic hydrophobicity, 1,2'-dinaphthylamine (DN) was selected because its wavelength of the maximum emission (λmax) was significantly dependent on the concentration and microenvironment of the ultrafine bubble. The λmax value of DN in water was 486 nm, while it shifted to shorter wavelength (408 nm) in the presence of 1.09 × 109 mL-1 of ultrafine bubbles. The shift of λmax value indicates that DN adsorbs on the surfaces of ultrafine bubbles and exists in hydrophobic region rather than in bulk water. By comparing with the λmax values in different solvents, the surface of ultrafine bubble was found to have similar solvent property to ethyl ether or ethyl acetate that are widely used as extracting solvents for hydrophobic organic compounds.

Curcumin-Loaded Liposome Preparation in Ultrasound Environment under Pressurized Carbon Dioxide.

Curcumin-loaded liposomes were prepared using a supercritical carbon dioxide (SCCO2)−ultrasound environment system. The experiments were performed at temperatures of 40−70 °C and pressures of 10−25 MPa in a batch system with ultrasonication for 60 min. Transmission electron microscopy (TEM) images revealed liposome products with spherical morphologies and diameters of <100 nm. Dynamic light scattering (DLS) analysis indicated that the curcumin-loaded liposome nanosuspension exhibited good stability. Changing the operating conditions influenced the amount of liposome-encapsulated curcumin; as the operating temperature or pressure increased, the diameter of the liposome products and the amount of liposome-encapsulated curcumin increased and decreased, respectively. Herein, we described an innovative and practical organic-solvent-free method for generating liposomes from phospholipids.

Frequency and power dependence of ultrasonic degassing.

We investigated the time variation of ultrasonic degassing for air-saturated water and degassed water with a sample volume of 100 mL at frequencies of 22, 43, 129, 209, 305, 400, 514, 1018, and 1960 kHz and ultrasonic power of 15 W. Ultrasonic degassing was evaluated by dissolved oxygen concentration. Ultrasonic degassing was also investigated at a frequency of 1018 kHz and ultrasonic powers of 5, 10, 15, and 20 W. The dissolved oxygen concentration varied with the ultrasonic irradiation time and became constant after prolonged ultrasonic irradiation. The constant dissolved oxygen concentration value depended on the frequency and ultrasonic power but not the initial dissolved oxygen concentration. The degassing rate at 101.3 kPa was higher in the frequency range of 200 kHz to 1 MHz. The frequency dependence of the degassing rate was almost the same as that of the sonochemical efficiency obtained by the potassium iodide (KI) method. Ultrasonic degassing in the frequency range of 22-1960 kHz was also investigated under reduced pressure of 5 kPa. Degassing was accelerated when ultrasonic irradiation was applied under reduced pressure. However, under a reduced pressure of 5 kPa, the lower the frequencies, the higher is the degassing rate. The sonochemical reaction rate was examined by the KI method for varying dissolved air concentrations before ultrasonic irradiation. Cavitation did not occur when the initial dissolved oxygen concentration was less than 2 mg·L-1. Therefore, the lower limit of ultrasonic degassing under 101.3 kPa equals 2 mg·L-1 dissolved oxygen concentration. A model equation for the time variation of dissolved oxygen concentration due to ultrasonic irradiation was developed, and the degassing mechanism was discussed.

Frequency and power dependence of the sonochemical reaction.

The dependence of the sonochemical reaction on ultrasonic intensity was studied over a wide frequency range of 22-1960 kHz and sample volume range of 25-200 mL. The effect of a stainless steel reflector set on the water surface was also considered. Experiments were carried out by direct ultrasonic irradiation of a sample in a vessel. The potassium iodide (KI) method was used to evaluate the sonochemical reaction in terms of efficiency and reaction rate, and calorimetry was used to determine ultrasonic power. A quenching phenomenon, where the reaction rate decreased despite an increasing ultrasonic power, was observed at all frequencies and sample volumes, which indicated the existence of a maximum reaction rate. The maximum reaction rate increased with the frequency, except at 1960 kHz, and with the sample volume. The ultrasonic power at which quenching occurred increased with the frequency and sample volume. Sudden quenching occurred without the reflector, whereas gradual quenching occurred with the reflector. Based on the results, ultrasonic power density (i.e., ultrasonic power divided by the sample volume) can be used to estimate the ultrasonic power at which quenching occurs for various sample volumes.

Measurement of distribution of broadband noise and sound pressures in sonochemical reactor.

Cross-sectional area distribution of broadband noise in a sonochemical reactor was measured to estimate reaction fields. A needle-type hydrophone scanned the sonochemical reactor in horizontal and vertical directions at one-millimeter interval. To show an absolute value of broadband noise, average of broadband sound pressure was defined. The distribution of sound pressures at the fundamental and second harmonic frequencies were also measured. In the case of driving frequency at 130 kHz, sonochemical reaction fields were observed in several ellipse shapes. The reaction fields in upper part of the reactor was high because cavitation bubbles moved upper part due to radiation force. The sound pressure distribution at the fundamental frequency showed existence of standing wave and reaction fields were weak at pressure antinode because cavitation bubbles were repelled by primary Bjerknes force. The sound pressure distribution at the second harmonic frequency indicated that the pattern of bubbles distribution resembled to that of reaction fields closely. In the case at 43 kHz, distributions of reaction fields and sound pressures were complex due to coupled vibration. The reaction fields were relatively weak in areas which had very high sound pressures at the fundamental frequency.

Dependence of cavitation, chemical effect, and mechanical effect thresholds on ultrasonic frequency.

Cavitation, chemical effect, and mechanical effect thresholds were investigated in wide frequency ranges from 22 to 4880kHz. Each threshold was measured in terms of sound pressure at fundamental frequency. Broadband noise emitted from acoustic cavitation bubbles was detected by a hydrophone to determine the cavitation threshold. Potassium iodide oxidation caused by acoustic cavitation was used to quantify the chemical effect threshold. The ultrasonic erosion of aluminum foil was conducted to estimate the mechanical effect threshold. The cavitation, chemical effect, and mechanical effect thresholds increased with increasing frequency. The chemical effect threshold was close to the cavitation threshold for all frequencies. At low frequency below 98kHz, the mechanical effect threshold was nearly equal to the cavitation threshold. However, the mechanical effect threshold was greatly higher than the cavitation threshold at high frequency. In addition, the thresholds of the second harmonic and the first ultraharmonic signals were measured to detect bubble occurrence. The threshold of the second harmonic approximated to the cavitation threshold below 1000kHz. On the other hand, the threshold of the first ultraharmonic was higher than the cavitation threshold below 98kHz and near to the cavitation threshold at high frequency.

Simulation of the formation and characteristics of ultrasonic fountain.

In order to design an ultrasonic apparatus with a high throughput rate for generating atomization, the mechanism of fountain characteristics is important because the throughput rate of the ultrasonic atomization is decided by the area of the fountain surface. The formation of the fountain can be numerically studied by taking into account the effect of surface tension and radiation pressure. We have investigated the shape of the fountain with different ultrasound parameters or different kinds of solutions. When the amplitude of input sound pressure is higher than 1.3×10(5)Pa, the liquid separates from the ultrasonic fountain after irradiation for a very short period. It is further found that the area of the fountain surface increases with the concentration of the ethanol due to its low surface tension, density and sound speed. Finally, we discuss the difference between the ultrasonic fountain and the pump fountain, and find that the velocity field in the reactor induced by the pump is higher than that by the ultrasound.

Development of plants resistant to Papaya leaf distortion mosaic virus by intergeneric hybridization between Carica papaya and Vasconcellea cundinamarcensis.

In this study, we confirmed that Vasconcellea cundinamarcensis resists Papaya leaf distortion mosaic virus (PLDMV), and used it to produce intergeneric hybrids with Carica papaya. From the cross between C. papaya and V. cundinamarcensis, we obtained 147 seeds with embryos. Though C. papaya is a monoembryonic plant, multiple embryos were observed in all 147 seeds. We produced 218 plants from 28 seeds by means of embryo-rescue culture. All plants had pubescence on their petioles and stems characteristic of V. cundinamarcensis. Flow cytometry and PCR of 28 plants confirmed they were intergeneric hybrids. To evaluate virus resistance, mechanical inoculation of PLDMV was carried out. The test showed that 41 of 134 intergeneric hybrid plants showed no symptoms and were resistant. The remaining 93 hybrids showed necrotic lesions on the younger leaves than the inoculated leaves. In most of the 93 hybrids, the necrotic lesions enclosed the virus and prevented further spread. These results suggest that the intergeneric hybrids will be valuable material for PLDMV-resistant papaya breeding.

Separation characteristics of alcohol from aqueous solution by ultrasonic atomization.

The generation rate of ultrasonically atomized droplets and the alcohol concentration in droplets were estimated by measuring the flow rate and the alcohol concentration of vapors from a bulk solution with a fountain. The effect of the alcohol concentration in the bulk solution on the generation rate of droplets and the alcohol concentration in droplets were investigated. The ultrasonic frequency was 2.4MHz, and ethanol and methanol aqueous solutions were used as samples. The generation rate of droplets for ethanol was smaller than that for methanol at the same alcohol molar fraction in the bulk solution. For both solutions, at low alcohol concentration in the bulk solution, the alcohol concentration in droplets was lower than that in vapors and the atomized droplets were visible. On the other side, at high concentration, the concentration in droplets exceeded that in vapors and the atomized droplets became invisible. These results could be explained that the alcohol-rich clusters in the bulk solution were preferentially atomized by ultrasonic irradiation. The concentration in droplets for ethanol was higher than that for methanol at low alcohol concentration because the amount of alcohol-rich clusters was larger. When the alcohol molar fraction was greater than 0.6, the atomized droplets almost consisted of pure alcohol.

Numerical simulation of liquid velocity distribution in a sonochemical reactor.

Ultrasonically induced flow is an important phenomenon observed in a sonochemical reactor. It controls the mass transport of sonochemical reaction and enhances the reaction performance. In the present paper, the liquid velocity distribution of ultrasonically induced flow in the sonochemical reactor with a transducer at frequency of 490 kHz has been numerically simulated. From the comparison of simulation results and experimental data, the ultrasonic absorption coefficient in the sonochemical reactor has been evaluated. To simulate the liquid velocity near the liquid surface above the transducer, which is the main sonochemical reaction area, it is necessary to include the acoustic fountain shape into the computational domain. The simulation results indicate that the liquid velocity increases with acoustic power. The variation of liquid height also influences the behavior of liquid velocity distribution and the mean velocity above the transducer centre becomes a maximum when the liquid height is 0.4m. The liquid velocity decreases with increasing the transducer plate radius at the same ultrasonic power.

Unreliable pesticide control of the vector psyllid Diaphorina citri (Hemiptera: Psyllidae) for the reduction of microorganism disease transmission.

Systemic insecticides and application methods were examined for the control of the vector psyllid of citrus greening disease, Diaphorina citri, on grown king mandarin trees in an orchard in southern Vietnam from May 2007 to September 2008. Leaf spraying of imidacloprid, thiamethoxam, and clothianidin attained about 50 % to 70 % mortality of the psyllid for one month after the application and showed decreased efficacy thereafter. Imidacloprid was more effective than the other two insecticides, but the efficacy on grown trees was still much lower than that following application to young seedlings. Trunk injection of these insecticides accomplished similar mortality, about 50 %, and the efficacy of the insecticides continued for one month. An adjuvant was used with the goal of protecting the insecticide applied on leaves from precipitation, and mineral oil was used for the same reason, as well as its potential to control the psyllid. Neither the adjuvant nor the mineral oil played an evident role in the increase of insecticide efficacy or longevity. Application of systemic insecticides at even 50 times the dose described above did not show an apparent increase in psyllid mortality. The insecticides commonly used for the control of the psyllid were not as effective on this insect on grown trees as we had expected they would be.

Enhancement of sonochemical reaction of terephthalate ion by superposition of ultrasonic fields of various frequencies.

The ultrasonic reactor with dual frequency was used and the effect of frequency on the fluorescence intensity of terephthalate ion was experimentally investigated in the frequency range from 176 to 635 kHz. The sonochemical reaction fields were visualized by using sonochemical luminescence of luminol solution. Compared with the fluorescence intensity of terephthalate ion for single frequency, the fluorescence intensity for dual frequency increased. The fluorescence intensity ratio of dual frequency to single frequency had maximum value when the frequency of transducer attached at the bottom wall was comparable in magnitude to that at the side wall. In the case of dual frequency, the sonochemical reaction fields became more extensive in the reactor and more intensive around the center of the reactor.

Dynamics of ultrasonically induced birefringence of in rod-like colloidal solutions.

This review summarized our experimental studies of ultrasonically induced birefringence on aqueous solution of rigid rod-like colloids and rod-like micelles from the view point of dynamics of particle orientation. For rigid rod-like colloids in dilute concentration, the orientational relaxation time was described in terms of the Debye-Einstein equation. This indicated that the ultrasonically induced birefringence could be one of useful tools for determining the size of particles of anisotropic shape. For rod-like micelles, the birefringence showed anomalous damping oscillation when the rod-like micelle was in an entangling state. The mechanism of damping oscillation was discussed using the results of the rheological measurements.

Analysis of concentration characteristics in ultrasonic atomization by droplet diameter distribution.

The droplet diameter distribution and concentration characteristics in ultrasonic atomization were experimentally studied. The samples were aqueous solutions of methanol, ethanol and 1-propanol. The diameter distribution of atomized droplets showed the normal distribution, and the median diameter and standard deviation were expressed by means of the ultrasonic condition and the liquid properties. The concentration characteristic in ultrasonic atomization was analyzed by using the model of shell and core to the atomized droplet, where the former and latter consist of solute and solution, respectively. The value, which was surface solute amount in droplet multiplied by the molecular volume, increased with increasing solute molar fraction in bulk liquid and was independent of alcohol kinds. The rate of accompanying liquid and the solute molar fraction in accompanied liquid were estimated from the diameter distribution and the surface solute amount in droplet.