Sonoluminescence Signal Research Articles

Sonoluminescence optical confocal tomography of tissue

Summary In this paper, we report experiments on optical confocal tomography by use of sonoluminescence signal in both biological tissue and tissue-simulating media. A high-sensitive confocal scanning setup based on photon counting technique was developed. With the system, we obtained images of the objects embedded in tissue-simulating turbid media. The images showed a high contrast and a lateral resolution of about 100 μm. We finally imaged a carbon stick buried in muscle tissue with the sonoluminescence confocal scanning tomography. This technique has potential applications in clinical diagnosis.

Experimental investigation of dynamics of sonoluminescing bubbles

Light scattering was carried out for a cavitation bubble trapped in a spherical flask. A He–Ne laser of 7 mW was used as the light source and the scattering angle was 90 deg. A function generator was used as the trigger source and a digital phospher oscilloscope for averaging the data. Changing the drive voltage resulted in differences in the signal waveform above and below the sonoluminescence threshold; a sonoluminescing bubble had the maximum radius greater than a dark bubble did, but showed smaller rebounds. This suggests that energy concentration is made possible by tight and symmetric collapse of the bubble. Sonoluminescence signals were also retrieved for a few hours with no laser light, and a discontinous drift was noted in the appearance time on the oscilloscope, suggesting that a bubble may have drifted in space discontinuously. [Work supported by Grant-in-Aid for Scientific Research, Ministry of Education, Science, and Culture, Japan.]

Two-dimensional imaging of dense tissue-simulating turbid media by use of sonoluminescence

An optical imaging technique that is believed to be novel was developed for noninvasive cross-sectional imaging of tissuelike turbid media. By use of a sonoluminescence signal generated internally in the media with a 1-MHz continuous-wave ultrasound, two-dimensional images were produced for objects embedded in turbid media by a raster scan of the media. Multiple objects of different shapes were resolved with this imaging technique. The images showed a high contrast and good spatial resolution. The spatial resolution was limited by the focal size of the ultrasonic focus.

Sonoluminescence and sonochemistry in aqueous solutions containing surface active solutes

The ultrasound induced reduction of gold chloride in aqueous alcohol solutions has been measured and compared with the extent of sonoluminescence (SL) quenching observed in the same solutions, as a function of alcohol concentration. Both ultrasound initiated phenomena were found to be directly related to the Gibbs surface excess concentration of the alcohol at the gas/water interface. The SL quenching occurs in two distinct surface excess regimes. The first region accounts for about 90% quenching of the SL signal. The second quenching region extends over a broader surface excess range and the profile matches the extent of enhancement in the reduction of gold chloride. When the nonvolatile surfactant sodium dodecylsulfate (SDS) was used instead of alcohol, the trends in the SL signal and in the sonochemical reduction process were quite different. At low concentrations (<2 mM) of SDS, the SL signal was enhanced over that obtained from water without surfactant. At higher SDS concentrations, the SL signal declined and leveled off to about 80% of the water signal at about 10 mM. In contrast, the reduction of gold chloride increased to about 8 mM SDS and then remained constant above this value. Possible mechanisms that explain the results will be presented.

Influence of the Sound Field on the Intensity of Sonoluminescence

Cavitation-field sonoluminescence intensity was measured in correlation with sound pressure and its harmonic and subharmonic component signals generated from a well-defined cavitation field in a distilled-water filled rectangular cell by changing the acoustic frequency and the voltage applied to the transducer. Optics was designed to ensure that all the sonoluminescing positions in the cell were detectable by a photomultiplier tube. The results show that it is the second harmonic component of the sound pressure waveform, rather than the subharmonic one, which gives a reliable indication of the threshold of the cavitation and the onset of the cavitation-field sonoluminescence. The sonoluminescence signal exhibits a linear relationship with the simultaneously measured second harmonic component signal and is likely to originate mainly from the subset of stable cavitation bubbles in the cavitation field.

Sonoluminescence from Aqueous Alcohol and Surfactant Solutions

The sonoluminescence generated in water with pulsed 515 kHz ultrasound has been studied in the presence of different chain length (C1−C5) aliphatic alcohols and the surfactants sodium dodecyl sulfate (SDS), dodecyltrimethylammonium chloride (DTAC), and N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (DAPS). The ultrasound pulse widths used ranged from 1 to 10 ms, with duty cycles (on/off ratios) of 1:3 to 1:9. It was found that the sonoluminescence from the initial pulses was very low but increased in intensity and reached a maximum after 20−50 pulses, for all systems studied, depending on the pulse width and duty cycle. In the presence of alcohol the maximum signal decreased with increasing alcohol concentration, and the signal decline was more pronounced with increasing chain length of the alcohol. A good correlation was found to exist between the decline in the sonoluminescence signal and the Gibbs surface excess of the alcohol at the air/water interface. In the presence of SDS (an anionic surfactant) and DTAC (a cationic surfactant), quite different behavior was observed. At low concentrations of these two surfactants the maximum signal was significantly enhanced over that obtained in pure water, reaching a maximum at about 1 mM of surfactant. At higher concentrations the signal decreased again reaching a limiting value similar to that obtained in pure water. The sonoluminescence signal in DAPS (a zwitterionic surfactant) solutions remained much the same as in pure water. On the addition of 0.1 M NaCl to the three different types of surfactant solutions, the intensities of the emission signals obtained were essentially the same as in pure water. Possible mechanisms responsible for the different behavior in the sonoluminescence signal in the presence of the alcohols and surfactants are discussed.

Laser ablation of organic molecules from frozen matrices

AbstractThe technique of frozen matrix‐assisted laser ablation coupled with resonance‐enhanced multiphoton ionization and reflectron time‐of‐flight mass spectrometry was used to detect intact organic molecules directly from solutions. When frozen at the temperature of liquid nitrogen, the matrices of interest were ablated by a pulsed CO2 single‐mode laser. The analyte molecules emerging from the ablated plume were then ionized by a tunable XeCl excimer laser‐pumped dye laser and analysed with a gridless reflectron time‐of‐flight mass spectrometer. The ablation process from an ice matrix was studied with the amino acids tryptophan and tyrosine dissolved in an aqueous ethanol solution to a concentration level of 5 × 10−4 M. It was found that fragmentation of the analyte molecules is strongly dependent on the ablating laser fluence and that there is a laser fluence range just above the ablation threshold where the decomposition is negligible. The different fragmentation mechanisms are discussed and a cavitation under the liquid surface, causing the sonoluminescence signal from an ice matrix, was shown to be responsible for the decomposition of the analyte molecules ablated by a low photon energy IR laser. Under the appropriate conditions, the analyte molecules were found to have a low rotational temperature of about 150 K resulting from the jet‐like cooling in multiple collisions with matrix molecules.

Measurement and interpretation of ultrasonic velocity and attenuation in low concentration polystyrene dispersions

The multibubble sonoluminescence (MBSL) intensities from water exposed to the simultaneous ultrasonic irradiation from 20 kHz (fixed at 6.3 W) and 355 kHz (variable power) ultrasound sources have been compared to the MBSL from the individual ultrasound sources under the same power conditions. A synergistic enhancement of the sonoluminescence (SL) signal, >30-fold, at low powers (4.6 W) of the higher frequency was observed. At a higher acoustic power level (15.8 W) the dual frequency operation produced a decrease in the SL signal. These results are in agreement with previously reported data [P. Ciuti, N.V. Dezhkunov, A. Francescutto, F. Calligaris, F. Sturman, Ultrasonics Sonochem. 10 (2003) 337; N.V. Dezhkunov, J. Eng. Phys. Therm. 76 (2003) 142] under similar experimental conditions. Numerical single bubble (SB) dynamics calculations have been used to help interpret the experimental results. It is suggested that the observed effects are caused by a combination of changes to the peak collapse temperature of individual bubbles as well as to changes in the active bubble population.

Electrochemical potential difference variation by pulsed ultrasound

The multibubble sonoluminescence (MBSL) intensities from water exposed to the simultaneous ultrasonic irradiation from 20 kHz (fixed at 6.3 W) and 355 kHz (variable power) ultrasound sources have been compared to the MBSL from the individual ultrasound sources under the same power conditions. A synergistic enhancement of the sonoluminescence (SL) signal, >30-fold, at low powers (4.6 W) of the higher frequency was observed. At a higher acoustic power level (15.8 W) the dual frequency operation produced a decrease in the SL signal. These results are in agreement with previously reported data [P. Ciuti, N.V. Dezhkunov, A. Francescutto, F. Calligaris, F. Sturman, Ultrasonics Sonochem. 10 (2003) 337; N.V. Dezhkunov, J. Eng. Phys. Therm. 76 (2003) 142] under similar experimental conditions. Numerical single bubble (SB) dynamics calculations have been used to help interpret the experimental results. It is suggested that the observed effects are caused by a combination of changes to the peak collapse temperature of individual bubbles as well as to changes in the active bubble population.