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This paper presents an experimental study of the ultrasonic degradation of organic pollutants in terms of the effect of ultrasonic frequency (40–380–850–1000 kHz). The removal efficiency of two endocrine disrupting compounds [17β-estradiol (E2) and 17α-ethinylestradiol (EE2)] is investigated using laboratory scale ultrasonic baths at low power intensities. Higher ultrasonic frequencies were found to be more effective for pollutant degradation with 850 kHz the best: 9.0 × 10−1 mg/kW h for E2 and 6.8 × 10−1 mg/kW h for EE2 at initial concentrations of 1 ppm. Additionally, the removal of p-nitrophenol was investigated under the same conditions, as a dosimetry reaction for estimating the hydroxyl radical production, key component in organic pollutant removal. In order to describe the overall phenomena occurring inside the reactor and to predict the apparent hydroxyl radical production, a simulation algorithm is proposed. It incorporates the solution of ODE systems that embodies bubble dynamics, heat and mass transfer through the bubble wall and chemical reactions in the gas–vapor phase for an initial bubble nuclei population. The experimental degradation measures of p-nitrophenol over the range of frequencies studied were found to be comparable with the model results of hydroxyl radicals produced during the sonication treatment.

Cataloged from PDF version of article. Capacitive micromachined ultrasonic transducers (cMUT) have become an alternative to piezoelectric transducers in the past few years. They consist of many small circular membranes that are connected in parallel. In this work, we report; a new detection method for cMUTs. We model the membranes as capacitors and the interconnections between the membranes as inductors. This kind of LC net-work is called an artificial transmission line. The vibrations of the membranes modulate the electrical length of the transmission line, which is proportional to the frequency of the signal through it. By measuring the electrical length of the artificial line at a high RF frequency (in the gigahertz range), the vibrations of the membranes can be detected in a very sensitive manner. Far the devices we measured, we calculated the minimum detectable displacement to be in the order of 10(-5) Angstrom/root Hz with a possible improvement to 10(-7) Angstrom/root Hz.

Ultrasound is a promising non-thermal clean technology in the fresh-cut industry of vegetables due to the inactivation of microorganism caused by cavitation [1]. Depending on the intensity of the ultrasound, time of application and temperature, reduction levels up to 1.3 Log UFC/g have been achieved [2]. However, there are fewer studies that evaluate the effect of the frequency of the ultrasonic wave and treatment time on the reduction of microorganism. ¿e main aim of this work was to evaluate the effect of bath sonication treatments of 25 and 42 kHz during 10 and 20 minutes on slices of carrots. Experiments were conducted at 24.0 ± 1.0°C. ¿e temperature of the water bath and carrot slices was monitored during treatments. Mesophilic aerobic microorganisms, yeast and moulds were evaluated in accordance with ISO 4833:2003 and ISO 7954:1987 protocols. Additionally, instrumental colour and texture of carrot slices were also evaluated. ¿e higher the frequency–time applied the higher core temperature obtained. A¿er 20 minutes at 42 kHz, the core temperature raised 7.3 ± 0.2°C. However, at 25 kHz half of the increase was found, 3.3 ± 0.2°C. ¿e effect of ultrasound frequency and time was evaluated through two way-Anova analysis (¿ < 0.05). From our results there were no significant interaction between the studied factors (¿ > 0.05). ¿e reduction of mesophilic bacteria was higher at 25 kHz but there were a significant effect of the time of application. ¿e maximum reduction achieved was 1 Log10 at 10 minutes. ¿ere were no significant differences on the reduction of moulds and yeast and 1 Log10 reduction was achieved. Alegria et al. [3] obtained lesser microbial reduction in sonicated fresh-cut carrots (45 kHz / 1 min). ¿e authors reported a maximum of 0.5 Log10 reductions for both mesophilic flora and yeast and moulds group. ¿e instrumental firmness and colour of the all the sonicate carrot slices were no significantly different to the raw carrot (¿ > 0.05). From our results, ultrasonic treatment can be an alternative to reduce the microbial load in fresh-cut products with no effect on texture and colour. However, higher microorganism reductions may be needed by the fresh-cut industry. Further studies on the possible combination of clean treatments may be the solution to reduce the chlorine concentration used on these food products.