查看更多>>摘要：The use of cavitation for improving biofilm cleaning is of great interest. There is no system at present that removes the biofilm from medical implants effectively and specifically from dental implants. Cavitation generated by a vibrating dental ultrasonic scaler tip can clean biomaterials such as dental implants. However, the cleaning process must be significantly accelerated for clinical applications. In this study we investigated whether the cavitation could be increased, by operating the scaler in carbonated water with different CO2 concentrations. The cavitation around an ultrasonic scaler tip was recorded with high speed imaging. Image analysis was used to calculate the area of cavitation. Bacterial biofilm was grown on surfaces and its removal was imaged with a high speed camera using the ultrasonic scaler in still and carbonated water. Cavitation increases significantly with increasing carbonation. Cavitation also started earlier around the tips when they were in carbonated water compared to non-carbonated water. Significantly more biofilm was removed when the scaler was operated in carbonated water. Our results suggest that using carbonated water could significantly increase and accelerate cavitation around ultrasonic scalers in a clinical situation and thus improve biofilm removal from dental implants and other biomaterials.
查看更多>>摘要：Water with small volume (a few microlitres or less) often maintains its liquid state even at temperatures much lower than 0 degrees C. In this study, we examine the onset of ice nucleation in micro-sized water droplets with immersed solid particles under weak ultrasonic vibrations. The experimental results show that ice nucleation inside the water droplets can be successfully induced at relatively high temperatures. The experimental observations indicate that the nucleation sites are commonly encountered in the region between the particle and the substrate. A numerical study is conducted to gain insight into the possible underlying phenomenon for ice nucleation in such systems. The simulation results show that the collapse of cavitation bubbles in the crevice at the particle surface is structure sensitive with the hemisphere-shape crevice generating pressures as high as 1.63 GPa, which is theoretically suitable for inducing ice nucleation.
查看更多>>摘要：Investigation of the cavitation activity during ultrasonic treatment of magnesium particles during nanostructuring has been performed. Cavitation activity is recorded in the continuous mode after switching the ultrasound on with the use of ICA-5DM cavitometer. It has been demonstrated that this characteristic of the cavitation zone may be varied in a wide range of constant output parameters of the generator. The speed and nature of the cavitation activity alteration depended on the concentration of Mg particles in the suspension and the properties of the medium in which the sonochemical treatment has been performed. Three stages of the cavitation area evolution can be distinguished: 1 - the initial increase in cavitation activity, 2 - reaching a maximum with a subsequent decrease, and 3 - reaching the plateau (or the repeated cycles with feedback loops of enlargement/reduction of the cavitation activity).
Vargas, Sara A.Delgado-Macuil, R. J.Ruiz-Espinosa, H.Rojas-Lopez, M....
12页
查看更多>>摘要：The aim of this work was to evaluate the influence of high-intensity ultrasound (HIUS) treatment on whey protein isolate (WPI) molecular structure as a previous step for complex coacervation (CC) with kappa-carrageenan (KC) and its influence on CC functional properties. Protein suspension of WPI (1% w/w) was treated with an ultrasound probe (24 kHz, 2 and 4 min, at 50 and 100% amplitude), non HIUS pretreated WPI was used as a control. Coacervation was achieved by mixing WPI and KC dispersions (10 min). Time and amplitude of the sonication treatment had a direct effect on the molecular structure of the protein, FTIR-ATR analysis detected changes on pretreated WPI secondary structure (1600-1700 cm(-1)) after sonication. CC electrostatic interactions were detected between WPI positive regions, KC sulfate group (1200-1260 cm(-1)), and the anhydrous oxygen of the 3,6 anhydro-D-galactose (940-1066 cm(-1)) with a partial negative charge. After ultrasound treatment, a progressive decrease in WPI particle size (nm) was detected. Rheology results showed pseudoplastic behavior for both, KC and CC, with a significant change on the viscosity level. Further, volume increment, stability, and expansion percentages of CC foams were improved using WPI sonicated. Besides, HIUS treatment had a positive effect on the emulsifying properties of the CC, increasing the time emulsion stability percentage. HIUS proved to be an efficient tool to improve functional properties in WPI-KC CC.
查看更多>>摘要：Emulsion gels with low oil contents have been continuously developed in recent decades. In this study, the use of high-intensity ultrasound for the preparation of low oil emulsion gel (oil fraction of 0.25) was investigated. Specifically, defatted Antarctic krill protein (dAKP) was used to stabilize the interface of soybean oil and water. Then, the microstructure and the stabilization mechanism of the formed emulsion gel were evaluated by cryoSEM, CLSM, zeta potential, rheological measurements, and FTIR. Besides, the particle diameter was measured to be around 5 mu m. The results of CLSM indicated that the emulsion gel was the oil-in-water type. The emulsion gel exhibited gel-like viscoelastic behavior even at a low concentration of dAKP due to the formation of a rigid particle network while the rheological behavior of the emulsion gel was significantly affected by the concentration of dAKP. The stabilization of the emulsion gel can be maintained by space steric hindrance and hydrophobic interactions between particles in the emulsion gel system.
查看更多>>摘要：In a previous study, we found that cavitation bubbles cause the ultrasonic destruction of microcapsules containing oil in a shell made of melamine resin. The cavitation bubbles can be smaller or larger than the resonance size; smaller bubbles cause Rayleigh contraction, whereas larger bubbles are not involved in the sonochemical reaction. The activity in and around the bubble (e.g., shear stress, shock wave, microjet, sonochemical reaction, and sonoluminescence) varies substantially depending on the bubble size. In this study, we investigated the mechanism of the ultrasonic destruction of microcapsules by examining the correlations between frequency and microcapsule destruction rate and between microcapsule size and cavitation bubble size. We evaluated the bubbles using multibubble sonoluminescence and the bubble size was changed by adding a surfactant to the microcapsule suspension. The microcapsule destruction was frequency dependent. The main cause of micro capsule destruction was identified as mechanical resonance, although the relationship between bubble size and microcapsule size suggested that bubbles smaller than or equal to the microcapsule size may also destroy microcapsules by applying shear stress locally.
查看更多>>摘要：Hydrodynamic cavitation (HC) is being increasingly used in a wide range of applications. Unlike ultrasonic cavitation, HC is scalable and has been used at large scale industrial applications. However, no information about influence of scale on performance of HC is available in the open literature. In this work, we present for the first time, experimental data on use of HC for degradation of complex organic pollutants in water on four different scales (similar to 200 times scale-up in terms of capacity). Vortex based HC devices offer various advantages like early inception, high cavitational yield and significantly lower propensity to clogging and erosion. We have used vortex based HC devices in this work. 2,4 dichloroaniline (DCA) - an aromatic compound with multiple functional groups was considered as a model pollutant. Degradation of DCA in water was performed using vortex-based HC devices with characteristic throat dimension, dt as 3, 6, 12 and 38 mm with scale-up of almost 200 time based on the flow rates (1.3 to 247 LPM). Considering the experimental constraints on operating the largest scale HC device, the experimental data is presented here at only one value of pressure drop across HC device (280 kPa). A previously used per-pass degradation model was extended to describe the experimental data for the pollutant used in this study and a generalised form is presented. The degradation performance was found to decrease with increase in the scale and then plateaus. Appropriate correlation was developed based on the experimental data. The developed approach and presented results provide a sound basis and a data set for further development of comprehensive multi-scale modelling of HC devices.
Elizabeth Alcantara-Zavala, Alejandrade Dios Figueroa-Cardenas, JuanFrancisco Perez-Robles, JuanArambula-Villa, Geronimo...
9页
查看更多>>摘要：The aim of this study was to evaluate thermosonication as an alternative method for the pasteurization of pulque in order to improve its shelf life and retain its quality parameters.
Sharipov, Glyus L.Gareev, Bulat M.Vasilyuk, Kristina S.Galimov, Dim I....
6页
查看更多>>摘要：The moving single-bubble sonoluminescence of Ce3+ in water and ethylene glycol solutions of CeCl3 and (NH4)(2)Ce(NO3)(6) was studied. As found, a significant part of intensity of the luminescence (100% with cerium concentration less than 10(-4) M) is due to the sonochemiluminescence. A key reaction of sonochemiluminescence is the Ce4+ reduction by a solvated (or hydrated in water) electron: Ce4+ + e(s) (e(aq)) -> *Ce3+. Solvated electrons are formed in a solution via electrons ejection from a low-temperature plasma periodically generated in de formable moving bubble at acoustic vibrations. Reactions of heterolytic dissociation of solvents make up the source of electrons in the plasma. In aqueous CeCl3 solutions, the Ce4+ ion is formed at the oxidation of Ce3+ by OH radical. The latter species originates from homolytic dissociation of water in the plasma of the bubble, also penetrating from the moving bubble into the solution. The sonochemiluminescence in cerium trichloride solutions are quenched by the Br- (acceptor of OH) and H+ ions (acceptor of e(aq)). In water and ethylene glycol solutions of (NH4)(2)Ce(NO3)(6), the sonochemiluminescence also quenched by the H+ ion. The sonochemiluminescence in CeCl3 solutions is registered at [Ce3+] >= 10(-5) M. Then the sonochemiluminescence intensity increases with the cerium ion concentration and reaches the saturation plateau at 10(-2) M. It was shown that sonophotoluminescence (re-emission of light of bubble plasma emitters by cerium ions) also contributes to the luminescence of Ce3+ in solutions with [Ce3+] >= 10(-4) M. If the cerium concentration is more than 10(-2) M, a third source contributes to luminescence, viz., the collisional excitation of Ce3+ ions penetrating into the moving bubble.
查看更多>>摘要：In this study, modified citrus pectin treated with a combination of microfluidization and ultrasonication was compared to the original and ultrasonication treated pectin on hydrodynamic diameter, molecular weight, polydispersity, zeta potential, apparent viscosity, Fourier-transform infrared spectroscopy (FTIR), 2,2-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging capacity, scanning electron microscope (SEM), atomic force microscopy (AFM), their emulsifying properties and encapsulation properties. Modified pectin treated with a combination of microfluidization and moderate ultrasonication (MUB) was found to have lowest hydrodynamic diameter (418 nm), molecular weight (237.69 kDa) and polydispersity (0.12), and relatively low apparent viscosity among all pectin samples. Furthermore, it showed significantly higher DPPH radical scavenging capacity than the original pectin although only slightly higher than that of ultrasonication treated one (UB). MUB showed a thin fibrous morphology and decreased degree of branching from SEM and AFM. Emulsion stabilized by MUB had highest centrifugal and thermal stability compared to emulsions stabilized by UB and the original pectin. This could be attributed to higher interfacial loading of MUB (17.90 mg/m(2)) forming more compact interfacial layer observed by confocal laser scanning microscopy (CLSM). Moreover, both MUB and UB exhibited improved encapsulation functionality to protect cholecalciferol (vitamin D-3) from UV degradation compared to the original pectin.
NSTL
Elsevier