Corneal endothelial cells and acoustic cavitation in phacoemulsification

Postoperative complications of phacoemulsification,such as corneal edema caused by human corneal endothelial cell(CEC)injury,are still a matter of concern.Although several factors are known to cause CEC damage,the influence of ultrasound on the formation of free radicals during surgery should be considered.Ultrasound in aqueous humor induces cavitation and promotes the formation of hydroxyl radicals or reactive oxygen species(ROS).ROS-induced apoptosis and autophagy in phacoemulsification have been suggested to significantly promote CEC injury.CEC cannot regenerate after injury,and measures must be taken to prevent the loss of CEC after phacoemulsification or other CEC injuries.Antioxidants can reduce the oxidative stress injury of CEC during phacoemulsification.Evidence from rabbit eye studies shows that ascorbic acid infusion during operation or local application of ascorbic acid during phacoemulsification has a protective effect by scavenging free radicals or reducing oxidative stress.Both in experiments and clinical practice,hydrogen dissolved in the irrigating solution can also prevent CEC damage during phacoemulsification surgery.Astaxanthin(AST)can inhibit oxidative damage,thereby protecting different cells from most pathological conditions,such as myocardial cells,luteinized granulosa cells of the ovary,umbilical vascular endothelial cells,and human retina pigment epithelium cell line(ARPE-19).However,existing research has not focused on the application of AST to prevent oxidative stress during phacoemulsification,and the related mechanisms need to be studied.The Rho related helical coil kinase inhibitor Y-27632 can inhibit CEC apoptosis after phacoemulsification.Rigorous experiments are required to confirm whether its effect is realized through improving the ROS clearance ability of CEC.

Mass Transfer During Osmotic Dehydration Using Acoustic Cavitation

An experimental study on intensifying osmotic dehydration was carried out ina state of nature and with acoustic cavitation of different cavitating intensity (0.5A, 0.7A and0.9A) respectively, in which the material is apple slice of 5mm thickness. The result showed thatacoustic cavitation remarkably enhanced the osmotic dehydration, and the water loss was acceleratedwith the increase of cavitating intensity. The water diffusivity coefficients ranged from1.8x10^(-10)m^2·s^(-1) at 0.5A to 2.6x10^(-10)m^2·s^(-1) at 0.9A, and solute diffusivitycoefficients ranged from 3.5x10^(-11) m^2·s^(-1) at 0.5A to 4.6X10^(-11)m^2·s^(-1) at 0.9A. On thebasis of experiments, a mathematical model was established about mass transfer during osmoticdehydration, and the numerical simulation was carried out. The calculated results agree well withexperimental data, and represent the rule of mass transfer during osmotic dehydration intensified byacoustic cavitation.

Boiling Heat Transfer in an Acoustic Cavitation Field

An experimental study has been carried out investigatesystematically the effects of acoustic cavi- tation parameters andfluid subcooling on boiling of acetone around a horizontal circulartube. The experimental results show that acoustic cavitation enhancedremarkably the boiling heat transfer and decreased the incipientboiling superheat and that cavitation bubbles effect on boiling heattransfer reduced with cavitation distance. For boiling curves in aform of h-q', elevated cavitation distance shift nucleate boilingcurves to the right of the cor- responding ordinary pool boilingcurve. The associated mechanism of heat transfer enhancement isanalyzed with the consideration of cavitation bubble influence onvapor embryo.

The Relationship of Cavitation to the Negative Acoustic Pressure Amplitude in Ultrasonic Therapy

The relationship between the cavitation and acoustic peak negative pressure in the high-intensity focused ultrasound （HIFU） field is analyzed in water and tissue phantom. The peak negative pressure at the focus is determined by a hybrid approach combining the measurement with the simulation. The spheroidal beam equation is utilized to describe the nonlinear acoustic propagation. The waveform at the focus is measured by a fiber optic probe hydrophone in water. The relationship between the source pressure amplitude and the excitation voltage is determined by fitting the measured ratio of the second harmonic to the fundamental component at the focus, based on the model simulation. Then the focal negative pressure is calculated for arbitrary voltage excita- tion in water and tissue phantom. A portable B-mode ultrasound scanner is applied to monitor HIFU-indueed cavitation in real time, and a passive cavitation detection （PCD） system is used to acquire the bubble scattering signals in the HIFU focal volume for the cavitation quantification. The results show that： （1） unstable cavitation starts to appear in degassed water when the peak negative pressure of HIFU signals reaches 13.5 MPa; and （2） the cavitation activity can be detected in tissue phantom by B-mode images and in the PCD system with HIFU peak negative pressures of 9.0 MPa and 7.8 MPa, respectively, which suggests that real-time B-mode images could be used to monitor the cavitation activity in two dimensions, while PCD systems are more sensitive to detect scattering and emission signals from cavitation bubbles.

Effect of inertial acoustic cavitation on antibiotic efficacy in biofilms

Bacterial biofilms can lead to chronic infections,increase tolerance to antibiotics and disinfectants,resistance to phagocytosis,and other components of the body’s immune system.Biofilm formation is implicated in the persistence of staphylococcal infections and chronic Pseudomonas aeruginosa lung infections in cystic fibrosis(CF)patients(which can result from biofilm-growing mucoid strains).Conventional treatments utilize aggressive antibiotic prophylaxis/therapy to prevent/eliminate biofilms,followed by chronic suppressive therapy.Recently,the use of enzymes to dissolve the biofilm matrix was investigated,in addition to quorum sensing inhibitors to increase biofilm susceptibility to antibiotics.Here,we propose a novel strategy,utilizing ultrasound-induced inertial cavitation,to increase antibiotic efficacy.The wall shear stress at the biofilm interface is calculated,and viscoplastic constitutive equations are used to examine the biofilm response to the mechanical stress.Our simulations suggest that the maximum biofilm detachment occurs at high pressure/low frequency,and the mechanical disruption can affect the biochemical processes inside the biofilm resulting in vulnerability to antibiotics.

Correlation between microbubble-induced acoustic cavitation and hemolysis in vitro

Microbubbles promise to enhance the efficiency of ultrasound-mediated drug delivery and gene therapy by taking advantage of artificial cavitation nuclei. The purpose of this study is to examine the ultrasound-induced hemolysis in the application of drug delivery in the presence of microbubbles. To achieve this goal, human red blood cells mixed with microbubbles were exposed to 1-MHz pulsed ultrasound. The hemolysis level was measured by a flow cytometry, and the cavitation dose was detected by a passive cavitation detecting system. The results demonstrate that larger cavitation dose would be generated with the increase of acoustic pressure, which might give rise to the enhancement of hemolysis. Besides the experimental observations, the acoustic pressure dependence of the radial oscillation of microbubble was theoretically estimated. The comparison between the experimental and calculation results indicates that the hemolysis should be highly correlated to the acoustic cavitation.

Localization in an Acoustic Cavitation Cloud

Using a nonlinear sound wave equation for a bubbly liquid in conjunction with an equation for bubble pulsation, we theoretically predict and experimentally demonstrate the appearance of a gap in the frequency spectrum of a sound wave propagating in a cavitation cloud comprising bubbles. For bubbles with an ambient radius of 100μm, the calculations reveal that this gap corresponds to the phenomenon of sound wave localization. For bubbles with an ambient radius of 120 μm, this spectral gap is related to a forbidden band of the sound wave. In the experiment, we observe the predicted gap in the frequency spectrum in soda water. However, in tap water, no spectral gap is present because the bubbles are much smaller than 100μm.

Distribution pattern of acoustic and streaming field during multi-source ultrasonic melt treatment process

The ultrasonic melt treatment(UMT)is widely used in the fields of casting and metallurgy.However,there are certain drawbacks associated with the conventional process of single-source ultrasonic(SSU)treatment,such as the fast attenuation of energy and limited range of effectiveness.In this study,the propagation models of SSU and four-source ultrasonic(FSU)in Al melt were respectively established,and the distribution patterns of acoustic and streaming field during the ultrasonic treatment process were investigated by numerical simulation and physical experiments.The simulated results show that the effective cavitation zone is mainly located in a small spherical region surrounding the end of ultrasonic horn during the SSU treatment process.When the FSU is applied,the effective cavitation zone is obviously expanded in the melt.It increases at first and then decreases with increasing the vibration-source spacing(Lv)from 30 mm to 100 mm.Especially,when the Lv is 80 mm,the area of effective cavitation zone reaches the largest,indicating the best effect of cavitation.Moreover,the acoustic streaming level and flow pattern in the melt also change with the increase of Lv.When the Lv is 80 mm,both the average flow rate and maximum flow rate of the melt reach the highest,and the flow structure is more stable and uniform,with the typical morphological characteristics of angular vortex,thus significantly expanding the range of acoustic streaming.The accuracy of the simulation results was verified by physical experiments of glycerol aqueous solution and tracer particles.

Study on Desorbing Sulfur Dioxide from Citrate Solution by Ultrasonlficatlon

Using a sonochemical reactor designed by the authors,the process of removing sulfur dioxide from cit- rate solution simulating the flue gas desulfurization was studied.The influence of ultrasonic frequency,ultrasonic power,reaction temperature,stirring speed,inert gases,initial concentration of sulfur dioxide and concentration of citrate on the efficiency of sulfur dioxide desorption,the stability of citrate solution and the concentration of sulfate radical was examined systematically.By comparing the desorption of sulfur dioxide with and without ultrasonifica- tion,it was concluded that(1)lower ultrasonic frequency results in a better degassing efficiency;(2)the use of ul- trasonification in desorbing sulfur dioxide from citrate solution improves the desorbing efficiency in some condi- tions,without changing the essence of chemical reactions;(3)sparging inert gas into the liquid can lower the vis- cosity of solution and the cavitating threshold,and raise the desorption efficiency.These results demonstrate a technical way for deep desorption of sulfur dioxide and provide the fundamental data for future industrial disposal of sulfur dioxide.

Theoretical estimation of sonochemical yield in bubble cluster in acoustic field

In order to learn more about the physical phenomena occurring in cloud cavitation,the nonlinear dynamics of a spherical cluster of cavitation bubbles and cavitation bubbles in cluster in an acoustic field excited by a square pressure wave are numerically investigated by considering viscosity,surface tension,and the weak compressibility of the liquid.The theoretical prediction of the yield of oxidants produced inside bubbles during the strong collapse stage of cavitation bubbles is also investigated.The effects of acoustic frequency,acoustic pressure amplitude,and the number of bubbles in cluster on bubble temperature and the quantity of oxidants produced inside bubbles are analyzed.The results show that the change of acoustic frequency,acoustic pressure amplitude,and the number of bubbles in cluster have an effect not only on temperature and the quantity of oxidants inside the bubble,but also on the degradation types of pollutants,which provides a guidance in improving the sonochemical degradation of organic pollutants.

Experimental Research on Antiscale and Scale Removal by Ultrasonic Cavitation

Aiming at the scale problem in heat-transfer equipments, experimental investigation on antiscale and scale removalby ultrasonic cavitation is performed. By means of microscopic magnifying photography system, thesedimentary phenomenon can be observed. The experimental research reveals the influencing rule of acoustic intensity,cavitational distance, liquid temperature and solution concentration. The experimental results indicate thatliquid temperature has different effects on antiscale and scale removal. Different experimental liquids are used forantiscale and scale removal experiments. The results show that every liquid has a respective Cavitational activetemperature. When ultrasonic is used for antiscale, the smaller acoustic intensity is, the better effect is. But, whenultrasonic is used for scale removal, acoustic intensity has a reverse influence. In addition, biggish solution concentrationis propitious to antiscale for long-time running. Distance of test sample to ultrasonic transducer alsohas certain influence on antiscale and scale removal. The smaller the distance to ultrasonic transducer is, the bettereffects antiscale and scale removal have.

Ordered mesoporous carbon-silica frameworks confined magnetic mesoporous TiO_(2) as an efficient catalyst under acoustic cavitation energy

Herein,we report a biphase stratification strategy that enables the encapsulation of magnetic mesoporous TiO_(2) inside an ordered mesoporous C/SiO_(2) framework.The obtained composites exhibit high surface areas(up to 600 m^(2) g^(-1)),large perpendicular pore sizes(up to 9 nm)and a strong magnetic response(~10.0 emu g^(-1)),presenting significantly enhanced degradation activities toward pentachlorophenol(PCP)and bisphenol-A(BPA)under acoustic cavitation energy.The remarkable performance is ascribed to the synergistic effect from the unique structural modulation:1)The large ordered mesopores favors the mass transfer,2)The mesoporous C/SiO_(2) frameworks promote the adsorption of organic pollutants and enrich them close to the TiO_(2) surface and 3)The special spatial arrangement of different components facilitates the generation of cavitation bubbles,leading to the increase in the overall hydroxyl-radical-production rate.Moreover,owing to the effective confinement,the as-prepared materials possess an excellent stability and durability.More importantly,the catalysts can easily be recovered by a magnet and show an excellent reusability.It is believed that these results could provide an important insight for the development of an efficient,stable and facile recoverable catalyst for the acoustic chemical process.

Role of ultrasonic oscillation in chemical processes in microreactors:A mesoscale issue

The integration of microreactor and ultrasound represents an emerging area for process intensification and has attracted considerable attention in recent years.One of the most important meso-scientific issues in ultrasound techniques is acoustic cavitation,which plays a vital role in the macroscopic performance of an ultrasonic microreactor.In this review,we first briefly summarize the latest research on acoustic cavitation phenomena in microreactors.The effects of channel configuration,solvent properties,and ultrasound parameters are systematically reviewed.In addition,the role of acoustic cavitation in various chemical processes(e.g.,mixing,absorption,emulsification,and particle synthesis)is presented from a mesoscale perspective,which in turn provides guidance for ultrasound applications.A thorough under-standing of the ultrasound intensification mechanism will contribute to the future development of this promising technology.

Sonochemical synthesis of photocatalysts and their applications

Sonochemical synthesis has flourished significantly in the last few decades for the preparation of photocatalysts.A large number of photocatalysts have been prepared through sonochemical techniques.This review highlights the scope of sonochemistry in the preparation of photocatalysts,and their applications in energy production and environmental remediation.Beside,the sonochemical degradation of pollutants is discussed in detail.The progress made in sonochemical synthesis and the future perspective for this technique are summarized here.This review may create more enthusiasm among researchers to pay extra attention to the sonochemical synthesis of materials and add their useful contribution to the investigation of new materials for photocatalytic and other applications.This will propel this technique toward commercial sonosynthesis of nanomaterials.

Ultrasound-Assisted Solidifi cation of a Cu–Cr Alloy

Ultrasonic cavitation radiates huge power in a small solidifying bulk,leading to significant grain refinement,purification and homogenization of the final alloys.Ultrasound vibration has mostly been used for treating the solidification of light metals,but it is difficult to directly introduce ultrasonic vibration into copper alloy due to the lack of proper sonotrode.In this work,we have used a Sialon ceramic sonotrode to propagate acoustic waves in a Cu-Cr alloy melt.Significant grain refinement and modification of primary Cr have been obtained.With the ultrasound vibration treatment,the mechanical properties of the as-cast Cu-Cr alloy have been improved.The wear resistance of the Cu-Cr alloy has also shown enhancement with respect to the untreated alloy.