High Frequency Ultrasound Waves Research Articles

Curso de ecografía abdominal. Introducción a la técnica ecográfica. Principios físicos. Lenguaje ecográfico

Ultrasound is a non-invasive, accessible, and versatile diagnostic technique that uses high frequency ultrasound waves to define outline the organs of the human body, with no ionising radiation, in real time and with the capacity to visual several planes.The high diagnostic yield of the technique, together with its ease of uses plus the previously mentioned characteristics, has currently made it a routine method in daily medical practice. It is for this reason that the multidisciplinary character of this technique is being strengthened every day.To be able to perform the technique correctly requires knowledge of the physical basis of ultrasound, the method and the equipment, as well as of the human anatomy, in order to have the maximum information possible to avoid diagnostic errors due to poor interpretation or lack of information.

Computational Fluid Dynamics modeling of micromixing performance in presence of microparticles in a tubular sonoreactor

This paper reports the results of CFD modeling for evaluating micromixing efficiency in presence of polymeric microparticles in a continuous tubular sonoreactor. The studied tubular sonoreactor was equipped with four 1.7MHz ultrasound transducers and micromixing efficiency was analyzed using Villermaux/Dushman reaction. The main objective of this study is to illustrate the simultaneous effects of 1.7MHz ultrasound waves and polymeric microparticles on micromixing performance from the fluid dynamics point of view. In order to model the presence of these microparticles, the Eulerian multiphase model was applied based on kinetic theory of granular flow. The dynamic mesh method was used to model the vibration of 1.7MHz piezoelectric transducers. CFD modeling results indicate the positive effects of the presence of microparticles on micromixing efficiency and more efficient velocity distribution inside the sonoreactor. This was interpreted as the ability of high frequency ultrasound waves (1.7MHz) to move and disperse the microparticles.

Using microparticles to enhance micromixing in a high frequency continuous flow sonoreactor

In this paper, an experimental study was conducted to investigate the effect of high frequency ultrasound wave on micromixing efficiency in the presence of polymeric microparticles in a tubular sonoreactor. The size and volume fraction of polymeric microparticles were varied and the micromixing efficiency was studied by adopting the Dushman reaction coupled with a neutralization reaction. In addition, the effect of flow rate and liquid viscosity on the segregation index was studied. The experimental results showed that the movement and dispersion of the polymeric microparticles by ultrasound wave could improve the micromixing efficiency. The results showed that the size of the polymeric microparticles has great effect on mixing. Moreover, it was found that in the presence of these microparticles, segregation index decreases significantly and their effect reduces with increase in the solution viscosity. The presented results show that using high frequency ultrasound waves in the range of MHz and in the presence of microparticles can promise to reach an efficient micromixing in tubular sonoreactors.

Experimental study on the effects of acoustic streaming of high frequency ultrasonic waves on convective heat transfer: Effects of transducer position and wave interference

In the present study, an experimental study was carried out in order to find the effect of high frequency ultrasound wave transducer position on heat transfer rate. For this purpose, a thin platinum wire, which was used as a heater and sensor, was submerged in deionized water. The high frequency ultrasound transducers were installed at various positions including; two on lateral wall and three at the bottom of a cylindrical container. The interference effects of multiple transducers were investigated and it was found that a single transducer installed at the lateral wall works more efficiently than other layouts from heat transfer enhancement point of view.

Advancements in Catheter-Directed Ultrasound-Accelerated Thrombolysis

To review all available literature on catheter-directed ultrasound-accelerated thrombolysis for peripheral artery occlusions, stroke, deep venous thrombosis, and pulmonary embolism. A systematic literature search was performed, using MEDLINE, EMBASE and Cochrane databases. A total of 77 reports focusing on catheter-delivered ultrasound-accelerated thrombolysis were identified. Experimental studies show that high intensity ultrasound may induce thrombolysis, with and without the addition of plasminogen activators, mainly by acoustic cavitation and mechanical disruption, while low intensity, high frequency ultrasound waves may actually enhance plasmin-mediated thrombolysis. In a total of 340 clinical cases of various thromboembolic conditions, catheter-directed ultrasound-accelerated thrombolysis was related to rapid revascularization and a reduction in treatment time, drug dosage, hospitalization time, and possibly major bleeding complications compared to standard thrombolysis. Reported complication rates, including bleeding and embolization, were low. Ultrasound enhanced thrombolysis seems to be a promising concept in the treatment of various thromboembolic conditions. The technique has shown to be safe and efficacious in vitro, in vivo, and in clinical studies. Randomized controlled trials are warranted and should be awaited before considering catheter-directed ultrasound-accelerated thrombolysis as a new standard treatment.

Wastewater Treatment Resulting From an Oil Shale Retorting at High Frequency Ultrasound Waves With a Chemical Elemental Analysis

This study aims at applying ultrasound techniques with high frequency to treat wastewater. One application that was chosen here is to apply ultrasound wave on spent wastewater resulting from Jordanian oil shale retorting, which is known as retort water. The proposed process has shown an excellent ability on retort water treatment. At a fixed high ultrasound wave of 1.7 MHz, the spent wastewater evaporated in a mist form and was drawn out by shaft fans for condensation in a vessel immersed in ice. The only parameter studied here is the spent wastewater volume used to apply an ultrasound wave on it, while ultrasound wave frequency and the exposing time were fixed in all experimental works. Physical properties like pH for condensate were measured and found to be close to 7 compared to its original value which was 4. The measured conductivity for condensate has been reduced in a significant value compared to its original sample. The best condition for reduced conductivity was obtained at 35 ml of spent wastewater. At this volume, the ultrasound wave has the ability to decrease the conductivity to its lowest value. Spent wastewater samples before and after the ultrasound exposing period of time were analyzed using mass spectrometer, and all scanned heavy metals that have been identified to be existing in retort water are listed here.

Quantum oscillations in the high frequency magnetoacoustic response of aquasi-two-dimensional metal

In this work we present the results of theoretical analysis of magnetic quantum oscillationsof the velocity and attenuation of high frequency ultrasound waves traveling inquasi-two-dimensional (Q2D) conductors. We chose a geometry where both the wavevectorof the longitudinal sound wave and the external magnetic field are directed alongthe axis of symmetry of the Fermi surface. Assuming a moderately weak Fermisurface corrugation, we showed that the oscillating correction to the sound velocitymay include a special term besides an ordinary contribution originating fromquantum oscillations of the charge carrier density of states at the Fermi surface. Thisadditional term is generated by a ‘phase stability’ resonance occurring when thecharge carrier velocity in the direction of the wave propagation equals the soundvelocity. The two oscillating contributions to the sound velocity are shown todiffer in phase and shape, and they may have the same order of magnitude. Theappearance of the extra term may bring about significant changes in magnetic quantumoscillations of the velocity of sound in Q2D conductors, especially at low temperatures.

Intensification of sonochemical decolorization of anthraquinonic dye Acid Blue 25 using carbon tetrachloride

In this work, the influence of CCl 4 on the sonochemical decolorization of anthraquinonic dye Acid Blue 25 (AB25) in aqueous medium was investigated using high frequency ultrasound (1700 kHz). This frequency, reputed ineffective, was tested in order to introduce the ultrasound waves with high frequency in the field of degradation or removal of dyes from wastewater, due to its limited use in this field, and to increase the application of high frequency ultrasound wave in the field of environmental protection. The effects of various parameters such as the concentration of CCl 4, frequency (22.5 and 1700 kHz), solution pH, temperature and tert-butyl alcohol adding on the decolorization rate of AB25 was studied. The obtained results clearly demonstrated the significant intensification of AB25 decolorization in the presence of CCl 4. The enhancement effect of CCl 4 increased by decreasing temperature and by increasing the CCl 4 concentration. The pH has a significant influence on the bleaching of dye both in the absence and presence of CCl 4. The three investigated dosimeter methods (KI oxidation, Fricke reaction and H 2O 2 production) well corroborate the improvement of the sonochemical effects in the presence of CCl 4. The best sonochemical decolorization rate of AB25 in aqueous solution both in the absence and presence of CCl 4 is observed to occur at 1700 kHz compared to 22.5 kHz. The sonochemical oxidation of CCl 4 generates oxidizing species in the liquid phase that are highly beneficial for oxidation of hydrophilic and non-volatile pollutant, such as dyes, because they are less susceptible to free radical attack due to lower stability of the generated free radicals.

Degradation of Acid Blue 25 in aqueous media using 1700 kHz ultrasonic irradiation: ultrasound/Fe(II) and ultrasound/H 2O 2 combinations

In this work, the sonolytic degradation of an anthraquinonic dye, C.I. Acid Blue 25 (AB25), in aqueous phase using high frequency ultrasound waves (1700 kHz) for an acoustic power of 14 W was investigated. The sonochemical efficiency of the reactor was evaluated by potassium iodide dosimeter, Fricke reaction and hydrogen peroxide production yield. The three investigated methods clearly show the production of oxidizing species during sonication and well reflect the sonochemical effects of high frequency ultrasonic irradiation. The effect of operational conditions such as the initial AB25 concentration, solution temperature and pH on the degradation of AB25 was studied. Additionally, the influence of addition of salts on the degradation of dye was examined. The rate of AB25 degradation was dependent on initial dye concentration, pH and temperature. Addition of salts increased the degradation of dye. Experiments conducted using distilled and natural waters demonstrated that the degradation was more efficient in the natural water compared to distilled water. To increase the efficiency of AB25 degradation, experiments combining ultrasound with Fe(II) or H 2O 2 were conducted. Fe(II) induced the dissociation of ultrasonically produced hydrogen peroxide, leading to additional OH radicals which enhance the degradation of dye. The combination of ultrasound with hydrogen peroxide looks to be a promising option to increase the generation of free radicals. The concentration of hydrogen peroxide plays a crucial role in deciding the extent of enhancement obtained for the combined process. The results of the present work indicate that ultrasound/H 2O 2 and ultrasound/Fe(II) processes are efficient for the degradation of AB25 in aqueous solutions by high frequency ultrasonic irradiation.

Degradation of dissolved diazinon pesticide in water using the high frequency of ultrasound wave

This article aims to apply the ultrasound technique in the field of clean technology to protect environment. The principle of sonochemistry is conducted here to degrade pesticides in simulated industrial wastewater resulted from a factory manufacturing pesticides namely diazinon. Diazinon pesticide selected in this study for degradation under high frequency ultrasound wave. Three different initial concentrations of diazinon (800, 1200, and 1800ppm), at different solution volumes were investigated in to degrade dissolved diazinon in water. Ultrasound device with 1.7MHz, and 0.044cm diameter, was used to study the degradation process.It is found that as the concentration of diazinon increased, the degradation is also increasing, and when the solution volume increases, the ability to degraded pesticides decreases. The experimental results showed an optimum condition achieved for degradation of diazinon at 1200ppm as initial concentration and 50ml solution volume. Kinetic modeling applied for the obtained results showed that the degradation of diazinon by high ultrasound frequency wave followed a pseudo-first-order model with apparent rate constant of around of 0.01s−1.

The application of high frequency ultrasound waves to remove ammonia from simulated industrial wastewater

This article aims at applying the ultrasound technique in the field of clean technology to protect environment. The principle of ultrasound was conducted here to remove and recover ammonia from industrial wastewater. Three different concentrations of ammonia namely 5%, 15% and 25% (vol.%) were used to study the efficiency of removing ammonia from water. These concentrations are exactly similar to what may be found in wastewater resulting from strippers at petroleum refinery. High ultrasound frequency device with 2.4 and 1.7 MHz was conducted to study the effect of waves on the removal of ammonia. It was found that the ultrasound has the ability to remove ammonia with 5% concentration to meet the local standard of treated wastewater within less than 2 h for 0.080 L solution. It was also found that as the concentration of the ammonia increases the removing of ammonia within 2 h decreases, still the concentration of the ammonia meets the standard of the treated wastewater. The ability of the ultrasound to remove the ammonia failed to produce any mist when the height of the liquid solution increased, namely when the height reached (0.0337 m). This is equivalent to liquid volume of 0.150 L. It means that the device capacity to remove ammonia has certain limitations based on liquid heights. The best condition for ammonia removal was obtained at 5% concentration and 0.080 L liquid volume (equivalent to 0.0165 m).

New method to make high frequency ultrasound waves visible: the sliding light diffractometer

A diffractometric system is described, geometrically simple, that can reveal high frequency ultrasound waves propagating in a solid body. The system can be utilized for nondestructive testing, for example, to discover defects in steel samples.

An Acoustic Microscope for Subsurface Defect Characterization

Abstmct-A scanning acoustic microscope operating in the frequency range 0.1 - L GHz has been developed. The acoustic micrographs obtained have clearly demonstrated that this device can be used nondestructively to observe spike defects at the edge of the local oxidation of silicon structures in semiconductor devices and hydrogenion-doped regions in silicon crystals. The acoustic data have been compared with results obtained through the scanning electron microscope and the optical microscope. ICROANALYSIS techniques used to measure and examine microscopic regions in materials with highfrequency ultrasound waves have recently received a great deal of attention as a new and highly promising means for measurement and observation. Typical of these new methods is the mechanical scanning acoustic microscope developed by Professor C. F. Quate at Stanford University in 1973 [l]. This device directs a narrow focused acoustic beam at a specimen being scanned two-dimensionally, and detects acoustic waves that are reflected from or transmitted through the specimen to obtain a two-dimensional image. The image contrast obtained reflects changes in the mechanical properties of materials in the specimen, such as elasticity, density, and viscosity. Applications of the acoustic microscope include, for example, fault detection in materials, the examination of semiconductor devices, and materials evaluation using surface acoustic waves [2]-161. In this paper we report the results of studies conducted on spike defects that arise in isolation regions between elements in semiconductor devices and regions bombarded by hydrogen ions on silicon substrates. 11. CONSTRUCTION OF THE ACOUSTIC MICROSCOPE The operating principles and construction of acoustic microscopes in general have already been described in a number of papers and will be omitted here. We intend to discuss here only several specific features particular to our reflection scanning acoustic microscope. The most important technical problems that had to solved during development of this device were the development of a process for forming high-performance piezoelectric film; a process for fabricating microspherical