bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic Characteristics of a Tissue Mimicking Phantom for Visualization of Thermal Distribution
Authors: Kim Jungsoon , Kim Moojoon , Park Yejoon , Ha Kanglyel
Published: July 2012

An ultrasonic tissue mimicking phantom is a useful tool for the performance testing and calibration of ultrasonic medical devices. However, it is hard to estimate the thermal distribution caused by the ultrasound in the human body using a conventional phantom. In this study, a tissue mimicking phantom to visualize the thermal distribution was developed by using thermochromic particles. The acoustic characteristics of the phantom were investigated according to the ingredient ratio of the phantom. Changing the ingredient ratio, the acoustic characteristics of the phantom can be adjusted to those of human tissue.
A Finite-Difference Time-Domain Technique for Nonlinear Elastic Media and Its Application to Nonlinear Lamb Wave Propagation
Authors: Matsuda Naoki , Biwa Shiro
Published: July 2012

A finite-difference time-domain technique for nonlinear elastic media is proposed, which can be applied to analyze finite amplitude elastic waves in solids. The kinematic and the material nonlinearities are considered, employing a general expression for the strain energy of an isotropic solid containing the second- and third-order terms of the strain components. The accuracy of the proposed technique is demonstrated by comparison with the analytical solution for the plane longitudinal wave propagation with finite amplitude. Two-dimensional simulations are performed to demonstrate the effectiveness of this formulation for Lamb waves. First, numerical simulations without the nonlinear effects are carried out, and the spectral peaks obtained from the calculated waveforms are shown to agree well with the theoretical dispersion curves of Lamb waves. As an example with the nonlinear effects, the harmonic generation in Lamb wave propagation is also demonstrated. The results show that the growth of the second-harmonic mode occurs for an incident-wave frequency selected in accordance with the analytical phase matching condition.
Nondestructive Evaluation of Plane Crack Tip in a Thin Plate Using Laser-Induced Pulse Wave and Symmetric Lamb Wave
Authors: Nakase Ryosuke , Nakata Kazuki , Matsukawa Mami
Published: July 2012

A new measurement system for detecting microcrack tips was investigated for the nondestructive evaluation of thin plates. In this system, we combined two different techniques. One technique is the use of a low-power pulsed laser to induce ultrasonic pulse waves, which are generated by the thermoelastic effect. The other technique is the vibration of samples using a symmetric mode Lamb wave at low frequencies, which causes the fluctuation of crack tips. Taking account of the Lamb wave propagation in the plate sample, laser-induced waves were excited to pass through plane cracks under two different fluctuation conditions (compression and extension). The characteristic difference between the frequency spectra of these waves gave us information on fluctuating cracks. Using an acrylic sample, we confirmed that the difference in phase could be used for the detection of crack tips.
Focal Length Controllable Ultrasonic Array Transducer with Adjustable Curvature
Authors: Kim Jungsoon , Kim Moojoon , Ha Kanglyel
Published: July 2012

In the underwater imaging field, the control of the focal length of a transducer is very useful. As one of the control methods, we suggested an ultrasonic array transducer with adjustable curvature by using air pressure. The curvature of the transducer was investigated according to the air pressure level in the back space of the transducer. Concave-, planar-, and convex-type transducers were obtained with different air pressure levels. The acoustic fields of the transducer were measured for different shapes of the radiation surface.
Development of a Long-Focal-Range Annular Array Ultrasonic Transducer
Authors: Korai Yusuke , Baba Atsushi
Published: July 2012

Conventional annular array transducers designed with Fresnel divided elements have a limited maximum size of the aperture of the transducer. In this study, we designed and fabricated a prototype of a large-aperture annular array transducer to inspect next-generation semiconductors. A new annular array pattern was designed with a wide focal range and a large focal length using equal areas for the inner elements and equal stroke widths for the outer elements. The prototype was fabricated by epoxy bonding with a patterned metal electrode on a flexible printed circuit and a piezoelectric copolymer. As a result of evaluation, we obtained a fine spatial resolution below 100 µm and a narrow relative sensitivity variation of 6.5 dB for a large focal length and a wide focal range from 10 to 30 mm.
Precision Test Fixture for Measuring Equivalent Circuit Parameters of GHz Surface-Mounted Quarts Crystal Units
Authors: Watanabe Yasuaki , Wada Manabu , Sakuta Yukinori , Hattori Masashi , Takahashi Osamu
Published: July 2012

We developed a coaxial-type fixture for precisely measurement of the impedance characteristics of small surface-mounted quartz crystal units. This fixture is applicable to the one-port S-parameter reflection method proposed in IEC60444-5, and measures the frequency impedance characteristics of a device under test (DUT) from its reflection coefficients. This measurement fixture uses a 65 GHz coaxial connector and calibrators with a 1.85 mm inside diameter. Using a “zero-length” coaxial center pin method, this fixture can be applied to up to 2 GHz devices without the need for electrical length compensation.
Polarization Control by Leaky Surface Acoustic Wave in Reverse-Proton-Exchanged LiNbO3 Optical Waveguide
Authors: Kakio Shoji , Sato Sho
Published: July 2012

Polarization control of the optical guided wave in a new configuration using a reverse-proton-exchanged (RPE) LiNbO3 straight waveguide and a leaky surface acoustic wave (LSAW) which propagates perpendicular to the straight waveguide was proposed. First, the perturbation of the dielectric tensor was estimated by using coupled mode theory. When a Love-type SAW on a proton-exchanged layer/YX-LiNbO3 was assumed, comparable perturbations to those in conventional Bragg diffraction due to a Rayleigh wave were confirmed. Next, a sample device with an LSAW wavelength Λ of 136 µm was fabricated on YX-LiNbO3 using an RPE channel waveguide. It was found that the incident linearly polarized wave was rotated by -90° in addition to the inherent rotation due to the perturbation of the LSAW without adding the LSAW wavenumber vector to the propagation constant of the incident optical guided mode. The maximum conversion efficiencies for optical wavelengths of 633, 532, and 473 nm were 87, 43, and 40%, respectively. The measured response time of 280 ns was almost equivalent to the time required for the propagation of the LSAW through the interdigital transducer width.
Study of Relationship between Cut Angle of Substrate and Characteristics of Surface Acoustic Wave Resonators with Shape-Controlled SiO2
Authors: Takayama Ryoichi , Nakanishi Hidekazu , Goto Rei , Satoh Takahiro , Hashimoto Ken-ya
Published: July 2012

This study provides the relationship between cut angles of the rotated Y–X LiTaO3 (LT) substrate and characteristics of surface acoustic wave (SAW) resonators with shape-controlled SiO2 in the SiO2/Al/LT system. The 32–48° Y-cut of LT is well known as the leaky-SAW (LSAW) cut of LT. The propagation characteristics of an LSAW are affected by the surface condition of the substrate, and the optimum cut of LT should be determined with respect to such condition. In this study, we investigated the dependence of SAW resonator characteristics on the shape of SiO2 and on the cut angle of LT by simulation and experiment. The dependence of the reflection coefficient and coupling factor on the shape of SiO2 is not changed by the cut angle of LT, but the dependence of the quality factor (Q-factor) on the shape of SiO2 is changed by the cut angle of LT. Additionally, the dependence of the Q-factor on the cut angle at resonance frequency was different from that at antiresonance frequency. It was shown that LT with the rotation angle of 39–42° gives the optimal balance in this system.
Resonance Properties of Surface Acoustic Wave Resonator in Supercritical CO2
Authors: Kakio Shoji , Hayashi Katsuhiro , Kondoh Eiichi
Published: July 2012

A supercritical fluid is a fluid at a temperature and pressure above its critical point. Supercritical CO2 functions as a moderate solvent, has zero surface tension, and has high permeability in fine structures. These properties are regarded as ideal for the processing of nano- and microscale substances. A problem of applying supercritical fluids is fluctuations in their density. By utilizing a surface acoustic wave (SAW), it may be possible to realize a sensor for measuring the density fluctuation. In this study, the resonance property of a shear-horizontal-type SAW resonator fabricated on a 36° Y–X LiTaO3 substrate and the impedance of an interdigitated electrode (IDE) fabricated on a nonpiezoelectric substrate were measured in high-pressure CO2. Abrupt changes in the resonance property owing to discontinuous changes in the density and viscosity were observed at a certain CO2 pressure between gas and liquid phases. The impedance change of the IDE owing to discontinuous changes in the permittivity was also observed.
Continuous Measurement of Multiple Gases Using Ball Surface Acoustic Wave Gas Chromatograph
Authors: Sakamoto Toshihiro , Akao Shingo , Iwaya Takamitsu , Tsuji Toshihiro , Nakaso Noritaka , Yamanaka Kazushi
Published: July 2012

Although portable gas chromatographs (GCs) have been developed for the monitoring of volatile organic compounds (VOCs) in working environments, they still need high power consumption for the heating column. Thus, we previously developed a portable surface acoustic wave (SAW) GC equipped with a ball SAW sensor and a micro-electromechanical-system column (ball SAW GC) and proved the usefulness of the forward flush (FF) method for realizing the fast analysis of multiple gases without a heater. However, its ability to measure ten kinds of VOCs at ppm order and automatic continuous measurement were not demonstrated. In this study, a ball SAW GC employing the FF method and equipped with a gas sampler for continuous injection was developed. Then, the performance of monitoring multiple gases in working environments was verified by measuring ten kinds of VOCs with maximum acceptable concentrations. Moreover, real-time monitoring of seven kinds of VOCs with a linear change in the response value to concentration changes was demonstrated.
Second Harmonic Component in Focused Gaussian Beam Propagating through Nonuniform Sound-Speed Layer
Authors: Saito Shigemi
Published: July 2012

The fundamental and second harmonic components in a focused sound transmitting through a layer of an inhomogeneous medium with a nonuniform sound speed are analyzed. The nonlinear wave equation including the perturbation of the sound speed is solved with a successive approximation. The influence of the nonuniformity on the measurement of the acoustic nonlinearity parameter B/A in biological samples inserted in the focal region is also investigated. The axial sound-speed variation causes the relative uncertainty of the measured B/A to be the same as the rate of the sound speed within the sample. On the other hand, since the sound beam is refracted owing to the lateral variation of the sound speed, the second harmonic amplitude of the sound detected with the receiver noticeably decreases. Thus, the B/A is underestimated by half the rate of change of the sound speed within a lateral range equivalent to the sample thickness.
Measurement of Spatial Distribution in Vertical Direction of Cavitation Generation by Using High Resolution Cavitation Sensor
Authors: Uchida Takeyoshi , Takeuchi Shinichi , Kikuchi Tsuneo
Published: July 2012

We have been studying measurement techniques of acoustic cavitation using a cavitation sensor. Cavitation was investigated using broadband integrated voltage (BIV) calculated from broadband noise. In this study, the distribution of BIV in the vertical direction in a water vessel was measured with a novel cavitation sensor with improved spatial resolution. As a result, it was found that the pattern of standing wave acoustic field could be measured with the novel cavitation sensor. Also, the values of BIV measured in the vertical direction agreed well with sonochemical luminescence. The novel sensor has potential as a tool for accurate evaluation using acoustic cavitation in several fields.
Effects of Operational Conditions on 1,4-Dioxane Degradation by Combined Use of Ultrasound and Ozone Microbubbles
Authors: Xu Zheng , Mochida Kyosuke , Naito Tetsuya , Yasuda Keiji
Published: July 2012

1,4-Dioxane is regarded as a priority pollutant because it is hardly degraded by conventional methods of wastewater treatment. In this study, the degradation of 1,4-dioxane in water by the combined use of ultrasound and ozone microbubbles has been investigated. 1,4-Dioxane degradation by ultrasound and/or ozone followed a first-order reaction kinetics. The reaction constant for ozone microbubbles was higher than that for ozone millibubbles. The synergistic effect on reaction constant has been observed by the combined use of ultrasound and ozone microbubbles. The effect of hydroxyl radicals on reaction has also been investigated. Compared with the direct reactions of ultrasound and ozone, hydroxyl radicals play a major role in 1,4-dioxane degradation. The synergistic effect is enhanced with increasing ultrasonic input power and ozone concentration. Empirical equations of the relationships between ultrasonic input power, ozone concentration, and reaction rate constant have been established.
Sonophotolytic Degradation of Estriol at Various Ultraviolet Wavelength in Aqueous Solution
Authors: Na Seungmin , Park Beomguk , Cho Eunju , Koda Shinobu , Khim Jeehyeong
Published: July 2012

This study investigated degradation of the hormone estriol by sonolysis, photolysis and sonophotolysis at various UV wavelengths. Degradation was determined with UVA (365 nm), UVC (254 nm), or VUV (185 nm) irradiation and/or ultrasound exposure (283 kHz). The pseudo-first order degradation rate constants were in the order of 10-1 to 10-4 min-1 depending on the processes. The dominant reaction mechanism of estriol in sonolysis was estimated as hydroxyl radical reaction by the addition of tert-butanol (t-BuOH), which is a common hydroxyl radical scavenger. Photolytic and sonophotolytic estriol degradation rate also were high at shortest UV wavelength (VUV) due to the higher energy of photons, higher molar absorption coefficient of estriol and increased hydroxyl radical generation from the homolysis of water. Small synergistic effects were observed for sonophotolytic degradation with UVA and UVC irradiation. No synergy was observed for sonophotolysis with VUV irradiation.
Sonochemical Oxidation of Cyanide Using Potassium Peroxydisulfate as an Oxidizing Agent
Authors: Cui Mingcan , Jang Min , Lee Seban , Khim Jeehyeong
Published: July 2012

In this study, the sonochemical oxidation of cyanide in the presence of peroxydisulfate (PDS) ions has been investigated. As a result of experiments, sulfate anion radicals (·SO4
-) and hydroxide radicals (·OH) produced by PDS ions in acoustic cavitation could readily oxidize and even mineralize cyanide in an aqueous environment. When the frequency of ultrasound and PDS ions were applied at 450 kHz and 60 mg·L-1, the efficiencies of mineralization for free cyanide (CN-) and thiocyanate (SCN-) were 99.3 and 99%, respectively. The kinetics of total organic carbon (TOC) reduction for CN- and SCN- oxidation were interpreted using the modified pseudo-first-order kinetic model. In this study, carbonate and nitrate were found to be by-products of CN- oxidation while sulfate, carbonate and nitrate were by-products of SCN- oxidation.
Removal of Arsenic from Sulfuric Acid Solutions Using Jarosite and Sonication
Authors: Hosokawa Ryota , Okawa Hirokazu
Published: July 2012

We investigated the effect of ultrasound irradiation at 200 kHz on As(III) and As(V) removal using jarosite. When the solution containing As(V) was irradiated in air, Ar, or O2 atmospheres, As(V) removal rate increased with irradiation time as compared with treatment by stirring. Likewise, when the solution containing As(III) was sonicated in Ar or O2 atmospheres, the As removal rate increased with irradiation time because As(III) was oxidized to As(V) by the sonication and As(V) was removed from the solution by the adsorption onto jarosite. However, in air, the removal rate increased only slightly with irradiation time. This is partly because As(III) removal was interfered by the adsorption of HNO3, which was generated during sonication, onto jarosite. Therefore, As(V) removal by the simultaneous application of jarosite and ultrasound irradiation can be performed in air, Ar and O2 atmospheres, while As(III) removal can be performed efficiently in either Ar or O2 atmosphere.
Stress Analysis of Contact Surface in Ultrasonically Forced Insertion Process
Authors: Ono Satoshi , Aoyagi Manabu , Tamura Hideki , Takano Takehiro
Published: July 2012

To clarify the mechanism of an ultrasonically forced insertion (USFI), frictional stresses and displacements on the contact surface of a metal rod and a metal plate in the USFI process were analyzed by finite element method. Frictional stresses under two conditions were compared. One of the conditions was a horn and the metal rod moving with static displacement. The other was the horn and the metal rod moving with vibrational displacement. The amplitude and distribution of frictional stresses under the vibrational condition were small and almost flat, respectively. Axial and radial displacements of the plate and rod on the contact surface in a USFI process were also analyzed. As results, it was clarified that the USFI had the effect of reduction of frictional stress.
An Ultrasonic Motor for Use at Ultralow Temperature Using Lead Magnesium Niobate–Lead Titanate Single Crystal
Authors: Yamaguchi Daisuke , Kanda Takefumi , Suzumori Koichi , Kuroda Masataka , Takeda Dai
Published: July 2012

In this study, an ultrasonic motor for use at ultralow temperatures has been fabricated and evaluated. The motor has a bolt-clamped Langevin-type transducer using lead magnesium niobate–lead titanate (PMN–PT) single crystal. The transducer is proposed as an oscillator for use at ultralow temperatures by simulation of the thermal stress and evaluation of the pre-load. The thermal effect of the transducer was evaluated when the temperature was changed. As a result, the pre-load of the transducer was concluded to be affected by thermal stress. In addition, the ultrasonic motor using the transducer was fabricated and evaluated. By adjusting the contact pre-load between the rotor and the transducer, the motor has successfully rotated at an ultralow temperature. The rotation speed was 144 rpm at 4.4 K when the applied voltage was 150 Vp–p. This rotation speed is larger than that of previous same size actuators that can be used at ultralow temperatures.
A Method for Improving Signal-to-Noise Ratio of Tissue Harmonic Imaging Based on Bayesian Inference Using Information of Fundamental Echoes
Authors: Yamamura Takuya , Tanabe Masayuki , Okubo Kan , Tagawa Norio
Published: July 2012

A medical ultrasound imaging technique with a high spatial resolution and a high signal-to-noise ratio (SNR) is strongly required for precise diagnosis. To obtain high-resolution images, tissue harmonic imaging (THI) can be effectively adopted because of its wide bandwidth characteristics compared with fundamental imaging. However, the amplitude of harmonic components is much smaller than that of a fundamental component. Additionally, frequency dependent attenuation is severe, especially for harmonic components. These phenomena mean that THI is susceptible to noise. From these considerations, in this study, we propose a method for improving the SNR of THI by reducing noise using a signal processing technique. The proposed method is constructed based on the Bayesian inference using fundamental components of echoes, and it can hold the high-resolution nature of THI. We show the effectiveness of the proposed method through simulations.
Evaluation of Rate of Change in Thickness of Heart Wall by Measuring Time Variation of Ultrasonic Integrated Backscatter during a Cardiac Cycle
Authors: Shida Hiro , Hasegawa Hideyuki , Kanai Hiroshi
Published: July 2012

Integrated backscatter (IB) from the heart wall is gaining attention as a quantitative tissue characterization method and the cyclic variation (CV) in IB during a cardiac cycle offers potential for the evaluation of myocardial contractility. Since there is large motion in the heart wall owing to the heartbeat, in the conventional method, the position of the region of interest (ROI) for calculating the IB is manually assigned in each frame during one cardiac cycle. Moreover, the change in the size of the ROI during contraction and relaxation of the myocardium is not considered. In this study, the phased tracking method was applied to multiple points in the heart wall for automatic tracking of the position and size of the ROI and, then, IB in the same site of the heart wall was measured in each frame by improving temporal resolution and spatial resolution in the axial direction. As a result, cyclic variations, which differed site by site, were found. Furthermore, the rate of change in thickness was estimated by using the interference cycle obtained by applying the discrete Fourier transform (DFT) to IB signals. According to the results, the rate of change in thickness estimated using the interference cycle of IB was in good agreement with that estimated by the phased tracking method. These results indicate the possibility of estimating the rate of change in thickness using the IB signal.
Experimental Evaluation of Quantitative Diagnosis Technique for Hepatic Fibrosis Using Ultrasonic Phantom
Authors: Koriyama Atsushi , Yasuhara Wataru , Hachiya Hiroyuki
Published: July 2012

Since clinical diagnosis using ultrasonic B-mode images depends on the skill of the doctor, the realization of a quantitative diagnosis method using an ultrasound echo signal is highly required. We have been investigating a quantitative diagnosis technique, mainly for hepatic disease. In this paper, we present the basic experimental evaluation results on the accuracy of the proposed quantitative diagnosis technique for hepatic fibrosis by using a simple ultrasonic phantom. As a region of interest crossed on the boundary between two scatterer areas with different densities in a phantom, we can simulate the change of the echo amplitude distribution from normal tissue to fibrotic tissue in liver disease. The probability density function is well approximated by our fibrosis distribution model that is a mixture of normal and fibrotic tissue. The fibrosis parameters of the amplitude distribution model can be estimated relatively well at a mixture rate from 0.2 to 0.6. In the inversion processing, the standard deviation of the estimated fibrosis results at mixture ratios of less than 0.2 and larger than 0.6 are relatively large. Although the probability density is not large at high amplitude, the estimated variance ratio and mixture rate of the model are strongly affected by higher amplitude data.
Mechanical Model Analysis for Quantitative Evaluation of Liver Fibrosis Based on Ultrasound Tissue Elasticity Imaging
Authors: Shiina Tsuyoshi , Maki Tomonori , Yamakawa Makoto , Mitake Tsuyoshi , Kudo Masatoshi , Fujimoto Kenji
Published: July 2012

Precise evaluation of the stage of chronic hepatitis C with respect to fibrosis has become an important issue to prevent the occurrence of cirrhosis and to initiate appropriate therapeutic intervention such as viral eradication using interferon. Ultrasound tissue elasticity imaging, i.e., elastography can visualize tissue hardness/softness, and its clinical usefulness has been studied to detect and evaluate tumors. We have recently reported that the texture of elasticity image changes as fibrosis progresses. To evaluate fibrosis progression quantitatively on the basis of ultrasound tissue elasticity imaging, we introduced a mechanical model of fibrosis progression and simulated the process by which hepatic fibrosis affects elasticity images and compared the results with those clinical data analysis. As a result, it was confirmed that even in diffuse diseases like chronic hepatitis, the patterns of elasticity images are related to fibrous structural changes caused by hepatic disease and can be used to derive features for quantitative evaluation of fibrosis stage.
Effect of Cortical Bone Layer on Fast and Slow Waves in Cancellous Bone: Investigations Using Stratified Models
Authors: Hosokawa Atsushi , Nagatani Yoshiki
Published: July 2012

Fast and slow longitudinal waves can propagate through cancellous bone in the direction of the strong trabecular orientation. In in vivo experiments, the cortical bone layer surrounding cancellous bone is considered to affect the fast and slow wave propagations. In this study, the effects of the cortical bone layer were investigated using the stratified models of cancellous bone. In the experimental and simulated results, it was shown that the boundary condition between the cancellous and cortical bone regions affected both the fast and slow waves, particularly the slow wave. The slow wave could be clearly observed for the stratified bone model with a distinct boundary, but the slow wave amplitude decreased as the boundary became less distinct. This was because the generation of the slow wave was interrupted by the gradually varying pore spaces. Moreover, it was shown that the reflected waves within the cortical bone layer could affect the observation of the fast and slow waves. Despite the effects of the cortical bone layer, both the fast and slow waves could be observed for all stratified bone models.
Propagation Velocity of Bone-Conducted Ultrasound in the Human Head
Authors: Hotehama Takuya , Nakagawa Seiji
Published: July 2012

In this study, we investigated the propagation velocity of bone-conducted ultrasound (BCU) in a living human head. The propagation velocity was calculated using the pattern of acoustic interference, which was extracted from the distribution of the acceleration responses induced as a function of frequency and inter lateral phase difference of bilaterally presented BCU stimuli. Stepped sine signals from 28 to 32 kHz in 100 Hz steps with an interlateral phase difference from -2π to 2π in π/8 steps were used as excitation signals. The estimated propagation velocities were approximately 300 m/s. Furthermore, a simple numerical simulation for the bilateral presentation of BCU stimuli using the estimated velocity was conducted. The simulated acoustic interference pattern was similar to the results of the actual measurements, supporting the fact that the acoustical interference of BCU stimuli induced by bilateral presentation can be estimated with this model.
High Voltage Staircase Drive Circuit for Triggered High-Intensity Focused Ultrasound Treatment
Authors: Takada Keisuke , Okada Jumpei , Nakamura Kotaro , Yoshizawa Shin , Umemura Shin-ichiro
Published: July 2012

In triggered high-intensity focused ultrasound (HIFU) treatment, cavitation clouds are produced by extremely high intensity trigger pulses and enhance the effect of following heating waves. The ultrasound intensity must be quickly changed from that for trigger pulses to that for heating waves before cavitation clouds vanish. We newly designed and constructed a class D amplifier based on a staircase voltage drive concept, which has the capability of outputting high voltage waves for trigger pulses and continuous waves for heating waves and the capability of fast switching between the two modes. Its efficacy was confirmed by an experiment with a BSA containing polyacrylamide gel.
Monitoring of Lesion Induced by High-Intensity Focused Ultrasound Using Correlation Method Based on Block Matching
Authors: Matsuzawa Ryo , Shishitani Takashi , Yoshizawa Shin , Umemura Shin-ichiro
Published: July 2012

High-intensity focused ultrasound (HIFU) is a noninvasive therapeutic application that focuses ultrasound to the target tissue, such as a malignant tumor, and thermally coagulates it. Monitoring methods for evaluating the formation of thermal lesions induced by HIFU are required to perform safe and accurate HIFU treatment. However, the conventional ultrasonic B-mode image incurs difficulties in assessing the formation of HIFU-induced lesions. In this study, ultrasound RF signals were acquired during HIFU exposure. A correlation coefficient was used to evaluate the changes occurring in the RF signals backscattered from the thermal lesion. Also, a block matching algorithm has been implemented to compensate the tissue motion during HIFU exposure. The experimental results show that correlation coefficients in the focal spot decreased significantly with HIFU exposure, which indicates that the backscattered RF signals changed owing to tissue coagulation.
Observation of Microhollows Produced by Bubble Cloud Cavitation
Authors: Yamakoshi Yoshiki , Miwa Takashi
Published: July 2012

When an ultrasonic wave with sound pressure less than the threshold level of bubble destruction irradiates microbubbles, the microbubbles aggregate by an acoustic radiation force and form bubble clouds. The cavitation of bubble clouds produces a large number of microhollows (microdips) on the flow channel wall. In this study, microhollow production by bubble cloud cavitation is evaluated using a blood vessel phantom made of N-isopropylacrylamide (NIPA) gel. Microbubble dynamics in bubble cloud cavitation is observed by a microscope with a short pulse light emitted diode (LED) light source. Microhollows produced on the flow channel wall are evaluated by a confocal laser microscope with a water immersion objective. It is observed that a mass of low-density bubbles (bubble mist) is formed by bubble cloud cavitation. The spatial correlation between the bubble mist and the microhollows shows the importance of the bubble mist in microhollow production by bubble cloud cavitation.
Ultrasound-Mediated Gene Transfection In vitro: Enhanced Efficiency by Complexation of Plasmid DNA
Authors: Zhang Yiwei , Tachibana Rie , Okamoto Akio , Azuma Takashi , Sasaki Akira , Yoshinaka Kiyoshi , Osada Kensuke , Kataoka Kazunori , Takagi Shu , Matsumoto Yoichiro
Published: July 2012

Ultrasound-mediated gene transfection in the presence of microbubbles is a recently developed promising nonviral gene delivery method. The main obstacle towards its clinical application is its low transfection efficiency. In this work, we investigate the effect of the complexation of plasmid DNA (pDNA) into polyplex micelles on the transfection efficiency. Complexation changes the structure of pDNA and results in the condensation in size and enhanced stability. Both naked and complexed pDNAs were transfected into cultured cells using ultrasound in the presence of microbubbles. The transfection rate using complexed pDNA is considerably enhanced (from ∼0.92 to ∼1.67%, by ∼82%) compared with the rate using naked pDNA. Our method provides an alternative for the improvement of the transfection efficiency of the ultrasound-mediated method.
Geoacoustic Inversion of Mid-Frequency Bottom Loss Data in Shallow Water off the East Coast of Korea
Authors: Lee Changil , Cho Sungho , Choi Jee Woong , Shim Taebo , Lee Yong-Kuk
Published: July 2012

Mid-frequency bottom loss measurements over a grazing angle range of 25 to 70° at frequencies of 6, 8, and 10 kHz were made off the east coast of Korea in October 2008. In this paper, geoacoustic parameters including the sediment sound speed, density, attenuation coefficient, and thickness of the surficial sediment layer are estimated via comparison between the measured bottom loss and a bottom reflection forward model based on the two-layered fluid sediment structure. A global search is performed over the search space of geoacoustic parameters by a genetic algorithm method, in which the weighted squared error between the data and the model predictions is used as an objective function to be minimized. The inversion result shows that a thin lower sound speed layer with a thickness of 0.4 m overlies the higher sound speed sediment. This result is consistent with marine geological observations conducted at the experimental site.
Underwater Target Echo Signal Separation Using Independent Component Analysis and Principal Component Analysis
Authors: Son Kweon , Lee Yonggon , Cho Jinho , Lee Minho
Published: July 2012

Experimental results, measured in the open ocean using a real target for true target echo signal separation from a mixture of reverberations and noises are presented. The proposed modified independent component analysis (ICA) in conjunction with principal component analysis (PCA), which can preserve the original source signal amplitude, separated the true target echoes from the reflected active sonar signals. In addition, the signal-to-noise ratio (SNR) of the proposed method output was about 3 dB better than that of the conventional beamforming technique.
Experimental Study of Doppler Effect for Underwater Acoustic Communication Using Orthogonal Signal Division Multiplexing
Authors: Ebihara Tadashi , Mizutani Keiichi
Published: July 2012

This paper is about the underwater acoustic (UWA) communication using orthogonal signal division multiplexing (OSDM) in shallow water, whose environment is time spread and frequency spread. In this paper, the Doppler effect – Doppler shift and spread – for UWA communication using OSDM is mainly considered. The effects of Doppler shift and Doppler spread are evaluated in a test tank with a moving platform on a stable water surface and with a stable platform with a moving water surface, respectively. Doppler shift correction, which has been considered in simulation-based studies, is found to work effectively. In relation to the effect of Doppler spread, the experimental result well agrees with the simulation result. Through this study, it is confirmed that a smaller frame length is preferable because it enables the measurement of the UWA channel frequently so that it can keep up with channel changes.
Seawater Temperature and Wind Speed Dependences and Diurnal Variation of Ambient Noise at the Snapping Shrimp Colony in Shallow Water of Southern Sea of Korea
Authors: Jung Seom-Kyu , Choi Bok Kyoung , Kim Bong-Chae , Kim Byoung-Nam , Kim Seong Hyeon , Park Yosup , Lee Yong-Kuk
Published: July 2012

The seawater temperature and wind dependences and diurnal variation of the ambient noise at the snapping shrimp colony in shallow water of the southern sea of Korea were investigated. The ambient noise levels are significantly affected by the snapping shrimp sound, when the bottom seawater temperature increases and the wind speed decreases. However, they are not exceptively almost affected by the snapping shrimp sound when the wind speed decreases at low seawater temperatures (<10 °C). In diurnal variation, the ambient noise levels are also significantly affected by the snapping shrimp sound in the morning and night time zones. This study shows that the activity of the snapping shrimp affecting the variation in ambient noise level in shallow water can be related to the wind speed as well as the seawater temperature. This study also shows that the snapping shrimp in diurnal activity can be more active in the morning and night time zones.
Extraction of Target Scatterings from Received Transients on Target Detection Trial of Ambient Noise Imaging with Acoustic Lens
Authors: Mori Kazuyoshi , Ogasawara Hanako , Nakamura Toshiaki , Tsuchiya Takenobu , Endoh Nobuyuki
Published: July 2012

We have already designed and fabricated an aspherical lens with an aperture diameter of 1.0 m to develop a prototype system for ambient noise imaging (ANI). It has also been verified that this acoustic lens realizes a directional resolution, which is a beam width of 1° at the center frequency of 120 kHz over the field of view from -7 to +7°. In this study, a sea trial of silent target detection using the prototype ANI system was conducted under only natural ocean ambient noise at Uchiura Bay, in November of 2010. There were many transients in the received sound. These transients were classified roughly into directly received noises and target scatterings. We proposed a classification method to extract transients of only target scatterings. By analyzing transients extracted as target scatterings, it was verified that the power spectrum density levels of the on-target directions were greater than those of the off-target directions in the higher frequency band over 60 kHz. These results showed that the targets are successfully detected under natural ocean ambient noise, mainly generated by snapping shrimps.
Basic Study of Properties of Planate Acoustic Lens Constructed with Phononic Crystal Structure
Authors: Tsuchiya Takenobu , Anada Tetsuo , Endoh Nobuyuki , Matsumoto Sayuri , Mori Kazuyoshi
Published: July 2012

We developed a planate acoustic lens with a phononic crystal structure for acoustic imaging technology in ocean. To determine the properties of the planate acoustic lens, we simulated the sound field converged by the lens using a finite difference time domain (FDTD) method. In addition, we manufactured a prototype of the planate acoustic lens using stainless-steel rods. In this study, we performed a small-scale trial to reduce the scale to one-tenth the original size of the lens. We measured the sound field converged by the manufactured prototype lens in a water tank. A burst pulse with a frequency of 740 kHz radiated from a transducer. Measurement results agree well with analysis results. The focal distances of measurement and analysis were 12.5 and 11.7 mm, respectively. The measured -3 dB beam width at 3.1 mm almost agrees with the analysis result at 2.3 mm.
InAlAs Graded Metamorphic Buffer with Digital Alloy Intermediate Layers
Authors: Gu Yi , Zhang Yonggang , Wang Kai , Fang Xiang , Liu Kehui
Published: July 2012

In this work, the threading dislocation suppression effects of InAs/In0.52Al0.48As digital alloy intermediate layers in an InP-based InAlAs graded metamorphic buffer were investigated to improve the structural and optical qualities of the buffer. Cross-sectional transmission electron microscopy, atomic force microscopy, and photoluminescence measurements proved that the insertion of thin digital alloy layers in the graded buffer markedly improves the surface quality, decreases the threading dislocation density, and enhances the photoluminescence efficiency of In0.8Ga0.2As/In0.8Al0.2As quantum wells. This study shows great potentials by incorporating digital alloy intermediate layers in metamorphic buffers to improve the quality of metamorphic devices.
Characteristic Variations of Graphene Field-Effect Transistors Induced by CF4 Gas
Authors: Park Jaehoon , Park Kun-Sik , Jeong Ye-Sul , Baek Kyu-Ha , Lee Bong Kuk , Kim Dong-Pyo , Ryu Jin-Hwa , Do Lee-Mi , Imamura Hiroshi , Yase Kiyoshi , Choi Jong Sun
Published: July 2012

The influence of tetrafluoromethane (CF4) gas on the electrical characteristics of monolithic graphene field-effect transistors (FETs) is reported. Compared with the results in nitrogen ambient, FETs in CF4 ambient exhibit a positive shift in the Dirac point voltage and an increase in drain current. These changes are ascribed to the electronegative nature of the fluorine atoms in CF4 gas, which is found to induce p-type doping and excess charge carriers in graphene. The electrical response to CF4 gas exposure demonstrates the feasibility of using monolithic graphene FETs as chemical sensors.
Effects of Synthesis Process on Luminescence Properties and Structure of Mesoporous Carbon–Silica Nanocomposite
Authors: Sato Koji , Ishikawa Yukari , Ishii Yosuke , Kawasaki Shinji , Muto Shunsuke , Yamamoto Yuta
Published: July 2012

The effects of hydrolysis and polycondensation reactions for synthesizing light-emitting mesoporous carbon–silica (MPCS) nanocomposite on the structure, chemical bonding state, and luminescence properties of MPCS were investigated by controlling the concentration (0.02 to 5 M) of HCl, which was used as a catalyst for hydrolysis and polycondensation. The progress of hydrolysis and polycondensation reactions provides a nanometer-order pore/wall structure and results in a strong light-emitting property. The pore/wall structure was obtained using HCl at concentrations of 0.2 M and higher, but it became disordered with increasing HCl concentration (2 and 5 M). The luminescence color of the MPCS nanocomposite can be changed from yellowish-white to bluish-white by changing the concentration of HCl.
Graphene Made by Mechanical Exfoliation of Graphite Intercalation Compound
Authors: Fukada Seiya , Shintani Yumi , Shimomura Midori , Tahara Fumiya , Yagi Ryuta
Published: July 2012

We report a method of making few-layer graphene flakes by mechanically exfoliating SbCl5–graphite intercalation compounds (GICs). The number of layers of exfoliated graphene flakes had a particular distribution relevant to the stage structure of the GICs. The carrier doping of the few-layer graphene flakes was about two orders of magnitude smaller than that expected from the stoichiometry of the GICs. The measured electric mobility was comparable to that made from pristine graphite.
Line-Profiles and Translational Temperatures of Pb Atoms in Multi-Micro Hollow Cathode Lamp Measured by Diode Laser Absorption Spectroscopy
Authors: Inoue Mari , Ohta Takayuki , Takota Naoki , Tsuchitani Shigeki , Ito Masafumi , Takashima Seigo , Kano Hiroyuki , Yamakawa Koji , Takeda Keigo , Hori Masaru
Published: July 2012

The behaviors of Pb and metastable He atoms in the multi-micro hollow cathode lamp (multi-MHCL) at pressures of the order of kPa have been investigated by diode laser absorption spectroscopy. The pressure broadening effect for absorption line-profile was overlapped to Doppler profile and was estimated to be 0.26 MHz/Pa from line-profiles of metastable He atoms in the range from 5 to 10 kPa. The translational temperatures of metastable He atoms decreased from 830 to 410 K with increasing the pressure from 5 to 10 kPa. From line-profiles of Pb atoms, the temperatures and densities of Pb in the multi-MHCL were evaluated to decrease from 820 to 610 K and 9.0×1011 to 4.6×1011 cm-3 with increasing He pressure from 4.9 to 7.4 kPa, respectively. The Lorentz broadenings was larger than those of He atom and the pressure dependence were estimated to be 0.22 MHz/Pa. The behaviors of emission intensities corresponded with those of atomic densities due to enhancement of sputtering. From these results, the multi-MHCL with line-profile guaranteed has been realized for measuring multi-metallic atom densities precisely.
Microfabrication of Si and GaAs by Plasma Etching Process Using Bacterial Cells as an Etching Mask Material
Authors: Matsutani Akihiro , Takada Ayako
Published: July 2012

We demonstrated that bacterial cells can be used as a mask material for microfabrication of GaAs and Si by a Cl2 inductively coupled plasma (ICP) etching process. The etching rate of Escherichia coli cells was similar to that of electron beam resist or nanoimprint resist. We also demonstrated the degradation of bacterial cells by low-pressure plasma treatment using O2, Ar, air, and H2O for removal of bacterial cells as the etching mask material. Bacterial cells were efficiently degraded by ions in the low-pressure discharge plasma. The proposed process using bacterial cells can be expected to be applied to semiconductor dry etching processes.
Peak Intensity Stabilization of Fundamental Laser through Second-Harmonic Generation Process
Authors: Harimoto Tetsuo , Tsugane Hidetomo
Published: July 2012

In this paper, we report on numerical and experimental results for the peak intensity stabilization of a fundamental laser through the second-harmonic generation process by introducing a phase-mismatching factor. The peak intensity fluctuation of a nanosecond-order fundamental laser at 1064 nm is reduced from 7.0 to 1.1% with a type-I noncritical phase-mismatching lithium triborate crystal heated at a phase-mismatching temperature of 146.7 °C. The method is applicable to the power stabilization of the laser with a flat-top beam profile.
Regional differences in rat conjunctival ion transport activities
Authors: Yu Dongfang , Thelin William R. , Rogers Troy D. , Stutts M. Jackson , Randell Scott H. , Grubb Barbara R. , Boucher Richard C.
Published: July 2012

Active ion transport and coupled osmotic water flow are essential to maintain ocular surface health. We investigated regional differences in the ion transport activities of the rat conjunctivas and compared these activities with those of cornea and lacrimal gland. The epithelial sodium channel (ENaC), sodium/glucose cotransporter 1 (Slc5a1), transmembrane protein 16 (Tmem16a, b, f, and g), cystic fibrosis transmembrane conductance regulator (Cftr), and mucin (Muc4, 5ac, and 5b) mRNA expression was characterized by RT-PCR. ENaC proteins were measured by Western blot. Prespecified regions (palpebral, fornical, and bulbar) of freshly isolated conjunctival tissues and cell cultures were studied electrophysiologically with Ussing chambers. The transepithelial electrical potential difference (PD) of the ocular surface was also measured in vivo. The effect of amiloride and UTP on the tear volume was evaluated in lacrimal gland excised rats. All selected genes were detected but with different expression patterns. We detected αENaC protein in all tissues, βENaC in palpebral and fornical conjunctiva, and γENaC in all tissues except lacrimal glands. Electrophysiological studies of conjunctival tissues and cell cultures identified functional ENaC, SLC5A1, CFTR, and TMEM16. Fornical conjunctiva exhibited the most active ion transport under basal conditions amongst conjunctival regions. PD measurements confirmed functional ENaC-mediated Na+ transport on the ocular surface. Amiloride and UTP increased tear volume in lacrimal gland excised rats. This study demonstrated that the different regions of the conjunctiva exhibited a spectrum of ion transport activities. Understanding the specific functions of distinct regions of the conjunctiva may foster a better understanding of the physiology maintaining hydration of the ocular surface.
Identification of the spinal pathways involved in the recovery of baroreflex control after spinal lesion in the rat using pseudorabies virus
Authors: Castillo Deborah G. , Zahner Matthew R. , Schramm Lawrence P.
Published: July 2012

Neurons in the rostroventrolateral medulla (RVLM) mediate baroreflex regulation (BR) of spinal sympathetic preganglionic neurons. Previously, our laboratory has shown that recovery of BR occurs in the rat after spinal hemisection. (Zahner MR, Kulikowicz E, and Schramm LP. Am J Physiol Regul Integr Comp Physiol 301: R1584–R1590, 2011). The goal of these experiments was to determine whether the observed recovery of BR is mediated by the reorganization of ipsilateral pathways or by compensation by spared contralateral pathways. To determine this, we infected the left kidney in rats with the retrograde transynaptic tracer, pseudorabies virus (PRV), either 1 or 8 wk after left spinal hemisection at either T3 or T8, or after a sham lesion. In sham-lesioned rats, PRV infection of RVLM neurons was bilateral. In all rats with a left hemisection, regardless of the location of the lesion (T3 or T8) or postlesion recovery time (1 or 8 wk), PRV infection of left RVLM neurons was significantly reduced compared with sham-lesioned rats ( P < 0.05). In a separate group of rats, we performed BR tests by measuring responses of left renal sympathetic nerve activity to pharmacologically induced decreases and increases in arterial pressure. In rats with T8 left hemisection and 8-wk recovery, BR was robust, and acute right upper thoracic hemisection abolished all BR of left renal sympathetic nerve activity. Collectively, these data suggest that the recovery of BR is not mediated by reorganization of ipsilateral bulbospinal connections, but instead by improved efficacy of existing contralateral pathways.