MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'Ultrasonics' source. Mon, 06 Feb 2012 20:25:04 +0100 http://www.medworm.com/index.php?rid=5637738&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22273150%26dopt%3DAbstract Authors: Fu Z, Xian X, Lin S, Wang C, Hu W, Li G Abstract In this paper, the resonance frequency equation and expression of displacement amplitude magnifications of a full-wave barber ultrasonic horn are obtained. By discussing the relationships between the displacement amplitude magnifications and the geometrical dimensions, the optimized design of the horn for the largest magnification is proposed, which is helpful to improve the radiation power and the transfer efficiency of the acoustic energy of the ultrasonic oscillatory system. Based on the optimized design of the horn, we introduced a barbell ultrasonic transducer operated in the longitudinal full-wave vibrational model and obtained the resonance frequency equations. For comparison, the resonance frequencies of the full-wav... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5637738 Sun, 08 Jan 2012 05:00:00 +0100 5637738 http://www.medworm.com/index.php?rid=5619398&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22261345%26dopt%3DAbstract This study aims mainly to investigate the adverse effects of this inherent removal phenomena on the hole integrity such as entrance chipping, wall roughness and subsurface damage. It also presents the material removal mechanism happens in the gap between the tool periphery and the hole wall (called 'lateral gap'). To do so, experiments were conducted for drilling holes on three advanced structural ceramics, namely, silicon carbide, zirconia, and alumina. Earlier published basic studies on the initiation of different crack modes and their growth characteristics are employed to explain the experimental findings in this USM study. It is realized that the radial and the lateral cracks formed due to adjacent abrasives, which are under the tool face, extends towards radial direction of the hole ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5619398 Tue, 03 Jan 2012 05:00:00 +0100 5619398 http://www.medworm.com/index.php?rid=5596611&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22239830%26dopt%3DAbstract Authors: Son KT, Lee CC Abstract Silver epoxy was selected to bond transducer plates on glass substrates. The properties and thickness of the bonding medium affect the electrical input impedance of the transducer. Thus, the thickness of the silver epoxy bonding layer was used as a design parameter to optimize the structure for the transducer input impedance to match the 50Ω output impedance of most radio frequency (RF) generators. Simulation and experimental results show that nearly perfect matching is achieved without using any matching circuit. At the matching condition, the transducer operates at a frequency band a little bit below the half-wavelength resonant frequency of the piezoelectric plate. In experiments, lead titanate (PT) piezoelectric plates were employed. Both full-... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5596611 Sat, 24 Dec 2011 05:00:00 +0100 5596611 http://www.medworm.com/index.php?rid=5577199&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22218222%26dopt%3DAbstract Authors: Yan ZZ, Zhang C Abstract The localization properties of in-plane elastic waves propagating in two-dimensional porous phononic crystals with one-dimensional aperiodicity are initially analyzed by introducing the concept of the localization factor that is calculated by the plane-wave-based transfer-matrix method in this paper. The band structures characterized by using localization factors are calculated for different phononic crystals by altering matrix material properties and geometric structure parameters. Numerical results show that the effect of matrix material properties on wave localization can be ignored, while the effect of geometric structure parameters is obvious. For comparison, the periodic porous system and Fibonacci system with rigid inclusion are also analyze... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5577199 Wed, 21 Dec 2011 05:00:00 +0100 5577199 http://www.medworm.com/index.php?rid=5577198&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22222180%26dopt%3DAbstract Authors: Belovickis J, Rimeika R, Ciplys D Abstract The acousto-optic interaction with leaky surface acoustic wave radiation into the bulk of YX-cut LiTaO(3) crystals has been investigated. The light incidence and diffraction angles corresponding to the strongest acousto-optic interaction were calculated and measured as functions of the acoustic wave frequency. The dependencies of the diffracted light intensity on the amplitude of radio-frequency voltage applied to the interdigital transducer (IDT) were studied. Our acousto-optic measurements revealed generation, by the IDTs, of slow shear bulk acoustic waves propagating at different angles depending on their frequency. A secondary acousto-optic interaction from the bulk waves radiated by the receiving IDT has been studied. PMI... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5577198 Wed, 21 Dec 2011 05:00:00 +0100 5577198 http://www.medworm.com/index.php?rid=5558841&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22209089%26dopt%3DAbstract Authors: Lobkis OI, Yang L, Li J, Rokhlin SI Abstract An analytical solution for a three dimensional integral representation of the backscattering (BS) coefficient in polycrystals with elongated (generally ellipsoidal) grains is obtained; it is a natural generalization of the known explicit result for the BS coefficient in polycrystals with spherical grains. New insights into the dependence of the BS signal on frequency and averaged ellipsoidal grain radii are obtained. In particular it has been shown that the dominant factor for the backscattering is the averaged interaction length of the ellipsoidal grain in the direction of wave propagation, instead of the ellipsoidal cross-section. The theory was applied to a simplified model of Ti alloy duplex microstructure and was compared w... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5558841 Tue, 20 Dec 2011 05:00:00 +0100 5558841 http://www.medworm.com/index.php?rid=5558842&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22209088%26dopt%3DAbstract Authors: He T, Pan Q, Liu Y, Liu X, Hu D Abstract This paper attempts to introduce a near-field acoustic emission (AE) beamforming method to estimate the AE source locations by using a small array of sensors closely placed in a local region. The propagation characteristics of AE signals are investigated based on guided wave theory to discuss the feasibility of using beamforming techniques in AE signal processing. To validate the effectiveness of the AE beamforming method, a series of pencil lead break tests at various regions of a thin steel plate are conducted. The potential of this method for engineering applications are explored through rotor-stator rubbing tests. The experimental results demonstrate that the proposed method can effectively determine the region where rubbing occ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5558842 Sat, 17 Dec 2011 05:00:00 +0100 5558842 http://www.medworm.com/index.php?rid=5558843&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22204917%26dopt%3DAbstract We present the results of two different approaches to generating a collimated beam in three types of highly attenuating drilling mud. In the first approach, the drilling mud itself was used as a nonlinear mixing medium to create a parametric array. However, the short absorption length in mud limits the mixing length and, consequently, the resulting beam is weak and broad. In the second improved approach, the beam generation process was confined to a separate "frequency mixing tube" that contained an acoustically non-linear, low attenuation medium (e.g., water) that allowed establishing a usable parametric array in the mixing tube. A low-frequency collimated beam was thus created prior to its propagation into the drilling fluid. Using the latter technique, the penetration depth of the low f... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5558843 Sun, 11 Dec 2011 05:00:00 +0100 5558843 http://www.medworm.com/index.php?rid=5545768&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22197152%26dopt%3DAbstract We present experiments for applying a bivariate Nakagami distribution that facilitates modeling of several scattering scenarios prominent in medical ultrasound. Depending on the number of scatterers per resolution cell and the presence of coherent structures, different Nakagami parameters are required to obtain a valid approximation of the intensity statistics and to account for distributional locality. Our registration results on radio-frequency ultrasound data confirm the theoretical necessity for a spatial adaptation of similarity metrics. PMID: 22197152 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5545768 Tue, 06 Dec 2011 05:00:00 +0100 5545768 http://www.medworm.com/index.php?rid=5528125&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22182403%26dopt%3DAbstract The objective of this study is to investigate the relative contributions of porosity and mineralized matrix properties to the bulk compressional wave velocity (BCV) along the long bone axis. Cross-sectional slabs from the diaphysis of four human femurs were included in the study. Seven regions of interest (ROIs) were selected in each slab. BCV was measured in through-transmission at 5MHz. Impedance of the mineralized matrix (Z(m)) and porosity (Por) were obtained from 50MHz scanning acoustic microscopy. Por and Z(m) had comparable effects on BCV along the bone axis (R=-0.57 and R=0.72, respectively). PMID: 22182403 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5528125 Sat, 03 Dec 2011 05:00:00 +0100 5528125 http://www.medworm.com/index.php?rid=5528126&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22172458%26dopt%3DAbstract CONCLUSIONS: Our data demonstrated that hypocrellin B-mediated sonodynamic action remarkably induced apoptosis of HepG2 cells, suggesting that apoptosis is an important mechanism of cell death induced by hypocrellin B-mediated SDT. PMID: 22172458 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5528126 Mon, 28 Nov 2011 05:00:00 +0100 5528126 http://www.medworm.com/index.php?rid=5509450&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22154208%26dopt%3DAbstract Authors: Rajendra Acharya U, Vinitha Sree S, Muthu Rama Krishnan M, Molinari F, Garberoglio R, Suri JS Abstract Ultrasound-based thyroid nodule characterization into benign and malignant types is limited by subjective interpretations. This paper presents a Computer Aided Diagnostic (CAD) technique that would present more objective and accurate classification and further would offer the physician a valuable second opinion. In this paradigm, we first extracted the features that quantify the local changes in the texture characteristics of the ultrasound off-line training images from both benign and malignant nodules. These features include: Fractal Dimension (FD), Local Binary Pattern (LBP), Fourier Spectrum Descriptor (FS), and Laws Texture Energy (LTE). The resulting feature vectors... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5509450 Fri, 25 Nov 2011 05:00:00 +0100 5509450 http://www.medworm.com/index.php?rid=5509449&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22169591%26dopt%3DAbstract Authors: El-Naggar SA, Mostafa SI, Rafat NH Abstract Much of previous work has been devoted in studying complete band gaps for bulk phononic crystal (PC). In this paper, we theoretically investigate the existence and widths of these gaps for PC plates. We focus our attention on steel rods of square cross sectional area embedded in epoxy matrix. The equations for calculating the dispersion relation for square rods in a square or a triangular lattice have been derived. Our analysis is based on super cell plane wave expansion (SC-PWE) method. The influence of inclusions filling factor and plate thickness on the existence and width of the phononic band gaps has been discussed. Our calculations show that there is a certain filling factor (f=0.55) below which arrangement of square rods i... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5509449 Fri, 25 Nov 2011 05:00:00 +0100 5509449 http://www.medworm.com/index.php?rid=5491443&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22133735%26dopt%3DAbstract We present a computational study of ultrasonic assisted manufacturing processes including sheet metal forming, upsetting, and wire drawing. A fully variational porous plasticity model is modified to include ultrasonic softening effects and then utilized to account for instantaneous softening when ultrasonic energy is applied during deformation. Material model parameters are identified via inverse modeling, i.e. by using experimental data. The versatility and predictive ability of the model are demonstrated and the effect of ultrasonic intensity on the manufacturing process at hand is investigated and compared qualitatively with experimental results reported in the literature. PMID: 22133735 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5491443 Thu, 17 Nov 2011 05:00:00 +0100 5491443 http://www.medworm.com/index.php?rid=5491441&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22133737%26dopt%3DAbstract The objective was an in vitro assessment of the different working conditions and signal processing methods for the visual detection (especially in small vessels) of such microbubbles, while avoiding their destruction. Polymer-shelled microbubbles have recently been proposed as ultrasound contrast agents with some important advantages. The major drawback is a shell that is less elastic than that of the traditional lipidic microbubbles. Weaker echoes are expected, and their detection at low concentrations may be critical. In vitro experiments were performed with a commercial ultrasound scanner equipped with a dedicated acquisition board. A concentration of 100bubbles/mm(3), excitation pressure amplitudes from 120kPa to 320kPa, and a central frequency of 3MHz or 4.5MHz were used. Three multi-... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5491441 Sun, 13 Nov 2011 05:00:00 +0100 5491441 http://www.medworm.com/index.php?rid=5491442&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22133736%26dopt%3DAbstract Authors: Warriner RK, Cobbold RS Abstract It has sometimes been assumed that the phased-array plane piston transducer and the spherically-shaped concave piston transducer are equivalent structures when both have the same aperture and focal point. This assumption has not been previously examined, nor has an expression for the on-axis impulse response of the focused, phased-array plane piston transducer been derived. It is shown in this paper how such an expression can be obtained. Comparisons of the impulse response for both structures show similarities, as well as some differences that could be significant as the observation point approaches the focal point. Comparisons are also performed for wide-band pulses close to the focus as well as for sinusoidal excitation. A physical expla... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5491442 Sat, 12 Nov 2011 05:00:00 +0100 5491442 http://www.medworm.com/index.php?rid=5454208&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22119324%26dopt%3DAbstract Authors: Liu C, Djuth F, Li X, Chen R, Zhou Q, Kirk Shung K Abstract This paper reports the design, fabrication, and performance of miniature micromachined high frequency PMN-PT/epoxy 1-3 composite ultrasonic annular arrays. The PMN-PT single crystal 1-3 composites were made with micromachining techniques. The area of a single crystal pillar was 9×9μm. The width of the kerf among pillars was ∼5μm and the kerfs were filled with a polymer. The composite thickness was 25μm. A six-element annular transducer of equal element area of 0.2mm(2) with 16μm kerf widths between annuli was produced. The aperture size the array transducer is about 1.5mm in diameter. A novel electrical interconnection strategy for high density array elements was implemented. After the transducer was attach... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5454208 Fri, 11 Nov 2011 05:00:00 +0100 5454208 http://www.medworm.com/index.php?rid=5454210&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22112792%26dopt%3DAbstract Authors: Flückiger M, Neild A, Nelson BJ Abstract Passive localization of an object from its emission can be based on time difference of arrival or phase shift measurements for different receiver groups in sensor arrays. The accuracy of the localization primarily depends on accurate time and/or phase measurements. The frequency of the emission and the number and arrangement of the receivers mainly effect the resolution of the emitter localization. In this paper optimal receiver positions for passive localization methods are proposed, resulting in a maximal resolution for the emitter location estimate. The optimization is done by analyzing the uncertainty of the emitted signal, including its frequency. The technique has been developed specifically for ultrasound signals obtained fr... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5454210 Wed, 09 Nov 2011 05:00:00 +0100 5454210 http://www.medworm.com/index.php?rid=5454209&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22115526%26dopt%3DAbstract This study was to identify the cytotoxic effects of ultrasound-activated protoporphyrin IX (PpIX) on MDA-MB-231 cells. The fluorescence microscope was used to detect the sub-cellular localization of PpIX. Several distinct sonochemical effects were found after SDT treatment, including the decrease of cell viability, generation of intracellular ROS, the loss of mitochondrial membrane potential. The activation of some special apoptosis-associated proteins [Caspase-9, Caspase-3 and polypeptide poly (ADP-robose) polymerase] was evaluated by western blotting. The results show that PpIX mediated SDT (PpIX-SDT) treatment could obviously inhibit the proliferation of MDA-MB-231 cells, and which was significantly reduced by the pan-Caspase inhibitor z-VAD-fmk and the reactive oxygen species (ROS) sca... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5454209 Sun, 06 Nov 2011 04:00:00 +0100 5454209 http://www.medworm.com/index.php?rid=5454212&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22099252%26dopt%3DAbstract Authors: Octavio Manzanares A, Montero de Espinosa F Abstract This work reports performance improvements of air-coupled capacitive micromachined ultrasonic transducers (CMUTs) using resonant cavities. In order to perform this work, we have designed and manufactured a CMUT employing multi-user microelectromechanical systems (MEMS) processes (MUMPs). The transducer was designed using Helmholtz resonator principles. This was characterised by the dimensions of the cavity and several acoustic ports, which had the form of holes in the CMUT plate. The MUMPs process has the advantage of being low cost which allows the manufacture of economic prototypes. In this paper we show the effects of the resonant cavities and acoustic ports in CMUTs using laser Doppler vibrometry and acoustical measu... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5454212 Fri, 04 Nov 2011 04:00:00 +0100 5454212 http://www.medworm.com/index.php?rid=5454211&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22099253%26dopt%3DAbstract Authors: Wu J, Chen D, Langevin HM, Nyborg WL Abstract The purpose of this article is to develop a simple mathematical model to address some bioeffects which may be caused by a static attractive force between two long neighboring parallel thin fibers (for example, a pair of collagen bundles of connective tissue) when they are insonificated by a continuous (CW) traveling plane ultrasound (US) under the condition that the fiber length (L)≫the distance between them (h) and h≪the wavelength of US (λ). The theory predicts that there is an attractive force between these fibers when they are exposed to the CW US with an intensity of a magnitude of 100mW/cm(2). The relationship between the relative approaching velocity of the fibers and the acoustic pressure amplitude can be calculate... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5454211 Mon, 31 Oct 2011 04:00:00 +0100 5454211 http://www.medworm.com/index.php?rid=5416050&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22074815%26dopt%3DAbstract This study is a revisit to the stiffened Love wave propagation done previously. Closed-form dispersion equations are obtained in a very simple mathematical form for both electrically open and shorted cases. From the viewpoint of physical situation, two transverse surface waves (i.e., the stiffened Love wave and the FDLW-type wave) are separately found in a PZT-4/steel system and a PZT-4/zinc system. All the observed dispersion curves are theoretically validated through the discussion on the limit values of phase velocity using the obtained dispersion equations. Those validation and discussion give rise to a deeper understanding on the existence of transverse surface waves in such piezoelectric coupled structures. The results can be used as a benchmark for the study of the wave propagation ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5416050 Fri, 21 Oct 2011 04:00:00 +0100 5416050 http://www.medworm.com/index.php?rid=5416052&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22055342%26dopt%3DAbstract Authors: Takahashi S Abstract Highly effective piezoelectric polymer transducers operating in air at high frequencies have been successfully made by casting a solution of ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) P(VDF/TrFE) directly on a backing metal plate, and their performance has been evaluated. By utilizing this method, it has been possible to develop the three kinds of transducers that operate respectively at 4, 6 and 10MHz in air. For precise evaluation of the performance of the P(VDF/TrFE) transducers, the absorption loss in air was measured up to 10MHz. It was confirmed that the empirical formula obtained from the measured absorption values in air at high frequencies was in alignment with its theoretical value. In addition, a high lateral resolution aco... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5416052 Tue, 18 Oct 2011 04:00:00 +0100 5416052 http://www.medworm.com/index.php?rid=5416051&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22071268%26dopt%3DAbstract Authors: Samet N, Maréchal P, Duflo H Abstract A measurement method is proposed for the ultrasonic characterization of a fluid layer, corresponding to the resin transfer molding (RTM) manufacturing process. The ultrasonic velocity and attenuation of the silicone oil are measured in three samples having different viscosities. The measurement method is established on the basis of the attenuation of ultrasonic waves in fluids. A correction of the beam diffraction is implemented to improve measurement precision. A single element transducer with central frequency of 15 MHz is used. The tested fluids simulate the industrial resin used to manufacture composite materials. When injecting this resin, its viscosity increases until it reaches a critical state of polymerization. In this paper ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5416051 Tue, 18 Oct 2011 04:00:00 +0100 5416051 http://www.medworm.com/index.php?rid=5416049&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22078093%26dopt%3DAbstract CONCLUSIONS: The study demonstrates that ultrasound, strain rate and photoacoustic imaging can be used to simultaneously evaluate the structure, the mechanics and the composition of atherosclerotic lesions to improve the assessment of plaque vulnerability. PMID: 22078093 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5416049 Tue, 18 Oct 2011 04:00:00 +0100 5416049 http://www.medworm.com/index.php?rid=5416048&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22078094%26dopt%3DAbstract Authors: Burkov SI, Zolotova OP, Sorokin BP Abstract Paper is presented the results of computer simulation. Effect of the homogeneous dc electric field influence on the propagation of zero and first order Lamb and SH waves in piezoelectric langasite single crystal plates for a lot of cuts and directions have been calculated. Crystalline directions and cuts with maximal and minimal influence of dc electric field have indicated. Effect of hybridization of plate modes has been discussed. PMID: 22078094 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5416048 Sat, 15 Oct 2011 04:00:00 +0100 5416048 http://www.medworm.com/index.php?rid=5377950&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22040650%26dopt%3DAbstract Authors: Zhang GM, Zhang CZ, Harvey DM Abstract Many sparse signal representation (SSR) algorithms have been developed in the past decade. The advantages of SSR such as compact representations and super resolution lead to the state of the art performance of SSR for processing ultrasonic non-destructive evaluation (NDE) signals. Choosing a suitable SSR algorithm and designing an appropriate overcomplete dictionary is a key for success. After a brief review of sparse signal representation methods and the design of overcomplete dictionaries, this paper addresses the recent accomplishments of SSR for processing ultrasonic NDE signals. The advantages and limitations of SSR algorithms and various overcomplete dictionaries widely-used in ultrasonic NDE applications are explored in depth. ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5377950 Mon, 10 Oct 2011 04:00:00 +0100 5377950 http://www.medworm.com/index.php?rid=5377951&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D22036247%26dopt%3DAbstract Authors: Estrada H, Gómez-Lozano V, Uris A, Candelas P, Belmar F, Meseguer F Abstract The ultrasonic transmission through plates perforated with 2×2 or 3×3 square array of subwavelength holes per unit cell are studied by numerical simulations. Calculations are obtained by means of a theoretical model under the rigid-solid assumption. It is demonstrated that when the inter-hole distance within the unit cell is reduced, new transmission dips appear resulting from Wood anomalies that have influence on the second and the third order Fabry-Perot peak. When the inter-hole distance within the unit cell is reduced, the transmission spectrum of the multiple-sublattice holes arrays tends to the transmission spectrum of a plate perforated with only one hole in the unit cell. PMID: 2203... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=5377951 Sun, 02 Oct 2011 04:00:00 +0100 5377951 http://www.medworm.com/index.php?rid=4903067&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21616517%26dopt%3DAbstract In this study, we aim to investigate the activation of p53 in sonodynamic therapy. Three murine tumor models with distinct aggressiveness (S180, H-22 and EAC) were treated with 1.75MHz continuous ultrasound at an acoustic intensity (I(SATA)) of 1.4W for 3min in the presence of 20μg/ml hematoporphyrin. The DNA fragment and nuclear damage were observed by TUNEL and single cell gel electrophoresis. Western blotting and RT-PCR were used to analyze the expression of p53, PUMA, Bax and Fas. Then we checked the translocation of p53 by confocal microscopy. DNA sequencing was used to determine the status of p53 gene in three tumor cell lines. Our results indicated that the level of p53 protein and mRNA increased significantly, and p53 activated the expression of its downstream pro-apoptosis gene P... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4903067 Tue, 07 Jun 2011 09:45:12 +0100 4903067 http://www.medworm.com/index.php?rid=4903066&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21621239%26dopt%3DAbstract CONCLUSIONS: These results demonstrate the feasibility of dual grayscale and SHI on a modified commercial scanner. The ability to simultaneously visualize both imaging modes in real time should improve the applicability of SHI as a future primary clinical imaging modality. PMID: 21621239 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4903066 Mon, 09 May 2011 23:00:00 +0100 4903066 http://www.medworm.com/index.php?rid=4397605&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21215981%26dopt%3DAbstract Authors: Han ZH, Yang B, Qi Y, Cumings J A one-step, economical nanoemulsion method has been introduced to synthesize low-melting-point metallic nanoparticles. This nanoemulsion technique exploits the extremely high shear rates generated by the ultrasonic agitation and the relatively large viscosity of the continuous phase - polyalphaolefin (PAO), to rupture the molten metal down to diameter below 100nm. Field's metal nanoparticles and Indium nanoparticles of respective average diameters of 15nm and 30nm have been obtained. The nanoparticles size and shape are determined by transmission electron microscopy (TEM). Their phase transition behavior is examined using a differential scanning calorimeter (DSC). It is found that these nanoparticles dispersed in PAO can undergo reversible, melt... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4397605 Wed, 26 Jan 2011 09:47:21 +0100 4397605 http://www.medworm.com/index.php?rid=4397553&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21216422%26dopt%3DAbstract Authors: Song J, Chang JH, Song TK, Yoo Y Coded tissue harmonic imaging with pulse inversion (CTHI-PI) based on a linear chirp signal can improve the signal-to-noise ratio with minimizing the peak range sidelobe level (PRSL), which is the main advantage over CTHI with bandpass filtering (CTHI-BF). However, the CTHI-PI technique could suffer from motion artifacts due to decreasing frame rate caused by two firings of opposite phase signals for each scanline. In this paper, a new CTHI method based on a nonlinear chirp signal (CTHI-NC) is presented, which can improve the separation of fundamental and harmonic components without sacrificing frame rate. The nonlinear chirp signal is designed to minimize the PRSL value by optimizing its frequency sweep rate and time duration. The performance ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4397553 Wed, 26 Jan 2011 06:28:12 +0100 4397553 http://www.medworm.com/index.php?rid=4324754&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21168892%26dopt%3DAbstract Authors: Sharma JN, Sharma R The out-of-plane vibrations of a generalized thermoelastic circular plate are studied under different environmental temperature, plate dimensions and boundary conditions. The analytical expressions for thermoelastic damping of vibration and phase velocity of circumferential surface wave modes are obtained. It is noticed that the damping of vibrations and phase velocities of circumferential surface wave modes significantly depend on thermal relaxation time in addition to thermoelastic coupling in circular plates under resonance conditions. The surface conditions also impose significant effects on the vibrations of such resonators. The expressions for displacement and temperature fields in the plate resonator are also derived and obtained. Some numerical resu... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4324754 Sat, 08 Jan 2011 20:47:40 +0100 4324754 http://www.medworm.com/index.php?rid=4324746&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21211809%26dopt%3DAbstract CONCLUSION: The results show that the beam's width reduces and becomes narrower, the side-lobes decrease in magnitude, and the hollow region diameter (or null in magnitude) increases as the order of nonlinearity increases. Furthermore, the nonlinearity of the medium preserves the non-diffracting feature of the beam's second-harmonic generation within the pre-shock range. PMID: 21211809 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4324746 Tue, 14 Dec 2010 00:00:00 +0100 4324746 http://www.medworm.com/index.php?rid=4324747&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21208634%26dopt%3DAbstract Authors: Sorohan S, Constantin N, Găvan M, Anghel V This paper presents a fast and reliable method, for obtaining all the range of dispersion curves for wave propagation usually used in practice, by numerical simulation only, via common commercial finite element codes. Essentially, the method is based on a simple and robust approach, consisting in a few series of modal analyses for a representative part of the inspected structure. In this way, for different wave lengths, one can find the mode shapes and corresponding natural frequencies by solving some real, symmetric and well numerically conditioned eigenvalue problems. The method allows the extraction of propagating modes only and, in spite of not producing continuous dispersion curves, it is not susceptible to aliasing effects, as ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4324747 Mon, 13 Dec 2010 00:00:00 +0100 4324747 http://www.medworm.com/index.php?rid=4324745&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21211810%26dopt%3DAbstract This study provides an investigation with theoretical modeling, experimental measurements, and a simplex-based inversion procedure to explore the similarity and difference between the axial guided waves and circumferential guided waves, aiming at providing useful information while axial and circumferential guided waves are applied in the area of material characterization. The sensitivity to the radius curvature for the circumferential guided waves dispersion spectra is a major point that makes circumferential guided waves different from axial guided waves. For the purpose of material characterization, both axial and circumferential guided waves are able to extract an elastic moduli and wall-thickness information from the dispersion spectra, however, radius information can only be extracted... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4324745 Fri, 10 Dec 2010 00:00:00 +0100 4324745 http://www.medworm.com/index.php?rid=4324748&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21190706%26dopt%3DAbstract Authors: Michaels TE, Michaels JE, Ruzzene M Full wavefield measurements obtained with either an air-coupled transducer mounted on a scanning stage or a scanning laser vibrometer can be combined with effective signal and imaging processing algorithms to support characterization of guided waves as well as detection, localization and quantification of structural damage. These wavefield images contain a wealth of information that clearly shows details of guided waves as they propagate outward from the source, reflect from specimen boundaries, and scatter from discontinuities within the structure. The analysis of weaker scattered waves is facilitated by the removal of source waves and the separation of wave modes, which is effectively achieved via frequency-wavenumber domain filtering in c... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4324748 Sun, 05 Dec 2010 00:00:00 +0100 4324748 http://www.medworm.com/index.php?rid=4324750&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21186038%26dopt%3DAbstract This study analytically investigates the propagation of shear waves (SH waves) in a coupled plate consisting of a piezoelectric layer and an elastic layer with initial stress. The piezoelectric material is polarized in z-axis direction and perfectly bonded to an elastic layer. The mechanical displacement and electrical potential function are derived for the piezoelectric coupled plates by solving the electromechanical field equations. The effects of the thickness ratio and the initial stress on the dispersion relations and the phase and group velocities are obtained for electrically open and mechanically free situations. The numerical examples are provided to illustrate graphically the variations of the phase and group velocities versus the wave number for the different layers comparativel... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4324750 Sat, 04 Dec 2010 00:00:00 +0100 4324750 http://www.medworm.com/index.php?rid=4324753&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21183195%26dopt%3DAbstract Authors: Xu J, Xia X, Leung AW, Xiang J, Jiang Y, Yu H, Bai D, Li X, Xu C Sonodynamic therapy with pyropheophorbide-a methyl ester (MPPa) presents a promising aspect in treating liver cancer. The present study aims to investigate the mitochondrial damage of liver cancer cells induced by MPPa-mediated sonodynamic action. Mouse hepatoma cell line H(22) cells were incubated with MPPa (2μM) for 20h and then exposed to ultrasound with an intensity of 0.97W/cm(2) for 8s. Cytotoxicity was investigated 24h after sonodynamic action using MTT assay and light microscopy. Mitochondrial membrane potential (ΔΨm) was analyzed using flow cytometry with rhodamine 123 staining and ultrastructural changes were observed using transmission electron microscopy (TEM). The cytotoxicity of MPPa-mediated SDT... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4324753 Fri, 03 Dec 2010 00:00:00 +0100 4324753 http://www.medworm.com/index.php?rid=4324752&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21183196%26dopt%3DAbstract Authors: Wang S, Huang S, Zhao W Lamb wave's interactions with transverse internal defects in an elastic plate are investigated in this paper to help practical inspection work with guided wave. A 2D frequency domain hybrid boundary element method approach previously mainly used to study Lamb wave's interactions with external defects in elastic plates is adopted in this work and extended to study the cases of internal defects. Simulation examples are presented to illustrate the reflection and transmission coefficients' variations with various parameters including defect's height, width, testing fd for internal symmetrical and non-symmetrical cracks, with symmetry defined with respect to the middle plane of the plate. This simulation could be a valuable tool for the research of Lamb wave... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4324752 Tue, 30 Nov 2010 00:00:00 +0100 4324752 http://www.medworm.com/index.php?rid=4324749&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21186039%26dopt%3DAbstract Authors: Shi Y, Zhao C This paper presents a new standing-wave-type linear ultrasonic motor using combination of the first longitudinal and the second bending modes. Two piezoelectric plates in combination with a metal thin plate are used to construct the stator. The superior point of the stator is its isosceles triangular structure part of the stator, which can amplify the displacement in horizontal direction of the stator in perpendicular direction when the stator is operated in the first longitudinal mode. The influence of the base angle θ of the triangular structure part on the amplitude of the driving foot has been analyzed by numerical analysis. Four prototype stators with different angles θ have been fabricated and the experimental investigation of these stators has validated ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4324749 Tue, 30 Nov 2010 00:00:00 +0100 4324749 http://www.medworm.com/index.php?rid=4324751&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21185582%26dopt%3DAbstract Authors: Maák P, Takács T, Barócsi A, Kollár E, Richter P In the present paper we analyze the electric and acoustic losses in acousto-optic devices, especially in their ultrasonic transducers and the related thermal effects. We include electric and acoustic losses into the classical electric equivalent model of the transducer, to explain the characteristics of the measured electric and thermal behavior. Measured temperature distributions on the acousto-optic crystal faces serve visualization of the conversion efficiency of the radio-frequency input to bulk acoustic waves. We show that the pronounced acoustic frequency dependence of the temperature distribution is in correlation with the frequency dependent losses in the transducer and in the bulk. We also demonstrate experimentally... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4324751 Sat, 27 Nov 2010 00:00:00 +0100 4324751 http://www.medworm.com/index.php?rid=4272958&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21147492%26dopt%3DAbstract CONCLUSIONS: Our findings demonstrated that MB-mediated sonodynamic action significantly induced apoptosis of HO-8910 cells and an increase in intracellular ROS level. This indicates that apoptosis is an important mechanism of cell death induced by MB-mediated SDT. Thus, MB-mediated SDT might be a potential therapeutic strategy for combating ovarian cancer. PMID: 21147492 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4272958 Sat, 27 Nov 2010 00:00:00 +0100 4272958 http://www.medworm.com/index.php?rid=4272956&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21163507%26dopt%3DAbstract Authors: Luo S, Kim EH, Dighe M, Kim Y The non-surgical diagnosis of thyroid nodules is currently made via a fine needle aspiration (FNA) biopsy. It is estimated that somewhere between 250,000 and 300,000 thyroid FNA biopsies are performed in the United States annually. However, a large percentage (approximately 70%) of these biopsies turn out to be benign. Since the aggressive FNA management of thyroid nodules is costly, quantitative risk assessment and stratification of a nodule's malignancy is of value in triage and more appropriate healthcare resources utilization. In this paper, we introduce a new method for classifying the thyroid nodules based on the ultrasound (US) elastography features. Unlike approaches to assess the stiffness of a thyroid nodule by visually inspecting the ps... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4272956 Sat, 27 Nov 2010 00:00:00 +0100 4272956 http://www.medworm.com/index.php?rid=4272955&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21163508%26dopt%3DAbstract Authors: Kiss MZ, Varghese T, Kliewer MA Attenuation estimation and imaging in the cervix has been utilized to evaluate the onset of cervical ripening during pregnancy. This feature has also been utilized for the acoustic characterization of leiomyomas and myometrial tissue. In this paper, we present direct narrowband substitution measurement values of the variation in the ultrasonic attenuation coefficient in ex vivo human uterine and cervical tissue, in the 5-10MHz frequency range. At 5MHz, the attenuation coefficient values are similar for the different orientations of uterine tissue with values of 4.1-4.2dB/cm, 5.1dB/cm for the leiomyoma, and 6.3dB/cm for the cervix. As the frequency increases, the attenuation coefficient values increase and are also spread out, with a value of app... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4272955 Sat, 27 Nov 2010 00:00:00 +0100 4272955 http://www.medworm.com/index.php?rid=4272954&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21163509%26dopt%3DAbstract Authors: Zeqiri B, Zauhar G, Hodnett M, Barrie J Progress in developing a new measurement method for ultrasound output power is described. It is a thermal-based technique with the acoustic power generated by a transducer being absorbed within a specially developed polyurethane rubber material, whose high absorption coefficient ensures energy deposition within a few mm of the ultrasonic wave entering the material. The rate of change of temperature at the absorber surface is monitored using the pyroelectric voltage generated from electrodes disposed either side of a 60mm diameter, 0.061mm thick membrane of the piezoelectric polymer polyvinylidene fluoride (pvdf) bonded to the absorber. The change in the pyroelectric output voltage generated by the sensor when the transducer is switched O... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4272954 Thu, 25 Nov 2010 00:00:00 +0100 4272954 http://www.medworm.com/index.php?rid=4272959&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21145572%26dopt%3DAbstract Authors: Liu B, Jiang Q, Xie H, Yang J We study coupled face-shear (FS) and thickness-twist (TT) motions of a piezoelectric plate of monoclinic crystals with mass layers on the central parts of the plate surfaces. The plate is driven by a lateral electric field. Mindlin's first-order theory of piezoelectric plates is used. An analytical solution is obtained. Numerical results are presented for an AT-cut quartz plate, including the motional capacitance of the plate as a resonator and the vibration modes trapped under the mass layers in the central portion of the plate. The relationship between the dimension of the mass layers and the number of trapped modes is examined. PMID: 21145572 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4272959 Wed, 24 Nov 2010 00:00:00 +0100 4272959 http://www.medworm.com/index.php?rid=4272957&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21147493%26dopt%3DAbstract Authors: Solberg OV, Lindseth F, Bø LE, Muller S, Bakeng JB, Tangen GA, Hernes TA Freehand 3D ultrasound is increasingly being introduced in the clinic for diagnostics and image-assisted interventions. Various algorithms exist for combining 2D images of regular ultrasound probes to 3D volumes, being either voxel-, pixel- or function-based. Previously, the most commonly used input to 3D ultrasound reconstruction has been digitized analog video. However, recent scanners that offer access to digital image frames exist, either as processed or unprocessed data. To our knowledge, no comparison has been performed to determine which data source gives the best reconstruction quality. In the present study we compared both reconstruction algorithms and data sources using novel comparison methods... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4272957 Tue, 23 Nov 2010 00:00:00 +0100 4272957 http://www.medworm.com/index.php?rid=4272960&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21144543%26dopt%3DAbstract Authors: Wang ZB, Wu J, Fang LQ, Wang H, Li FQ, Tian YB, Gong XB, Zhang H, Zhang L, Feng R High intensity focused ultrasound (HIFU) has become a new noninvasive surgical modality in medicine. A portion of tissue seated inside a patient's body may experience coagulative necrosis after a few seconds of insonification by high intensity focused ultrasound (US) generated by an extracorporeal focusing US transducer. The region of tissue affected by coagulative necrosis (CN) usually has an ellipsoidal shape when the thermal effect due to US absorption plays the dominant role. Its long and short axes are parallel and perpendicular to the US propagation direction respectively. It was shown by numerical computations using a nonlinear Gaussian beams model to describe the sound field in a focal zo... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4272960 Fri, 19 Nov 2010 00:00:00 +0100 4272960 http://www.medworm.com/index.php?rid=4272961&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21144542%26dopt%3DAbstract In conclusion, the largest study of contrast US of murine xenografts to date has been conducted and quantitative contrast enhanced US measures of tumor neovascularity in glioma and breast cancer xenograft models appear to provide a noninvasive marker for angiogenesis; although the best method for monitoring angiogenesis was not conclusively established. PMID: 21144542 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4272961 Thu, 18 Nov 2010 00:00:00 +0100 4272961 http://www.medworm.com/index.php?rid=4248918&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21134687%26dopt%3DAbstract Authors: Liu JX, Wang ZQ, Li GF, Wang NH This paper describes a method for obtaining the pressure reflection coefficient by using a half-wave layer. Two transducers were placed in reference liquid and test liquid respectively. The reference and test liquid were separated by the thin half-wave layer. Both transducers could operate in two modes. One acted as a transmitter and worked in pulse-echo mode, and the other operated in receiver mode. By adjusting the frequency of drive signal according to the thickness and material property of the half-wave layer, it was possible to generate the maximum interference signal of multiple waves reflected at the two interfaces of the layer. Therefore, the amplitude of reflection wave in steady-state depended only on the reflection coefficient at the ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4248918 Thu, 18 Nov 2010 00:00:00 +0100 4248918 http://www.medworm.com/index.php?rid=4215835&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21094966%26dopt%3DAbstract Authors: Dobie G, Spencer A, Burnham K, Gareth Pierce S, Worden K, Galbraith W, Hayward G A computer simulator, to facilitate the design and assessment of a reconfigurable, air-coupled ultrasonic scanner is described and evaluated. The specific scanning system comprises a team of remote sensing agents, in the form of miniature robotic platforms that can reposition non-contact Lamb wave transducers over a plate type of structure, for the purpose of non-destructive evaluation (NDE). The overall objective is to implement reconfigurable array scanning, where transmission and reception are facilitated by different sensing agents which can be organised in a variety of pulse-echo and pitch-catch configurations, with guided waves used to generate data in the form of 2-D and 3-D images. The abi... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4215835 Wed, 03 Nov 2010 00:00:00 +0100 4215835 http://www.medworm.com/index.php?rid=4215834&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21106214%26dopt%3DAbstract Authors: Giannoula A, Cobbold RS Localized narrowband low-frequency shear waves can be non-invasively generated within tissue, by a modulated finite-amplitude radiation force, resulting from the interference of two focused quasi-CW ultrasound beams of slightly different frequencies. Assuming a Voigt viscoelastic model, this paper describes the use of a finite-element-method model, to simulate two-dimensional shear-wave propagation in viscoelastic media, containing circular inclusions (lesions). Using this model, an inverse approach is used to extract maps of the local shear modulus and viscosity. The performance is evaluated based on three metrics: the lesion contrast, the contrast-transfer-efficiency (CTE), and the contrast-to-noise ratio (CNR). Modified definitions of these metrics a... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4215834 Wed, 03 Nov 2010 00:00:00 +0100 4215834 http://www.medworm.com/index.php?rid=4215831&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21112601%26dopt%3DAbstract Authors: Chang JH, Raphael DT, Zhang YP, Kirk Shung K An acoustic guidance method for pedicle screw placement during spine fixation surgery was recently investigated, with a view toward preventing complications such as injury to the spinal cord, thecal sac, and spinal nerve roots due to screw misplacement. The method relies upon the change in the ultrasound amplitude reflected at different sites-from the outer posterior cortex, through the pedicle, and towards the distal ventral cortex. The amplitude change was empirically observed through in vitro measurement of ultrasound amplitude at the different sites by inserting a 2.5-MHz single element transducer into a vertebral body through insertion pathway created by an advancing screw. This paper provides a theoretical and experimental rat... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4215831 Wed, 03 Nov 2010 00:00:00 +0100 4215831 http://www.medworm.com/index.php?rid=4215836&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21094965%26dopt%3DAbstract Authors: Loosvelt M, Lasaygues P Methods of measuring ultrasonic wave velocity in an elastic sample require data on the thickness of the sample and/or the distances between the transducers and the sample. The uncertainty of the ultrasonic wave velocity measurements generally depends on that of the data available. Conversely, to determine the thickness of a material, it is necessary to have a priori information about the wave velocity. This problem is particularly hard to solve when measuring the parameters of biological specimens such as bones having a greater acoustical impedance contrast (typically 3-5 MRayl) than that of the surrounding soft tissues (typically 1.5 MRayl). Measurements of this kind cannot easily be performed. But obtaining the thickness of a bone structure and/or the... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4215836 Tue, 02 Nov 2010 00:00:00 +0100 4215836 http://www.medworm.com/index.php?rid=4215833&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21111437%26dopt%3DAbstract Authors: Hajzargerbashi T, Kundu T, Bland S Conventional triangulation techniques fail to correctly predict the acoustic source location in anisotropic plates due to the direction dependent nature of the elastic wave speeds. To overcome this problem, Kundu et al. [1] proposed an alternative method for acoustic source prediction based on optimizing an objective function. They defined an objective function that uses the time of flight information of the acoustic waves to the passive transducers attached to the plate and the wave propagation direction (θ) from the source point to the receiving sensors. Some weaknesses of the original algorithm proposed in Ref. [1] were later overcome by developing a modified objective function [2]. A new objective function is introduced here to further s... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4215833 Sat, 30 Oct 2010 00:00:00 +0100 4215833 http://www.medworm.com/index.php?rid=4215832&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D21112066%26dopt%3DAbstract Authors: Josserand T, Wolley J This paper discusses the design and development of a miniature, high resolution 3-D imaging sonar. The design utilizes frequency steered phased arrays (FSPA) technology. FSPAs present a small, low-power solution to the problem of underwater imaging sonars. The technology provides a method to build sonars with a large number of beams without the proportional power, circuitry and processing complexity. The design differs from previous methods in that the array elements are manufactured from a monolithic material. With this technique the arrays are flat and considerably smaller element dimensions are achievable which allows for higher frequency ranges and smaller array sizes. In the current frequency range, the demonstrated array has ultra high image resolut... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4215832 Fri, 29 Oct 2010 00:00:00 +0100 4215832 http://www.medworm.com/index.php?rid=4107413&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20971489%26dopt%3DAbstract Authors: Zhang X, Qiang B, Hubmayr RD, Urban MW, Kinnick R, Greenleaf JF Lung diseases, such as acute respiratory distress syndrome (ARDS) and idiopathic pulmonary fibrosis (IPF), are closely associated with altered lung elastic properties. Pulmonary function testing and imaging are routinely performed for evaluating lung diseases. However, lung compliance, a measure of lung elastic properties, is rarely used in clinic, because it is invasive and provides only a global and arguably biased estimate of lung elastic properties. Current ultrasound methods also cannot be used for imaging lungs because ultrasound cannot penetrate the lung tissue. In this paper, an ultrasound image guided and surface wave based method is proposed to measure regional lung surface wave speed and estimate lung e... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4107413 Thu, 21 Oct 2010 23:00:00 +0100 4107413 http://www.medworm.com/index.php?rid=4107414&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20965537%26dopt%3DAbstract Authors: Angle SR, Sena K, Sumner DR, Virdi AS Bone growth and repair are under the control of biochemical and mechanical signals. Low-intensity pulsed ultrasound (LIPUS) stimulation at 30mW/cm(2) is an established, widely used and FDA approved intervention for accelerating bone healing in fractures and non-unions. Although this LIPUS signal accelerates mineralization and bone regeneration, the actual intensity experienced by the cells at the target site might be lower, due to the possible attenuation caused by the overlying soft tissue. The aim of this study was to investigate whether LIPUS intensities below 30mW/cm(2) are able to provoke phenotypic responses in bone cells. Rat bone marrow stromal cells were cultured under defined conditions and the effect of 2, 15, 30mW/cm(2) and sha... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4107414 Sat, 25 Sep 2010 23:00:00 +0100 4107414 http://www.medworm.com/index.php?rid=4040970&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20888614%26dopt%3DAbstract Authors: Benoudjit N, Ferroudji K, Bahaz M, Bouakaz A Emboli classification is of high clinical importance for selecting appropriate treatment for patients. Several ultrasonic (US) methods using Doppler processing have been used for emboli detection and classification as solid or gaseous matter. We suggest in this experimental study exploiting the Radio-Frequency (RF) signal backscattered by the emboli since they contain additional information on the embolus than the Doppler signal. The aim of the study is the analysis of RF signals using Multilayer Perceptron (MLP) and Radial-Basis Function Network (RBFN) in order to classify emboli. Anthares scanner with RF access was used with a transmit frequency of 1.82MHz at two mechanical indices (MI) 0.2 and 0.6. The mechanical index is given a... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=4040970 Tue, 14 Sep 2010 23:00:00 +0100 4040970 http://www.medworm.com/index.php?rid=3998618&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20855096%26dopt%3DAbstract Authors: Parenthoine D, Tran-Huu-Hue LP, Haumesser L, Vander Meulen F, Lematre M, Lethiecq M Quadratic nonlinear equations of a piezoelectric element under the assumptions of 1D vibration and weak nonlinearity are derived by the perturbation theory. It is shown that the nonlinear response can be represented by controlled sources that are added to the classical hexapole used to model piezoelectric ultrasonic transducers. As a consequence, equivalent electrical circuits can be used to predict the nonlinear response of a transducer taking into account the acoustic loads on the rear and front faces. A generalisation of nonlinear equivalent electrical circuits to cases including passive layers and propagation media is then proposed. Experimental results, in terms of second harmonic generati... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3998618 Tue, 07 Sep 2010 23:00:00 +0100 3998618 http://www.medworm.com/index.php?rid=3998619&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20855095%26dopt%3DAbstract Authors: Honarvar F, Enjilela E, Sinclair AN Scattering of obliquely incident plane acoustic waves from immersed infinite solid elastic cylinders is a complex phenomenon that involves generation of various types of surface waves on the body of the cylinder. Mitri [F.G. Mitri, Acoustic backscattering enhancement resulting from the interaction of an obliquely incident plane wave with an infinite cylinder, Ultrasonics 50 (2010) 675-682] recently showed that for a solid aluminum cylinder, there exist acoustic backscattering enhancements at a normalized frequency of ka⩽0.1. The incidence angle α(c) at which these enhancements are observed lies between the first (longitudinal) and second (shear) coupling angles of the cylinder. He also confirmed the observations previously reported b... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3998619 Fri, 03 Sep 2010 23:00:00 +0100 3998619 http://www.medworm.com/index.php?rid=3998620&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20843533%26dopt%3DAbstract Authors: Norisuye T, Sasa S, Takeda K, Kohyama M, Tran-Cong-Miyata Q Ultrasound spectroscopy is a powerful tool to investigate the viscoelastic properties of materials. The longitudinal elastic moduli M' and M(″), or the adiabatic compressibility κ(S) can be evaluated from ultrasound velocity v and attenuation coefficient α via the relation M'=ρv(2) and M(″)=2ραv(3)ω, where ρ is the density and ω is the angular frequency. So far, the density was independently measured by other equipments or its variation during the chemical reaction has been ignored in the previous literatures. Here we propose a multiple echo method to simultaneously evaluate α, v, ρ, from a single acquisition, enabling us to monitor the polymerization process of acrylamide, wher... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3998620 Fri, 20 Aug 2010 23:00:00 +0100 3998620 http://www.medworm.com/index.php?rid=3962155&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20825961%26dopt%3DAbstract Authors: Liu P, Wang X, Zhou S, Hua X, Liu Z, Gao Y This work investigated the effect of infusion of a self-made ultrasound contrast agent with long persistence (named ZHIFUXIAN) on rat right ventricular pressure and made a preliminary evaluation on the relative safety of the novel microbubbles. Normal saline, SonoVue and ZHIFUXIAN were injected through caudal vein at the total volume of 0.5ml for each injection. The right ventricular systolic pressure (RVSP) and end-diastolic pressure (RVEDP) were monitored and the changes of the pressure were compared with baseline readings. RVSP increased when saline, SonoVue or ZHIFUXIAN were injected, the greatest change being after SonoVue (about 2mmHg), but there was no statistical significance compared with baseline (P>0.05). There was no si... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3962155 Thu, 19 Aug 2010 23:00:00 +0100 3962155 http://www.medworm.com/index.php?rid=3938914&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20804997%26dopt%3DAbstract Authors: Klima J An overview of possible mechanisms by which sonication can influence electrochemical processes is given. Four mechanisms are discussed:and possible effects are illustrated on several examples. The most effective process is formation of microjets, which can not only decrease diffusion layer thickness under 1mum, but also activate (depassivate) electrode surface. Design of experimental arrangement with maximum participation of microjets is proposed. Two approaches are proposed: PMID: 20804997 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3938914 Fri, 13 Aug 2010 23:00:00 +0100 3938914 http://www.medworm.com/index.php?rid=3938913&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20810143%26dopt%3DAbstract Authors: Nam KH, Choi MJ, Yoo ES, Paeng DG High-frequency ultrasound (HFUS) signals backscattered from RBL-2H3 cell pellets prepared under different centrifugal forces were analyzed to investigate the packing effect of cell aggregates. The measurements were performed in a pulse-echo setup with a 40-MHz transducer. The changes of ultrasound signals from cell pellet in backscattered power, statistical parameter, and pellet thickness were monitored after centrifugation at between 100g and 1600g. Experimental results showed that the HFUS backscattered power from cell pellets was inversely proportional to centrifugal force and increased to a plateau within 1-2h after centrifugation. The initial thickness of cell pellets decreased with higher centrifugal force, but the changes in thickness a... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3938913 Fri, 13 Aug 2010 23:00:00 +0100 3938913 http://www.medworm.com/index.php?rid=3938915&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20800866%26dopt%3DAbstract Authors: Zhu X, Zhang P, Shao J, Cheng Y, Zhang Y, Bai J Image segmentation for detection of vessel walls is necessary for quantitative assessment of vessel diseases by intravascular ultrasound. A new segmentation method based on gradient vector flow (GVF) snake model is proposed in this paper. The main characteristics of the proposed method include two aspects: one is that nonlinear filtering is performed on GVF field to reduce the critical points, change the morphological structure of the parallel curves and extend the capture range; the other is that balloon snake is combined with the model. Thus, the improved GVF and balloon snake can be automatically initialized and overcome the problem caused by local energy minima. Results of 20 in vivo cases validated the accuracy and stability... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3938915 Fri, 06 Aug 2010 23:00:00 +0100 3938915 http://www.medworm.com/index.php?rid=3854897&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20692675%26dopt%3DAbstract Authors: Baron C As a non-destructive, non-invasive and non-ionizing evaluation technique for heterogeneous media, the ultrasonic method is of major interest in industrial applications but especially in biomedical fields. Among the unidirectionally heterogeneous media, the continuously varying media are a particular but widespread case in natural materials. The first studies on laterally varying media were carried out by geophysicists on the Ocean, the atmosphere or the Earth, but the teeth, the bone, the shells and the insects wings are also functionally graded media. Some of them can be modeled as planar structures but a lot of them are curved media and need to be modeled as cylinders instead of plates. The present paper investigates the influence of the tubular geometry of a wavegui... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3854897 Thu, 05 Aug 2010 23:00:00 +0100 3854897 http://www.medworm.com/index.php?rid=3854896&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20696448%26dopt%3DAbstract Authors: Toonkum P, Suwanwela NC, Chinrungrueng C This paper presents a new three-dimensional (3D) ultrasound reconstruction algorithm for generation of 3D images from a series of two-dimensional (2D) B-scans acquired in the mechanical linear scanning framework. Unlike most existing 3D ultrasound reconstruction algorithms, which have been developed and evaluated in the freehand scanning framework, the new algorithm has been designed to capitalize the regularity pattern of the mechanical linear scanning, where all the B-scan slices are precisely parallel and evenly spaced. The new reconstruction algorithm, referred to as the Cyclic Regularized Savitzky-Golay (CRSG) filter, is a new variant of the Savitzky-Golay (SG) smoothing filter. The CRSG filter has been improved upon the original S... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3854896 Sat, 24 Jul 2010 23:00:00 +0100 3854896 http://www.medworm.com/index.php?rid=3854895&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20696449%26dopt%3DAbstract Authors: Wang DA, Chuang WY, Hsu K, Pham HT A new horn for high displacement amplification is developed. The profile of the horn is a cubic Bézier curve. The ultrasonic actuation of the horn exploits the first longitudinal displacement mode of the horn. A design method of the horn using an optimization scheme and finite element analyses is developed. Prototypes of the horns are manufactured by a numerical control machining process. Performances of the proposed horn have been evaluated by experiments. Experimental results of the harmonic response of the fabricated horn confirm the effectiveness of the design method. The displacement amplification of the proposed horn is 71% higher than that of the traditional catenoidal horn with the same length and end surface diameters. PMID: 2... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3854895 Sat, 17 Jul 2010 23:00:00 +0100 3854895 http://www.medworm.com/index.php?rid=3803384&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20656313%26dopt%3DAbstract Authors: Carvell KJ, Bigelow TA Medical ultrasound has shown great potential as a minimally invasive therapy technique. It can be used in areas such as histotripsy, thermal ablation, and administering medication. The success of these therapies is improved by the cavitation of small microbubbles, and often it is useful to know which bubbles might provide the most effective therapy. When using therapies based on stable cavitation, the optimal bubble size is approximately given by R(0) congruent with3MHzmum/f(0)(lin). However, a similar expression is not available for therapies involving inertial cavitation. Therefore, the goal of our study was to develop an approximate expression relating the initial size of the bubble that resulted in the maximum response to the ultrasound operating fre... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3803384 Wed, 14 Jul 2010 23:00:00 +0100 3803384 http://www.medworm.com/index.php?rid=3777112&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20637485%26dopt%3DAbstract Authors: Saletes I, Gilles B, Bera JC Enhancing cavitation activity with minimal acoustic intensities could be interesting in a variety of therapeutic applications where mechanical effects of cavitation are needed with minimal heating of surrounding tissues. The present work focuses on the relative efficiency of a signal combining two neighbouring frequencies and a one-frequency signal for initiating ultrasound inertial cavitation. Experiments were carried out in a water tank, using a 550kHz piezoelectric composite spherical transducer focused on targets with 46mum roughness. The acoustic signal scattered, either by the target or by the cavitation bubbles, is filtered using a spectral and cepstral-like method to obtain an inertial cavitation activity measurement. The ultrasound excitat... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3777112 Thu, 24 Jun 2010 23:00:00 +0100 3777112 http://www.medworm.com/index.php?rid=3777111&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20643467%26dopt%3DAbstract The objective of this study was to assess the impact of dynamic range and gain on perfusion quantification using linearized log-compressed data. An indicator-dilution experiment was developed with an in vitro flow phantom setup used with SonoVue contrast agent (Bracco SpA, Milan, Italy). Imaging was performed with a Philips iU22 scanner and a C5-1 curvilinear transducer using a contrast-specific nonlinear pulse sequence (power modulation) at 1.7MHz. Clinical dynamic contrast-enhanced ultrasound image loops of liver tumors were also collected for preliminary validation of the in vitro findings. Time-intensity curves were extracted from image loops with two different approaches: from linearized log-compressed data and from linear (uncompressed) data. The error of time-intensity curve paramet... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3777111 Thu, 24 Jun 2010 23:00:00 +0100 3777111 http://www.medworm.com/index.php?rid=3759078&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20619866%26dopt%3DAbstract Authors: Molero M, Segura I, Hernández MG, Izquierdo MA, Anaya JJ This paper examines ultrasonic wave propagation through strongly heterogeneous materials such as cementitious materials, and deals meanly with the formulation of a multiphase approach of a self-consistent multiple scattering model, the so-called dynamic generalized self-consistent model (DGSCM) proposed by Yang [J. Appl. Mech. 70(2003) 575-582]. This extended model can describe the influence of the size and volume fraction of aggregates on cementitious materials, as well as the interaction, contribution, and influence of entrapped air voids together with the aggregates on frequency-dependent parameters such as the phase velocity and the attenuation coefficient. To show the performance of this approach, theoretical pre... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3759078 Tue, 22 Jun 2010 23:00:00 +0100 3759078 http://www.medworm.com/index.php?rid=3742498&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20598334%26dopt%3DAbstract Authors: Rommetveit T, Johansen TF, Johnsen R When using ultrasound for detecting low impedance materials on the surface of high impedance materials, a major challenge is the contrast difference between the strong reverberations from the high impedance material and the weak echoes received from the low impedance material. The purpose of this work is to present the theoretical and experimental validation of an ultrasonic methodology for estimating the acoustical properties of paraffin wax on the surface of steel. The method is based on modeling and inversion of the complete electro-acoustic channel from the transmitted voltage over the active piezoelectric element, to the received voltage resulting from the acoustic reverberations in the multilayered structure. In the current work, two ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3742498 Sat, 12 Jun 2010 23:00:00 +0100 3742498 http://www.medworm.com/index.php?rid=3724858&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20594568%26dopt%3DAbstract In this study, we use the first-order Mindlin plate equations of piezoelectric plates for thickness-shear vibrations of a simple resonator model with partial electrodes. We derive the expressions of electrical parameters with emphasis on the resistance that is related to the imaginary part of complex elastic constants, or the viscosity, of quartz crystal. Since all electrical parameters are frequency dependent, this procedure provides the chance to study the frequency behavior of crystal resonators with a direct formulation. We understand that the electrical parameters are strongly affected by the manufacturing process, with the plating techniques in particular, but the theoretical approach we presented here will be the first step for the precise estimation of such parameters and their fur... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3724858 Thu, 03 Jun 2010 23:00:00 +0100 3724858 http://www.medworm.com/index.php?rid=3707938&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20580389%26dopt%3DAbstract This article presents a numerical study of dispersion characteristics of some symmetric and antisymmetric composites modelled as multilayered packets of layers with arbitrary anisotropy of each layer. The authors introduce a subsidiary boundary problem of three-dimensional elasticity theory for the system of partial differential equations describing the harmonic oscillations of the composite caused by a surface load. The problem reduces to a boundary problem for ordinary differential equations by employing the Fourier transform. An algorithm of constructing the Fourier transform of the Green's matrix of the given boundary problem is presented. The wave numbers of Lamb waves propagating in composites, their phase velocity surfaces and group wave surfaces are presented through the poles of t... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3707938 Thu, 03 Jun 2010 23:00:00 +0100 3707938 http://www.medworm.com/index.php?rid=3691456&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20561660%26dopt%3DAbstract Authors: Chen Z, Yang L This paper establishes a model evaluating the signal loss of double transmitted acoustic beams through random rough liquid-solid surfaces based on Fresnel approximation and the phase-screen approximation. The numerical solution is replaced with a simple analytical solution through using the exponential substitution approach to remove the nonlinear integral terms. Therefore, the real-time inspection by using C-scan imaging systems of flaws in materials can be achieved through the proposed model. The research results show that the signal loss of double transmissions from random rough surfaces mainly depends on two factors: the root-mean-square (RMS) of the roughness and the depth of the flaw in materials. The experimentally measured signal loss is in good agreemen... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3691456 Mon, 31 May 2010 23:00:00 +0100 3691456 http://www.medworm.com/index.php?rid=3680415&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20542310%26dopt%3DAbstract In conclusion, these results suggest that the novel polymer-shelled microbubbles have a potential to be used for perfusion evaluation. PMID: 20542310 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3680415 Sun, 23 May 2010 23:00:00 +0100 3680415 http://www.medworm.com/index.php?rid=3653280&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20538312%26dopt%3DAbstract Authors: Nguyen DQ, Gan WS The DORT (French acronym for Décomposition de l'Opérateur de Retournement Temporel) method is a novel approach for active detection and focusing of acoustic waves on the targets in the scattering medium. This technique involves the determination of the invariant of the time-reversal operator obtained by measurement of the scattering data in a pulse-echo mode. In this paper, a proposed approach based on the DORT method is developed to solve the acoustic inverse scattering problem of a small metallic scatterer. The proposed approach not only estimates the position of the scatterer, but also determines the physical properties of an unknown metallic scatterer such as the shape (cylinder or sphere), the material (density), and the size (radius) in an anisotr... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3653280 Tue, 18 May 2010 23:00:00 +0100 3653280 http://www.medworm.com/index.php?rid=3653283&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20537363%26dopt%3DAbstract Authors: Molero M, Segura I, Aparicio S, Hernández MG, Izquierdo MA This paper deals with the measurement of frequency-dependent ultrasonic attenuation in strongly heterogeneous materials, such as cementitious materials. To improve the measurement of this parameter on this kind of materials, a linear swept-frequency signal is used to drive an emitter transducer to conduct a through-transmission inspection in immersion. To filter out undesirable frequency content, time-frequency filtering and detection process are performed. The use of this method has been compared with two excitation techniques, the broadband and the narrowband pulses. The results obtained using the swept-frequency excitation together with the time-frequency filtering, allows the determination of the attenuation cur... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3653283 Sun, 09 May 2010 23:00:00 +0100 3653283 http://www.medworm.com/index.php?rid=3653282&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20537364%26dopt%3DAbstract Authors: van Neer PL, Vos HJ, de Jong N Recently, the measurement of phase transfer functions (PTFs) of piezoelectric transducers has received more attention. These PTFs are useful for e.g. coding and interference based imaging methods, and ultrasound contrast microbubble research. Several optical and acoustic methods to measure a transducer's PTF have been reported in literature. The optical methods require a setup to which not all ultrasound laboratories have access to. The acoustic methods require accurate distance and acoustic wave speed measurements. A small error in these leads to a large error in phase, e.g. an accuracy of 0.1% on an axial distance of 10cm leads to an uncertainty in the PTF measurement of +/-97 degrees at 4MHz. In this paper we present an acoustic pulse-echo met... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3653282 Thu, 06 May 2010 23:00:00 +0100 3653282 http://www.medworm.com/index.php?rid=3653281&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20537365%26dopt%3DAbstract Authors: Dixon S, Burrows SE, Dutton B, Fan Y A pulsed Nd:YAG laser with an approximately Gaussian beam shape is directed onto the surface of an aluminium sheet at an energy density below which damage by laser ablation occurs, generating Lamb waves in the sheet. The laser beam is raster scanned across the surface of the sample. The Lamb waves travel radially outwards from the generation point and are detected some distance away by an electromagnetic acoustic transducer with sensitivity to in-plane displacements of the sheet. A number of static EMATs are located around the edges of the sheet, some distance from the generation point. The presence of a crack-like defect on the sheet can be detected by either a sudden change in the ultrasonic waveform or by an enhancement in the frequency ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3653281 Thu, 06 May 2010 23:00:00 +0100 3653281 http://www.medworm.com/index.php?rid=3564440&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20462623%26dopt%3DAbstract The objective of this research was to find an ultrasonic parameter sensitive to DMD, which could give relevant information related to microstructure if compared to traditional investigations such as morphometrical analysis. This "in vitro" study focused on the Mdx mouse model and investigated the potential differences between wild-type and dystrophin-deficient mice diaphragms. Using a 50MHz ultrasonic sensor built in our group, we recorded an increase in ultrasonic wave attenuation in the dystrophin-deficient samples in comparison with normal muscles. A correlation between attenuation, mouse age and the percentage of non-muscular proportion in muscle was observed. As Mdx mouse is the best animal model for DMD and reproduces the degenerative pattern observed in human DMD muscles, this appro... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3564440 Wed, 21 Apr 2010 23:00:00 +0100 3564440 http://www.medworm.com/index.php?rid=3564439&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20462624%26dopt%3DAbstract Authors: Kim W, Park K, Oh J, Choi J, Kim HY Although ultrasonic technology has been successfully adopted for semiconductor cleaning, a recent trend of extreme miniaturization of patterns calls for a novel process that can remove contaminant particles without damaging nanoscale patterns. Unstable bubble oscillations have been hypothesized to cause such surface damages, and here we show direct visualization results that a high acoustic pressure induces bubble instability leading to pattern damages. As a remedy for the conventional ultrasonic cleaning scheme, we introduce a novel cleaning system using dual transducers, in which one transducer generates bubbles with a high acoustic pressure in an acoustically isolated sub-chamber and the other drives the oscillation of bubbles around the ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3564439 Sat, 17 Apr 2010 23:00:00 +0100 3564439 http://www.medworm.com/index.php?rid=3465669&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20385398%26dopt%3DAbstract Authors: Lohakan M, Jamnongkan T, Pintavirooj C, Kaewpirom S, Boonsang S This paper presents a numerical model for the evaluation of mechanical properties of a relatively thin hydrogel. The model utilizes a system identification method to evaluate the acoustical parameters from ultrasonic measurement data. The model involves the calculation of the forward model based on an ultrasonic wave propagation incorporating diffraction effect. Ultrasonic measurements of a hydrogel are also performed in a reflection mode. A Nonlinear Least Square (NLS) algorithm is employed to minimize difference between the results from the model and the experimental data. The acoustical parameters associated with the model are effectively modified to achieve the minimum error. As a result, the parameters of PVA... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3465669 Tue, 23 Mar 2010 00:00:00 +0100 3465669 http://www.medworm.com/index.php?rid=3465676&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20381823%26dopt%3DAbstract CONCLUSION: 5-ALA pretreatment significantly enhanced the cytotoxicity of ultrasound radiation in K562 cells. The damage of mitochondria structure and function might be an important cause of cell death in K562 cells induced by the treatment of ultrasound radiation and 5-ALA together. PMID: 20381823 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3465676 Sun, 21 Mar 2010 00:00:00 +0100 3465676 http://www.medworm.com/index.php?rid=3465667&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20385399%26dopt%3DAbstract We present solutions for non-spherical bubbles, with asphericity being addressed by means of Legendre polynomials or associated Legendre functions. A parametric investigation of the bubble dynamical oscillatory response as a function of the fluid rheological properties shows that the amplitude of bubble oscillations drastically increases as liquid elasticity (quantified by the Deborah number) increases or as liquid viscosity decreases (quantified by the Reynolds number). Extensive numerical calculations demonstrate that increasing elasticity and/or viscosity of the surrounding liquid tend to stabilize the shape anisotropy of an initially non-spherical bubble. Results are shown for pressure amplitudes 0.2-2MPa and Deborah, Reynolds numbers in the intervals of 1-8 and 0.094-1.256, respective... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3465667 Mon, 15 Mar 2010 00:00:00 +0100 3465667 http://www.medworm.com/index.php?rid=3449794&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20371093%26dopt%3DAbstract Authors: Maznev AA, Gostein M Surface acoustic waves guided by a copper line embedded in a silica film on a silicon wafer were generated and detected optically using the laser-induced transient grating technique. Lines as narrow as approximately 0.2mum yield a good signal despite the much larger size of the laser spot. The phase velocity of the guided mode is slightly lower than the surface acoustic wave velocity in the thin film structure. Good correlation between the acoustic frequency and the electrical resistivity of the copper lines results from the dependence of both measurements on the line width. PMID: 20371093 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3449794 Mon, 15 Mar 2010 00:00:00 +0100 3449794 http://www.medworm.com/index.php?rid=3425926&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20350735%26dopt%3DAbstract Authors: Huang Y, Li XF In this paper, propagation of shear waves along a weak interface of two dissimilar magnetoelectric or magnetoelectroelastic materials is considered. Two exact dispersion relations are obtained for an imperfect electrode interface and an unelectroded interface, respectively. The existence condition of the interfacial waves is studied. Our results show that the interfacial imperfection strongly affects the velocity of the interfacial shear waves. In particular, for certain bi-magnetoelectric material, the interfacial shear waves may do not exist for a perfect interface and exist only for an imperfect interface. These findings are useful for the design of high-frequency wave devices. PMID: 20350735 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3425926 Sun, 07 Mar 2010 00:00:00 +0100 3425926 http://www.medworm.com/index.php?rid=3408845&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20334887%26dopt%3DAbstract This study, using the dynamic light scattering and transmission electron microscopic observation, demonstrated 21.2% of encapsulated fluorescent materials (FITC) could be released from liposomes with an average diameter of 210nm when exposed to continuous (cw) ultrasound at 1.1MHz (I(SPTA)=900W/cm(2)) for 10s and the percentage release efficiency can reach to 70% after 60s irradiation. This result also reveals that rupture of relatively large liposomes (>100nm) and generation of pore-like defects in the membrane of small liposomes (<100nm) due to HIFU excitation might be the main causes of the release; the inertial cavitation took place during the irradiation. The controlled drug release from liposomes by HIFU may be proven to be a potential useful modality for clinical applications.... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3408845 Mon, 01 Mar 2010 00:00:00 +0100 3408845 http://www.medworm.com/index.php?rid=3371179&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20231025%26dopt%3DAbstract Authors: Wang X, Subramaniam KV, Lin F A test procedure for measuring changes in amplitude and phase of SH ultrasonic waves from the interface between fused-quartz and cement paste samples is presented. The phase change is determined from the temporal shift in the reflected signal relative to the incident signal. The sensitivity of the measured parameters to changes in acoustic impedance of the materials in contact with fused-quartz is evaluated for different angles of incidence. It is shown that a reflection measurement at normal incidence at nano-second temporal resolution does not provide sufficient sensitivity to measure the viscous component of shear modulus of low viscosity fluids and cannot be applied to cement paste while it is in a fluid state. Monitoring the measured amplitud... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3371179 Thu, 18 Feb 2010 00:00:00 +0100 3371179 http://www.medworm.com/index.php?rid=3371178&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20231026%26dopt%3DAbstract Authors: Shin HC, Prager R, Gomersall H, Kingsbury N, Treece G, Gee A The speed of sound in soft tissues is usually assumed to be 1540m/s in medical pulse-echo ultrasound imaging systems. When the true speed is different, the mismatch can lead to distortions in the acquired images, and so reduce their clinical value. Previously we reported a new method of sound-speed estimation in the context of image deconvolution. Unlike most other sound-speed estimation methods, this enables the use of unmodified ultrasound machines and a normal scanning pattern. Our approach was validated for largely homogeneous media with single sound speeds. In this article, we demonstrate that sound speeds of dual-layered media can also be estimated through image deconvolution. An ultrasound simulator has been d... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3371178 Wed, 17 Feb 2010 00:00:00 +0100 3371178 http://www.medworm.com/index.php?rid=3354814&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20206956%26dopt%3DAbstract Authors: Camara VC, Laux D, Arnould O In this work, we propose a study dedicated to the influence of the delay line nature in transverse ultrasonic sensors, dedicated to dynamic high frequency elastic moduli of viscoelastic materials estimation. In literature, these shear ultrasonic rheometers are using delay lines in glass or quartz and normal or oblique incidence of ultrasonic rays. The oblique incidence is used in order to improve the sensitivity of the measurements. We theoretically demonstrate in this work that the use of delay lines in polymers is recommended to improve the sensitivity. Due to modifications, performed on a 10MHz commercial ultrasonic sensor, we experimentally show on glycerin (which is a Newtonian material) that it is possible to multiply by a factor 10 the sensi... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3354814 Wed, 17 Feb 2010 00:00:00 +0100 3354814 http://www.medworm.com/index.php?rid=3354813&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20207388%26dopt%3DAbstract Authors: Ferrari CB, Andrade MA, Adamowski JC, Guirro RR The therapeutic ultrasound (US) is one of the resources mostly used by physiotherapists; however the use of uncalibrated equipments results in inefficient or even harmful therapies to the patient. In this direction, the objective of this study was to evaluate the performance and the procedures of utilization and maintenance of US in use in clinics and Physical-therapy offices. A questionnaire with questions related to the procedures applied in service during the use of therapeutic ultrasound was applied to physiotherapists. The performance of 31 equipments of 6 different brands and 13 different models was evaluated according to the IEC 61689 norm. The parameters measured were: acoustic power; effective radiating area (AER); non-u... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3354813 Sun, 14 Feb 2010 00:00:00 +0100 3354813 http://www.medworm.com/index.php?rid=3328099&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20193957%26dopt%3DAbstract CONCLUSION: These results corroborate our hypothesis that, in addition to the considerably higher penetration depth of dual-frequency excitation due to the lower attenuation at 3MHz than that at 8.5 and 11.5MHz, the sample volume of dual-frequency excitation is also smaller than that of linear 3-MHz method for more spatially confined destruction of microbubbles. PMID: 20193957 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3328099 Sun, 14 Feb 2010 00:00:00 +0100 3328099 http://www.medworm.com/index.php?rid=3328100&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20193956%26dopt%3DAbstract Authors: Chakraborty A This work investigates the possibility of the propagation of Lamb waves in thin solid layers with external traction free surfaces, in the presence of surface elasticity, inertia and residual stress. It is demonstrated that such waves do exist and that their characteristics can be quite different from their classical counterparts. The governing equations with non-classical boundary conditions involving the bulk and surface stress are solved exactly in the frequency-wavenumber domain. This solution is utilized to compute the Lamb wave modes for different layer thicknesses. An efficient strategy to capture all the modes of Lamb waves within a given frequency window is outlined. It is shown that the effect of surface elasticity and inertia becomes significant with in... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3328100 Fri, 12 Feb 2010 00:00:00 +0100 3328100 http://www.medworm.com/index.php?rid=3319216&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20189622%26dopt%3DAbstract Authors: Wang P, Xiao L, Wang X, Li X, Liu Q The cytotoxic effect of protoporphyrin IX disodium salt (PPIX) on isolated Ehrlich ascetic tumor (EAT) cells induced by ultrasound exposure was investigated. Tumor cells suspended in air-saturated phosphate buffer solution (PBS, pH 7.2) were exposed to ultrasound at 2.2MHz for up to 60 s in the presence and absence of PPIX. The viability of cells was determined by a trypan blue exclusion test. The morphological changes of cells in SDT were observed by scanning electron microscope (SEM). And the sub-cellular localization of PPIX in EAT cells was detected by confocal laser scanning microscopy (CLSM). The ultrasonically-induced cell damage increased as PPIX concentration increased, while no cell damage was observed with PPIX alone. CLSM observa... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3319216 Sat, 06 Feb 2010 00:00:00 +0100 3319216 http://www.medworm.com/index.php?rid=3312046&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20181372%26dopt%3DAbstract CONCLUSION: The plots of the partial-wave series reveal acoustic backscattering enhancements (not shown in previous investigations) generally occurring at ka less, similar 0.1 at a critical angle alpha(c) bounded by the longitudinal and shear waves coupling angles theta(L)=sin(-1)(c/c(L)) and theta(S)=sin(-1)(c/c(S)) such that theta(L)<alpha(c)<theta(S) (where c(L) and c(S) are the phase velocities of the longitudinal and shear waves inside the elastic cylinder, and c is the speed of sound in the surrounding medium). It is shown here that the backscattering enhancements with a critical angle theta(L)<alpha(c)<theta(S) result from the excitation of the monopole (n=0) resonance mode. Moreover, additional acoustic backscattering enhancements still occur in the range 1 less, simila... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3312046 Tue, 02 Feb 2010 00:00:00 +0100 3312046 http://www.medworm.com/index.php?rid=3291343&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20167344%26dopt%3DAbstract Authors: Mitri FG The aim of this short communication is to report that Gegenbauer's (partial-wave) expansion, that may be used (under some specific conditions) to represent the incident field of an acoustical (or optical) high-order Bessel beam (HOBB) in spherical coordinates, anticipates earlier expressions for undistorted waves. The incident wave-field is written in terms of the spherical Bessel function of the first kind, the gamma function as well as the Gegenbauer or ultraspherical functions given in terms of the associated Legendre functions when the order m of the HOBB is an integer number. Expressions for high-order and zero-order Bessel beams as well as for plane progressive waves reported in prior works can be deduced from Gegenbauer's partial-wave expansion by appropriate c... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3291343 Tue, 02 Feb 2010 00:00:00 +0100 3291343 http://www.medworm.com/index.php?rid=3284675&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20156630%26dopt%3DAbstract Authors: Hu J, Qian S, Ding Y Temperature control of hyperthermia treatments is generally implemented with multipoint feedback system comprised of phased-array transducer, which is complicated and high cost. Our simulations to the acoustic field induced by a self-focused concave spherical transducer (0.5MHz, 9cm aperture width, 8.0cm focal length) show that the distribution of temperature can keep the same "cigar shape" in the focal region during ultrasound insonation. Based on the characteristic of the temperature change, a two-dimensional model of a "cigar shape" tumor is designed and tested through numerical simulation. One single-point on the border of the "cigar shape" tumor is selected as the control target and is controlled at the temperature of 43 degrees C by using a self-tuni... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3284675 Thu, 28 Jan 2010 00:00:00 +0100 3284675 http://www.medworm.com/index.php?rid=3276826&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20153008%26dopt%3DAbstract Authors: Marion A, Aoudi W, Basarab A, Delachartre P, Vray D Ultrasonic imaging is often used to estimate blood flow velocity. Currently, estimates are carried out using Doppler-based techniques. However, there are a number of shortcomings such as the limited spatial resolution and the inability to estimate longitudinal flows. Thus, alternative methods have been proposed to overcome them. Difficulties are notably encountered with high-frequency imaging systems that use swept-scan techniques. In this article, we propose to compare four vector velocity estimation methods that are complementary to Doppler, focusing on 40MHz, high-frequency imaging. The goal of this study is to evaluate which method could circumvent the limitations of Doppler methods for evaluation of microcirculation, in ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3276826 Mon, 25 Jan 2010 00:00:00 +0100 3276826 http://www.medworm.com/index.php?rid=3276825&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20153497%26dopt%3DAbstract This study demonstrates that large macromolecules, up to 2MDa in size, can be delivered with high efficiency to cells which undergo reversible permeabilisation, maintaining long-term viability in approximately half of the cells. PMID: 20153497 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3276825 Mon, 25 Jan 2010 00:00:00 +0100 3276825 http://www.medworm.com/index.php?rid=3255138&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20138640%26dopt%3DAbstract In conclusion, our novel methodology can assess the stress-strain relationship of the aortic wall locally in vivo and quantify important parameters for the detection and characterization of vascular disease. PMID: 20138640 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3255138 Thu, 14 Jan 2010 00:00:00 +0100 3255138 http://www.medworm.com/index.php?rid=3220828&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20106496%26dopt%3DAbstract Authors: Song J, Kim S, Sohn HY, Song TK, Yoo YM Coded excitation can improve the signal-to-noise ratio (SNR) in ultrasound tissue harmonic imaging (THI). However, it could suffer from the increased sidelobe artifact caused by incomplete pulse compression due to the spectral overlap between the fundamental and harmonic components of ultrasound signal after nonlinear propagation in tissues. In this paper, three coded tissue harmonic imaging (CTHI) techniques based on bandpass filtering, power modulation and pulse inversion (i.e., CTHI-BF, CTHI-PM, and CTHI-PI) were evaluated by measuring the peak range sidelobe level (PRSL) with varying frequency bandwidths. From simulation and in vitro studies, the CTHI-PI outperforms the CTHI-BF and CTHI-PM methods in terms of the PRSL, e.g., -43.5dB ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3220828 Thu, 07 Jan 2010 00:00:00 +0100 3220828 http://www.medworm.com/index.php?rid=3212951&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20096435%26dopt%3DAbstract Authors: Schmerr LW, Lopez-Sanchez AL, Sedov A The expansion coefficients of a multi-Gaussian ultrasonic beam model are obtained by a new approach that applies Prony s method in a K-space domain. This method allows the fitting of the Gaussian beam directly at the face of the transducer with very high computational efficiency. It is demonstrated that the K-space Prony's method can be used to accurately model the transducer field of planar and focused piston transducers, as well as probes that do not act as pistons. The choice of parameters appearing in the method and their influence on performance are discussed. PMID: 20096435 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3212951 Thu, 07 Jan 2010 00:00:00 +0100 3212951 http://www.medworm.com/index.php?rid=3194621&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20083291%26dopt%3DAbstract Authors: Heo SW, Kim H An estimation of ultrasound attenuation in soft tissues is critical in the quantitative ultrasound analysis since it is not only related to the estimations of other ultrasound parameters, such as speed of sound, integrated scatterers, or scatterer size, but also provides pathological information of the scanned tissue. However, estimation performances of ultrasound attenuation are intimately tied to the accurate extraction of spectral information from the backscattered radiofrequency (RF) signals. In this paper, we propose two novel techniques for calculating a block power spectrum from the backscattered ultrasound signals. These are based on the phase-compensation of each RF segment using the normalized cross-correlation to minimize estimation errors due to phase... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3194621 Wed, 30 Dec 2009 00:00:00 +0100 3194621 http://www.medworm.com/index.php?rid=3186286&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20080278%26dopt%3DAbstract Authors: Zhao L, Zhao Q, Zhou J, Tian S, Zhang H In this paper, we have investigated the interaction between acoustic waves generated by an incident light beam propagating through two-dimensional transducers. A set of coupled mode equations for two-dimensional multi-channel acousto-optic inter-modulation are derived, and the solutions are obtained. A new type of two-dimensional multi-channel Bragg acousto-optic modulator is designed by analyzing two-dimensional multi-channel acousto-optic inter-modulation based on the coupled mode theory, and its performance has also been experimentally characterized. The experimental results are in accordance with our theoretical analysis. PMID: 20080278 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3186286 Mon, 21 Dec 2009 00:00:00 +0100 3186286 http://www.medworm.com/index.php?rid=3179093&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20071000%26dopt%3DAbstract In this study DPSM has been employed to model the Lorentz type EMAT with a meander line and flat spiral type coil. The problem of wave propagation has been solved and eddy currents and Lorentz forces have been calculated. The displacement field has been obtained as well. While modeling the Lorentz force the effect of dynamic magnetic field has been considered that most current analyses ignore. Results from this analysis have been compared with the finite element method (FEM) based predictions. It should be noted that with the current state of knowledge this problem can be solved only by FEM. PMID: 20071000 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3179093 Mon, 21 Dec 2009 00:00:00 +0100 3179093 http://www.medworm.com/index.php?rid=3139611&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20045166%26dopt%3DAbstract Authors: Zhou XW, Zou XY, Wang TH, Cheng JC The effective velocity of elastic waves for two-dimensional (2D) phononic crystals with rectangular lattice in the long-wavelength limit is studied by numerical simulations. It is demonstrated that, for all three propagating modes, not only the modes polarized in-plane (L wave and SV wave), but also the mode polarized out-plane (SH wave), the effective velocities are distinctly anisotropic and the slowness curves exhibit twofold symmetry. The anisotropy increases as the filling fraction increases or as the width to length ratio of the lattice decreases, and high anisotropy can be obtained in phononic crystals with large contrast between material parameters, which is much higher in rectangular lattice than in square lattice with the same mater... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3139611 Wed, 16 Dec 2009 00:00:00 +0100 3139611 http://www.medworm.com/index.php?rid=3122597&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20031182%26dopt%3DAbstract Authors: Croxford AJ, Moll J, Wilcox PD, Michaels JE The application of temperature compensation strategies is important when using a guided wave structural health monitoring system. It has been shown by different authors that the influence of changing environmental and operational conditions, especially temperature, limits performance. This paper quantitatively describes two different methods to compensate for the temperature effect, namely optimal baseline selection (OBS) and baseline signal stretch (BSS). The effect of temperature separation between baseline time-traces in OBS and the parameters used in the BSS method are investigated. A combined strategy that uses both OBS and BSS is considered. Theoretical results are compared, using data from two independent long-term experiments... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3122597 Thu, 26 Nov 2009 00:00:00 +0100 3122597 http://www.medworm.com/index.php?rid=3122596&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D20031183%26dopt%3DAbstract Authors: Ozeri S, Shmilovitz D This paper investigates ultrasonic transcutaneous energy transfer (UTET) as a method for energizing implanted devices at power level up to a few 100mW. We propose a continuous wave 673kHz single frequency operation to power devices implanted up to 40mm deep subcutaneously. The proposed UTET demonstrated an overall peak power transfer efficiency of 27% at 70mW output power (rectified DC power at the load). The transducers consisted of PZT plane discs of 15mm diameter and 1.3mm thick acoustic matching layer made of graphite. The power rectifier on the implant side attained 88.5% power transfer efficiency. The proposed approach is analyzed in detail, with design considerations provided to address issues such as recommended operating frequency range, acoustic... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3122596 Thu, 26 Nov 2009 00:00:00 +0100 3122596 http://www.medworm.com/index.php?rid=3057267&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19954806%26dopt%3DAbstract Authors: Fradkin LJ, Stacey R High-frequency approximations that can be interpreted in terms of the Uniform Geometrical Theory of Diffraction (UGTD) and Uniform Kirchhoff Approximation (UKA) are used to develop a code for modeling ultrasonic scatter of a plane compressional wave by an elliptic crack in the radiating near field. The approximations are intercompared and partially validated against a direct numerical code based on an FD (Finite-Difference) scheme. At present, in many realistic situations the approximate codes of the type described here offer the only viable simulation tool; purely numeric codes are not only much slower, they still require too much computer memory to simulate the complex structure of the radiating near fields. PMID: 19954806 [PubMed - as supplied by pu... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=3057267 Tue, 10 Nov 2009 00:00:00 +0100 3057267 http://www.medworm.com/index.php?rid=2977969&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19897219%26dopt%3DAbstract Authors: Manasseh R, Bouakaz A PMID: 19897219 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2977969 Sat, 31 Oct 2009 00:00:00 +0100 2977969 http://www.medworm.com/index.php?rid=2977971&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19897217%26dopt%3DAbstract Authors: Ramos A PMID: 19897217 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2977971 Tue, 27 Oct 2009 00:00:00 +0100 2977971 http://www.medworm.com/index.php?rid=2977970&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19897218%26dopt%3DAbstract Authors: State M, Brands PJ, Vosse FN Novel ultrasound backing materials based on polymer composites with improved dimensional stability and low coefficient of thermal expansion are being developed and analyzed. For this purpose a filled epoxy resin (Stycast(1265)), a commonly used backing material, was considered reference material and polyurethane composites (PU(2305), PU(2350)) were proposed as better alternatives. When compared to the reference, the PU(2350) filled with a mixture of Al(2)O(3) and tungsten exhibited an approximately 15 times lower glassy transition temperature and a 2.5 time lower longitudinal thermal expansion at 20 degrees C. This ensures that within the entire operational temperature range the backing material is flexible, minimizing the thermal stresses induced ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2977970 Tue, 27 Oct 2009 00:00:00 +0100 2977970 http://www.medworm.com/index.php?rid=2977973&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19896156%26dopt%3DAbstract Authors: Li YD, Yong Lee K Under harsh in situ conditions, the interface in piezoelectric sensors may be damaged mechanically and/or electrically. The damaged interface would in turn affect the electromechanical behaviors of the sensors. The purpose of the present work is to study the effect of the imperfect interface on SH wave propagating in a cylindrical piezoelectric sensor. The dispersion relations of SH wave are derived analytically and the phase velocity are obtained numerically. Parametric studies on the phase velocity indicate that the mechanical imperfection may reduce the phase velocity under certain circumstances; however, the electrical imperfection has no obvious effect on the phase velocity in any cases; with the thickness of the piezoelectric layer increasing, the phase... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2977973 Tue, 13 Oct 2009 00:00:00 +0100 2977973 http://www.medworm.com/index.php?rid=2977972&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19896683%26dopt%3DAbstract Authors: Collis J, Manasseh R, Liovic P, Tho P, Ooi A, Petkovic-Duran K, Zhu Y Cavitation microstreaming plays a role in the therapeutic action of microbubbles driven by ultrasound, such as the sonoporative and sonothrombolytic phenomena. Microscopic particle-image velocimetry experiments are presented. Results show that many different microstreaming patterns are possible around a microbubble when it is on a surface, albeit for microbubbles much larger than used in clinical practice. Each pattern is associated with a particular oscillation mode of the bubble, and changing between patterns is achieved by changing the sound frequency. Each microstreaming pattern also generates different shear stress and stretch/compression distributions in the vicinity of a bubble on a wall. Analysis of ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2977972 Tue, 13 Oct 2009 00:00:00 +0100 2977972 http://www.medworm.com/index.php?rid=2951548&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19880152%26dopt%3DAbstract Authors: Sarvazyan A This manuscript is a summary of the paper presented at the ICU'2009 on biomedical applications of acoustic radiation force with emphasis on emerging applications in microfluidics, biotechnology, biosensors and assessment of the skeletal system. In this brief overview of current and projected applications of radiation force, no detailed description of the experiments illustrating particular applications are given as this would result in a far different and longer paper. Various mechanisms of acoustic radiation force generations and their biomedical applications are considered. These mechanisms include: (a) change in the density of energy of the propagating wave due to absorption and scattering; (b) spatial variations of energy density in standing acoustic waves; (c)... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2951548 Mon, 12 Oct 2009 00:00:00 +0100 2951548 http://www.medworm.com/index.php?rid=2951547&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19880153%26dopt%3DAbstract Authors: Dagois-Bohy S, Ngo S, Pont SC, Douady S Some desert sand dunes have the peculiar ability to emit a loud sound up to 110dB, with a well-defined frequency: this phenomenon, known since early travelers (Darwin, Marco Polo, etc.), has been called the song of dunes. But only in late 19th century scientific observations were made, showing three important characteristics of singing dunes: first, not all dunes sing, but all the singing dunes are composed of dry and well-sorted sand; second, this sound occurs spontaneously during avalanches on a slip face; third this is not the only way to produce sound with this sand. More recent field observations have shown that during avalanches, the sound frequency does not depend on the dune size or shape, but on the grain diameter only, and scal... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2951547 Fri, 09 Oct 2009 00:00:00 +0100 2951547 http://www.medworm.com/index.php?rid=2951546&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19880154%26dopt%3DAbstract Authors: Zhou FM, Li Z, Fan L, Zhang SY, Shui XJ Experimental study of Love-mode immunosensors based on structures of ZnO/36 degrees YX-LiTaO(3) is presented, in which the ZnO films with c-axis (002) orientation have been successfully grown on the 36 degrees YX-LiTaO(3) substrates by RF magnetron sputtering technique. Then the Love-mode immunosensors based on the ZnO/36 degrees YX-LiTaO(3) structures and monitoring antibody-antigen immunoreactions in aqueous solutions in real time are fabricated. The experimental results show that the optimal thickness of ZnO layers is about 1.20mum in the structures deposited on 36 degrees YX-LiTaO(3) substrates, which is much less than that of SiO(2) overlayers about 6mum. The antibody-antigen immunoreaction experiments also show that the frequency s... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2951546 Fri, 09 Oct 2009 00:00:00 +0100 2951546 http://www.medworm.com/index.php?rid=2935434&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19854458%26dopt%3DAbstract Authors: Griffiths S, Rescaglio A, Melo F This paper deals with an experimental description of the acoustic behaviour of non-consolidated granular materials submitted to static force. The aim of this work is to investigate the effect of a small amount of an interstitial fluid on the acoustic propagation. Measurements of the velocity and of the transmission of the coherent wave are performed for different values of the applied force. It is shown that the behaviour of the speed of the ultrasonic coherent wave according to pressure have a slope close to the one of the Hertz-Mindlin's model in the case of a dry medium. When a small amount of a low viscosity fluid is added in a mono-disperse granular medium, the speed of the ultrasonic wave increases according to the power 1/6 to the force ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2935434 Wed, 07 Oct 2009 00:00:00 +0100 2935434 http://www.medworm.com/index.php?rid=2935432&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19857885%26dopt%3DAbstract Authors: Delalande A, Bureau MF, Midoux P, Bouakaz A, Pichon C Our study aimed at evaluating the use of ultrasound-assisted microbubbles gene transfer in mice Achilles tendons. Using a plasmid encoding luciferase gene, it was found that an efficient and stable gene expression for more than two weeks was obtained when tendons were injected with 10mug of plasmid in the presence of 5x10(5) BR14 microbubbles with the following acoustic parameters: 1MHz, 200kPa, 40% duty cycle and 10min of exposure time. The rate of gene expression was 100-fold higher than that obtained with naked plasmid injected alone without ultrasound or with ultrasound in absence of microbubbles. The long term expression of transgene makes ultrasound-assisted microbubble a suitable method for gene therapy in tendons. ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2935432 Wed, 07 Oct 2009 00:00:00 +0100 2935432 http://www.medworm.com/index.php?rid=2935430&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19857887%26dopt%3DAbstract Authors: Gibiat V, Sahuguet P Time Domain Topological Energy (TDTE), uses the reflected ultrasonic field recorded by an array of transducers placed on the boundary of the inspected medium. Two numerical determinations (forward and adjoint problems) of the acoustical field inside a reference medium are necessary to compute an image. Topological Energy is defined as a variation of topological sensitivity or gradient and comes from the field of mathematical optimisation. Recent developments for Non-Destructive Testing have shown the analogy with Time Reversal concepts. Time Reversal mirrors have been employed for various applications in a wide number of situations including wave guides where very good re-focalization performances have been obtained with a reduced number of transducers ins... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2935430 Sun, 04 Oct 2009 00:00:00 +0100 2935430 http://www.medworm.com/index.php?rid=2935433&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19857884%26dopt%3DAbstract Authors: Stepanenko DA, Minchenya VT The article presents the mathematical model allowing to investigate longitudinal and flexural vibrations of stepped flexible waveguides with transitional section without regard to various vibration modes interaction. The model uses original numerical-analytic calculations based on analytical solutions of the equation of waveguide steps vibrations and their continuous matching with numerical solution of the equation of transitional section vibrations. The proposed model can be considered as an initial approximation to the solution of the problem of flexible waveguides design, which makes it possible to determine and validate effective methods of its addressing. Resonant curves of longitudinal and flexural vibrations of two-step waveguide are traced f... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2935433 Fri, 02 Oct 2009 00:00:00 +0100 2935433 http://www.medworm.com/index.php?rid=2935431&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19857886%26dopt%3DAbstract Authors: Jiangong Y, Bin W, Cunfu H In this article, the propagation of guided thermoelastic waves in the circumferential direction of orthotropic cylindrical curved plates subjected to stress-free, isothermal boundary conditions is investigated in the context of the Green-Naghdi (GN) generalized thermoelastic theory (without energy dissipation). The coupled wave equations and heat conduction equation are solved by the Legendre orthogonal polynomial series expansion approach. The convergency of the method is discussed through a numerical example. The dispersion curves of thermal modes and elastic modes are illustrated simultaneously. Dispersion curves of the corresponding pure elastic cylindrical plate are also shown to analyze the influence of the thermoelasticity on elastic modes. Th... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2935431 Thu, 01 Oct 2009 00:00:00 +0100 2935431 http://www.medworm.com/index.php?rid=2935436&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19853268%26dopt%3DAbstract Authors: Costa C, Doche ML, Hihn JY, Bisel I, Moisy P, Lévêque JM The present work deals with the hydrodynamic behavior of several room-temperature ionic liquids presenting the same bis(trifluoromethanesulfonyles)imide anion, associated with four different cations: 1-butyl-3-methylimidazolium, 1-octyl-3-methylimidazolium, N-trimethyl-N-propylammonium and 1-butyl-1-methylpyrrolidinium cations. Steady state voltammetry was used as an electrochemical technique to characterize mass transfer in both silent and sonicated conditions, using a rotating disk electrode. Results obtained in RTILs media are compared to those acquired in synthetic solutions of controlled viscosity, in order to develop a better understanding of the phenomena involved in such media. PMID: 19853268 [PubMe... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2935436 Sun, 27 Sep 2009 00:00:00 +0100 2935436 http://www.medworm.com/index.php?rid=2935435&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19853270%26dopt%3DAbstract Authors: González-García J, Esclapez MD, Bonete P, Hernández YV, Garretón LG, Sáez V Sonoelectrochemistry is undergoing a reemerging activity in the last years with an increasing number of papers appearing in a wide range of peer review journals. Applied studies which cover environmental treatments, synthesis or characterization of nanostructures, polymeric materials synthesis, analytical procedures, films preparations, membrane preparations among other interesting applications have been reviewed. The revised fundamental analyses trying to elucidate the mechanism of the interactions between the ultrasound and electrical fields, are focused on test electrochemical processes, on the use of unconventional solvents and combination with other techniques. After the r... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2935435 Sat, 26 Sep 2009 00:00:00 +0100 2935435 http://www.medworm.com/index.php?rid=2924061&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19850312%26dopt%3DAbstract Authors: Maurel A, Pagneux V, Barra F, Lund F A surface acoustic wave can interact with dislocations that are close to the surface. We characterize this interaction and its manifestations as scattered surface acoustic waves for different orientations with respect to the surface of an edge dislocation. For dislocations that are parallel or perpendicular to the free surface, we present an analytical result for short dislocations with respect to the wave-length that reproduce qualitatively the main features observed for dislocations of various sizes. PMID: 19850312 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2924061 Thu, 24 Sep 2009 00:00:00 +0100 2924061 http://www.medworm.com/index.php?rid=2911287&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19836817%26dopt%3DAbstract Authors: Costa-Félix RP, Alvarenga AV This paper discloses results of measuring the effective radiating area (A(ER)) and the beam non-uniformity ratio (R(BN)) for US transducers at 5.0MHz. Measurements were carried out at Laboratory of Ultrasound of the Brazilian National Institute of Metrology, Standardization, and Industrial Quality. As reliability proof of system's adequacy, uncertainties were assessed. The calculation protocol was developed based on standard IEC 61689:2007. Type A uncertainty was estimated after four repetitions of the full procedure for the determination of A(ER) and R(BN), and Type B uncertainty was estimated from the mathematical model for both calculations, obtained from IEC 61689:2007 and the guide to the expression of uncertainty in measurement. The proc... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2911287 Wed, 23 Sep 2009 23:00:00 +0100 2911287 http://www.medworm.com/index.php?rid=2911286&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19837446%26dopt%3DAbstract Authors: Oberti S, Möller D, Neild A, Dual J, Beyeler F, Nelson BJ, Gutmann S Acoustic radiation forces have often been used for the manipulation of large amounts of micrometer sized suspended particles. The nature of acoustic standing wave fields is such that they are present throughout the whole fluidic volume; this means they are well suited to such operations, with all suspended particles reacting at the same time upon exposure. Here, this simultaneous positioning capability is exploited to pre-align particles along the centerline of channels, so that they can successively be removed by means of an external tool for further analysis. This permits a certain degree of automation in single particle manipulation processes to be achieved as initial identification of particles' loca... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2911286 Tue, 22 Sep 2009 23:00:00 +0100 2911286 http://www.medworm.com/index.php?rid=2911289&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19836044%26dopt%3DAbstract Authors: Castellanos L, Calás H, Ramos A The main interest of using limited diffracting waves is motivated by their potential applications in the enlargement of the field depth in acoustic imaging systems, under collimated conditions. In this work, an approach for simplifying the experimental arrangement, needed to generate limited diffracting waves, is proposed. The main idea is to approximate the theoretical X-wave electrical excitations by means of simple driving rectangular pulses. In order to optimize these driving signals in each array annulus, the L2 curve criterion is applied. The differences between theoretical X-wave signals and approximate driving pulses, related to their excitation effects, were minimized by using the time widths and amplitudes of the rectangular pulse... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2911289 Sat, 19 Sep 2009 23:00:00 +0100 2911289 http://www.medworm.com/index.php?rid=2911288&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19836816%26dopt%3DAbstract Authors: Safarik DJ, Schwarz RB, Paglieri SN, Quintana RL, Tuggle DG, Byler DD We have measured the composition and temperature dependence of the shear moduli C' and C(44) for two-phase (alpha+beta)- and single-phase beta-PdH(x). In the two-phase region, the alpha- and beta-phases are coherent. Here, the composition dependence of C(44) and C' deviate negatively from a Vegard-type volume average. We attribute the deviations to two effects: (1) the partly in-series arrangement of the precipitate and matrix phases, relative to the externally applied stress, and (2) thermally activated anelastic relaxations involving the rapid motion of H interstitial atoms, leading to slight changes in the shape of coherent precipitates. The first effect is present for both C' and C(44) and is temperature... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2911288 Sat, 19 Sep 2009 23:00:00 +0100 2911288 http://www.medworm.com/index.php?rid=2902076&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19828171%26dopt%3DAbstract Authors: Riera E, Blanco A, García J, Benedito J, Mulet A, Gallego-Juárez JA, Blasco M Oil is an important component of almonds and other vegetable substrates that can show an influence on human health. In this work the development and validation of an innovative, robust, stable, reliable and efficient ultrasonic system at pilot scale to assist supercritical CO(2) extraction of oils from different substrates is presented. In the extraction procedure ultrasonic energy represents an efficient way of producing deep agitation enhancing mass transfer processes because of some mechanisms (radiation pressure, streaming, agitation, high amplitude vibrations, etc.). A previous work to this research pointed out the feasibility of integrating an ultrasonic field inside a supercritical e... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2902076 Sat, 19 Sep 2009 23:00:00 +0100 2902076 http://www.medworm.com/index.php?rid=2902075&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19833369%26dopt%3DAbstract Authors: Hallez L, Touyeras F, Hihn JY, Klima J, Guey JL, Spajer M, Bailly Y Acoustic field distribution was determined in HIFU sonoreactors as well as localization of cavitation activity by crossing different techniques: modeling, hydrophone measurements, laser tomography and SCL measurements. Particular care was taken with quantification of this last technique by pixels or photon counting. Cavitation bubbles generated by HIFU are mainly located on the outer layer of the propagation cone in the post-focal zone. Greatest acoustic activity is not located at the geometrical focal, but corresponds to a high concentration of bubbles zone. On the contrary, the main sonochemical activity shifts slightly toward the transducer, whereas quenching of inertial cavitation is observed directly at t... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2902075 Sat, 19 Sep 2009 23:00:00 +0100 2902075 http://www.medworm.com/index.php?rid=2895349&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19822339%26dopt%3DAbstract Authors: Andersen KS, Jensen JA Local blood pressure measurements provide important information on the state of health of organs in the body and can be used to diagnose diseases in the heart, lungs, and kidneys. This paper presents an approach for investigating the ambient pressure sensitivity of a contrast agent using diagnostic ultrasound. The experimental setup resembles a realistic clinical setup utilizing a single array transducer for transmit and receive. The ambient pressure sensitivity of SonoVue (Bracco, Milano, Italy) was measured twice using two different acoustic driving pressures, which were selected based on a preliminary experiment. To compensate for variations in bubble response and to make the estimates more robust, the relation between the energy of the subharmonic an... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2895349 Sat, 19 Sep 2009 23:00:00 +0100 2895349 http://www.medworm.com/index.php?rid=2887398&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19819511%26dopt%3DAbstract The objective of this study was to analyze the influence of cavitation and energy density on stone fragmentation. A research lithotripter was used to expose a large set of artificial kidney stones to shock waves varying different parameters. Hundreds of pressure records were used to calculate the energy density of the lithotripter at different settings. Results indicate that energy density is a crucial parameter and that better SWL treatment outcomes could be obtained placing the calculus at a prefocal position. PMID: 19819511 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2887398 Sat, 19 Sep 2009 23:00:00 +0100 2887398 http://www.medworm.com/index.php?rid=2887400&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19818980%26dopt%3DAbstract Authors: Sun D, Wang S, Hata S, Shimokohbe A A circular cylindrical piezoelectric transducer with radial polarization is proposed. The axial vibration characteristics of the transducer are studied by three different methods: analytical calculation, FEM simulation and experiment. The symmetric and asymmetric excitation conditions are discussed in the Haskins and Walsh model. For the resonance frequencies of the transducer, the results from the above three methods coincide well with each other. For the vibration amplitude, there are some deviations between the FEM simulation and measurement results; some possible reasons for this are discussed. The influence of the electrode patterns on the excitation modes are also investigated in detail. Based on the study described in this paper, the ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2887400 Fri, 18 Sep 2009 23:00:00 +0100 2887400 http://www.medworm.com/index.php?rid=2887399&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19819510%26dopt%3DAbstract Authors: Martínez-Graullera O, Martín CJ, Godoy G, Ullate LG The main challenge faced by 3D ultrasonic imaging with 2D array transducers is the large number of elements required to achieve an acceptable level of quality in the images. Therefore, the optimisation of the array layout, in order to reduce the number of active elements in the aperture, has been a research topic in the last years. Nowadays, array technology has made viable the production of 2D arrays with larger flexibility on elements size, shape and position, allowing to study other configurations different to the classical matrix organisation, such as circular, archimedes spiral or polygonal layout between others. In this work, the problem of designing an imaging system array with large apertures and a very limi... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2887399 Fri, 18 Sep 2009 23:00:00 +0100 2887399 http://www.medworm.com/index.php?rid=2887397&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19819512%26dopt%3DAbstract Authors: Gómez Álvarez-Arenas TE A method that combines transmission of air-coupled ultrasound pulses through solid plates and amplitude and phase spectral analysis is presented. In particular, the method analyzes the first thickness resonance of the plates. The purpose is to determine, simultaneously, velocity and attenuation coefficient of the ultrasounds in the material and the thickness of the plate. This is especially useful when thickness can not be measured independently. The method is successfully applied to soft membranes, biological samples and FRP composites. PMID: 19819512 [PubMed - as supplied by publisher] (Source: Ultrasonics) Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2887397 Fri, 18 Sep 2009 23:00:00 +0100 2887397 http://www.medworm.com/index.php?rid=2887401&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19818979%26dopt%3DAbstract Authors: Zhang H, Zhang SY, Fan L Based on the Rayleigh energy theory combining with Timoshenko beam model, the flexural vibration characteristics of piezoelectric tubes in ultrasonic micro-actuators are investigated. Additionally, the simplified formulae are derived to study the fundamental flexural resonance frequencies of the piezoelectric tubes with free-free ends and cantilevers. By changing the sizes of the tubes and the mass loads at the free ends, the variations of the flexural resonance frequencies of the piezoelectric tubes and cantilevers are calculated theoretically. To verify accuracy of the simplified formulae, by changing the lengths of the tubes and the mass loads the flexural resonance frequencies of the piezoelectric tube with free-free ends are measured experimentall... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2887401 Thu, 17 Sep 2009 23:00:00 +0100 2887401 http://www.medworm.com/index.php?rid=2863564&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19800646%26dopt%3DAbstract Authors: Alvarenga AV, Teixeira CA, Ruano MG, Pereira WC In this work, the feasibility of texture parameters extracted from B-Mode images were explored in quantifying medium temperature variation. The goal is to understand how parameters obtained from the gray-level content can be used to improve the actual state-of-the-art methods for non-invasive temperature estimation (NITE). B-Mode images were collected from a tissue mimic phantom heated in a water bath. The phantom is a mixture of water, glycerin, agar-agar and graphite powder. This mixture aims to have similar acoustical properties to in vivo muscle. Images from the phantom were collected using an ultrasound system that has a mechanical sector transducer working at 3.5MHz. Three temperature curves were collected, and variations b... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2863564 Sat, 12 Sep 2009 23:00:00 +0100 2863564 http://www.medworm.com/index.php?rid=2829277&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19775716%26dopt%3DAbstract Authors: Dominguez N, Gibiat V The time domain topological gradient has recently been presented as a promising technique for imaging of complex structures [N. Dominguez, et al., Wave Motion 42 (1) (2005) 31-52], showing results obtained on simulated data. The method relies on the adequate combination of two computed ultrasonic fields, one forward and one adjoint. The adjoint field, that carries the information about the defects, is analogous to a time reversal operation. The forward field plays the role of a "photographic developer". The great interest of the method is that the time reversal operation is not done experimentally but numerically, allowing implementation of low cost systems. The expected low sensitivity of the method to the presence of measurement or structure noise had b... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2829277 Wed, 02 Sep 2009 23:00:00 +0100 2829277 http://www.medworm.com/index.php?rid=2824460&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19767053%26dopt%3DAbstract Authors: Nakamura N, Nakashima T, Oura S, Ogi H, Hirao M In this paper, we study the elastic property of thin films using resonant-ultrasound spectroscopy (RUS). RUS determines the elastic constants of a solid from its resonance frequencies of free vibration. There were two problems to be solved for applying RUS to thin films: accurate measurement of the resonance frequencies and mode identification of each resonance frequency. We solve these problems using the tripod needle transducers and the laser-Doppler interferometry (LDI). In this paper, we describe the RUS/LDI measurement setup we developed, and show the relationship between the elastic constant and annealing temperature for Cu thin films. Then, we discuss the effects of recrystallization and recovery on the elastic constant re... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2824460 Mon, 31 Aug 2009 23:00:00 +0100 2824460 http://www.medworm.com/index.php?rid=2810224&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19762059%26dopt%3DAbstract Authors: Tiefensee F, Becker-Willinger C, Heppe G, Herbeck-Engel P, Jakob A A new class of materials for ultrasonic matching layers is presented. The materials consist of nanoscale cerium oxide particles in an epoxy functionalized organic inorganic hybrid polymer matrix. The cerium oxide agglomerates to particles with 20nm diameters. The content of particles in the polymer matrix could be increased to 75wt.% which corresponds to 37vol.%. The most technical important piezoelectrical ceramics have an acoustic impedance of about 30 MRayl, to improve coupling into water or biological tissue with an acoustic impedance of about 1.5 MRayl a matching layer should have an acoustic impedance of about 6.8 MRayl. With a filling degree of 75wt.% the new composite material reaches an acoustic impeda... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2810224 Mon, 31 Aug 2009 23:00:00 +0100 2810224 http://www.medworm.com/index.php?rid=2789209&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19740505%26dopt%3DAbstract Authors: Bernard V, Skorpíková J, Mornstein V, Slaninová I The effects of low-power ultrasound, the anti-cancer drug cisplatin, and their combined application were studied in two lines of human ovarian carcinoma cells, A2780 and A2780cis. Four modes of treatment were used: exposure to ultrasonic field, application of cisplatin, exposure to ultrasound followed by cisplatin, and presence of cisplatin followed by exposure to application ultrasound. Ultrasound was used at intensities of 0.5W/cm(2) and 1.0W/cm(2) for 10min, cisplatin was applied at concentrations of 1muM and 6muM per cell suspension treated in A2780 and cisplatin-resistant A2780cis cells, respectively. The results of each experimental treatment were assessed by the resultant cell viability related to the viab... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2789209 Tue, 18 Aug 2009 23:00:00 +0100 2789209 http://www.medworm.com/index.php?rid=2775244&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19732930%26dopt%3DAbstract In this study, we present a model study of guided wave dispersion and resonance behavior of an array of piezoelectric plates with arbitrary cross-sections. The objective of this work is to analyze the influence of the geometry of an element of a 1D-array ultrasound transducer on generating multi-resonance frequency so as to increase the frequency bandwidth of the transducers. A semi-analytical finite-element (SAFE) method is used to model guided wave propagation in multi-layered 1D-array ultrasound transducers. Each element of the array is composed of LiNbO(3) piezoelectric material with rectangular or subdiced cross-section. Four-node bilinear finite-elements have been used to discretize the cross-section of the transducer. Dispersion curves showing the dependence of phase and group veloc... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2775244 Wed, 12 Aug 2009 23:00:00 +0100 2775244 http://www.medworm.com/index.php?rid=2775245&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19732929%26dopt%3DAbstract Authors: Delrue S, Van Den Abeele K, Blomme E, Deveugele J, Lust P, Matar OB Non-contact air-coupled ultrasonic inspection of materials using single-sided access offers interesting possibilities for the development of in-line non-destructive testing (NDT) systems. This contribution reports observations and simulations obtained from a single-sided air-coupled pitch-catch configuration. The pitch-catch technique involves a set-up in which transmitter and receiver are located at the same side of the test object. Sound waves, reflected once or multiple times from the back-wall of the object or refracted by a discontinuity, are recorded and analyzed for visualization. The feasibility of the technique is demonstrated, experimentally, in the case of artificial defects in aluminium samples. De... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2775245 Tue, 11 Aug 2009 23:00:00 +0100 2775245 http://www.medworm.com/index.php?rid=2775246&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19732928%26dopt%3DAbstract Authors: Longo R, Vanlanduit S, Vanherzeele J, Guillaume P The goal of non-destructive testing (NDT) is to determine the position and size of structural defects, in order to measure the quality and evaluate the safety of building materials. Most NDT techniques are rather complex, however, requiring specialized knowledge. In this article, we introduce an experimental method for crack detection that uses Surface Acoustic Waves (SAWs) and optical measurements. The method is tested on a steel beam engraved with slots of known depth. A simple model to determine the cracks size is also proposed. At the end of the article, we describe a possible application: fatigue crack sizing on a damaged slat track. This technique represents a first step toward a better understanding of the crack growth, ... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2775246 Sat, 08 Aug 2009 23:00:00 +0100 2775246 http://www.medworm.com/index.php?rid=2759102&cid=s_36215_75_f&fid=36215&url=http%3A%2F%2Fwww.ncbi.nlm.nih.gov%2Fentrez%2Fquery.fcgi%3Ftmpl%3DNoSidebarfile%26db%3DPubMed%26cmd%3DRetrieve%26list_uids%3D19720388%26dopt%3DAbstract Authors: Le LH, Zhang C, Ta D, Lou E The slow compressional wave in air-saturated aluminum foams was studied by means of ultrasonic transverse transmission method over a frequency range from 0.2MHz to 0.8MHz. The samples investigated have three different cell sizes or pores per inch (5, 10 and 20ppi) and each size has three aluminum volume fractions (5%, 8% and 12% AVF). Phase velocities show minor dispersion at low frequencies but remain constant after 0.7MHz. Pulse broadening and amplitude attenuation are obvious and increase with increasing ppi. Attenuation increases considerably with AVF for 20ppi foams. Tortuosity ranges from 1.003 to 1.032 and increases with AVF and ppi. However, the increase of tortuosity with AVF is very small for 10 and 20ppi samples. PMID: 19720388 [PubMe... Ultrasonics journals http://www.medworm.com/rss/comments.php?id=2759102 Thu, 06 Aug 2009 23:00:00 +0100 2759102