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1

History of Acoustical Imaging  

Microsoft Academic Search

\\u000a A historical snapshot is presented of the development of acoustical imaging in the context of a Research Program in Quantitative\\u000a Non-Destructive Evaluation (QNDE). This was an interdisciplinary program involving researchers at the Rockwell Science Center\\u000a and several other institutes at universities, government laboratories, and industries. This program was first initiated by\\u000a the Wright Patterson Air Force Base and continued by

B. R. Tittmann

2

Acoustic subwavelength imaging of subsurface objects with acoustic resonant metalens  

SciTech Connect

Early research into acoustic metamaterials has shown the possibility of achieving subwavelength near-field acoustic imaging. However, a major restriction of acoustic metamaterials is that the imaging objects must be placed in close vicinity of the devices. Here, we present an approach for acoustic imaging of subsurface objects far below the diffraction limit. An acoustic metalens made of holey-structured metamaterials is used to magnify evanescent waves, which can rebuild an image at the central plane. Without changing the physical structure of the metalens, our proposed approach can image objects located at certain distances from the input surface, which provides subsurface signatures of the objects with subwavelength spatial resolution.

Cheng, Ying; Liu, XiaoJun, E-mail: liuxiaojun@nju.edu.cn [Key Laboratory of Modern Acoustics, Nanjing University, Nanjing 210093 (China) [Key Laboratory of Modern Acoustics, Nanjing University, Nanjing 210093 (China); State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190 (China); Zhou, Chen; Wei, Qi; Wu, DaJian [Key Laboratory of Modern Acoustics, Nanjing University, Nanjing 210093 (China)] [Key Laboratory of Modern Acoustics, Nanjing University, Nanjing 210093 (China)

2013-11-25

3

Acoustic Waves in Medical Imaging and Diagnostics  

PubMed Central

Up until about two decades ago acoustic imaging and ultrasound imaging were synonymous. The term “ultrasonography,” or its abbreviated version “sonography” meant an imaging modality based on the use of ultrasonic compressional bulk waves. Since the 1990s numerous acoustic imaging modalities started to emerge based on the use of a different mode of acoustic wave: shear waves. It was demonstrated that imaging with these waves can provide very useful and very different information about the biological tissue being examined. We will discuss physical basis for the differences between these two basic modes of acoustic waves used in medical imaging and analyze the advantages associated with shear acoustic imaging. A comprehensive analysis of the range of acoustic wavelengths, velocities, and frequencies that have been used in different imaging applications will be presented. We will discuss the potential for future shear wave imaging applications.

Sarvazyan, Armen P.; Urban, Matthew W.; Greenleaf, James F.

2013-01-01

4

Acoustic Daylight: Passive acoustic imaging using ambient noise  

NASA Astrophysics Data System (ADS)

Active and passive sonar are the best methods of exploring the ocean over large distances since the ocean is rather transparent to sound. Ambient noise often decreases the performance of sonar by masking the desired signal. It has been proposed that the ambient noise itself can be used to detect and image targets (Buckingham, et.al., 1996), a technique often called 'Acoustic Daylight'. The ambient noise field is focused into a large number of narrow beams. Targets are detected via the acoustic contrasts between those beams which intersect the target and those that do not. A prototype acoustic daylight system has been constructed to test this concept. The Acoustic Daylight Ocean Noise Imaging System (ADONIS) forms 126 receive-only beams spanning 10o in the horizontal and 8o in the vertical. The -3 dB beamwidth approaches 0.6o at 75 kHz. The noise in each beam is filtered into 16 frequency bins logarithmically spaced over the decade of frequencies 8-80 kHz. The frequency and intensity information from each beam is mapped into a color pixel to form an acoustic image. Two acoustic daylight experiments were conducted in San Diego bay. A wide variety of planar, cylindrical, and spherical targets were detected and imaged at ranges up to 40 m using ambient noise as the sole source of acoustic illumination. Targets constructed from different materials could be discriminated based on differences in the spectral content of the scattered energy. The spatial and temporal characteristics of the ambient noise field were examined over the frequencies 5-100 kHz using a pair of broadband hydrophones synchronized to ADONIS. The character of the high-frequency ambient noise field is found to be primarily dependent on the snapping frequency of local snapping shrimp, which in turn is dependent on the time of day. Knowledge of the ambient noise field is used to explain many of the curious features in the acoustic images.

Epifanio, Chad Lawrence

1997-12-01

5

Acoustic cloaking and imaging using complementary media  

Microsoft Academic Search

Base on the concept of complementary media, a scheme to achieve cloak an object outside the shell is proposed by Yun lai et al [PRL 102, 093901].We generalize the concept in acoustic waves and demonstrate numerically how to achieve the acoustic cloaking and imaging with complementary media.

Jin Han; Yuancheng Fan; Hongqiang Li; Zhanshan Wang

2009-01-01

6

UHF acoustic microscopic imaging of resonator motion  

Microsoft Academic Search

An important characteristic of acoustic resonator design at ultra high frequencies (UHF) is the efficiency of the device, which is affected by leakage radiation beyond the active transducer area. In order to directly measure leakage radiation, acoustic microscopic imaging of the ultrasonic resonant motion at 880 MHz has been performed with an autocompensating interferometer and heterodyne demodulation. A method of

Ken L. Telschow; Vance A. Deason; David L. Cottle

2000-01-01

7

Ultrasonic liquid crystal-based underwater acoustic imaging  

Microsoft Academic Search

A new approach to underwater ultrasonic imaging is described and demonstrated which directly converts a 2D acoustic pressure image formed from an acoustic lens into an intensity-mapped visual image. There are no computers nor electronic requirements, nor piezo arrays necessary. The imager relies on the acoustic coupling, which occurs between directed acoustic energy and aligned nematic liquid crystals. The aligned

David W. Gerdt; Martin C. Baruch; Charles M. Adkins

1999-01-01

8

Multiparameter Acoustic Imaging in the Born Approximation.  

National Technical Information Service (NTIS)

Computer-based acoustic imaging techniques have been studied intensively during the last decade. Typical techniques involve irradiating a sample with prescribed sound fields, measuring the resulting scattered fields and applying a computational algorithm ...

C. H. Wilcox

1982-01-01

9

Magnetic resonance acoustic radiation force imaging  

PubMed Central

Acoustic radiation force impulse imaging is an elastography method developed for ultrasound imaging that maps displacements produced by focused ultrasound pulses systematically applied to different locations. The resulting images are “stiffness weighted” and yield information about local mechanical tissue properties. Here, the feasibility of magnetic resonance acoustic radiation force imaging (MR-ARFI) was tested. Quasistatic MR elastography was used to measure focal displacements using a one-dimensional MRI pulse sequence. A 1.63 or 1.5 MHz transducer supplied ultrasound pulses which were triggered by the magnetic resonance imaging hardware to occur before a displacement-encoding gradient. Displacements in and around the focus were mapped in a tissue-mimicking phantom and in an ex vivo bovine kidney. They were readily observed and increased linearly with acoustic power in the phantom (R2=0.99). At higher acoustic power levels, the displacement substantially increased and was associated with irreversible changes in the phantom. At these levels, transverse displacement components could also be detected. Displacements in the kidney were also observed and increased after thermal ablation. While the measurements need validation, the authors have demonstrated the feasibility of detecting small displacements induced by low-power ultrasound pulses using an efficient magnetic resonance imaging pulse sequence that is compatible with tracking of a dynamically steered ultrasound focal spot, and that the displacement increases with acoustic power. MR-ARFI has potential for elastography or to guide ultrasound therapies that use low-power pulsed ultrasound exposures, such as drug delivery.

McDannold, Nathan; Maier, Stephan E.

2008-01-01

10

Video imaging of dust acoustic waves  

Microsoft Academic Search

Imaging dust clouds is often the primary source of data acquisition, especially in situations where the dust grains participate directly in the dynamics, as in the case of very low frequency “dust waves”. A sample image of a dust acoustic wave is presented

C. Thompson; A. Barkan; R. L. Merlino; N. D'Angelo

1999-01-01

11

Imaging of Acoustic Waves in Sand  

SciTech Connect

There is considerable interest in detecting objects such as landmines shallowly buried in loose earth or sand. Various techniques involving microwave, acoustic, thermal and magnetic sensors have been used to detect such objects. Acoustic and microwave sensors have shown promise, especially if used together. In most cases, the sensor package is scanned over an area to eventually build up an image or map of anomalies. We are proposing an alternate, acoustic method that directly provides an image of acoustic waves in sand or soil, and their interaction with buried objects. The INEEL Laser Ultrasonic Camera utilizes dynamic holography within photorefractive recording materials. This permits one to image and demodulate acoustic waves on surfaces in real time, without scanning. A video image is produced where intensity is directly and linearly proportional to surface motion. Both specular and diffusely reflecting surfaces can be accomodated and surface motion as small as 0.1 nm can be quantitatively detected. This system was used to directly image acoustic surface waves in sand as well as in solid objects. Waves as frequencies of 16 kHz were generated using modified acoustic speakers. These waves were directed through sand toward partially buried objects. The sand container was not on a vibration isolation table, but sat on the lab floor. Interaction of wavefronts with buried objects showed reflection, diffraction and interference effects that could provide clues to location and characteristics of buried objects. Although results are preliminary, success in this effort suggests that this method could be applied to detection of buried landmines or other near-surface items such as pipes and tanks.

Deason, Vance Albert; Telschow, Kenneth Louis; Watson, Scott Marshall

2003-08-01

12

Underwater Acoustic Imaging by Diversity Techniques  

Microsoft Academic Search

In this paper, the underwater acoustic imaging is given by diversity techniques. The diversity techniques utilized in this study include the angular and the frequency diversity. The angular diversity means the scattered fields are collected under various angles with respect to the target. The frequency diversity means the scattered fields are collected under various frequencies. Both the angular diversity and

Kun-Chou Lee; Lan-Ting Wang; Jyun-Gu Ou

2007-01-01

13

Acoustic Imaging of Snowpack Physical Properties  

NASA Astrophysics Data System (ADS)

Measurements of snowpack depth, density, structure and temperature have often been conducted by the use of snowpits and invasive measurement devices. Previous research has shown that acoustic waves passing through snow are capable of measuring these properties. An experimental observation device (SAS2, System for the Acoustic Sounding of Snow) was used to autonomously send audible sound waves into the top of the snowpack and to receive and process the waves reflected from the interior and bottom of the snowpack. A loudspeaker and microphone array separated by an offset distance was suspended in the air above the surface of the snowpack. Sound waves produced from a loudspeaker as frequency-swept sequences and maximum length sequences were used as source signals. Up to 24 microphones measured the audible signal from the snowpack. The signal-to-noise ratio was compared between sequences in the presence of environmental noise contributed by wind and reflections from vegetation. Beamforming algorithms were used to reject spurious reflections and to compensate for movement of the sensor assembly during the time of data collection. A custom-designed circuit with digital signal processing hardware implemented an inversion algorithm to relate the reflected sound wave data to snowpack physical properties and to create a two-dimensional image of snowpack stratigraphy. The low power consumption circuit was powered by batteries and through WiFi and Bluetooth interfaces enabled the display of processed data on a mobile device. Acoustic observations were logged to an SD card after each measurement. The SAS2 system was deployed at remote field locations in the Rocky Mountains of Alberta, Canada. Acoustic snow properties data was compared with data collected from gravimetric sampling, thermocouple arrays, radiometers and snowpit observations of density, stratigraphy and crystal structure. Aspects for further research and limitations of the acoustic sensing system are also discussed.

Kinar, N. J.; Pomeroy, J. W.

2011-12-01

14

Laser-induced acoustic imaging of underground objects  

Microsoft Academic Search

This paper introduces a new demining technique based on the photo-acoustic interaction, together with results from photo- acoustic experiments. We have buried different types of targets (metal, rubber and plastic) in different media (sand, soil and water) and imaged them by measuring reflection of acoustic waves generated by irradiation with a CO2 laser. Research has been focused on the signal

Wen Li; Charles A. Dimarzio; Stephen W. McKnight; Gerhard O. Sauermann; Eric L. Miller

1999-01-01

15

Some advances of underwater acoustic imaging research for UUV  

Microsoft Academic Search

In this paper, some research results for underwater acoustic imaging are presented. Three different structures of the systems are included: first one is composed of a sonar head of SeaBat 6012 and related digital electronics. The second and third systems use rectangular acoustic transducer array and linear array respectively. Both of acoustic signals acquired by the arrays are totally digitized

Wang Xiaofeng; Sang Enfang; Bian Hongyu

2010-01-01

16

Fast Transforms for Acoustic Imaging—Part I: Theory  

Microsoft Academic Search

The classical approach for acoustic imaging consists of beamforming, and produces the source distribution of interest convolved with the array point spread function. This convolution smears the image of interest, significantly reducing its effective resolution. Deconvolution methods have been proposed to enhance acoustic images and have produced significant improvements. Other proposals involve covariance fitting techniques, which avoid deconvolution altogether. However,

Flávio P. Ribeiro; Vitor H. Nascimento

2011-01-01

17

Acoustic imaging of subtle porosity variations in ceramics  

NASA Technical Reports Server (NTRS)

Acoustic images of silicon carbide ceramic disks were obtained using a precision scanning contact pulse-echo technique. Phase and cross-correlation velocity and attenuation maps were used to form color images of microstructural variations. These acoustic images reveal microstructural variations not observable with X-radiography.

Generazio, E. R.; Roth, D. J.; Baaklini, G. Y.

1988-01-01

18

Acoustic imaging of an inhomogeneous sediment matrix  

NASA Astrophysics Data System (ADS)

This paper presents and applies a new acoustic imaging approach to quantitatively determine geophysical parameters of complex inhomogeneous sediment layers. The concept is called an ‘Acoustic Sub-seabed Interrogator’ or ASI and it is based on optimising the criteria of temporal and spatial resolution and of coherence by utilizing broadband, narrow beam calibrated sources and fixed receivers on a stationary platform. The ASI concept was experimentally tested over a complex pseudo-glacial till built at a scale of 20:1. Compressional velocity, attenuation losses and thickness values were easily attained using the ASI's coherent spatial scanning approach and through a discrete application of the Hilbert transform in the post processing of data. The simulations provided indepth insight into the model's physical and spatial variations and by statistical distribution emphasized the depositional processes involved in creating the layer. It is believed that the fundamental internal information elucidated by the ASI for the pseudo-till structure and illustrated in the resultant acoustic core cannot be attained using current marine geophysical and geotechnical techniques.

Guigné, J. Y.; Chin, V. H.

1989-12-01

19

Acoustic imaging of thick biological tissue.  

PubMed

Up to now, biomedical imaging with ultrasound for observing a cellular tissue structure has been limited to very thinly sliced tissue at very high ultrasonic frequencies, i.e., 1 GHz. In this paper, we present the results of a systematic study to use a 150 to 200 MHz frequency range for thickly sliced biological tissue. A mechanical scanning reflection acoustic microscope (SAM) was used for obtaining horizontal cross-sectional images (C-scans) showing cellular structures. In the study, sectioned specimens of human breast cancer and tissues from the small intestine were prepared and examined. Some accessories for biomedical application were integrated into our SAM (Sonix HS-1000 and Olympus UH-3), which operated in pulse-wave and tone-burst wave modes, respectively. We found that the frequency 100 to 200 MHz provides optimal balance between resolution and penetration depth for examining the thickly sliced specimens. The images obtained with the lens focused at different depths revealed cellular structures whose morphology was very similar to that seen in the thinly sectioned specimens with optical and scanning acoustic microscopy. The SAM operation in the pulse-echo mode permits the imaging of tissue structure at the surface, and it also opens up the potential for attenuation imaging representing reflection from the substrate behind the thick specimen. We present such images of breast cancer proving the method's applicability to overall tumor detection. SAM with a high-frequency tone-burst ultrasonic wave reveals details of tissue structure, and both methods may serve as additional diagnostic tools in a hospital environment. PMID:19574146

Maeva, Elena; Severin, Fedar; Miyasaka, Chiaki; Tittmann, Bernhard R; Maev, Roman Gr

2009-07-01

20

Acoustic and Photoacoustic Molecular Imaging of Cancer  

PubMed Central

Ultrasound and combined optical and ultrasonic (photoacoustic) molecular imaging have shown great promise in the visualization and monitoring of cancer through imaging of vascular and extravascular molecular targets. Contrast-enhanced ultrasound with molecularly targeted microbubbles can detect early-stage cancer through the visualization of targets expressed on the angiogenic vasculature of tumors. Ultrasonic molecular imaging can be extended to the imaging of extravascular targets through use of nanoscale, phase-change droplets and photoacoustic imaging, which provides further molecular information on cancer given by the chemical composition of tissues and by targeted nanoparticles that can interact with extravascular tissues at the receptor level. A new generation of targeted contrast agents goes beyond merely increasing imaging signal at the site of target expression but shows activatable and differential contrast depending on their interactions with the tumor microenvironment. These innovations may further improve our ability to detect and characterize tumors. In this review, recent developments in acoustic and photoacoustic molecular imaging of cancer are discussed.

Wilson, Katheryne E.; Wang, Tzu Yin; Willmann, Jurgen K.

2014-01-01

21

Acoustic Mine Imaging (AMI) project: An underwater acoustic camera for use in mine warfare  

Microsoft Academic Search

This paper is submitted to detail the advances in sonar and imaging techniques and synthetic apertures being made in Australia by Thales Underwater Systems within a Australian Defence Acquisition Project termed Acoustic Mine Imaging (AMI). This paper will detail the development of the AMI underwater acoustic camera for the detection, classification and characterization of mines and other underwater objects in

Colin Ellis; Ed Murphy

2001-01-01

22

Synthetic Aperture Acoustic Imaging of Non-Metallic Cords.  

National Technical Information Service (NTIS)

This work presents a set of measurements collected with a research prototype synthetic aperture acoustic (SAA) imaging system. SAA imaging is an emerging technique that can serve as an inexpensive alternative or logical complement to synthetic aperture ra...

A. A. Glean C. E. Good J. A. Judge J. F. Vignola T. J. Ryan

2012-01-01

23

Optimization of a Biometric System Based on Acoustic Images  

PubMed Central

On the basis of an acoustic biometric system that captures 16 acoustic images of a person for 4 frequencies and 4 positions, a study was carried out to improve the performance of the system. On a first stage, an analysis to determine which images provide more information to the system was carried out showing that a set of 12 images allows the system to obtain results that are equivalent to using all of the 16 images. Finally, optimization techniques were used to obtain the set of weights associated with each acoustic image that maximizes the performance of the biometric system. These results improve significantly the performance of the preliminary system, while reducing the time of acquisition and computational burden, since the number of acoustic images was reduced.

Izquierdo Fuente, Alberto; Del Val Puente, Lara; Villacorta Calvo, Juan J.; Raboso Mateos, Mariano

2014-01-01

24

Magnetostriction transducer and an intraoperative probe for acoustic imaging  

US Patent & Trademark Office Database

This invention is a magnetostriction transducer and an intraoperative probe for acoustic imaging. The magnetostriction transducer has a coil and a magnetostriction element deposited on a portion of the acoustic waveguide that is inserted inside the coil. The magnetic field of the coil threads into the magnetostriction element and, due to the alternating magnetic field, the magnetostriction element changes its length at a rate equal to the frequency of the magnetic field. These length changes excite, among others, longitudinal waves in the core of the acoustic waveguide. The intraoperative probe has an array of acoustic waveguides bonded together. Each acoustic waveguide in the intraoperative probe has a transducer, such as a magnetostriction transducer of a piezoelectric transducer, that couples acoustic signals into the acoustic waveguides. The intraoperative probe can image the body without the extra hardware needed to rotate an acoustic waveguide by stepping an acoustic beam across the aperture of the intraoperative probe. This invention has the advantage of imaging internal organs without exposing them to danger of leakage currents.

1996-02-06

25

Laser Acoustic Imaging of Film Bulk Acoustic Resonator (FBAR) Lateral Mode Dispersion  

NASA Astrophysics Data System (ADS)

A laser acoustic imaging microscope has been developed that measures acoustic motion with high spatial resolution without scanning. Images are recorded at normal video frame rates and heterodyne principles are used to allow operation at any frequency from Hz to GHz. Fourier transformation of the acoustic amplitude and phase displacement images provides a direct quantitative determination of excited mode wavenumbers at any frequency. Results are presented at frequencies near the first longitudinal thickness mode (~ 900 MHz) demonstrating simultaneous excitation of lateral modes with nonzero wavenumbers in an electrically driven AlN thin film acoustic resonator. Images combined at several frequencies form a direct visualization of lateral mode dispersion relations for the device under test allowing mode identification and a direct measure of specific lateral mode properties. Discussion and analysis of the results are presented in comparison with plate wave modeling of these devices taking account for material anisotropy and multilayer films.

Telschow, Ken L.

2005-04-01

26

Laser Acoustic Imaging of Film Bulk Acoustic Resonator (FBAR) Lateral Mode Dispersion  

SciTech Connect

A laser acoustic imaging microscope has been developed that measures acoustic motion with high spatial resolution without scanning. Images are recorded at normal video frame rates and heterodyne principles are used to allow operation at any frequency from Hz to GHz. Fourier transformation of the acoustic amplitude and phase displacement images provides a direct quantitative determination of excited mode wavenumbers at any frequency. Results are presented at frequencies near the first longitudinal thickness mode (~ 900 MHz) demonstrating simultaneous excitation of lateral modes with nonzero wavenumbers in an electrically driven AlN thin film acoustic resonator. Images combined at several frequencies form a direct visualization of lateral mode dispersion relations for the device under test allowing mode identification and a direct measure of specific lateral mode properties. Discussion and analysis of the results are presented in comparison with plate wave modeling of these devices taking account for material anisotropy and multilayer films.

Ken L. Telschow

2004-07-01

27

Image reconstruction in photoacoustic tomography involving layered acoustic media  

PubMed Central

Photoacoustic tomography (PAT), also known as thermoacoustic or optoacoustic tomography, is a rapidly emerging biomedical imaging technique that combines optical image contrast with ultrasound detection principles. Most existing reconstruction algorithms for PAT assume the object of interest possesses homogeneous acoustic properties. The images produced by such algorithms can contain significant distortions and artifacts when the object’s acoustic properties are spatially variant. In this work, we establish an image reconstruction formula for PAT applications in which a planar detection surface is employed and the to-be-imaged optical absorber is embedded in a known planar layered acoustic medium. The reconstruction formula is exact in a mathematical sense and accounts for multiple acoustic reflections between the layers of the medium. Computer-simulation studies are conducted to demonstrate and investigate the proposed method.

Schoonover, Robert W.; Anastasio, Mark A.

2012-01-01

28

An experimental acoustic cloak for generating virtual images  

NASA Astrophysics Data System (ADS)

A two-dimensional acoustic cloak is realized to generate virtual image in air. The cloak is designed to make the backscattering characteristics of a quadrangular prism the same as that of a plate based on transformation acoustics. The required anisotropic parameters of the cloak shell are obtained by acoustic metamaterial made of perforated plates, which are easy to fabricate and unitize. The measurements of the backward and near-backward scattering fields confirm the validity of the proposed cloak. Experimental results show the possibility to hide the shape of an object by changing the reflection properties by using transformation acoustics.

Hu, Wenlin; Fan, Yuxian; Ji, Peifeng; Yang, Jun

2013-01-01

29

Acoustic radiation force-based elasticity imaging methods  

PubMed Central

Conventional diagnostic ultrasound images portray differences in the acoustic properties of soft tissues, whereas ultrasound-based elasticity images portray differences in the elastic properties of soft tissues (i.e. stiffness, viscosity). The benefit of elasticity imaging lies in the fact that many soft tissues can share similar ultrasonic echogenicities, but may have different mechanical properties that can be used to clearly visualize normal anatomy and delineate pathological lesions. Acoustic radiation force-based elasticity imaging methods use acoustic radiation force to transiently deform soft tissues, and the dynamic displacement response of those tissues is measured ultrasonically and is used to estimate the tissue's mechanical properties. Both qualitative images and quantitative elasticity metrics can be reconstructed from these measured data, providing complimentary information to both diagnose and longitudinally monitor disease progression. Recently, acoustic radiation force-based elasticity imaging techniques have moved from the laboratory to the clinical setting, where clinicians are beginning to characterize tissue stiffness as a diagnostic metric, and commercial implementations of radiation force-based ultrasonic elasticity imaging are beginning to appear on the commercial market. This article provides an overview of acoustic radiation force-based elasticity imaging, including a review of the relevant soft tissue material properties, a review of radiation force-based methods that have been proposed for elasticity imaging, and a discussion of current research and commercial realizations of radiation force based-elasticity imaging technologies.

Palmeri, Mark L.; Nightingale, Kathryn R.

2011-01-01

30

Acoustic radiation force-based elasticity imaging methods.  

PubMed

Conventional diagnostic ultrasound images portray differences in the acoustic properties of soft tissues, whereas ultrasound-based elasticity images portray differences in the elastic properties of soft tissues (i.e. stiffness, viscosity). The benefit of elasticity imaging lies in the fact that many soft tissues can share similar ultrasonic echogenicities, but may have different mechanical properties that can be used to clearly visualize normal anatomy and delineate pathological lesions. Acoustic radiation force-based elasticity imaging methods use acoustic radiation force to transiently deform soft tissues, and the dynamic displacement response of those tissues is measured ultrasonically and is used to estimate the tissue's mechanical properties. Both qualitative images and quantitative elasticity metrics can be reconstructed from these measured data, providing complimentary information to both diagnose and longitudinally monitor disease progression. Recently, acoustic radiation force-based elasticity imaging techniques have moved from the laboratory to the clinical setting, where clinicians are beginning to characterize tissue stiffness as a diagnostic metric, and commercial implementations of radiation force-based ultrasonic elasticity imaging are beginning to appear on the commercial market. This article provides an overview of acoustic radiation force-based elasticity imaging, including a review of the relevant soft tissue material properties, a review of radiation force-based methods that have been proposed for elasticity imaging, and a discussion of current research and commercial realizations of radiation force based-elasticity imaging technologies. PMID:22419986

Palmeri, Mark L; Nightingale, Kathryn R

2011-08-01

31

Signal Processing and Acoustic Imaging Models for Animal Sonar.  

National Technical Information Service (NTIS)

A biologically inspired acoustic imaging process is obtained by considering the constraints (e.g., limited array/aperture size), and advantages (e.g., unrestricted motion, wide bandwidth) of biological sonar systems. The resulting system is easy to implem...

R. A. Altes

1999-01-01

32

Nondestructive imaging of shallow buried objects using acoustic computed tomography  

NASA Astrophysics Data System (ADS)

The nondestructive three-dimensional acoustic tomography concept of the present investigation combines computerized tomography image reconstruction algorithms using acoustic diffracting waves together with depth information to produce a three-dimensional (3D) image of an underground section. The approach illuminates the underground area of interest with acoustic plane waves of frequencies 200-3000 Hz. For each transmitted pulse, the reflected-refracted signals are received by a line array of acoustic sensors located at a diametrically opposite point from the acoustic source line array. For a stratified underground medium and for a given depth, which is represented by a time delay in the received signal, a horizontal tomographic 2D image is reconstructed from the received projections. Integration of the depth dependent sequence of cross-sectional reconstructed images provides a complete three-dimensional overview of the inspected terrain. The method has been tested with an experimental system that consists of a line array of four-acoustic sources, providing plane waves, and a receiving line array of 32-acoustic sensors. The results indicate both the potential and the challenges facing the new methodology. Suggestions are made for improved performance, including an adaptive noise cancellation scheme and a numerical interpolation technique.

Younis, Waheed A.; Stergiopoulos, Stergios; Havelock, David; Grodski, Julius

2002-05-01

33

Combination of acoustical radiosity and the image source method.  

PubMed

A combined model for room acoustic predictions is developed, aiming to treat both diffuse and specular reflections in a unified way. Two established methods are incorporated: acoustical radiosity, accounting for the diffuse part, and the image source method, accounting for the specular part. The model is based on conservation of acoustical energy. Losses are taken into account by the energy absorption coefficient, and the diffuse reflections are controlled via the scattering coefficient, which defines the portion of energy that has been diffusely reflected. The way the model is formulated allows for a dynamic control of the image source production, so that no fixed maximum reflection order is required. The model is optimized for energy impulse response predictions in arbitrary polyhedral rooms. The predictions are validated by comparison with published measured data for a real music studio hall. The proposed model turns out to be promising for acoustic predictions providing a high level of detail and accuracy. PMID:23742350

Koutsouris, Georgios I; Brunskog, Jonas; Jeong, Cheol-Ho; Jacobsen, Finn

2013-06-01

34

Respiratory acoustic thoracic imaging (RATHI): Assessing deterministic interpolation techniques  

Microsoft Academic Search

As respiratory sounds contain mechanical and clinical pulmonary information, technical efforts have been devoted during the\\u000a past decades to analysing, processing and visualising them. The aim of this work was to evaluate deterministic interpolating\\u000a functions to generate surface respiratory acoustic thoracic images (RATHIs), based on multiple acoustic sensors. Lung sounds\\u000a were acquired from healthy subjects through a 55 microphone array

S. Charleston-Villalobos; S. Cortés-Rubiano; R. González-Camerena; G. Chi-Lem; T. Aljama-Corrales

2004-01-01

35

Detection of Landmines from Acoustic Images Based on Cepstral Coefficients  

Microsoft Academic Search

This paper introduces a cepstral approach for the automatic detection of landmines from acoustic images. This approach is based on treating the problem of landmine detection as a pattern recognition problem. Cepstral features are extracted from a group of landmine images which are transformed first to 1-D signals by lexicographic ordering. Mel frequency cepstral coefficients (MFCCs) and polynomial shaping coefficients

Fathi E. Abd El-Samie

2009-01-01

36

Through lifetime monitoring of solder joints using acoustic micro imaging  

Microsoft Academic Search

Purpose – The purpose of this paper is to evaluate the application of an acoustic micro-imaging (AMI) inspection technique in monitoring solder joints through lifetime performance and demonstrate the robustness of the monitoring through analysis of AMI data. Design\\/methodology\\/approach – Accelerated thermal cycling (ATC) test data on a flip chip test board were collected through AMI imaging. Subsequently, informative features

Ryan S. H. Yang; Derek R. Braden; Guang-Ming Zhang; David M. Harvey

2012-01-01

37

Acoustic Radiation Force Impulse (ARFI) Imaging: a Review  

PubMed Central

Acoustic radiation force based elasticity imaging methods are under investigation by many groups. These methods differ from traditional ultrasonic elasticity imaging methods in that they do not require compression of the transducer, and are thus expected to be less operator dependent. Methods have been developed that utilize impulsive (i.e. < 1 ms), harmonic (pulsed), and steady state radiation force excitations. The work discussed herein utilizes impulsive methods, for which two imaging approaches have been pursued: 1) monitoring the tissue response within the radiation force region of excitation (ROE) and generating images of relative differences in tissue stiffness (Acoustic Radiation Force Impulse (ARFI) imaging); and 2) monitoring the speed of shear wave propagation away from the ROE to quantify tissue stiffness (Shear Wave Elasticity Imaging (SWEI)). For these methods, a single ultrasound transducer on a commercial ultrasound system can be used to both generate acoustic radiation force in tissue, and to monitor the tissue displacement response. The response of tissue to this transient excitation is complicated and depends upon tissue geometry, radiation force field geometry, and tissue mechanical and acoustic properties. Higher shear wave speeds and smaller displacements are associated with stiffer tissues, and slower shear wave speeds and larger displacements occur with more compliant tissues. ARFI images have spatial resolution comparable to that of B-mode, often with greater contrast, providing matched, adjunctive information. SWEI images provide quantitative information about the tissue stiffness, typically with lower spatial resolution. A review these methods and examples of clinical applications are presented herein.

Nightingale, Kathy

2012-01-01

38

Acoustic Radiation Force Impulse (ARFI) Imaging: a Review.  

PubMed

Acoustic radiation force based elasticity imaging methods are under investigation by many groups. These methods differ from traditional ultrasonic elasticity imaging methods in that they do not require compression of the transducer, and are thus expected to be less operator dependent. Methods have been developed that utilize impulsive (i.e. < 1 ms), harmonic (pulsed), and steady state radiation force excitations. The work discussed herein utilizes impulsive methods, for which two imaging approaches have been pursued: 1) monitoring the tissue response within the radiation force region of excitation (ROE) and generating images of relative differences in tissue stiffness (Acoustic Radiation Force Impulse (ARFI) imaging); and 2) monitoring the speed of shear wave propagation away from the ROE to quantify tissue stiffness (Shear Wave Elasticity Imaging (SWEI)). For these methods, a single ultrasound transducer on a commercial ultrasound system can be used to both generate acoustic radiation force in tissue, and to monitor the tissue displacement response. The response of tissue to this transient excitation is complicated and depends upon tissue geometry, radiation force field geometry, and tissue mechanical and acoustic properties. Higher shear wave speeds and smaller displacements are associated with stiffer tissues, and slower shear wave speeds and larger displacements occur with more compliant tissues. ARFI images have spatial resolution comparable to that of B-mode, often with greater contrast, providing matched, adjunctive information. SWEI images provide quantitative information about the tissue stiffness, typically with lower spatial resolution. A review these methods and examples of clinical applications are presented herein. PMID:22545033

Nightingale, Kathy

2011-11-01

39

Quantitative Determination of Lateral Mode Dispersion in Film Bulk Acoustic Resonators through Laser Acoustic Imaging  

SciTech Connect

Film Bulk Acoustic Resonators are useful for many signal processing applications. Detailed knowledge of their operation properties are needed to optimize their design for specific applications. The finite size of these resonators precludes their use in single acoustic modes; rather, multiple wave modes, such as, lateral wave modes are always excited concurrently. In order to determine the contributions of these modes, we have been using a newly developed full-field laser acoustic imaging approach to directly measure their amplitude and phase throughout the resonator. This paper describes new results comparing modeling of both elastic and piezoelectric effects in the active material with imaging measurement of all excited modes. Fourier transformation of the acoustic amplitude and phase displacement images provides a quantitative determination of excited mode amplitude and wavenumber at any frequency. Images combined at several frequencies form a direct visualization of lateral mode excitation and dispersion for the device under test allowing mode identification and comparison with predicted operational properties. Discussion and analysis are presented for modes near the first longitudinal thickness resonance (~900 MHz) in an AlN thin film resonator. Plate wave modeling, taking account of material crystalline orientation, elastic and piezoelectric properties and overlayer metallic films, will be discussed in relation to direct image measurements.

Ken Telschow; John D. Larson III

2006-10-01

40

Acoustic-optical imaging without immersion  

NASA Technical Reports Server (NTRS)

System using membraneous end wall of Bragg cell to separate test specimen from acoustic transmission medium, operates in real time and uses readily available optical components. System can be easily set up and maintained by people with little or no training in holography.

Liu, H.

1979-01-01

41

Acoustic-resolution photoacoustic imaging system with simple fiber illumination  

NASA Astrophysics Data System (ADS)

Acoustic-resolution photoacoustic microscopy (AR-PAM) with dark-field confocal illumination enables unique high-resolution visualization of chromophores in tissue, such as microvasculatures, within depths of a few millimeters. However, most current systems are bulky and use complex optical components for illumination, thus requiring highly sensitive alignment. In this study, we developed a compact alignment-free acoustic-resolution photoacoustic imaging system with simple fiber illumination. Four optical fibers were placed in four directions around a high-frequency (30-MHz) ultrasound sensor attached with the high-numerical-aperture acoustic lens. The setting angle of the fibers were determined to form a dark field on the tissue surface under the acoustic lens and for the four light beams from the fibers to be combined near the focal point of the acoustic lens, i.e., at a depth of around 1.2 mm in the tissue. The acoustic lens and output ends of the fibers were capped with an acoustically and optically transparent engineering plastic sheet, whose surface can be directly placed and scanned on the tissue surface with ultrasound gel. The diameter and height of this imaging head were as small as 32 mm and 27 mm respectively. The phantom study showed that the lateral signal spreading was 120 ?m, which agreed well with the theoretical value of 112 ?m. With the system, we attempted to image vasculatures in the rat skin, demonstrating high-contrast visualization of the blood vessels of a few hundred micrometers in diameter in the tissue.

Tsunoi, Yasuyuki; Sato, Shunichi; Watanabe, Ryota; Kawauchi, Satoko; Ashida, Hiroshi; Terakawa, Mitsuhiro

2013-03-01

42

Hybrid acousto-optic Fourier processor for imaging spatially inhomogeneous acoustic fields  

NASA Astrophysics Data System (ADS)

A new method is proposed for imaging spatially inhomogeneous acoustic fields. The approach is based on the Fourier transform of a coherent light field formed as a result of the Bragg diffraction of a probing laser beam on an ensemble of quasi-plane acoustic waves in a lithium niobate crystal. These waves appear as a result of the transformation of an imaged acoustic field by a spherical acoustic lens. The proposed method has been experimentally verified using model multielement acoustic sources.

Kolotyrin, A. A.; Zimnyakov, D. A.; Nikishin, E. L.; Zdrazhevskii, R. A.; Zavarin, S. V.

2011-11-01

43

System and Method for Acoustically Imaging an Underground Tank.  

National Technical Information Service (NTIS)

This invention provides a system and method for imaging the contents of a tank which includes a vertically arranged transducer array. The transducer array includes at least one transducer unit. This at least one transducer unit has at least a first acoust...

K. M. Walsh

1995-01-01

44

Detection of Landmines from Acoustic Images Based on Cepstral Coefficients  

Microsoft Academic Search

This paper introduces a cepstral approach for the automatic detection of landmines from acoustic images. This approach is\\u000a based on treating the problem of landmine detection as a pattern recognition problem. Cepstral features are extracted from\\u000a a group of landmine images which are transformed first to 1-D signals by lexicographic ordering. Mel frequency cepstral coefficients\\u000a (MFCCs) and polynomial shaping coefficients

Fathi E. Abd El-Samie

2009-01-01

45

Acoustic transmission imaging for flow diagnostics  

NASA Astrophysics Data System (ADS)

Wave propagation through a given flow field can be utilized to obtain information about the flow. Acoustic waves in particular offer the possibility of measuring velocity fields, because sound waves are convected with the flow, and temperature fields, because the acoustic index of refraction is a strong function of temperature. This work concentrates on situations where the first effect is dominating compared to the latter one.A sound system capable of "illuminating" a flow field with ultrasonic waves and measuring the amplitude and phase distribution of the transmitted wave as a function of time was constructed. A large area transmitter and a linear receiving array were used as transducers. Parallel signal processing and interleaved data conversion and acquisition result in a maximum frame rate of 10 kHz.The feasibility of measuring velocity disturbances with ultrasound was demonstrated by transmitting sound through a vortex, which was generated in a duct by an airfoil swirl generator. Assuming an exponential fit for the tangential velocity component, inner core radius and circulation can be determined directly from the phase change of the transmitted wave due to the vortex. A more accurate representation of the radial velocity profile can be found by digital reconstruction via the Abel inversion formula, which allows reconstruction of rotationally symmetric objects from line projections. Even though the flow field under investigation was steady, this is neither a restriction of the technique, nor of the apparatus. However, the repetition rate for consecutive data frames depends on the operating procedure.

Trebitz, Bernd Otto

46

A Parallel Tracking Method for Acoustic Radiation Force Impulse Imaging  

PubMed Central

Radiation force-based techniques have been developed by several groups for imaging the mechanical properties of tissue. Acoustic Radiation Force Impulse (ARFI) imaging is one such method that uses commercially available scanners to generate localized radiation forces in tissue. The response of the tissue to the radiation force is determined using conventional B-mode imaging pulses to track micron-scale displacements in tissue. Current research in ARFI imaging is focused on producing real-time images of tissue displacements and related mechanical properties. Obstacles to producing a real-time ARFI imaging modality include data acquisition, processing power, data transfer rates, heating of the transducer, and patient safety concerns. We propose a parallel receive beamforming technique to reduce transducer heating and patient acoustic exposure, and to facilitate data acquisition for real-time ARFI imaging. Custom beam sequencing was used with a Siemens SONOLINE AntaresTM scanner to track tissue displacements with parallel-receive beam-forming in tissue-mimicking phantoms. Using simulations, the effects of material properties on parallel tracking are observed. Transducer and tissue heating for parallel tracking are compared to standard ARFI beam sequencing. The effects of tracking beam position and size of the tracked region are also discussed in relation to the size and temporal response of the region of applied force, and the impact on ARFI image contrast and signal-to-noise ratio are quantified.

Dahl, Jeremy J.; Pinton, Gianmarco F.; Mark, L; Agrawal, Vineet; Nightingale, Kathryn R.; Trahey, Gregg E.

2007-01-01

47

Opto-acoustic breast imaging with co-registered ultrasound  

NASA Astrophysics Data System (ADS)

We present results from a recent study involving the ImagioTM breast imaging system, which produces fused real-time two-dimensional color-coded opto-acoustic (OA) images that are co-registered and temporally inter- leaved with real-time gray scale ultrasound using a specialized duplex handheld probe. The use of dual optical wavelengths provides functional blood map images of breast tissue and tumors displayed with high contrast based on total hemoglobin and oxygen saturation of the blood. This provides functional diagnostic information pertaining to tumor metabolism. OA also shows morphologic information about tumor neo-vascularity that is complementary to the morphological information obtained with conventional gray scale ultrasound. This fusion technology conveniently enables real-time analysis of the functional opto-acoustic features of lesions detected by readers familiar with anatomical gray scale ultrasound. We demonstrate co-registered opto-acoustic and ultrasonic images of malignant and benign tumors from a recent clinical study that provide new insight into the function of tumors in-vivo. Results from the Feasibility Study show preliminary evidence that the technology may have the capability to improve characterization of benign and malignant breast masses over conventional diagnostic breast ultrasound alone and to improve overall accuracy of breast mass diagnosis. In particular, OA improved speci city over that of conventional diagnostic ultrasound, which could potentially reduce the number of negative biopsies performed without missing cancers.

Zalev, Jason; Clingman, Bryan; Herzog, Don; Miller, Tom; Stavros, A. Thomas; Oraevsky, Alexander; Kist, Kenneth; Dornbluth, N. Carol; Otto, Pamela

2014-03-01

48

[Magnetic resonance imaging in the study of acoustic neurinoma].  

PubMed

Exploration of acoustic neurinoma, the most frequent benign tumor of posterior fossa, now includes magnetic resonance imaging, and an C.G.R. supraconductor apparatus (0.5 Tesla) has been in use since March 1986. This equipment provides high resolution frontal sections, not only of posterior fossa but of the two pontocerebellar angles and even the contents of the two IAC (thin, contiguous 4 mm sections in 256 x 256 matrix). A total of 43 patients were examined, 37 with surgically confirmed acoustic neurinoma and 2 with tumor recurrence. The neurinoma appears on the first echo as a hyposignal in relation to brain stem in sequences predominant in T1 and as a hypersignal in relation to peripontic CSF in sequences predominant in T2. Short sequences predominant in Tl (partial saturation or short ET and RT spin-echos) appear to be most effective for detection of acoustic neurinoma. Comparison of MRI and CT scan imaging showed that firstly, all cases detected by conventional scanography were correctly analyzed by MRI, with superiority for MRI for preoperative screening due to the frontal sections obtained without interference and, secondly, the non-invasive confirmation of diagnosis in doubtful or negative cases requiring computerized gaz meatocisternography. No false negative or false positive results were reported in our series or those documented in the literature using this new imaging technique, but high performance apparatus is necessary (thin sections ans powerful principal magnetic field of at least 0.5 resla). Improvements in this method could be obtained by the availability of more rapid programmes, the use of surface coils and the injection of paramagnetic substances (galodinium chelates) presently under study. NMR imaging is a reliable and non-invasive imaging method capable of replacing the scanner for study of acoustic neurinoma as soon as more apparatuses become available. PMID:3357149

Sarrat, P; Bouchet, J M; Cannoni, M; Pech, A; Bernard, P

1988-02-01

49

Three-dimensional acoustic wavefront imaging in anisotropic systems by picosecond acoustics  

NASA Astrophysics Data System (ADS)

We present a laser ultrasonics experiment with imaging capabilities performed in transmission through semiconductor substrates. Such experiment provides a new kind of bulk wavefront imaging using an ultrafast optical generation and detection scheme for gigahertz waves. The data may be viewed as two-dimensional slices of the three-dimensional acoustic wavefront revealing the basic anisotropy of the solid with 0.3 ps time resolution and 3 ?m space resolution and allowing the determination of the whole set of elastic constants for various experimental conditions. As examples, measurements are carried out in a Si(001), GaAs(001), and GaAs(111) sample at 20 and 300 K.

Zhang, Shuo; Péronne, Emmanuel; Belliard, Laurent; Vincent, Serge; Perrin, Bernard

2011-02-01

50

Contrast Enhancement for Thermal Acoustic Breast Cancer Imaging via Resonant Stimulation.  

National Technical Information Service (NTIS)

This research focuses on developing enhanced contrast thermal acoustic imaging (TAI) technology for the detection of breast cancer by combining amplitude-modulated (AM) electromagnetic (EM) field excitation, resonant acoustic scattering, and advanced sign...

J. Li

2010-01-01

51

Vector Acoustics, Vector Sensors, and 3D Underwater Imaging  

NASA Astrophysics Data System (ADS)

Vector acoustic data has two more dimensions of information than pressure data and may allow for 3D underwater imaging with much less data than with hydrophone data. The vector acoustic sensors measures the particle motions due to passing sound waves and, in conjunction with a collocated hydrophone, the direction of travel of the sound waves. When using a controlled source with known source and sensor locations, the reflection points of the sound field can be determined with a simple trigonometric calculation. I demonstrate this concept with an experiment that used an accelerometer based vector acoustic sensor in a water tank with a short-pulse source and passive scattering targets. The sensor consists of a three-axis accelerometer and a matched hydrophone. The sound source was a standard transducer driven by a short 7 kHz pulse. The sensor was suspended in a fixed location and the hydrophone was moved about the tank by a robotic arm to insonify the tank from many locations. Several floats were placed in the tank as acoustic targets at diagonal ranges of approximately one meter. The accelerometer data show the direct source wave as well as the target scattered waves and reflections from the nearby water surface, tank bottom and sides. Without resorting to the usual methods of seismic imaging, which in this case is only two dimensional and relied entirely on the use of a synthetic source aperture, the two targets, the tank walls, the tank bottom, and the water surface were imaged. A directional ambiguity inherent to vector sensors is removed by using collocated hydrophone data. Although this experiment was in a very simple environment, it suggests that 3-D seismic surveys may be achieved with vector sensors using the same logistics as a 2-D survey that uses conventional hydrophones. This work was supported by the Office of Naval Research, program element 61153N.

Lindwall, D.

2007-12-01

52

Application of time reversal acoustics focusing for nonlinear imaging ms  

NASA Astrophysics Data System (ADS)

Time reversal acoustic (TRA) focusing of ultrasound appears to be an effective tool for nonlinear imaging in industrial and medical applications because of its ability to efficiently concentrate ultrasonic energy (close to diffraction limit) in heterogeneous media. In this study, we used two TRA systems to focus ultrasonic beams with different frequencies in coinciding focal points, thus causing the generation of ultrasonic waves with combination frequencies. Measurements of the intensity of these combination frequency waves provide information on the nonlinear parameter of medium in the focal region. Synchronized stirring of two TRA focused beams enables obtaining 3-D acoustic nonlinearity images of the object. Each of the TRA systems employed an aluminum resonator with piezotransducers glued to its facet. One of the free facets of each resonator was submerged into a water tank and served as a virtual phased array capable of ultrasound focusing and beam steering. To mimic a medium with spatially varying acoustical nonlinearity a simplest model such as a microbubble column in water was used. Microbubbles were generated by electrolysis of water using a needle electrode. An order of magnitude increase of the sum frequency component was observed when the ultrasound beams were focused in the area with bubbles.

Sarvazyan, Armen; Sutin, Alexander

2001-05-01

53

Acoustic analysis of gradient-coil noise in MR imaging  

SciTech Connect

A survey was conducted of acoustic noise levels in magnetic resonance (MR) imaging systems. Static magnetic flux and radio-frequency pulses did not affect the function of shielded sound-pressure detection equipment. Noise levels were measured at bore isocenter during a variety of imaging sequences in six MR imaging systems with magnetic fields of 0.35-1.5 T. Measured noise ranged from 82 to 93 dB on the A-weighted scale and from 84 to 103 dB on the linear scale. Noise levels increased during sequences employing thinner section thickness and shorter repetition and echo times and were independent of field strength. Gradient-coil noise in MR imaging is an annoyance but is well within safety guidelines.

Hurwitz, R.; Lane, S.R.; Bell, R.A.; Brant-Zawadzki, M.N. (Hoag Memorial Hospital Presbyterian, Newport Beach, CA (USA))

1989-11-01

54

Magnetic resonance imaging of transverse acoustic strain waves.  

PubMed

We describe a phase contrast based MRI technique with high sensitivity to cyclic displacement that is capable of quantitatively imaging acoustic strain waves in tissue-like materials. A formalism for considering gradient waveforms as basis functions to measure arbitrary cyclic motion waveforms is introduced. Experiments with tissue-like agarose gel phantoms show that it is possible to measure small cyclic displacements at a submicron level by an appropriate choice of the applied gradient basis function and to use this capability to observe the spatial and temporal pattern of displacements caused by acoustic strain waves. The propagation characteristics of strain waves are determined by the mechanical properties of the media. It is therefore possible to use this technique to noninvasively estimate material properties such as elastic modulus. PMID:8843381

Muthupillai, R; Rossman, P J; Lomas, D J; Greenleaf, J F; Riederer, S J; Ehman, R L

1996-08-01

55

Two dimensional photoacoustic imaging based on an acoustic lens and the peak-hold technology  

Microsoft Academic Search

A new method of photoacoustic (PA) imaging based on an acoustic lens and the peak-hold technology is presented in this article. A fast PA imaging system, which consists of an acoustic lens, a 64-element linear transducer array, and a peak detection-and-hold circuit, is developed to obtain the two dimensional (2D) PA images of the experimental samples. By utilizing an acoustic

Hanchao Zhang; Zhilie Tang; Yongheng He; Lina Guo

2007-01-01

56

Imaging GHz-THz Acoustic Wave Propagation in Thin Films and Microstructures  

Microsoft Academic Search

Ultrashort light pulses absorbed in a medium generate both bulk and surface acoustic waves: we focus here on imaging the surface waves and on monitoring the bulk acoustic waves that propagate in the depth direction. This is done in the time domain by delayed probe light pulses. For the bulk acoustic waves, the generated frequency ranges up to 1 THz.

Osamu Matsuda; Oliver B. Wright

2010-01-01

57

Analysis of contrast in images generated with transient acoustic radiation force  

Microsoft Academic Search

Several mechanical imaging methods are under investigation that use focused ultrasound (US) as a source of mechanical excitation. Images are then generated of the tissue response to this localized excitation. One such method, acoustic radiation force impulse (ARFI) imaging, utilizes a single US transducer on a commercial US system to transmit brief, high-energy, focused acoustic pulses to generate radiation force

Kathryn Nightingale; Mark Palmeri; Gregg Trahey

2006-01-01

58

ANALYSIS OF CONTRAST IN IMAGES GENERATED WITH TRANSIENT ACOUSTIC RADIATION FORCE  

Microsoft Academic Search

Several mechanical imaging methods are under investigation that use focused ultrasound (US) as a source of mechanical excitation. Images are then generated of the tissue response to this localized excitation. One such method, acoustic radiation force impulse (ARFI) imaging, utilizes a single US transducer on a commercial US system to transmit brief, high-energy, focused acoustic pulses to generate radiation force

KATHRYN NIGHTINGALE; M ARK PALMERI; GREGG TRAHEY

2006-01-01

59

Micro-nondestructive evaluation of microelectronics using three-dimensional acoustic imaging  

NASA Astrophysics Data System (ADS)

Holographic-like three-dimensional (3D) acoustic imaging is developed for micro-nondestructive evaluation of microelectronics. It is implemented by stacking all the interface slices together to locate and identify hidden defects. Matching pursuit based acoustic time-frequency domain imaging is proposed to overcome the wavelength limit of axial resolution so that ultra-thin slices are generated. Experiments are performed on 3D acoustic data collected from microelectronic packages. Results show that the proposed technique resolves closely spaced features that are unavailable by conventional acoustic imaging, revealing more image details of defects.

Zhang, Guang-Ming; Harvey, David M.; Burton, David R.

2011-02-01

60

A Dual Communication and Imaging Underwater Acoustic System  

NASA Astrophysics Data System (ADS)

A dual communication and imaging underwater acoustic system is proposed and developed throughout this dissertation. Due to the wide variation in underwater channel characteristics, the research here focuses more on robustness to multipath in the shallow underwater acoustic environment, rather than high bit-rate applications and signaling schemes. Lower bit-rate (in the hundreds of bits per second (bps) to low kbps), applications such as the transfer of ecological telemetry data, e.g. conductivity or temperature data, are the primary focus of this dissertation. The parallels between direct sequence spread spectrum in digital communication and pulse-echo with pulse compression in imaging, and channel estimation in communication and range profile estimation in imaging are drawn, leading to a unified communications and imaging platform. A digital communication algorithm for channel order and channel coefficient estimation and symbol demodulation using Matching Pursuit (MP) with Generalized Multiple Hypothesis Testing (GMHT) is implemented in programmable DSP in real time with field experiment results in varying underwater environments for the single receiver (Rx), single transmitter (Tx) case. The custom and off-the-shelf hardware used in the single receiver, single transmitter set of experiments are detailed as well. This work is then extended to the single-input multiple-output (SIMO) case, and then to the full multiple-input multiple-output (MIMO) case. The results of channel estimation are used for simple range profile imaging reconstructions. Successful simulated and experimental results for both transducer array configurations are presented and analyzed. Non-real-time symbol demodulation and channel estimation is performed using experimental data from a scaled testing environment. New hardware based on cost-effective fish-finder transducers for a 6 Rx--1 Tx and 6 Rx--4 Tx transducer array is detailed. Lastly, in an application that is neither communication nor imaging, a generalized successive interference cancellation (GSIC)-based localization algorithm is used to localize discrete scatterers which are assumed to be more prominent than the surrounding clutter. Theory and experimental results are provided to support the feasability of GSIC localization for use with a dual communication and imaging underwater acoustic system.

Fu, Tricia C.

61

Acoustics.  

National Technical Information Service (NTIS)

The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or...

F. Grosveld J. R. Goodman

2007-01-01

62

Feasibility of High Frequency Acoustic Imaging for Inspection of Containments  

SciTech Connect

The Nuclear Regulatory Commission has a program at the Oak Ridge National Laboratory to provide assistance in their assessment of the effects of potential degradation on the structural integrity and Ieaktightness of metal containment vessels and steel liners of concrete containment in nuclear power plants. One of the program objectives is to identify a technique(s) for inspection of inaccessible portions of the containment pressure boundary. Acoustic imaging has been identified as one of these potential techniques. A numerical feasibility study investigated the use of high-frequency bistatic acoustic imaging techniques for inspection of inaccessible portions of the metallic pressure boundary of nuclear power plant containment. The range-dependent version of the OASES Code developed at the Massachusetts Institute of Technology was utilized to perform a series of numerical simulations. OASES is a well developed and extensively tested code for evaluation of the acoustic field in a system of stratified fluid and/or elastic layers. Using the code, an arbitrary number of fluid or solid elastic layers are interleaved, with the outer layers modeled as halfspaces. High frequency vibrational sources were modeled to simulate elastic waves in the steel. The received field due to an arbitrary source array can be calculated at arbitrary depth and range positions. In this numerical study, waves that reflect and scatter from surface roughness caused by modeled degradations (e.g., corrosion) are detected and used to identify and map the steel degradation. Variables in the numerical study included frequency, flaw size, interrogation distance, and sensor incident angle.Based on these analytical simulations, it is considered unlikely that acoustic imaging technology can be used to investigate embedded steel liners of reinforced concrete containment. The thin steel liner and high signal losses to the concrete make this application difficult. Results for portions of steel containment embedded in concrete are more encouraging in that they indicate that the intrinsic backscatter from degradations representing thickness reductions from 10 to 80% the shell thickness are sufficient to permit detection. It is recommended that a controlled experimental program be conducted in which sensor levels are calibrated against degradations to determine if current sensor technology can input sufficient power into the system to provide return levels within the dynamic range of the receivers.

C.N. Corrado; J.E. Bondaryk; V. Godino

1998-08-01

63

An acoustic charge transport imager for high definition television applications  

NASA Technical Reports Server (NTRS)

The primary goal of this research is to develop a solid-state high definition television (HDTV) imager chip operating at a frame rate of about 170 frames/sec at 2 Megapixels per frame. This imager offers an order of magnitude improvement in speed over CCD designs and will allow for monolithic imagers operating from the IR to the UV. The technical approach of the project focuses on the development of the three basic components of the imager and their integration. The imager chip can be divided into three distinct components: (1) image capture via an array of avalanche photodiodes (APD's), (2) charge collection, storage and overflow control via a charge transfer transistor device (CTD), and (3) charge readout via an array of acoustic charge transport (ACT) channels. The use of APD's allows for front end gain at low noise and low operating voltages while the ACT readout enables concomitant high speed and high charge transfer efficiency. Currently work is progressing towards the development of manufacturable designs for each of these component devices. In addition to the development of each of the three distinct components, work towards their integration is also progressing. The component designs are considered not only to meet individual specifications but to provide overall system level performance suitable for HDTV operation upon integration. The ultimate manufacturability and reliability of the chip constrains the design as well. The progress made during this period is described in detail in Sections 2-4.

Hunt, W. D.; Brennan, Kevin F.

1994-01-01

64

A magnetic resonance imaging-based articulatory and acoustic study of "retroflex" and "bunched" American English /r/  

PubMed Central

Speakers of rhotic dialects of North American English show a range of different tongue configurations for ?r?. These variants produce acoustic profiles that are indistinguishable for the first three formants [Delattre, P., and Freeman, D. C., (1968). “A dialect study of American English r’s by x-ray motion picture,” Linguistics 44, 28–69; Westbury, J. R. et al. (1998), “Differences among speakers in lingual articulation for American English ?r?,” Speech Commun. 26, 203–206]. It is puzzling why this should be so, given the very different vocal tract configurations involved. In this paper, two subjects whose productions of “retroflex” ?r? and “bunched” ?r? show similar patterns of F1–F3 but very different spacing between F4 and F5 are contrasted. Using finite element analysis and area functions based on magnetic resonance images of the vocal tract for sustained productions, the results of computer vocal tract models are compared to actual speech recordings. In particular, formant-cavity affiliations are explored using formant sensitivity functions and vocal tract simple-tube models. The difference in F4?F5 patterns between the subjects is confirmed for several additional subjects with retroflex and bunched vocal tract configurations. The results suggest that the F4?F5 differences between the variants can be largely explained by differences in whether the long cavity behind the palatal constriction acts as a half- or a quarter-wavelength resonator.

Zhou, Xinhui; Espy-Wilson, Carol Y.; Boyce, Suzanne; Tiede, Mark; Holland, Christy; Choe, Ann

2008-01-01

65

Characteristics of acoustic noise in echo-planar imaging.  

PubMed

Characteristics of the acoustic noise generated by magnetic resonance imagers of different systems and performance levels were studied when operating in echo-planar imaging (EPI) sequence. Continuous equivalent A-weighted sound pressure levels (Leq) and peak impulse sound pressure levels (Lpeak) during EPI were measured in 12 clinical super-conducting MRI systems (0.5-1.5 T). Sound pressure levels and frequency spectra of EPI were compared with those of nine different pulse sequences. EPI sound pressure levels differed among institutions (Leq = 94.2 +/- 2.7 dBA. Lpeak = 109.1 +/- 3.5 dB), but these were within permissible noise exposure levels. Sound pressure levels during EPI were not significantly different from those during other pulse sequences. However, compared to other pulse sequences. EPI had a significantly greater proportion of acoustic noise in the high octave-frequency band. Single-shot EPI had relatively higher frequency noise and greater Leq than multishot EPI, but the difference in Leq decreased when the number of slices in multishot EPI was increased. PMID:11334173

Miyati, T; Banno, T; Fujita, H; Mase, M; Narita, H; Imazawa, M; Sanada, S; Koshida, K; Kasuga, T

2001-01-01

66

Imaging of contact acoustic nonlinearity using synthetic aperture technique.  

PubMed

The angle beam incidence and reflection technique for the evaluation of contact acoustic nonlinearity (CAN) at solid-solid contact interfaces (e.g., closed cracks) has recently been developed to overcome the disadvantage of accessing both the inner and outer surfaces of structures for attaching pulsing and receiving transducers in the through-transmission of normal incidence technique. This paper proposes a technique for B-mode imaging of CAN based on the above reflection technique, which uses the synthetic aperture focusing technique (SAFT) and short-time Fourier transform (STFT) to visualize the distribution of the CAN-induced second harmonic magnitude as well as the nonlinear parameter. In order to verify the usefulness of the proposed method, a solid-solid contact interface was tested and the change of the contact acoustic nonlinearity according to the increasing contact pressure was visualized in images of the second harmonic magnitude and the relative nonlinear parameter. The experimental results showed good agreement with the previously developed theory identifying the dependence of the scattered second harmonics on the contact pressure. This technique can be used for the detection and improvement of the sizing accuracy of closed cracks that are difficult to detect using the conventional linear ultrasonic technique. PMID:23659874

Yun, Dongseok; Kim, Jongbeom; Jhang, Kyung-Young

2013-09-01

67

An acoustic charge transport imager for high definition television applications  

NASA Technical Reports Server (NTRS)

The primary goal of this research is to develop a solid-state television (HDTV) imager chip operating at a frame rate of about 170 frames/sec at 2 Megapixels/frame. This imager will offer an order of magnitude improvements in speed over CCD designs and will allow for monolithic imagers operating from the IR to UV. The technical approach of the project focuses on the development of the three basic components of the imager and their subsequent integration. The camera chip can be divided into three distinct functions: (1) image capture via an array of avalanche photodiodes (APD's); (2) charge collection, storage, and overflow control via a charge transfer transistor device (CTD); and (3) charge readout via an array of acoustic charge transport (ACT) channels. The use of APD's allows for front end gain at low noise and low operating voltages while the ACT readout enables concomitant high speed and high charge transfer efficiency. Currently work is progressing towards the optimization of each of these component devices. In addition to the development of each of the three distinct components, work towards their integration and manufacturability is also progressing. The component designs are considered not only to meet individual specifications but to provide overall system level performance suitable for HDTV operation upon integration. The ultimate manufacturability and reliability of the chip constrains the design as well. The progress made during this period is described in detail.

Hunt, W. D.; Brennan, K. F.; Summers, C. J.

1994-01-01

68

Acoustic Radiation Contrast in MR Images for Breast Cancer Diagnostics - Initial Phantom Study  

Microsoft Academic Search

Acoustic radiation contrast in magnetic resonance images is an approach to visualize the changes in ultrasonic loss and viscoelastic changes of the sample with the resolution of a magnetic resonance imaging (MRI) system. By irradiating ultrasound (US) into a tissue-mimicking sample, a displacement along the US beam path caused by the acoustic radiation force is obtained. This displacement varies with

M. Radicke; J. Mende; A.-L. Kofahl; J. Wild; D. Ulucay; B. Habenstein; M. Deimling; P. Trautner; B. Weber; K. Maier

2011-01-01

69

Acoustic resonances in microfluidic chips: full-image micro-PIV experiments and numerical simulations.  

PubMed

We show that full-image micro-PIV analysis in combination with images of transient particle motion is a powerful tool for experimental studies of acoustic radiation forces and acoustic streaming in microfluidic chambers under piezo-actuation in the MHz range. The measured steady-state motion of both large 5 microm and small 1 microm particles can be understood in terms of the acoustic eigenmodes or standing ultra-sound waves in the given experimental microsystems. This interpretation is supported by numerical solutions of the corresponding acoustic wave equation. PMID:17896019

Hagsäter, S M; Jensen, T Glasdam; Bruus, H; Kutter, J P

2007-10-01

70

Quantitative thermo-acoustic imaging: An exact reconstruction formula  

NASA Astrophysics Data System (ADS)

This paper aims to mathematically advance the field of quantitative thermo-acoustic imaging. Given several electromagnetic data sets, we establish for the first time an analytical formula for reconstructing the absorption coefficient from thermal energy measurements. Since the formula involves derivatives of the given data up to the third order, it is unstable in the sense that small measurement noises may cause large errors. However, in the presence of measurement noise, the obtained formula, together with a noise regularization technique, provides a good initial guess for the true absorption coefficient. We finally correct the errors by deriving a reconstruction formula based on the least square solution of an optimal control problem and prove that this optimization step reduces the errors occurring and enhances the resolution.

Ammari, Habib; Garnier, Josselin; Jing, Wenjia; Nguyen, Loc Hoang

71

4f7-4f7 transitions in Gd, oxidized Gd, and epitaxial Gd silicide  

Microsoft Academic Search

4f-4f transitions in the rare earths are investigated in a detailed study of the 4f7-4f7 excitations of Gd observed by electron-energy-loss spectroscopy in reflection mode. Consistent quasiatomic losses are observed in polycrystalline Gd metal, oxidized Gd, and an epitaxially ordered Gd silicide phase. Sharp 4f7-4f7 transitions, whose positions are independent of environment, are superposed on a broad loss background which

J. A. D. Matthew; W. A. Henle; M. G. Ramsey; F. P. Netzer

1991-01-01

72

Liver ablation guidance with acoustic radiation force impulse imaging  

PubMed Central

Previous studies have established the feasibility of monitoring radiofrequency (RF) ablation procedures with acoustic radiation force impulse (ARFI) imaging. However, questions remained regarding the utility of the technique in clinically realistic scenarios and at scanning depths associated with abdominal imaging in adults. We address several of these issues and detail recent progress towards the clinical relevance of the ARFI technique. Results from in vitro bovine tissues and an in vivo ovine model are presented. Additional experiments were conducted with a tissue-mimicking phantom and parallel receive tracking techniques in order to further support the clinical feasibility of the method. Thermal lesions created during RF ablation are visualized with high contrast in both in vitro and in vivo hepatic tissues, and radial lesion growth can be monitored throughout the duration of the procedure. ARFI imaging is implemented on a diagnostic ultrasonic scanner, and thus may be a convenient option to guide RF ablation procedures, particularly when electrode insertion is also performed with sonographic guidance.

Fahey, B J; Hsu, S J; Wolf, P D; Nelson, R C; Trahey, G E

2008-01-01

73

Comparison of active millimeter-wave and acoustic imaging for weapon detection  

NASA Astrophysics Data System (ADS)

Millimeter-wave holographic imaging techniques have recently been developed for personnel surveillance applications at airports and other high-security checkpoints. Millimeter- wave imaging is useful for this application since millimeter-waves easily pass through common clothing materials yet are reflected from the human body and any items concealed by clothing. This allows a high-resolution imaging system to form an image revealing items concealed on the person imaged. A prototype imaging system developed at Pacific Northwest National Laboratory uses a scanned linear array of millimeter-wave antennas to capture wideband millimeter-wave data in approximately one second. This data is then mathematically reconstructed to form a high- resolution 3D image of the person being scanned. Millimeter- wave imaging has been demonstrated to be effective for detecting concealed weapons on personnel. Another imaging technique which could be applied to the weapon detection problem is acoustic imaging. Like millimeter-waves, ultrasonic acoustic waves can also penetrate clothing, and can be used to form relatively high-resolution images which can reveal concealed weapons on personnel. Acoustic imaging results have been obtained using wideband holographic imaging techniques nearly identical to the imaging techniques used for millimeter-wave imaging. Preliminary imaging results at 50 kHz indicate that acoustic imaging can be used to penetrate some types of common clothing materials. Hard clothing materials, such as leather on vinyl, are essentially opaque to acoustic waves at 50 kHz. In this paper, millimeter-wave and acoustic wave imaging techniques are compared for their effectiveness and suitability in weapon detection imaging systems. Experimental results from both imaging modalities are shown.

Sheen, David M.; Collins, H. D.; Gribble, R. Parks; McMakin, Douglas L.

1997-02-01

74

APPLICATION OF HIGH-RESOLUTION ACOUSTIC IMAGING FOR ADHESIVE BOND EVALUATION  

Microsoft Academic Search

The quality of adhesive bond joints is characterized using acoustic methods and discussed in this paper. Acoustical images of basic types of defects in models and real industrial samples are represented. The material variety includes metal (steel, aluminium alloys, magnesium) bonded with epoxy-based structural adhesive. Three-dimensional data were obtained using an acoustic scanning microscope in the frequency range of 10-250

E. Yu. Maeva; I. A. Severina; F. M. Severin; R. Gr

75

Acoustic and Elastodynamic Redatuming for VSP Salt Dome Flank Imaging  

NASA Astrophysics Data System (ADS)

We apply an extension of the concept of Time Reversed Acoustics (TRA) for imaging salt dome flanks using Vertical Seismic Profile (VSP) data. We demonstrate its performance and capabilities on both synthetic acoustic and elastic seismic data from a Gulf of Mexico (GOM) model. This target-oriented strategy eliminates the need for the traditional complex process of velocity estimation, model building, and iterative depth migration to remove the effects of the salt canopy and surrounding overburden. In this study, we use data from surface shots recorded in a well from a walkaway VSP survey. The method, called redatuming, creates a geometry as if the source and receiver pairs had been located in the borehole at the positions of the receivers. This process generates effective downhole shot gathers without any knowledge of the overburden velocity structure. The resulting shot gathers are less complex since the VSP ray paths from the surface source are shortened and moved to be as if they started in the borehole, then reflected off the salt flank region and captured in the borehole. After redatuming, we apply multiple passes of prestack migration from the reference datum of the borehole. In our example, the first pass migration, using only simple vertical velocity gradient model, reveals the outline of the salt edge. A second pass of reverse-time prestack depth migration using the full, two-way wave equation, is performed with an updated velocity model that now consists of the velocity gradient and the salt dome. The second pass migration brings out the dipping sediments abutting the salt flank because these reflectors were illuminated by energy that bounced off the salt flank forming prismatic reflections.

Lu, R.; Willis, M.; Toksoz, N.

2007-12-01

76

Acoustic radiation force impulse imaging: ex vivo and in vivo demonstration of transient shear wave propagation  

Microsoft Academic Search

Acoustic radiation force impulse (ARFI) imaging utilizes brief, high energy, focused acoustic pulses to generate radiation force in remote locations in tissue, and conventional diagnostic ultrasound methods to detect the resulting tissue displacements in order to provide information about the mechanical properties of tissue. Tissue displacement magnitude is inversely related to local tissue stiffness, and the temporal response of the

Kathryn Nightingale; Deborah Stutz; Rex Bentley; Gregg E. Trahey

2002-01-01

77

Low frequency acoustic shear wave imaging in tissue-like media using magnetic resonance  

Microsoft Academic Search

We propose a phase contrast based magnetic resonance imaging technique that can measure small cyclic displacements (sub-micron level) like those caused by propagating acoustic shear waves in tissue-like media. Our preliminary experiments with agarose gel phantoms show that acoustic shear wave propagation can be studied and we speculate that this technique could find applications in materials science and in medical

R. Muthupillai; D. J. Lomas; P. J. Rossman; J. F. Greenleaf; A. Manduca; S. J. Riederer; R. L. Ehman

1995-01-01

78

Radar-acoustic measurement of temperature using a volume-imaging UHF wind profiler  

Microsoft Academic Search

The University of Massachusetts Microwave Remote Sensing Laboratory (MIRSL) has augmented the Turbulent Eddy Profiler (TEP) with an acoustic source to implement a radio acoustic sounding system (RASS). TEP is a volume-imaging 915 MHz radar wind profiler. It can be thought of as a densely packed array of 915 MHz wind profilers sharing a common transmitter. Using digital beamforming techniques,

Francisco J. Ldpez Dekker; Jie Li; Stephen J. Frasier

2000-01-01

79

Sensitivity of laser opto-acoustic imaging in detection of small deeply embedded tumors  

Microsoft Academic Search

Current imaging modalities fail to detect small tumors in the breast. Opto-acoustic tomography is a novel technique for early cancer detection with promising diagnostic capability. The experimental limit of sensitivity and maximal depth of the laser opto-acoustic detection for small model tumors located within bulk phantom tissue were studied. Two phantoms with optical properties similar to that of breast tissue

Rinat O. Esenaliev; Alexander A. Karabutov; Alexander A. Oraevsky

1999-01-01

80

Full-Field Imaging of Acoustic Motion at Nanosecond Time and Micron Length Scales  

SciTech Connect

A full-field view laser ultrasonic imaging method has been developed that measures acoustic motion at a surface without scanning. Images are recorded at normal video frame rates by employing dynamic holography using photorefractive interferometric detection. By extending the approach to ultra high frequencies, an acoustic microscope has been developed capable of operation on the nanosecond time and micron length scales. Both acoustic amplitude and phase are recorded allowing full calibration and determination of phases to within a single arbitrary constant. Results are presented of measurements at frequencies at 800-900 MHz illustrating a multitude of normal mode behavior in electrically driven thin film acoustic resonators. Coupled with microwave electrical impedance measurements, this imaging mode provides an exceptionally fast method for evaluation of electric to acoustic coupling and performance of these devices. Images of 256x240 pixels are recorded at 18Hz rates synchronized to obtain both in-phase and quadrature detection of the acoustic motion. Simple averaging provides sensitivity to the subnanometer level calibrated over the image using interferometry. Identification of specific acoustic modes and their relationship to electrical impedance characteristics show the advantages and overall high speed of the technique.

Telschow, Kenneth Louis; Deason, Vance Albert; Cottle, David Lynn; Larson III, John D.

2002-10-01

81

Characterizing Response to Elemental Unit of Acoustic Imaging Noise: An fMRI Study  

PubMed Central

Acoustic imaging noise produced during functional magnetic resonance imaging (fMRI) studies can hinder auditory fMRI research analysis by altering the properties of the acquired time-series data. Acoustic imaging noise can be especially confounding when estimating the time course of the hemodynamic response (HDR) in auditory event-related fMRI (fMRI) experiments. This study is motivated by the desire to establish a baseline function that can serve not only as a comparison to other quantities of acoustic imaging noise for determining how detrimental is one's experimental noise, but also as a foundation for a model that compensates for the response to acoustic imaging noise. Therefore, the amplitude and spatial extent of the HDR to the elemental unit of acoustic imaging noise (i.e., a single ping) associated with echoplanar acquisition were characterized and modeled. Results from this fMRI study at 1.5 T indicate that the group-averaged HDR in left and right auditory cortex to acoustic imaging noise (duration of 46 ms) has an estimated peak magnitude of 0.29% (right) to 0.48% (left) signal change from baseline, peaks between 3 and 5 s after stimulus presentation, and returns to baseline and remains within the noise range approximately 8 s after stimulus presentation.

Luh, Wen-Ming; Talavage, Thomas M.

2010-01-01

82

Negative refraction imaging of acoustic metamaterial lens in the supersonic range  

NASA Astrophysics Data System (ADS)

Acoustic metamaterials with negative refraction index is the most promising method to overcome the diffraction limit of acoustic imaging to achieve ultrahigh resolution. In this paper, we use localized resonant phononic crystal as the unit cell to construct the acoustic negative refraction lens. Based on the vibration model of the phononic crystal, negative quality parameters of the lens are obtained while excited near the system resonance frequency. Simulation results show that negative refraction of the acoustic lens can be achieved when a sound wave transmiting through the phononic crystal plate. The patterns of the imaging field agree well with that of the incident wave, while the dispersion is very weak. The unit cell size in the simulation is 0.0005 m and the wavelength of the sound source is 0.02 m, from which we show that acoustic signal can be manipulated through structures with dimensions much smaller than the wavelength of incident wave.

Han, Jianning; Wen, Tingdun; Yang, Peng; Zhang, Lu

2014-05-01

83

Acoustic resonances in microfluidic chips: full-image micro-PIV experiments and numerical simulations  

Microsoft Academic Search

We show that full-image micro-PIV analysis in combination with images of\\u000atransient particle motion is a powerful tool for experimental studies of\\u000aacoustic radiation forces and acoustic streaming in microfluidic chambers under\\u000apiezo-actuation in the MHz range. The measured steady-state motion of both\\u000alarge 5 um and small 1 um particles can be understood in terms of the acoustic\\u000aeigenmodes

S. M. Hagsater; Thomas Glasdam Jensen; Henrik Bruus; Jorg P. Kutter

2007-01-01

84

Acoustic shear-wave imaging using echo ultrasound compared to magnetic resonance elastography.  

PubMed

We compare a previously developed phase contrast-based magnetic resonance imaging technique (MRE) to a phase-based ultrasound (US) method for measuring small cyclic displacements (submicrometer level) caused by propagating acoustic shear waves in tissue-like media. Our preliminary experiments with gelatin phantoms show that acoustic shear-wave propagation can be measured with US, and we speculate that this technique could find applications in medical imaging. PMID:10773369

Dutt, V; Kinnick, R R; Muthupillai, R; Oliphant, T E; Ehman, R L; Greenleaf, J F

2000-03-01

85

De-Dopplerisation and acoustic imaging of aircraft flyover measurements  

NASA Astrophysics Data System (ADS)

The technique described in this paper eliminates the Doppler effect from aircraft flyover noise measurements and generates narrowband spectra at required angles. This new capability allows more accurate interpretation of flight data, and is essential for a detailed comparison with predictions and static measurements. Until now, only 1/3 octave levels, before de-Dopplerization, have been available, and these yield little information on tonal content. The paper explains how a single microphone output is de-Dopplerized, and includes details of aircraft tracking and computer simulation of flyover measurements. The technique is especially relevant to the analysis of noise from contra-rotating propeller driven aircraft, and results are shown for an Avro Shackleton. It is also applied to a Boeing 757, with high bypass ratio turbofan engines. Narrowband spectra at selected angles, density plots of complete flyovers, and field shapes at constant frequencies are all presented. Acoustic imaging, achieved by focusing the de-Dopplerized signals from an array of microphones, is also described, and results from a Lockheed TriStar graphically illustrate its capability.

Howell, G. P.; Bradley, A. J.; McCormick, M. A.; Brown, J. D.

1984-10-01

86

Tracking Energy Flow Using a Volumetric Acoustic Intensity Imager (VAIM)  

NASA Technical Reports Server (NTRS)

A new measurement device has been invented at the Naval Research Laboratory which images instantaneously the intensity vector throughout a three-dimensional volume nearly a meter on a side. The measurement device consists of a nearly transparent spherical array of 50 inexpensive microphones optimally positioned on an imaginary spherical surface of radius 0.2m. Front-end signal processing uses coherence analysis to produce multiple, phase-coherent holograms in the frequency domain each related to references located on suspect sound sources in an aircraft cabin. The analysis uses either SVD or Cholesky decomposition methods using ensemble averages of the cross-spectral density with the fixed references. The holograms are mathematically processed using spherical NAH (nearfield acoustical holography) to convert the measured pressure field into a vector intensity field in the volume of maximum radius 0.4 m centered on the sphere origin. The utility of this probe is evaluated in a detailed analysis of a recent in-flight experiment in cooperation with Boeing and NASA on NASA s Aries 757 aircraft. In this experiment the trim panels and insulation were removed over a section of the aircraft and the bare panels and windows were instrumented with accelerometers to use as references for the VAIM. Results show excellent success at locating and identifying the sources of interior noise in-flight in the frequency range of 0 to 1400 Hz. This work was supported by NASA and the Office of Naval Research.

Klos, Jacob; Williams, Earl G.; Valdivia, Nicolas P.

2006-01-01

87

Analysis of Particle Image Velocimetry (PIV) Data for Acoustic Velocity Measurements  

NASA Technical Reports Server (NTRS)

Acoustic velocity measurements were taken using Particle Image Velocimetry (PIV) in a Normal Incidence Tube configuration at various frequency, phase, and amplitude levels. This report presents the results of the PIV analysis and data reduction portions of the test and details the processing that was done. Estimates of lower measurement sensitivity levels were determined based on PIV image quality, correlation, and noise level parameters used in the test. Comparison of measurements with linear acoustic theory are presented. The onset of nonlinear, harmonic frequency acoustic levels were also studied for various decibel and frequency levels ranging from 90 to 132 dB and 500 to 3000 Hz, respectively.

Blackshire, James L.

1997-01-01

88

Acoustic\\/seismic identifications, imaging, and communications in Steel Rattler  

Microsoft Academic Search

Unattended ground sensors (UGS) utilize data from a variety of sensors (e.g., acoustic, seismic, and imagery) to make a determination about an unknown potential target. The Steel Rattler UGS derives its target identification solution from acoustic and seismic data. The identification solution and optional still imagery of the target are transmitted to the appropriate operating bases via satellite. This paper

Kevin T. Malone; Loren E. Riblett; Thomas J. Essenmacher

1997-01-01

89

Acoustic and optical borehole-wall imaging for fractured-rock aquifer studies  

USGS Publications Warehouse

Imaging with acoustic and optical televiewers results in continuous and oriented 360?? views of the borehole wall from which the character, relation, and orientation of lithologic and structural planar features can be defined for studies of fractured-rock aquifers. Fractures are more clearly defined under a wider range of conditions on acoustic images than on optical images including dark-colored rocks, cloudy borehole water, and coated borehole walls. However, optical images allow for the direct viewing of the character of and relation between lithology, fractures, foliation, and bedding. The most powerful approach is the combined application of acoustic and optical imaging with integrated interpretation. Imaging of the borehole wall provides information useful for the collection and interpretation of flowmeter and other geophysical logs, core samples, and hydraulic and water-quality data from packer testing and monitoring. ?? 2003 Elsevier B.V. All rights reserved.

Williams, J. H.; Johnson, C. D.

2004-01-01

90

An Acoustic Charge Transport Imager for High Definition Television  

NASA Technical Reports Server (NTRS)

This project, over its term, included funding to a variety of companies and organizations. In addition to Georgia Tech these included Florida Atlantic University with Dr. William E. Glenn as the P.I., Kodak with Mr. Mike Richardson as the P.I. and M.I.T./Polaroid with Dr. Richard Solomon as the P.I. The focus of the work conducted by these organizations was the development of camera hardware for High Definition Television (HDTV). The focus of the research at Georgia Tech was the development of new semiconductor technology to achieve a next generation solid state imager chip that would operate at a high frame rate (I 70 frames per second), operate at low light levels (via the use of avalanche photodiodes as the detector element) and contain 2 million pixels. The actual cost required to create this new semiconductor technology was probably at least 5 or 6 times the investment made under this program and hence we fell short of achieving this rather grand goal. We did, however, produce a number of spin-off technologies as a result of our efforts. These include, among others, improved avalanche photodiode structures, significant advancement of the state of understanding of ZnO/GaAs structures and significant contributions to the analysis of general GaAs semiconductor devices and the design of Surface Acoustic Wave resonator filters for wireless communication. More of these will be described in the report. The work conducted at the partner sites resulted in the development of 4 prototype HDTV cameras. The HDTV camera developed by Kodak uses the Kodak KAI-2091M high- definition monochrome image sensor. This progressively-scanned charge-coupled device (CCD) can operate at video frame rates and has 9 gm square pixels. The photosensitive area has a 16:9 aspect ratio and is consistent with the "Common Image Format" (CIF). It features an active image area of 1928 horizontal by 1084 vertical pixels and has a 55% fill factor. The camera is designed to operate in continuous mode with an output data rate of 5MHz, which gives a maximum frame rate of 4 frames per second. The MIT/Polaroid group developed two cameras under this program. The cameras have effectively four times the current video spatial resolution and at 60 frames per second are double the normal video frame rate.

Hunt, William D.; Brennan, Kevin; May, Gary; Glenn, William E.; Richardson, Mike; Solomon, Richard

1999-01-01

91

Acoustics  

NASA Technical Reports Server (NTRS)

The acoustics environment in space operations is important to maintain at manageable levels so that the crewperson can remain safe, functional, effective, and reasonably comfortable. High acoustic levels can produce temporary or permanent hearing loss, or cause other physiological symptoms such as auditory pain, headaches, discomfort, strain in the vocal cords, or fatigue. Noise is defined as undesirable sound. Excessive noise may result in psychological effects such as irritability, inability to concentrate, decrease in productivity, annoyance, errors in judgment, and distraction. A noisy environment can also result in the inability to sleep, or sleep well. Elevated noise levels can affect the ability to communicate, understand what is being said, hear what is going on in the environment, degrade crew performance and operations, and create habitability concerns. Superfluous noise emissions can also create the inability to hear alarms or other important auditory cues such as an equipment malfunctioning. Recent space flight experience, evaluations of the requirements in crew habitable areas, and lessons learned (Goodman 2003; Allen and Goodman 2003; Pilkinton 2003; Grosveld et al. 2003) show the importance of maintaining an acceptable acoustics environment. This is best accomplished by having a high-quality set of limits/requirements early in the program, the "designing in" of acoustics in the development of hardware and systems, and by monitoring, testing and verifying the levels to ensure that they are acceptable.

Goodman, Jerry R.; Grosveld, Ferdinand

2007-01-01

92

RGB representation of two-dimensional multi-spectral acoustic data for object surface profile imaging  

NASA Astrophysics Data System (ADS)

Conventionally, acoustic imaging has been performed using a single frequency or a limited number of frequencies. However, the rich information on surface profiles, structures hidden under surfaces and material properties of objects may exhibit frequency dependence. In this study, acoustic imaging on object surface was conducted over a wide frequency range with a fine frequency step, and a method for displaying the acquired multi-spectral acoustic data was proposed. A complicated rigid surface with different profiles was illuminated by sound waves sweeping over the frequency range from 1 to 20 kHz with a 30 Hz step. The reflected sound was two-dimensionally recorded using a scanning microphone, and processed using a holographic reconstruction method. The two-dimensional distributions of obtained sound pressure at each frequency were defined as ‘multi-spectral acoustic imaging data’. Next, the multi-spectral acoustic data were transformed into a single RGB-based picture for easy understanding of the surface characteristics. The acoustic frequencies were allocated to red, green and blue using the RGB filter technique. The depths of the grooves were identified by their colours in the RGB image.

Guo, Xinhua; Wada, Yuji; Mizuno, Yosuke; Nakamura, Kentaro

2013-10-01

93

Acoustic impedance micro-imaging for biological tissue using a focused acoustic pulse with a frequency range up to 100 MHz  

Microsoft Academic Search

We have proposed a new method for two-dimensional acoustic impedance imaging for biological tissue that can per- form micro-scale observation without slicing the specimen. A tissue was placed on a plastic plate of 0.5 mm in thickness. An acoustic pulse with a frequency range up to 100 MHz was trans- mitted from the \\

N. Hozumi; A. Kimura; S. Terauchi; M. Nagao; S. Yoshida; K. Kobayashi; Y. Saijo

2005-01-01

94

Photoacoustic section imaging using an elliptical acoustic mirror and optical detection.  

PubMed

A method is proposed that utilizes the advantages of optical ultrasound detection in two-dimensional photoacoustic section imaging, combining an optical interferometer with an acoustic mirror. The concave mirror has the shape of an elliptical cylinder and concentrates the acoustic wave generated around one focal line in the other one, where an optical beam probes the temporal evolution of acoustic pressure. This yields line projections of the acoustic sources at distances corresponding to the time of flight, which, after rotating the sample about an axis perpendicular to the optical detector, allows reconstruction of a section using the inverse Radon transform. A resolution of 120 [micro sign]m within and 1.5 mm between the sections can be obtained with the setup. Compared to a bare optical probe beam, the signal-to-noise ratio (SNR) is seven times higher with the mirror. Furthermore, the imaging system is tested on a biological sample. PMID:22502554

Nuster, Robert; Gratt, Sibylle; Passler, Klaus; Meyer, Dirk; Paltauf, Guenther

2012-03-01

95

Acoustic noise analysis in echo planar imaging: multicenter trial and comparison with other pulse sequences.  

PubMed

The purpose of this study was to evaluate acoustic noise in echo planar imaging (EPI) at various magnetic resonance imaging (MRI) centers and to compare EPI acoustic noise with that in other fast pulse sequences. We measured A-weighted root-mean-square sound pressure levels and peak impulse sound pressure levels for EPI, under the same conditions, in eleven clinical super-conducting MRI systems. We also compared sound pressure levels for the EPI and six different pulse sequences and analyzed the acoustic noise spectra. Sound pressure levels during the use of the EPI differed greatly among institutions. Moreover, sound pressure levels of the EPI were not significantly different from those of other fast pulse sequences and were within permissible noise exposure levels. In comparison to other fast sequences, the EPI had significantly greater acoustic noise in the high-octave band frequency. PMID:10534055

Miyati, T; Banno, T; Fujita, H; Mase, M; Narita, H; Imazawa, M; Ohba, S

1999-08-01

96

Acoustic dipole radiation based conductivity image reconstruction for magnetoacoustic tomography with magnetic induction  

NASA Astrophysics Data System (ADS)

Based on the acoustic dipole radiation theory, a tomograhic conductivity image reconstruction algorithm is developed for the magnetoacoustic tomography with magnetic induction (MAT-MI) in a cylindrical measurement configuration. It has been experimentally proved for a tissue-like phantom that not only the configuration but also the inner conductivity distribution can be reconstructed without any borderline stripe. Furthermore, the spatial resolution also can be improved without the limitation of acoustic vibration. The favorable results have provided solid verification for the feasibility of conductivity image reconstruction and suggested the potential applications of MAT-MI in the area of medical electrical impedance imaging.

Sun, Xiaodong; Zhang, Feng; Ma, Qingyu; Tu, Juan; Zhang, Dong

2012-01-01

97

Inferring fish school distributions from long range acoustic images: Main acoustic clutter experiment 2003  

Microsoft Academic Search

Long range scattering from fish schools and bottom reverberation in the New Jersey Continental Shelf environment are modeled using a unified, range-dependent, bistatic scattering, and reverberation model based on the parabolic equation [Ratilal and Makris, J. Acoust. Soc. Am. 114, 2302 (2003)]. The fish swim bladder is approximated as an air-filled bubble, while the bottom reverberation from volume inhomogeneities is

Deanelle T. Symonds; Purnima Ratilal; Nicholas C. Makris; Redwood W. Nero

2001-01-01

98

Acoustic shear-wave imaging using echo ultrasound compared to magnetic resonance elastography  

Microsoft Academic Search

We compare a previously developed phase contrast-based magnetic resonance imaging technique (MRE) to a phase-based ultrasound (US) method for measuring small cyclic displacements (submicrometer level) caused by propagating acoustic shear waves in tissue-like media. Our preliminary experiments with gelatin phantoms show that acoustic shear-wave propagation can be measured with US, and we speculate that this technique could find applications in

Vinayak Dutt; Randall R. Kinnick; Raja Muthupillai; Travis E. Oliphant; R. L. Ehman; James F. Greenleaf

2000-01-01

99

Liver ablation guidance with acoustic radiation force impulse imaging: challenges and opportunities  

Microsoft Academic Search

Previous studies have established the feasibility of monitoring radiofrequency (RF) ablation procedures with acoustic radiation force impulse (ARFI) imaging. However, questions remained regarding the utility of the technique in clinically realistic scenarios and at scanning depths associated with abdominal imaging in adults. We address several of these issues and detail recent progress towards the clinical relevance of the ARFI technique.

B J Fahey; S J Hsu; P D Wolf; R C Nelson; G E Trahey

2006-01-01

100

Investigating large 2D arrays for photoacoustic and acoustic imaging using CMUT technology  

Microsoft Academic Search

In this paper, we investigate using a large aperture (64 times 64 element array) to perform photoacoustic and acoustic imaging by mechanically scanning a smaller array (16 times 16 elements) of capacitive micromachined ultrasonic transducers (CMUTs). We show results from the imaging of: 1) A fishing-line phantom. 2) Tubes embedded in chicken breast tissue containing the contrast agent indocyanine green

Srikant Vaithilingam; Te-Jen Ma; Yukio Furukawa; Omer Oralkan; Aya Kamaya; Kazutoshi Torashima; Mario Kupnik; Ira O. Wygant; Xuefeng Zhuang; R. B. Jeffrey; Butrus T. Khuri-Yakub

2008-01-01

101

Image Quality, Tissue Heating, and Frame Rate Trade-offs in Acoustic Radiation Force Impulse Imaging  

PubMed Central

The real-time application of acoustic radiation force impulse (ARFI) imaging requires both short acquisition times for a single ARFI image and repeated acquisition of these frames. Due to the high energy of pulses required to generate appreciable radiation force, however, repeated acquisitions could result in substantial transducer face and tissue heating. We describe and evaluate several novel beam sequencing schemes which, along with parallel-receive acquisition, are designed to reduce acquisition time and heating. These techniques reduce the total number of radiation force impulses needed to generate an image and minimize the time between successive impulses. We present qualitative and quantitative analyses of the trade-offs in image quality resulting from the acquisition schemes. Results indicate that these techniques yield a significant improvement in frame rate with only moderate decreases in image quality. Tissue and transducer face heating resulting from these schemes is assessed through finite element method modeling and thermocouple measurements. Results indicate that heating issues can be mitigated by employing ARFI acquisition sequences that utilize the highest track-to-excitation ratio possible.

Bouchard, Richard R.; Dahl, Jeremy J.; Hsu, stephen J.; Palmeri, Mark L.; Trahey, Gregg E.

2013-01-01

102

A surface acoustic wave /SAW/ charge transfer imager  

NASA Technical Reports Server (NTRS)

An 80 MHz, 2-microsecond surface acoustic wave charge transfer device (SAW-CTD) has been fabricated in which surface acoustic waves are used to create traveling longitudinal electric fields in the silicon substrate and to replace the multiphase clocks of charge coupled devices. The traveling electric fields create potential wells which will carry along charges that may be stored in the wells; the charges may be injected into the wells by light. An optical application is proposed where the SAW-CTD structure is used in place of a conventional interline transfer design.

Papanicolauo, N. A.; Lin, H. C.

1981-01-01

103

Segmentation and classification of shallow subbottom acoustic data, using image processing and neural networks  

NASA Astrophysics Data System (ADS)

Subbottom acoustic profiler provides acoustic imaging of the subbottom structure constituting the upper sediment layers of the seabed, which is essential for geological and offshore geo-engineering studies. Delineation of the subbottom structure from a noisy acoustic data and classification of the sediment strata is a challenging task with the conventional signal processing techniques. Image processing techniques utilise the spatial variability of the image characteristics, known for their potential in medical imaging and pattern recognition applications. In the present study, they are found to be good in demarcating the boundaries of the sediment layers associated with weak acoustic reflectivity, masked by noisy background. The study deals with application of image processing techniques, like segmentation in identification of subbottom features and extraction of textural feature vectors using grey level co-occurrence matrix statistics. And also attempted classification using Self Organised Map, an unsupervised neural network model utilising these feature vectors. The methodology was successfully demonstrated in demarcating the different sediment layers from the subbottom images and established the sediments constituting the inferred four subsurface sediment layers differ from each other. The network model was also tested for its consistency, with repeated runs of different configuration of the network. Also the ability of simulated network was tested using a few untrained test images representing the similar environment and the classification results show a good agreement with the anticipated.

Yegireddi, Satyanarayana; Thomas, Nitheesh

2014-06-01

104

Segmentation and classification of shallow subbottom acoustic data, using image processing and neural networks  

NASA Astrophysics Data System (ADS)

Subbottom acoustic profiler provides acoustic imaging of the subbottom structure constituting the upper sediment layers of the seabed, which is essential for geological and offshore geo-engineering studies. Delineation of the subbottom structure from a noisy acoustic data and classification of the sediment strata is a challenging task with the conventional signal processing techniques. Image processing techniques utilise the spatial variability of the image characteristics, known for their potential in medical imaging and pattern recognition applications. In the present study, they are found to be good in demarcating the boundaries of the sediment layers associated with weak acoustic reflectivity, masked by noisy background. The study deals with application of image processing techniques, like segmentation in identification of subbottom features and extraction of textural feature vectors using grey level co-occurrence matrix statistics. And also attempted classification using Self Organised Map, an unsupervised neural network model utilising these feature vectors. The methodology was successfully demonstrated in demarcating the different sediment layers from the subbottom images and established the sediments constituting the inferred four subsurface sediment layers differ from each other. The network model was also tested for its consistency, with repeated runs of different configuration of the network. Also the ability of simulated network was tested using a few untrained test images representing the similar environment and the classification results show a good agreement with the anticipated.

Yegireddi, Satyanarayana; Thomas, Nitheesh

2014-05-01

105

Method and apparatus for detecting internal structures of bulk objects using acoustic imaging  

DOEpatents

Apparatus for producing an acoustic image of an object according to the present invention may comprise an excitation source for vibrating the object to produce at least one acoustic wave therein. The acoustic wave results in the formation of at least one surface displacement on the surface of the object. A light source produces an optical object wavefront and an optical reference wavefront and directs the optical object wavefront toward the surface of the object to produce a modulated optical object wavefront. A modulator operatively associated with the optical reference wavefront modulates the optical reference wavefront in synchronization with the acoustic wave to produce a modulated optical reference wavefront. A sensing medium positioned to receive the modulated optical object wavefront and the modulated optical reference wavefront combines the modulated optical object and reference wavefronts to produce an image related to the surface displacement on the surface of the object. A detector detects the image related to the surface displacement produced by the sensing medium. A processing system operatively associated with the detector constructs an acoustic image of interior features of the object based on the phase and amplitude of the surface displacement on the surface of the object.

Deason, Vance A. (Idaho Falls, ID); Telschow, Kenneth L. (Idaho Falls, ID)

2002-01-01

106

Development of a novel acoustic lens based pulse echo ultrasound imaging system  

NASA Astrophysics Data System (ADS)

Acoustic lens based focusing technology where the image reconstruction is achieved through the focusing of an acoustic lens, can potentially replace time consuming and expensive electronic focusing technology for producing high resolution real time ultrasound (US) images. A novel acoustic lens focusing based pulse echo US imaging system is explored here. In the system, a Polyvinylidene fluoride (PVDF) film transducer generates plane wave which is backscattered by the object and focused by a spherical acoustic lens on to a linear array of transducers. To improve the anticipated low signal to noise ratio (SNR) of the received US signal due to the low electromechanical coupling coefficient of the PVDF film, here we explored the possibility of implementing pulse compression technique using linear frequency modulated (FM) signals or chirp signals. Comparisons among the different SNR values obtained with short pulse and after pulse compression with chirp signal show a clear improvement of the SNR for the compressed pulse. The preliminary results show that the SNR achieved for the compressed pulse depends on time bandwidth product of the input chirp and the spectrum of the US transducers. The axial resolution obtained with compressed pulse improved with increasing sweep bandwidth of input chirp signals, whereas the lateral resolution remained almost constant. This work demonstrates the feasibility of using a PVDF film transducer as an US transmitter in an acoustic lens focusing based imaging system and implementing pulse compression technique into the same setup to improve SNR of the received US signal.

Sinha, Saugata; Rao, Navalgund A.

2014-03-01

107

Bubble-based acoustic radiation force elasticity imaging.  

PubMed

Acoustic radiation force is applied to bubbles generated by laser-induced optical breakdown (LIOB) to study viscoelastic properties of the surrounding medium. In this investigation, femtosecond laser pulses are focused in the volume of gelatin phantoms of different concentrations to form bubbles. A two-element confocal ultrasonic transducer generates acoustic radiation force on individual bubbles while monitoring their displacement within a viscoelastic medium. Tone burst pushes of varying duration have been applied by the outer element at 1.5 MHz. The inner element receives pulse-echo recordings at 7.44 MHz before, during, and after the excitation bursts, and crosscorrelation processing is performed offline to monitor bubble position. Maximum bubble displacements are inversely related to the Young's moduli for different gel phantoms, with a maximum bubble displacement of over 200 microm in a gel phantom with a Young's modulus of 1.7 kPa. Bubble displacements scale with the applied acoustic radiation force and displacements can be normalized to correct for differences in bubble size. Exponential time constants for bubble displacement curves are independent of bubble radius and follow a decreasing trend with the Young's modulus of the surrounding medium. These results demonstrate the potential for bubble-based acoustic radiation force methods to measure tissue viscoelastic properties. PMID:16118978

Erpelding, Todd N; Hollman, Kyle W; O'Donnell, Matthew

2005-06-01

108

An acoustic charge transport imager for high definition television applications  

NASA Technical Reports Server (NTRS)

In this report we present the progress during the second six month period of the project. This includes both experimental and theoretical work on the acoustic charge transport (ACT) portion of the chip, the theoretical program modelling of both the avalanche photodiode (APD) and the charge transfer and overflow transistor and the materials growth and fabrication part of the program.

Hunt, William D.; Brennan, Kevin F.; Summers, Chris J.

1992-01-01

109

Acoustic imaging of vapor bubbles through optically non-transparent media  

SciTech Connect

A preliminary investigation of the feasibility of acoustic imaging of vapor bubbles through optically nontransparent media is described. Measurements are reported showing the echo signals produced by air filled glass spheres of various sizes positioned in an aqueous medium as well as signals produced by actual vapor bubbles within a water filled steel pipe. In addition, the influence of the metallic wall thickness and material on the amplitude of the echo signals is investigated. Finally several examples are given of the imaging of spherical bubbles within metallic pipes using a simulated array of acoustic transducers mounted circumferentially around the pipe. The measurement procedures and a description of the measuring system are also given.

Kolbe, W.F.; Turko, B.T.; Leskovar, B.

1983-10-01

110

Exploration of amphoteric and negative refraction imaging of acoustic sources via active metamaterials  

NASA Astrophysics Data System (ADS)

The present work describes the design of three flat superlens structures for acoustic source imaging and explores an active acoustic metamaterial (AAM) to realise such a design. The first two lenses are constructed via the coordinate transform method (CTM), and their constituent materials are anisotropic. The third lens consists of a material that has both a negative density and a negative bulk modulus. In these lenses, the quality of the images is “clear” and sharp; thus, the diffraction limit of classical lenses is overcome. Finally, a multi-control strategy is developed to achieve the desired parameters and to eliminate coupling effects in the AAM.

Wen, Jihong; Shen, Huijie; Yu, Dianlong; Wen, Xisen

2013-11-01

111

Imaging Defects in Thin DLC Coatings Using High Frequency Scanning Acoustic Microscopy  

NASA Astrophysics Data System (ADS)

In this work high frequency scanning acoustic microscopy was employed to nondestructively characterize subsurface defects in chromium containing DLC (Cr-DLC) coatings. Subsurface defects as small as one micron were successfully detected in a flat Cr-DLC coated steel coupon. Depth of the imaged subsurface defects was estimated using a simple geometrical acoustics model. The nature of the subsurface defects was investigated by using FIB/SEM technique. Curved Cr-DLC coated components including a roller and gear tooth were also imaged, and the encountered challenges were addressed.

Fei, Dong; Rebinsky, Douglas A.; Zinin, Pavel; Koehler, Bernd

2004-02-01

112

Unified imaging theory for x-ray and acoustic computerized tomography  

NASA Astrophysics Data System (ADS)

X-ray computerized tomography (CT) and acoustic CT are two main medical imaging modalities based on two intrinsically different physical phenomena. X-ray CT is based on x-ray"s attenuation when x-ray passes through medium. It has been well known that the Radon transform is the imaging theory for x-ray CT. Photoacoustic CT is a type of acoustic CT, which is based on differentiating electromagnetic energy absorption among media. In 1998 a new 3D reconstruction concept, the P-transform, was proposed to serve the imaging theory for photoacoustic CT. In this paper it was rigorously proved that both x-ray CT and photoacoustic CT are governed by a unified imaging theory. 3D data acquisition can be completed in 2p stereoangle. This new imaging theory realized, in part, the dream of all physicists, including Albert Einstein, who have long believed that our world is ultimately governed by few simple rules.

Liu, Pingyu; Wang, Ge; Boyer, Arthur

2004-10-01

113

A Correlated Microwave-Acoustic Imaging method for early-stage cancer detection.  

PubMed

Microwave-based imaging technique shows large potential in detecting early-stage cancer due to significant dielectric contrast between tumor and surrounding healthy tissue. In this paper, we present a new way named Correlated Microwave-Acoustic Imaging (CMAI) of combining two microwave-based imaging modalities: confocal microwave imaging(CMI) by detecting scattered microwave signal, and microwave-induced thermo-acoustic imaging (TAI) by detecting induced acoustic signal arising from microwave energy absorption and thermal expansion. Necessity of combining CMI and TAI is analyzed theoretically, and by applying simple algorithm to CMI and TAI separately, we propose an image correlation approach merging CMI and TAI together to achieve better performance in terms of resolution and contrast. Preliminary numerical simulation shows promising results in case of low contrast and large variation scenarios. A UWB transmitter is designed and tested for future complete system implementation. This preliminary study inspires us to develop a new medical imaging modality CMAI to achieve real-time, high resolution and high contrast simultaneously. PMID:23365933

Gao, Fei; Zheng, Yuanjin

2012-01-01

114

Phase Time and Envelope Time in Time-Distance Analysis and Acoustic Imaging.  

National Technical Information Service (NTIS)

Time-distance analysis and acoustic imaging are two related techniques to probe the local properties of solar interior. In this study, we discuss the relation of phase time and envelope time between the two techniques. In this study, we use the data taken...

D. Y. Chou T. L. Duvall M. T. Sun H. K. Chang A. Jimenez M. C. Rabello-Soares G. Ai G. P. Wang W. Marquette S. Ehgamberdiev O. Landenkov

1999-01-01

115

P2E-8 Ex Vivo Acoustic Radiation Force Impulse Imaging of an Ovine Heart Model  

Microsoft Academic Search

Acoustic radiation force impulse (ARFI) imaging with an intra-cardiac probe has been demonstrated to be a suitable modality to monitor the progress of radiofrequency ablation (RFA) procedures. In order to continue studies while allowing increased control and repeatability in the procedure, an ovine heart model was used to artificially simulate a beating heart. The interior of the heart remained accessible

Stephen J. Hsu; Stephen W. Smith; Julia L. Hubert; Gregg E. Trahey

2006-01-01

116

Imaging of acoustic pressure radiation from vibrating microstructure in atmosphere using thermal microprobe  

NASA Astrophysics Data System (ADS)

This letter reports on an imaging technique of acoustic pressure radiation (APR) from vibrating micro-/nanostructures and their mechanical defects. Resonance oscillation of micro-/nanometer beams in use of viscous environments is important for various sensing applications. Viscous dumping is the main energy loss mechanism, which determines the quality factor of resonance in viscous fluid. The APR due to viscous dumping is imaged using a scanning thermal flow sensor. A platinum heater or micromachined silicon heater is heated up by flowing a current, and the acoustic particle velocity which originated from APR is detected. Imaging of APR is demonstrated and compared with the actual vibration image. Also, strong APR is observed from a crack on the support of a silicon beam.

Ono, Takahito; Kim, Sang-Jin; Esashi, Masayoshi

2007-05-01

117

Acoustically modulated x-ray phase contrast imaging  

Microsoft Academic Search

We report the use of ultrasonic radiation pressure with phase contrast x-ray imaging to give an image proportional to the space derivative of a conventional phase contrast image in the direction of propagation of an ultrasonic beam. Intense ultrasound is used to exert forces on objects within a body giving displacements of the order of tens to hundreds of microns.

Theron J. Hamilton; Claude J. Bailat; Christoph Rose-Petruck; Gerald J. Diebold

2004-01-01

118

Three-dimensional image generation and processing in underwater acoustic vision  

Microsoft Academic Search

Underwater exploration is becoming more and more important for many applications involving physical, biological, geological, archaeological, and industrial issues. This paper aims at surveying the up-to-date advances in acoustic acquisition systems and data processing techniques, especially focusing on three-dimensional (3-D) short-range imaging for scene reconstruction and understanding. In fact, the advent of smarter and more efficient imaging systems has allowed

VITTORIO MURINO; ANDREA TRUCCO

2000-01-01

119

Improvement of flaw image quality in the reconstruction of acoustic holograms  

SciTech Connect

A procedure is discussed for improving the quality of the images of flaws on the basis of the practical directivity pattern of the acoustic transducer. This characteristic is taken into account in the reconstruction of images by means of a standard hologram. Results are given to illustrate the efficiency of the method of models of a point flaw and a planar flaw. The transverse resolution is improved by a factor of 1.7.

Badalyan, V.G.; Bazulin, E.G.

1988-07-01

120

Passive imaging of cavitational acoustic emissions with ultrasound arrays  

NASA Astrophysics Data System (ADS)

A method is presented for imaging emissions from active microbubbles using an ultrasound array. Since bubble activity plays a role in ultrasound ablation, monitoring cavitation may assist in therapy guidance. This is often achieved by listening passively for bubble emissions with a single-element transducer. Such schemes do not capture the variation in cavitation in form of a two dimensional (2D) map or image. The technique presented here obtains spatial information by creating images solely from the beamformed cavitational-emission energy received by an array, dynamically focused at multiple depths. An analytic expression was derived for these passive images by numerically solving the Rayleigh-Sommerfield integral under the Fresnel approximation. To test accuracy in mapping of localized emissions, a 192-element array was employed to passively image scattering of 520-kHz ultrasound by a 1-mm steel wire. The wire position was estimated from the passive images with rms error 0.9 mm in azimuth and 17.2 mm in range. Bubbles created in air-saturated saline sonicated at 520-kHz were imaged passively from both ultraharmonic and broadband emissions. Good agreement was found between azimuthal brightness distributions of the passive images and B-scan images of the bubble cloud. Broadband emission images from ex vivo bovine liver sonicated with 2.2-MHz focused ultrasound were also recorded. The image brightness along the array azimuth was consistent with the source beam profile. This indicates the possibility of mapping therapeutic ultrasound beams in situ.

Salgaonkar, Vasant A.; Datta, Saurabh; Holland, Christy K.; Mast, T. Douglas

2009-04-01

121

A synchronized particle image velocimetry and infrared thermography technique applied to an acoustic streaming flow  

PubMed Central

Subsurface coherent structures and surface temperatures are investigated using simultaneous measurements of particle image velocimetry (PIV) and infrared (IR) thermography. Results for coherent structures from acoustic streaming and associated heating transfer in a rectangular tank with an acoustic horn mounted horizontally at the sidewall are presented. An observed vortex pair develops and propagates in the direction along the centerline of the horn. From the PIV velocity field data, distinct kinematic regions are found with the Lagrangian coherent structure (LCS) method. The implications of this analysis with respect to heat transfer and related sonochemical applications are discussed.

Sou, In Mei; Layman, Christopher N.; Ray, Chittaranjan

2013-01-01

122

Investigation of an acoustical holography system for real-time imaging  

NASA Astrophysics Data System (ADS)

A new prototype imaging system based on ultrasound transmission through the object of interest -- acoustical holography -- was developed which incorporates significant improvements in acoustical and optical design. This system is being evaluated for potential clinical application in the musculoskeletal system, interventional radiology, pediatrics, monitoring of tumor ablation, vascular imaging and breast imaging. System limiting resolution was estimated using a line-pair target with decreasing line thickness and equal separation. For a swept frequency beam from 2.6 - 3.0 MHz, the minimum resolution was 0.5 lp/mm. Apatite crystals were suspended in castor oil to approximate breast microcalcifications. Crystals from 0.425 - 1.18 mm in diameter were well resolved in the acoustic zoom mode. Needle visibility was examined with both a 14-gauge biopsy needle and a 0.6 mm needle. The needle tip was clearly visible throughout the dynamic imaging sequence as it was slowly inserted into a RMI tissue-equivalent breast biopsy phantom. A selection of human images was acquired in several volunteers: a 25 year-old female volunteer with normal breast tissue, a lateral view of the elbow joint showing muscle fascia and tendon insertions, and the superficial vessels in the forearm. Real-time video images of these studies will be presented. In all of these studies, conventional sonography was used for comparison. These preliminary investigations with the new prototype acoustical holography system showed favorable results in comparison to state-of-the-art pulse-echo ultrasound and demonstrate it to be suitable for further clinical study. The new patient interfaces will facilitate orthopedic soft tissue evaluation, study of superficial vascular structures and potentially breast imaging.

Fecht, Barbara A.; Andre, Michael P.; Garlick, George F.; Shelby, Ronald L.; Shelby, Jerod O.; Lehman, Constance D.

1998-07-01

123

Acoustic streaming in lithotripsy fields: preliminary observation using a particle image velocimetry method.  

PubMed

This study considers the acoustic streaming in water produced by a lithotripsy pulse. Particle image velocimetry (PIV) method was employed to visualize the acoustic streaming produced by an electromagnetic shock wave generator using video images of the light scattering particles suspended in water. Visualized streaming features including several local peaks and vortexes around or at the beam focus were easily seen with naked eyes over all settings of the lithotripter from 10 to 18 kV. Magnitudes of the peak streaming velocity measured vary in the range of 10-40 mm s(-1) with charging voltage settings. Since the streaming velocity was estimated on the basis of a series of the video images of particles averaged over 1/60s, the time resolution limited by the video frame rate which is 1-2 orders of magnitude larger than driving acoustic activities, measured velocities are expected to be underestimated and were shown a similar order of magnitude lower than those calculated from a simple theoretical consideration. Despite such an underestimation, it was shown that, as predicted by theory, the magnitude of the streaming velocity measured by the present PIV method was proportional to acoustic intensity. In particular it has almost a linear correlation with peak negative pressures (r=0.98683, p=0.0018). PMID:16376400

Choi, Min Joo; Doh, Doeg Hee; Hwang, Tae Gyu; Cho, Chu Hyun; Paeng, Dong Guk; Rim, Gun Hee; Coleman, A J

2006-02-01

124

Integrating Acoustic Imaging of Flow Regimes With Bathymetry: A Case Study, Main Endeavor Field  

NASA Astrophysics Data System (ADS)

A unified view of the seafloor and the hydrothermal flow regimes (plumes and diffuse flow) is constructed for three major vent clusters in the Main Endeavour Field (e.g., Grotto, S&M, and Salut) of the Endeavour Segment, Juan de Fuca Ridge. The Main Endeavour Field is one of RIDGE 2000's Integrated Study Sites. A variety of visualization techniques are used to reconstruct the plumes (3D) and the diffuse flow field (2D) based on our acoustic imaging data set (July 2000 cruise). Plumes are identified as volumes of high backscatter intensity (indicating high particulate content or sharp density contrasts due to temperature variations) that remained high intensity when successive acoustic pings were subtracted (indicating that the acoustic targets producing the backscatter were in motion). Areas of diffuse flow are detected using our acoustic scintillation technique (AST). For the Grotto vent region (where a new Doppler technique was used to estimate vertical velocities in the plume), we estimate the areal partitioning between black smoker and diffuse flow in terms of volume fluxes. The volumetric and areal regions, where plume and diffuse flow were imaged, are registered over the bathymetry and compared to geologic maps of each region. The resulting images provide a unified view of the seafloor by integrating hydrothermal flow with geology.

Bemis, K. G.; Rona, P. A.; Jackson, D. R.; Jones, C. D.

2003-12-01

125

Double-channel, frequency-steered acoustic transducer with 2-D imaging capabilities.  

PubMed

A frequency-steerable acoustic transducer (FSAT) is employed for imaging of damage in plates through guided wave inspection. The FSAT is a shaped array with a spatial distribution that defines a spiral in wavenumber space. Its resulting frequency-dependent directional properties allow beam steering to be performed by a single two-channel device, which can be used for the imaging of a two-dimensional half-plane. Ad hoc signal processing algorithms are developed and applied to the localization of acoustic sources and scatterers when FSAT arrays are used as part of pitch-catch and pulse-echo configurations. Localization schemes rely on the spectrogram analysis of received signals upon dispersion compensation through frequency warping and the application of the frequency-angle map characteristic of FSAT. The effectiveness of FSAT designs and associated imaging schemes are demonstrated through numerical simulations and experiments. Preliminary experimental validation is performed by forming a discrete array through the points of the measurement grid of a scanning laser Doppler vibrometer. The presented results demonstrate the frequency-dependent directionality of the spiral FSAT and suggest its application for frequency-selective acoustic sensors, for the localization of broadband acoustic events, or for the directional generation of Lamb waves for active interrogation of structural health. PMID:21768027

Baravelli, Emanuele; Senesi, Matteo; Ruzzene, Massimo; De Marchi, Luca; Speciale, Nicolò

2011-07-01

126

Ultrasound-mediated biophotonic imaging: A review of acousto-optical tomography and photo-acoustic tomography  

Microsoft Academic Search

This article reviews two types of ultrasound-mediated biophotonic imaging-acousto-optical tomography (AOT, also called ultrasound-modulated optical tomography) and photo-acoustic tomography (PAT, also called opto-acoustic or thermo- acoustic tomography)-both of which are based on non-ionizing optical and ultrasonic waves. The goal of these technologies is to combine the contrast advantage of the optical properties and the resolution advantage of ultrasound. In these

Lihong V. Wang

2004-01-01

127

An acoustic charge transport imager for high definition television applications  

NASA Technical Reports Server (NTRS)

This report covers: (1) invention of a new, ultra-low noise, low operating voltage APD which is expected to offer far better performance than the existing volume doped APD device; (2) performance of a comprehensive series of experiments on the acoustic and piezoelectric properties of ZnO films sputtered on GaAs which can possibly lead to a decrease in the required rf drive power for ACT devices by 15dB; (3) development of an advanced, hydrodynamic, macroscopic simulator used for evaluating the performance of ACT and CTD devices and aiding in the development of the next generation of devices; (4) experimental development of CTD devices which utilize a p-doped top barrier demonstrating charge storage capacity and low leakage currents; (5) refinements in materials growth techniques and in situ controls to lower surface defect densities to record levels as well as increase material uniformity and quality.

Hunt, William D.; Brennan, Kevin F.; Summers, Christopher J.

1993-01-01

128

Modern Techniques in Acoustical Signal and Image Processing  

SciTech Connect

Acoustical signal processing problems can lead to some complex and intricate techniques to extract the desired information from noisy, sometimes inadequate, measurements. The challenge is to formulate a meaningful strategy that is aimed at performing the processing required even in the face of uncertainties. This strategy can be as simple as a transformation of the measured data to another domain for analysis or as complex as embedding a full-scale propagation model into the processor. The aims of both approaches are the same--to extract the desired information and reject the extraneous, that is, develop a signal processing scheme to achieve this goal. In this paper, we briefly discuss this underlying philosophy from a ''bottom-up'' approach enabling the problem to dictate the solution rather than visa-versa.

Candy, J V

2002-04-04

129

Phase Time and Envelope Time in Time-Distance Analysis and Acoustic Imaging  

NASA Technical Reports Server (NTRS)

Time-distance analysis and acoustic imaging are two related techniques to probe the local properties of solar interior. In this study, we discuss the relation of phase time and envelope time between the two techniques. The location of the envelope peak of the cross correlation function in time-distance analysis is identified as the travel time of the wave packet formed by modes with the same w/l. The phase time of the cross correlation function provides information of the phase change accumulated along the wave path, including the phase change at the boundaries of the mode cavity. The acoustic signals constructed with the technique of acoustic imaging contain both phase and intensity information. The phase of constructed signals can be studied by computing the cross correlation function between time series constructed with ingoing and outgoing waves. In this study, we use the data taken with the Taiwan Oscillation Network (TON) instrument and the Michelson Doppler Imager (MDI) instrument. The analysis is carried out for the quiet Sun. We use the relation of envelope time versus distance measured in time-distance analyses to construct the acoustic signals in acoustic imaging analyses. The phase time of the cross correlation function of constructed ingoing and outgoing time series is twice the difference between the phase time and envelope time in time-distance analyses as predicted. The envelope peak of the cross correlation function between constructed ingoing and outgoing time series is located at zero time as predicted for results of one-bounce at 3 mHz for all four data sets and two-bounce at 3 mHz for two TON data sets. But it is different from zero for other cases. The cause of the deviation of the envelope peak from zero is not known.

Chou, Dean-Yi; Duvall, Thomas L.; Sun, Ming-Tsung; Chang, Hsiang-Kuang; Jimenez, Antonio; Rabello-Soares, Maria Cristina; Ai, Guoxiang; Wang, Gwo-Ping; Goode Philip; Marquette, William; Ehgamberdiev, Shuhrat; Landenkov, Oleg

1999-01-01

130

Acoustic Imaging Time Series of Plume Behavior at Grotto Vent, Endeavour Observatory, Juan de Fuca Ridge  

NASA Astrophysics Data System (ADS)

A time series (24 hours) of acoustic images record the behavior of the principal buoyant plume (height interval 0-40 m above seafloor) discharging from black smoker chimneys on the north tower of the Grotto Vent sulfide edifice in the Main Endeavour Vent Field. The plume imaging was performed using the Simrad SM2000 sonar system (frequency 200 kHz) mounted on ROV Jason from a fixed position on the seafloor with a nearly horizontal slant range to the vent of about 20 m at a water depth of about 2190 m. The acoustic imaging is based on Rayleigh backscattering from mineral particles suspended in the plume that are small (microns) relative to the wavelength of the acoustic pulse (centimeter) such that intensity of backscatter is proportional to particle load. The acoustic time series data were acquired on 26-27 July 2000 as part of the VIP (Vent Imaging Pacific) 2000 cruise. We applied our computer visualization and quantification methods to reconstruct the plume 3D volume object and to measure dimensions and orientation. Plume expansion with height corresponds to model prediction (diameter 2 to 20 meters). Particle load decreases with height following model predications. The plume centerline constructed by joining the local center of mass of successive horizontal slices with height through the buoyant plume alternately bends between 0 and 30 degrees to the northeast and southwest in a complex cycle. The plume bending appears to correspond to the regional mixed semidiurnal tidal cycle (H. Mofjeld, personal communication), with a component related to a prevailing northeasterly current (R. Thomson, personal communication). The effectiveness of tracking plume behavior for this short time series shows the potential of the acoustic method for long-term monitoring of the activity and interactions of plumes in seafloor hydrothermal fields.

Rona, P. A.; Bemis, K. G.; Jackson, D. R.; Jones, C. D.; Mitsuzawa, K.; Palmer, D. R.; Silver, D.

2001-12-01

131

Analysis of contrast in images generated with transient acoustic radiation force.  

PubMed

Several mechanical imaging methods are under investigation that use focused ultrasound (US) as a source of mechanical excitation. Images are then generated of the tissue response to this localized excitation. One such method, acoustic radiation force impulse (ARFI) imaging, utilizes a single US transducer on a commercial US system to transmit brief, high-energy, focused acoustic pulses to generate radiation force in tissue and correlation-based US methods to detect the resulting tissue displacements. Local displacements reflect relative mechanical properties of tissue. The resolution of these images is comparable with that of conventional B-mode imaging. The response of tissue to focused radiation force excitation is complex and depends upon tissue geometry, forcing function geometry (i.e., region of excitation, or ROE) and tissue mechanical and acoustic properties. Finite element method (FEM) simulations using an experimentally validated model and phantom experiments have been performed using varying systems, system configurations and tissue-mimicking phantoms to determine their impact on image quality. Image quality is assessed by lesion contrast. Due to the dynamic nature of ARFI excitation, lesion contrast is temporally-dependent. Contrast of spherical inclusions is highest immediately after force cessation, decreases with time postforce and then reverses, due to shear wave interaction with internal boundaries, differences in shear modulus between lesions and background and inertial effects. In images generated immediately after force cessation, contrast does not vary with applied force, increases with lesion stiffness and increases as the ROE size decreases relative to the size of the structure being imaged. These studies indicate that improved contrast in radiation force-generated images will be achieved as ROE size decreases; however, frame rate and thermal considerations present trade-offs with small ROE size. PMID:16364798

Nightingale, Kathryn; Palmeri, Mark; Trahey, Gregg

2006-01-01

132

Vibro-acoustography: An imaging modality based on ultrasound-stimulated acoustic emission  

PubMed Central

We describe theoretical principles of an imaging modality that uses the acoustic response of an object to a highly localized dynamic radiation force of an ultrasound field. In this method, named ultrasound-stimulated vibro-acoustography (USVA), ultrasound is used to exert a low-frequency (in kHz range) force on the object. In response, a portion of the object vibrates sinusoidally in a pattern determined by its viscoelastic properties. The acoustic emission field resulting from object vibration is detected and used to form an image that represents both the ultrasonic and low-frequency (kHz range) mechanical characteristics of the object. We report the relation between the emitted acoustic field and the incident ultrasonic pressure field in terms of object parameters. Also, we present the point-spread function of the imaging system. The experimental images in this report have a resolution of about 700 ?m, high contrast, and high signal-to-noise ratio. USVA is sensitive enough to detect object motions on the order of nanometers. Possible applications include medical imaging and material evaluation.

Fatemi, Mostafa; Greenleaf, James F.

1999-01-01

133

Full-wave Nonlinear Inverse Scattering for Acoustic and Electromagnetic Breast Imaging  

NASA Astrophysics Data System (ADS)

Acoustic and electromagnetic full-wave nonlinear inverse scattering techniques are explored in both theory and experiment with the ultimate aim of noninvasively mapping the material properties of the breast. There is evidence that benign and malignant breast tissue have different acoustic and electrical properties and imaging these properties directly could provide higher quality images with better diagnostic certainty. In this dissertation, acoustic and electromagnetic inverse scattering algorithms are first developed and validated in simulation. The forward solvers and optimization cost functions are modified from traditional forms in order to handle the large or lossy imaging scenes present in ultrasonic and microwave breast imaging. An antenna model is then presented, modified, and experimentally validated for microwave S-parameter measurements. Using the antenna model, a new electromagnetic volume integral equation is derived in order to link the material properties of the inverse scattering algorithms to microwave S-parameters measurements allowing direct comparison of model predictions and measurements in the imaging algorithms. This volume integral equation is validated with several experiments and used as the basis of a free-space inverse scattering experiment, where images of the dielectric properties of plastic objects are formed without the use of calibration targets. These efforts are used as the foundation of a solution and formulation for the numerical characterization of a microwave near-field cavity-based breast imaging system. The system is constructed and imaging results of simple targets are given. Finally, the same techniques are used to explore a new self-characterization method for commercial ultrasound probes. The method is used to calibrate an ultrasound inverse scattering experiment and imaging results of simple targets are presented. This work has demonstrated the feasibility of quantitative microwave inverse scattering by way of a self-consistent characterization formalism, and has made headway in the same area for ultrasound.

Haynes, Mark Spencer

134

Inferences of Particle Size and Composition From Video-like Images Based on Acoustic Data: Grotto Plume, Main Endeavor Field  

Microsoft Academic Search

Optical and acoustic scattering from particles in a seafloor hydrothermal plume can be related if the particle properties and scattering mechanisms are known. We assume Rayleigh backscattering of sound and Mie forward scattering of light. We then use the particle concentrations implicit in the observed acoustic backscatter intensity to recreate the optical image a camera would see given a particular

K. G. Bemis; P. A. Rona; K. Santilli; J. Dastur; D. Silver

2004-01-01

135

Methods And Systems For Using Reference Images In Acoustic Image Processing  

DOEpatents

A method and system of examining tissue are provided in which a field, including at least a portion of the tissue and one or more registration fiducials, is insonified. Scattered acoustic information, including both transmitted and reflected waves, is received from the field. A representation of the field, including both the tissue and the registration fiducials, is then derived from the received acoustic radiation.

Moore, Thomas L. (Livermore, CA); Barter, Robert Henry (Oakland, CA)

2005-01-04

136

Resolution estimation and bias reduction in acoustic radiation force impulse imaging  

NASA Astrophysics Data System (ADS)

Pathological conditions give rise to mechanical changes in tissue that can be exploited for the purpose of diagnosis and treatment of disease. Elasticity imaging is a field developed to creating images of tissue stiffness by mechanically exciting tissue and tracking the tissue response. Acoustic Radiation Force Impulse (ARFI) imaging is one such modality that measures the micron-scale displacements induced in tissue by local acoustic radiation forces using a high intensity ultrasound pulses generated by a standard diagnostic ultrasound scanner. Ultrasound pulses track displacements that are quantified using conventional correlation-based speckle-tracking methods. Generated displacement images can exhibit improved contrast of diseased tissue than conventional ultrasound techniques. In this thesis, the spatial resolution limits of ARFI imaging have been measured using novel simulation and experimental techniques. The full-width, half-maximum (FWHM) of the point-spread function (PSF), a measure of the resolution limit of an imaging system, was extracted by imaging a tissue-mimicking phantom composed of two bonded materials. The ARFI image of the material interface was an estimate of the step response of the system. The ARFI imaging resolution limit was further explored using FEM/acoustic field simulations and linear shift invariant (LSI) models. The ARFI imaging resolution limit was submillimeter, but was highly dependent on imaging parameters. ARFI axial resolution was limited by the correlation window length and tracking pulse parameters. When the correlation window length was less than 1 mm, FEM and LSI models suggest the mechanical response of the tissue influences the resolution, resulting in a larger FWHM than would be predicted by imaging and signal processing parameters alone. ARFI lateral resolution limit corresponded to the lateral two-way beamwidth of the tracking beam. Measuring ARFI imaging resolution capabilities on small phantom inclusions and tissue ablation lesions proved the validity of the step-response based estimated resolution limits on objects of relevant, circular geometry. ARFI imaging resolution was again primarily a function of imaging and signal processing parameters, in good agreement with modulus step phantom derived results. To improve the ability of ARFI imaging to resolve targets near bright boundaries, a method called envelope weighted normalization (EWN) was developed to reduce amplitude modulation of ultrasound signals, thereby reducing displacement estimation bias.

Menon, Manoj G.

137

Real Time Imaging of Surface Acoustic Waves on Crystals and Microstructures  

NASA Astrophysics Data System (ADS)

The use of acoustic pulses to image materials is well-known in echography or sonar applications. We are extending this field by generating point-excited sound pulses on solid surfaces with ultrashort laser pulses and imaging the resulting surface wave propagation in real time. To see the tiny vibrations of the surface, smaller in amplitude than the dimensions of a single atom, we use another set of laser pulses for scanned probing. The typical surface phonon wavelength is of the order of a few microns, corresponding to frequencies up to 1 GHz. With such a system we can watch coherent acoustic wave packets in two dimensions rippling across crystal surfaces and microscopic landscapes.

Wright, Oliver B.; Matsuda, Osamu; Sugawara, Yoshihiro

2005-06-01

138

Scanning Michelson interferometer for imaging surface acoustic wave f ields  

Microsoft Academic Search

25 nm p Hz, and it is capable of directly measuring SAW's with frequencies ranging from 0.5 MHz up to 1 GHz. The fast scheme used for locating the optimum operation point of the interferometer facilitates high measuring speeds, up to 50,000 pointsh. The measured field image has a lateral resolution of better than 1 mm. The fully optical noninvasive

J. V. Knuuttila; P. T. Tikka; M. M. Salomaa

2000-01-01

139

Vibro-Acoustography: An Imaging Modality Based on Ultrasound-Stimulated Acoustic Emission  

Microsoft Academic Search

We describe theoretical principles of an imaging modality that uses the acoustic response of an object to a highly localized dynamic radiation force of an ultrasound field. In this method, named ultrasound-stimulated vibro-acoustography (USVA), ultrasound is used to exert a low-frequency (in kHz range) force on the object. In response, a portion of the object vibrates sinusoidally in a pattern

Mostafa Fatemi; James F. Greenleaf

1999-01-01

140

Acoustic noise and functional magnetic resonance imaging: current strategies and future prospects.  

PubMed

Functional magnetic resonance imaging (fMRI) has become the method of choice for studying the neural correlates of cognitive tasks. Nevertheless, the scanner produces acoustic noise during the image acquisition process, which is a problem in the study of auditory pathway and language generally. The scanner acoustic noise not only produces activation in brain regions involved in auditory processing, but also interferes with the stimulus presentation. Several strategies can be used to address this problem, including modifications of hardware and software. Although reduction of the source of the acoustic noise would be ideal, substantial hardware modifications to the current base of installed MRI systems would be required. Therefore, the most common strategy employed to minimize the problem involves software modifications. In this work we consider three main types of acquisitions: compressed, partially silent, and silent. For each implementation, paradigms using block and event-related designs are assessed. We also provide new data, using a silent event-related (SER) design, which demonstrate higher blood oxygen level-dependent (BOLD) response to a simple auditory cue when compared to a conventional image acquisition. PMID:12412026

Amaro, Edson; Williams, Steve C R; Shergill, Sukhi S; Fu, Cynthia H Y; MacSweeney, Mairead; Picchioni, Marco M; Brammer, Michael J; McGuire, Philip K

2002-11-01

141

Adapting MRI Acoustic Radiation Force Imaging For In Vivo Human Brain Focused Ultrasound Applications  

PubMed Central

A variety of MRI acoustic radiation force imaging (MR-ARFI) pulse sequences as the means for image guidance of focused ultrasound therapy have been recently developed and tested ex vivo and in animal models. To successfully translate MR-ARFI guidance into human applications, ensuring that MR-ARFI provides satisfactory image quality in the presence of patient motion and deposits safe amount of ultrasound energy during image acquisition is necessary. The first aim of this work was to study the effect of motion on in vivo displacement images of the brain obtained with 2DFT spin-echo MR-ARFI. Repeated bipolar displacement encoding configuration was shown less sensitive to organ motion. The optimal signal-to-noise ratio of displacement images was found for the duration of encoding gradients of 12 ms. The second aim was to further optimize the displacement SNR for a particular tissue type by setting the time offset between the ultrasound emission and encoding based on the tissue response to acoustic radiation force. A method for measuring tissue response non-invasively was demonstrated. Finally, a new method for simultaneous monitoring of tissue heating during MR-ARFI acquisition was presented to enable timely adjustment of the ultrasound energy aimed at ensuring the safety of the MR-ARFI acquisition.

Kaye, Elena A.; Pauly, Kim Butts

2014-01-01

142

Novel methods for acoustic and elastic wave-based subsurface imaging  

NASA Astrophysics Data System (ADS)

Novel, accurate and computationally efficient methods for wave-based subsurface imaging in acoustic and elastic media are developed. The methods are based on Arbitrarily Wide-Angle Wave Equations (AWWE), which are highly-accurate space domain one-way wave equations, formulated in terms of displacement components. Main contributions of this research are as follows: (I) Acoustic-AWWE Imaging, a new time-domain migration technique that is highly accurate for imaging steep dips in heterogeneous media. Similar in form to conventional 15° equation, the acoustic AWWE is implemented using an efficient double-marching explicit finite-difference scheme. Its accuracy and efficiency is studied both analytically and through numerical experiments. The method is able to achieve highly accurate images with only a few times the computational cost of the conventional low-order methods. (II) A new class of highly-accurate Absorbing Boundary Conditions (ABCs) for modeling and imaging with high-order one-way wave equations and parabolic equations. These ABCs, are developed using special imaginary-length finite elements. They effectively absorb the incident wave front and generate artifact-free images with as few as three absorbing layers. They are essential tools in imaging in truncated domains and underwater acoustics. (III) Elastic-AWWE imaging: The first high-order space-domain displacement-based elastic imaging method is developed in this research. The method, which is applicable to complex elastic media, is implemented using a unique downward continuation technique. At each depth step, a half-space is attached to the physical layer to simulate one-way propagation. The half-space is effectively approximated using special imaginary-length finite elements. The method is eventually implemented in frequency-space domain using a finite difference method. Numerical instabilities due to improper mapping of complex wave modes are suppressed by rotating the AWWE parameters in complex wavenumber plane thus adjusting its mapping properties. Effectiveness of the method is illustrated through analytical studies and numerical experiments in homogeneous and heterogeneous elastic media.

Heidari, Amir Homayoun

143

Underwater acoustic imaging using capacitive micromachined ultrasonic transducer arrays  

Microsoft Academic Search

Capacitive micromachined ultrasonic transducers (CMUTs) have recently emerged as an alternative technology to piezoelectric transducers, offering advantages such as wide bandwidth, ease of fabricating large arrays and potential for integration with electronic circuits. In this paper, we present 2D and 3D pulse-echo imaging results using ID linear and 2D rectangular CMUT arrays, respectively. The aim of this paper is to

O. Oralkan; A. S. Ergun; C.-H. Cheng; J. A. Johnson; M. Karaman; B. T. Khuri-Yakub

2002-01-01

144

Acoustic radiation pressure: A 'phase contrast' agent for x-ray phase contrast imaging  

SciTech Connect

We show that the radiation pressure exerted by a beam of ultrasound can be used for contrast enhancement in high-resolution x-ray imaging of tissue and soft materials. Interfacial features of objects are highlighted as a result of both the displacement introduced by the ultrasound and the inherent sensitivity of x-ray phase contrast imaging to density variations. The potential of the method is demonstrated by imaging microscopic tumor phantoms embedded into tissue with a thickness typically presented in mammography. The detection limit of micrometer size masses exceeds the resolution of currently available mammography imaging systems. The directionality of the acoustic radiation force and its localization in space permits the imaging of ultrasound-selected tissue volumes. The results presented here suggest that the method may permit the detection of tumors in soft tissue in their early stage of development.

Bailat, Claude J.; Hamilton, Theron J.; Rose-Petruck, Christoph; Diebold, Gerald J. [Department of Chemistry, Brown University Providence, Rhode Island 02912 (United States)

2004-11-08

145

Two dimensional nonlinear frequency-mixing photo-acoustic imaging of a crack and observation of crack phantoms  

NASA Astrophysics Data System (ADS)

A two-dimensional imaging of a crack by nonlinear frequency-mixing photo-acoustic method is reported. The imaging contrast is due to nonlinear photo-thermo-acoustic processes taking place in case of simultaneous excitation by lasers of thermo-elastic and acoustic waves in the vicinity of the cracks. The images are obtained by scanning of two co-focused laser beams in region of crack location. The first cw laser beam, modulated in intensity at low frequency fL, generates a thermo-elastic wave, which is able to strongly periodically modulate the local crack rigidity up to complete closing/opening of the crack. The second cw laser beam, intensity modulated at much higher frequency fH, generates an acoustic wave incident on the breathing crack. The crack rigidity is also influenced by the stationary non-modulated inhomogeneous thermal stresses caused by the stationary heating of the sample by both lasers. The main contribution to imaging contrast comes from the strong dependence of the reflectivity of acoustic waves on the crack rigidity. The modulation of crack rigidity by thermo-elastic wave leads to the parametric modulation of the reflected acoustic waves and the generation in the spectrum of the acoustic field of the side lobes, which are separated from fH by the integer number of fL. Scan images of a crack with an amplitude dynamics up to 40 dB and a spatial resolution better than 100 ?m, are obtained through the mapping of nonlinear side lobe amplitudes. The observed dependences of the images on the power of the lasers are discussed and the physical explanation of the appearance of crack phantom images at high level of optical excitation is proposed. For comparison and elucidation of spatial resolution issues related to this imaging method, the one-dimensional images, obtained with one laser beam focus position fixed and the second beam focus position scanning, are also presented and discussed.

Mezil, Sylvain; Chigarev, Nikolay; Tournat, Vincent; Gusev, Vitalyi

2013-11-01

146

Acoustic cues to visual detection: a classification image study.  

PubMed

A non-informative sound is known to improve contrast detection thresholds for a synchronous visual target (M. Lippert, N. K. Logothetis, & C. Kayser, 2007). We investigated the spatio-temporal characteristics of the mechanisms underlying this crossmodal effect by using a classification image paradigm specifically suited to investigate perceptual templates across both space and time (P. Neri & D. J. Heeger, 2002). A bright bar was embedded in 2D (space-time) dynamic noise and observers were asked to detect its presence in both unimodal (only visual) and bimodal (audio-visual) conditions. Classification image analysis was performed and the 1st and 2nd order kernels were derived. Our results show that the cross-modal facilitation of detection consists in a reduction of activity of the early mechanisms elicited by the onset of the stimulation and not directly involved in the identification of the target. In fact, the sound sharpens the 2nd order kernels (involved in target detection) by suppressing the activation preceding the target, whereas it does not influence the 1st order kernels. These data suggest that the sound affects some non-linear process involved with the detection of a visual stimulus by, decreasing the activity of contrast energy filters temporally uncorrelated with the target, hence reducing temporal uncertainty. PMID:21562032

Pascucci, David; Megna, Nicola; Panichi, Michela; Baldassi, Stefano

2011-01-01

147

The development and potential of acoustic radiation force impulse (ARFI) imaging for carotid artery plaque characterization.  

PubMed

Stroke is the third leading cause of death and long-term disability in the USA. Currently, surgical intervention decisions in asymptomatic patients are based upon the degree of carotid artery stenosis. While there is a clear benefit of endarterectomy for patients with severe (> 70%) stenosis, in those with high/moderate (50-69%) stenosis the evidence is less clear. Evidence suggests ischemic stroke is associated less with calcified and fibrous plaques than with those containing softer tissue, especially when accompanied by a thin fibrous cap. A reliable mechanism for the identification of individuals with atherosclerotic plaques which confer the highest risk for stroke is fundamental to the selection of patients for vascular interventions. Acoustic radiation force impulse (ARFI) imaging is a new ultrasonic-based imaging method that characterizes the mechanical properties of tissue by measuring displacement resulting from the application of acoustic radiation force. These displacements provide information about the local stiffness of tissue and can differentiate between soft and hard areas. Because arterial walls, soft tissue, atheromas, and calcifications have a wide range in their stiffness properties, they represent excellent candidates for ARFI imaging. We present information from early phantom experiments and excised human limb studies to in vivo carotid artery scans and provide evidence for the ability of ARFI to provide high-quality images which highlight mechanical differences in tissue stiffness not readily apparent in matched B-mode images. This allows ARFI to identify soft from hard plaques and differentiate characteristics associated with plaque vulnerability or stability. PMID:21447606

Allen, Jason D; Ham, Katherine L; Dumont, Douglas M; Sileshi, Bantayehu; Trahey, Gregg E; Dahl, Jeremy J

2011-08-01

148

An In Vitro Assessment of Acoustic Radiation Force Impulse Imaging for Visualizing Cardiac Radiofrequency Ablation Lesions  

PubMed Central

Introduction Lesion placement and transmurality are critical factors in the success of cardiac transcatheter radiofrequency ablation (RFA) treatments for supraventricular arrhythmias. This study investigated the capabilities of catheter transducer based acoustic radiation force impulse (ARFI) ultrasound imaging for quantifying ablation lesion dimensions. Methods and Results RFA lesions were created in vitro in porcine ventricular myocardium and imaged with an intracardiac ultrasound catheter transducer capable of acquiring spatially registered B-mode and ARFI images. The myocardium was sliced along the imaging plane and photographed. The maximum ARFI-induced displacement images of the lesion were normalized and spatially registered with the photograph by matching the surfaces of the tissue in the B-mode and photographic images. The lesion dimensions determined by a manual segmentation of the photographed lesion based on the visible discoloration of the tissue were compared to automatic segmentations of the ARFI image using two different calculated thresholds. ARFI imaging accurately localized and sized the lesions within the myocardium. Differences in the maximum lateral and axial dimensions were statistically below 2 mm and 1 mm respectively for the two thresholding methods, with mean percent overlap of 68.7±5.21% and 66.3±8.4% for the two thresholds used. Conclusion ARFI imaging is capable of visualizing myocardial RFA lesion dimensions to within 2 mm in vitro. Visualizing lesions during transcatheter cardiac ablation procedures could improve the success of the treatment by imaging lesion line discontinuity and potentially reducing the required number of ablation lesions and procedure time.

Eyerly, Stephanie A.; Hsu, Stephen J.; Agashe, Shruti H.; Trahey, Gregg E.; Li, Yang; Wolf, Patrick D.

2009-01-01

149

Acoustic Radiation Force Impulse Imaging of Mechanical Stiffness Propagation in Myocardial Tissue  

PubMed Central

Acoustic radiation force impulse (ARFI) imaging has been shown to be capable of imaging local myocardial stiffness changes throughout the cardiac cycle. Expanding on these results, the authors present experiments using cardiac ARFI imaging to visualize and quantify the propagation of mechanical stiffness during ventricular systole. In vivo ARFI images of the left ventricular free wall of two exposed canine hearts were acquired. Images were formed while the heart was externally paced by one of two electrodes positioned on the epicardial surface and either side of the imaging plane. Two-line M-mode ARFI images were acquired at a sampling frequency of 120 Hz while the heart was paced from an external stimulating electrode. Two-dimensional ARFI images were also acquired, and an average propagation velocity across the lateral field of view was calculated. Directions and speeds of myocardial stiffness propagation were measured and compared with the propagations derived from the local electrocardiogram (ECG), strain, and tissue velocity measurements estimated during systole. In all ARFI images, the direction of myocardial stiffness propagation was seen to be away from the stimulating electrode and occurred with similar velocity magnitudes in either direction. When compared with the local epicardial ECG, the mechanical stiffness waves were observed to travel in the same direction as the propagating electrical wave and with similar propagation velocities. In a comparison between ARFI, strain, and tissue velocity imaging, the three methods also yielded similar propagation velocities.

Hsu, Stephen J.; Byram, Brett C.; Bouchard, Richard R.; Dumont, Douglas M.; Wolf, Patrick D.; Trahey, Gregg E.

2012-01-01

150

Fish population dynamics revealed by instantaneous continental-shelf scale acoustic imaging  

NASA Astrophysics Data System (ADS)

Video images of fish population densities over vast areas of the New Jersey continental shelf have been produced from acoustic data collected on a long range bistatic sonar system during the Acoustic Clutter 2003 experiment. Areal fish population densities were obtained after correcting the acoustic data for two-way transmission loss modeled using the range-dependent parabolic equation, spatially varying beampattern of the array, source level and mean target strength per fish. The wide-area fish density images reveal the temporal evolution of fish school distributions, their migration, as well as shoal formation and fragmentation at 50 s interval. Time series of the fish population within various density thresholds were made over the period of a day in an area containing millions of fish that at some instances formed a massive shoal extending over 12 km. The analysis shows that fish population in the area can be decomposed into a stable ambient population from lower-fish-density regions and a time-varying population composed from higher-density regions. Estimates of the differential speed between population centers of various shoals show that the average speed is on the order of a slow-moving surface vessel or submarine.

Ratilal, Purnima; Symonds, Deanelle; Makris, Nicholas C.; Nero, Redwood

2005-04-01

151

Full-Wave Iterative Image Reconstruction in Photoacoustic Tomography With Acoustically Inhomogeneous Media  

PubMed Central

Existing approaches to image reconstruction in photoacoustic computed tomography (PACT) with acoustically heterogeneous media are limited to weakly varying media, are computationally burdensome, and/or cannot effectively mitigate the effects of measurement data incompleteness and noise. In this work, we develop and investigate a discrete imaging model for PACT that is based on the exact photoacoustic (PA) wave equation and facilitates the circumvention of these limitations. A key contribution of the work is the establishment of a procedure to implement a matched forward and backprojection operator pair associated with the discrete imaging model, which permits application of a wide-range of modern image reconstruction algorithms that can mitigate the effects of data incompleteness and noise. The forward and backprojection operators are based on the k-space pseudospectral method for computing numerical solutions to the PA wave equation in the time domain. The developed reconstruction methodology is investigated by use of both computer-simulated and experimental PACT measurement data.

Huang, Chao; Wang, Kun; Nie, Liming; Wang, Lihong V.; Anastasio, Mark A.

2014-01-01

152

Advances in acoustic microscopy and high resolution ultrasonic imaging: from principles to new applications  

NASA Astrophysics Data System (ADS)

The goal of this lecture is to provide an overview of the recent advances in high-resolution ultrasonic imaging principles and techniques and their biomedical applications. This lecture will offer a number of new results from leading research groups worldwide who are engaged in aspects of the development of novel physical principles, new methods, or the implementation of modern technological solutions into current high resolution imaging techniques and methods. Together with the abovementioned academic and practical avenues in high resolution ultrasonic imaging research, intriguing scientific discussions, which have recently surfaced and will hopefully continue to bear fruit in the future, will be reviewed. Another goal of this lecture is to encourage a new generation of researchers to be more involved in research and development in the field to realize the great potential of high resolution acoustic imaging and advance the progress into its various biomedical applications.

Maev, Roman Gr.

2014-03-01

153

Novel acoustic radiation force impulse imaging methods for visualization of rapidly moving tissue.  

PubMed

Acoustic radiation force impulse (ARFI) imaging has been demonstrated to be capable of visualizing changes in local myocardial stiffness through a normal cardiac cycle. As a beating heart involves rapidly-moving tissue with cyclically-varying myocardial stiffness, it is desirable to form images with high frame rates and minimize susceptibility to motion artifacts. Three novel ARFI imaging methods, pre-excitation displacement estimation, parallel-transmit excitation and parallel-transmit tracking, were implemented. Along with parallel-receive, ECG-gating and multiplexed imaging, these new techniques were used to form high-quality, high-resolution epicardial ARFI images. Three-line M-mode, extended ECG-gated three-line M-mode and ECG-gated two-dimensional ARFI imaging sequences were developed to address specific challenges related to cardiac imaging. In vivo epicardial ARFI images of an ovine heart were formed using these sequences and the quality and utility of the resultant ARFI-induced displacement curves were evaluated. The ARFI-induced displacement curves demonstrate the potential for ARFI imaging to provide new and unique information into myocardial stiffness with high temporal and spatial resolution. PMID:19771961

Hsu, Stephen J; Bouchard, Richard R; Dumont, Douglas M; Ong, Cheng W; Wolf, Patrick D; Trahey, Gregg E

2009-07-01

154

Voice assessment: Updates on perceptual, acoustic, aerodynamic, and endoscopic imaging methods  

PubMed Central

Purpose of review This paper describes recent advances in perceptual, acoustic, aerodynamic, and endoscopic imaging methods for assessing voice production. Recent findings Perceptual assessment Speech-language pathologists are being encouraged to use the new CAPE-V inventory for auditory perceptual assessment of voice quality, and recent studies have provided new insights into listener reliability issues that have plagued subjective perceptual judgments of voice quality. Acoustic assessment Progress is being made on the development of algorithms that are more robust for analyzing disordered voices, including the capability to extract voice quality-related measures from running speech segments. Aerodynamic assessment New devices for measuring phonation threshold air pressures and air flows have the potential to serve as sensitive indices of glottal phonatory conditions, and recent developments in aeroacoustic theory may provide new insights into laryngeal sound production mechanisms. Endoscopic imaging The increased light sensitivity of new ultra high-speed color digital video processors is enabling high-quality endoscopic imaging of vocal fold tissue motion at unprecedented image capture rates, which promises to provide new insights into mechanisms of normal and disordered voice production. Summary Some of the recent research advances in voice quality assessment could be more readily adopted into clinical practice, while others will require further development.

Mehta, Daryush D.; Hillman, Robert E.

2013-01-01

155

Intracardiac Acoustic Radiation Force Impulse Imaging: A Novel Imaging Method for Intraprocedural Evaluation of Radiofrequency Ablation Lesions  

PubMed Central

Background Arrhythmia recurrence after cardiac radiofrequency ablation (RFA) for atrial fibrillation (AF) has been linked to conduction through discontinuous lesion lines. Intraprocedural visualization and corrective ablation of lesion line discontinuities could decrease post-procedure AF recurrence. Intracardiac acoustic radiation force impulse (ARFI) imaging is a new imaging technique that visualizes RFA lesions by mapping the relative elasticity contrast between compliant-unablated and stiff-RFA treated myocardium. Objective To determine if intraprocedure ARFI images can identify RFA treated myocardium in vivo. Methods In eight canines, an electroanatomical mapping (EAM) guided intracardiac echo catheter (ICE) was used to acquire 2D ARFI images along right atrial ablation lines before and after RFA. ARFI images were acquired during diastole with the myocardium positioned at the ARFI focus (1.5 cm) and parallel to the ICE transducer for maximal and uniform energy delivery to the tissue. Three reviewers categorized each ARFI image as depicting no lesion, non-contiguous, or contiguous lesion. For comparison, three separate reviewers confirmed RFA lesion presence and contiguity based on functional conduction block at the imaging plane location on EAM activation maps. Results Ten percent of ARFI images were discarded due to motion artifacts. Reviewers of the ARFI images detected RFA-treated sites with high sensitivity (95.7%) and specificity (91.5%). Reviewer identification of contiguous lesion had 75.3% specificity and 47.1% sensitivity. Conclusions Intracardiac ARFI imaging was successful in identifying endocardial RFA treatment when specific imaging conditions were maintained. Further advances in ARFI imaging technology would facilitate a wider range of imaging opportunities for clinical lesion evaluation.

Eyerly, Stephanie A.; Bahnson, Tristram D.; Koontz, Jason I.; Bradway, David P.; Dumont, Douglas M.; Trahey, Gregg E.; Wolf, Patrick D.

2012-01-01

156

Using numerical models and volume rendering to interpret acoustic imaging of hydrothermal flow  

NASA Astrophysics Data System (ADS)

Our acoustic imaging system will be installed onto the Neptune Canada observatory at the Main Endeavour Field, Juan de Fuca Ridge, which is a Ridge 2000 Integrated Study Site. Thereafter, 16-30 Gb of acoustic imaging data will be collected daily. We are developing a numerical model of merging plumes that will be used to guide expectations and volume rendering software that transforms volumetric acoustic data into photo-like images. Hydrothermal flow is modeled as a combination of merged point sources which can be configured in any geometry. The model stipulates the dissipation or dilution of the flow and uses potential fields and complex analysis to combine the entrainment fields produced by each source. The strengths of this model are (a) the ability to handle a variety of scales especially the small scale as the potential fields can be specified with an effectively infinite boundary condition, (b) the ability to handle line, circle and areal source configurations, and (c) the ability to handle both high temperature focused flow and low temperature diffuse flow. This model predicts the vertical and horizontal velocities and the spatial distribution of effluent from combined sources of variable strength in a steady ambient velocity field. To verify the accuracy of the model’s results, we compare the model predictions of plume centerlines for the merging of two relatively strong point sources with the acoustic imaging data collected at Clam Acres, Southwest Vent Field, EPR 21°N in 1990. The two chimneys are 3.5 m apart and the plumes emanating from their tops merge approximately 18 mab. The model is able to predict the height of merging and the bending of the centerlines. Merging is implicitly observed at Grotto Vent, Main Endeavour Field, in our VIP 2000 data from July 2000: although there are at least 5 vigorous black smokers only a single plume is discernable in the acoustic imaging data. Furthermore, the observed Doppler velocity data increases with height, consistent with multiple merging plumes. The numerical model assumes 5 sources in a circle and predicts that the plumes merge between 10 m and 15 m above the vents resulting in a 3-fold increase in velocity. The predictions of the numerical model are sensitive to the interplay between vent velocity, ambient velocity and entrainment rates. To better illustrate variations in expansion with ambient velocity, we have developed a two-phase volume rendering technique which substantially improves the illustration of expansion rates. The numerical model is also able to make predictions about the areal distribution of effluent from diffuse flow by modeling it as multiple weak sources. Comparisons with diffuse flow maps, particularly those based on July 2000 data from our acoustic imaging, suggest that interpretation of diffuse flow maps (and in situ temperature measurements) requires knowledge of the ambient currents in order to gauge how far the effluent may have shifted from its source, as merging may result in an increase in rise rate.

Bemis, K. G.; Bennett, K.; Takle, J.; Rona, P. A.; Silver, D.

2009-12-01

157

77 FR 321 - Section 4(f) Policy Paper  

Federal Register 2010, 2011, 2012, 2013

...FHWA-2011-0125] Section 4(f) Policy Paper AGENCY: Federal Highway Administration...comments on a draft Section 4(f) Policy Paper that will provide guidance on the procedures...of the proposed Section 4(f) Policy Paper is available for download and public...

2012-01-04

158

A new matlab® library to interactively analyze logging data and borehole wall images and to recenter borehole acoustic images  

NASA Astrophysics Data System (ADS)

Observations acquired downhole are basically of two types : standard logs and borehole wall images, i.e. scalars versus depth and images versus depth. While many freeware programs can deal with standard logs, very few are able to treat simultaneously and interactively both scalars and images, including standard treatments commonly applied to such data. The developed matlab library offers such a possibility, in the form of a set of matlab routines based on command line operations that can be injected in matlab scripts for automatic data treatments and plotting procedures. An integrated analysis of downhole observations at first requires to correct the depths coming from various tools so that they all are the same. The provided library enables such corrections, and it in particular can interactively display the tendency defined by the plotted links, so as to detect and possibly remove the links that appear not to be coherent with the others. It also includes standard pre-treatments like interactive removal of absurd or wrong points, dephasing and non dephasing filters, derivations, integrations, decimations, resampling, amplitude calibrations, cross plots, etc. It besides enables to derive and display in 3D the borehole geometry from continuous monitorings of the magnetic field and the borehole tilt. Finally it includes more specific routines dedicated to the analysis of acoustic images. Among them are included the standard 3D, spiral and cross section plots, plus a new routine that enables to recenter the tool axis at the borehole axis before the images are generated. This very last routines appears to drastically improve the information delivered by the acoustic images where the tool is badly centered. The impact of all provided routines is illustrated with a data set coming from the Lavalette Experimental Center in France, an experimental site near the Montpellier university with two 100 m deep boreholes that is devoted to borehole geophysics research and teaching.

Pinettes, P.

2003-04-01

159

Assessing and improving acoustic radiation force image quality using a 1.5D transducer design  

PubMed Central

A 1.5D transducer array was developed to improve acoustic radiation force impulse (ARFI) imaging signal-to-noise ratio (SNRARFI) and image contrast relative to a conventional 1D array. To predict performance gains from the proposed 1.5D transducer array, an analytical model for SNRARFI upper bound was derived. The analytical model and 1.5D ARFI array were validated using a finite element model-based numerical simulation framework. The analytical model demonstrated good agreement with numerical results (correlation coefficient = 0.995), and simulated lesion images yielded a significant (2.92 dB; p < 0.001) improvement in contrast-to-noise ratio when rendered using the 1.5D ARFI array.

Dhanaliwala, Ali .H.; Hossack, John A.; Mauldin, F. William

2014-01-01

160

Imaging of acoustic waves induced by excimer laser ablation of the cornea  

NASA Astrophysics Data System (ADS)

In this present study a pump-and-probe imaging set up was arranged to image and analyze the evolution of pressure waves induced by ArF ablation of the cornea, during their propagation into the eyeball. In vitro experiments simulating the effects of clinical PRK have been performed by using an artificial model of the human eyeball, composed of a cell filled with hyaluronic acid gel with a sample of freshly excised bovine cornea placed on the gel surface. LAser irradiation was provided at a fluence of 180 mJ/cm2. Irradiation spot diameters were varied in the range 2.0-5.0 mm. Images of the traveling acoustic waves evidenced diffraction effects, related to the diameter of laser spots on the corneal surface.

Rossi, F.; Pini, Roberto; Siano, S.; Salimbeni, Renzo

1996-12-01

161

Acoustic Image Reconstruction from Adaptive Microphone Array Signals Using Back Projection  

NASA Astrophysics Data System (ADS)

We propose a new technique for acoustic imaging that employs a back-projection algorithm to process signals from a static ultrasonic microphone array. To obtain the projection data for a target, we integrate the time distribution of received signal powers gained by pulse compression with the Radon transform of a sound field in polar coordinates. The proposed method is expected to improve angular resolution. In this paper, we describe the principle of this algorithm, explaining how it improves the resolution and performs better than conventional methods. Deconvolution is used to improve the quality of the images obtained. We have conducted computer simulations to verify the performance of the proposed algorithm. From these simulations, the angular resolution of the images achieved by the proposed technique was shown to be double that obtained by a conventional beamforming method. In our future work, we plan to conduct experiments with real environments and investigate the theoretical aspects of the proposed method more deeply.

Mizutani, Kyohei; Sugimoto, Masanori; Hashizume, Hiromichi

162

Imaging of Acoustically Coupled Oscillations Due to Flow Past a Shallow Cavity: Effect of Cavity Length Scale  

SciTech Connect

Flow-acoustic interactions due to fully turbulent inflow past a shallow axisymmetric cavity mounted in a pipe are investigated using a technique of high-image-density particle image velocimetry in conjunction with unsteady pressure measurements. This imaging leads to patterns of velocity, vorticity, streamline topology, and hydrodynamic contributions to the acoustic power integral. Global instantaneous images, as well as time-averaged images, are evaluated to provide insight into the flow physics during tone generation. Emphasis is on the manner in which the streamwise length scale of the cavity alters the major features of the flow structure. These image-based approaches allow identification of regions of the unsteady shear layer that contribute to the instantaneous hydrodynamic component of the acoustic power, which is necessary to maintain a flow tone. In addition, combined image analysis and pressure measurements allow categorization of the instantaneous flow patterns that are associated with types of time traces and spectra of the fluctuating pressure. In contrast to consideration based solely on pressure spectra, it is demonstrated that locked-on tones may actually exhibit intermittent, non-phase-locked images, apparently due to low damping of the acoustic resonator. Locked-on flow tones (without modulation or intermittency), locked-on flow tones with modulation, and non-locked-on oscillations with short-term, highly coherent fluctuations are defined and represented by selected cases. Depending on which of,these regimes occur, the time-averaged Q (quality)-factor and the dimensionless peak pressure are substantially altered.

P. Oshkai; M. Geveci; D. Rockwell; M. Pollack

2002-12-12

163

Normal Values in Healthy Liver in Central India by Acoustic Radiation Force Impulse Imaging  

PubMed Central

Aim: The aim of this study was to reliably measure and define the normal wave velocity values in a healthy liver by Acoustic radiation force impulse imaging (ARFI) technology in central India. Subjects and Methods: Fifty two healthy volunteers underwent acoustic radiation force impulse imaging tissue quantification and were enrolled in this prospective study. All patients were examined clinically by a clinician and blood samples were drawn and tested for liver function test and viral markers for hepatitis B virus, hepatitis C virus. The healthy volunteers were then examined by a certified sonologist and twenty-four measurements per subject were obtained and evaluations were performed. Statistical comparison of all mean data was performed with Student’s t-test was done. A valueof p < 0.05 was considered significant. A comparative analysis was performed, and interclasscorrelation coefficients were calculated. Results: The sonologist obtained 416 measurements. A statistically significant differencewas found between the mean shear wave velocity values in deep of the right lobe of the liver and the values obtained on the surface of the right lobe (1.2vs1.05 m/s) and between the mean values obtained deep in the right lobe and those obtained deep in the left lobe (1.2vs 1.0 m/s). In almost all cases, the shear wave speeds were between 1 and 2 m/s. Conclusion: Acoustic radiation force impulse imaging quantification of hepatic tissue is more reproducible when applied to the deeper portion of the right lobe of the liver.

Raghuwanshi, Babita; Jain, Niti; Jain, Manish

2013-01-01

164

Intracardiac acoustic radiation force impulse (ARFI) and shear wave imaging in pigs with focal infarctions.  

PubMed

Four pigs, three with focal infarctions in the apical intraventricular septum (IVS) and/or left ventricular free wall (LVFW), were imaged with an intracardiac echocardiography (ICE) transducer. Custom beam sequences were used to excite the myocardium with focused acoustic radiation force (ARF) impulses and image the subsequent tissue response. Tissue displacement in response to the ARF excitation was calculated with a phase-based estimator, and transverse wave magnitude and velocity were each estimated at every depth. The excitation sequence was repeated rapidly, either in the same location to generate 40 Hz M-modes at a single steering angle, or with a modulated steering angle to synthesize 2-D displacement magnitude and shear wave velocity images at 17 points in the cardiac cycle. Both types of images were acquired from various views in the right and left ventricles, in and out of infarcted regions. In all animals, acoustic radiation force impulse (ARFI) and shear wave elasticity imaging (SWEI) estimates indicated diastolic relaxation and systolic contraction in noninfarcted tissues. The M-mode sequences showed high beat-to-beat spatio-temporal repeatability of the measurements for each imaging plane. In views of noninfarcted tissue in the diseased animals, no significant elastic remodeling was indicated when compared with the control. Where available, views of infarcted tissue were compared with similar views from the control animal. In views of the LVFW, the infarcted tissue presented as stiff and non-contractile compared with the control. In a view of the IVS, no significant difference was seen between infarcted and healthy tissue, whereas in another view, a heterogeneous infarction was seen to be presenting itself as non-contractile in systole. PMID:25004538

Hollender, P; Bradway, D; Wolf, P; Goswami, R; Trahey, G

2013-08-01

165

A geometrical approach to the surface-fitting problem in underwater three-dimensional acoustic images  

NASA Astrophysics Data System (ADS)

This paper presents a technique for the segmentation of three-dimensional images acquired by an acoustic camera. The proposed algorithm aims at identifying reliable data derived from objects present in an underwater scene in order to determine elementary components. In this way, the estimation of geometrical parameters for each component is performed with the aim of subsequently performing object-recognition and reconstruction phases. The algorithm is composed of a series of processing steps, starting from a coarse segmentation stage, wherein the most reliable image points likely to correspond to man-made objects are identified, and leading to a refinement phase, in which accurate re-segmentation is performed, to accurately determine points belonging to the same surface. Once objects' components have been identified, geometrical parameters are estimated in order to build an adequate data structure that is easily comparable with a model database. In other words, it exploits the geometrical properties embedded in the sparse and noisy three-dimensional information to group the points better by fitting the current quadric surface. This algorithm can be applied for the reconstruction of virtual environments from acoustic data aimed at robotic applications (e.g. vehicle navigation) and was actually used in an off-shore application consisting of the recognition of the scene seen by an underwater vehicle navigating close to an oil rig. Results on synthetic images proved the goodness and the accuracy of the approach and real examples are also provided to prove the robustness and accuracy of the method.

Murino, Vittorio; Trucco, Andrea

1999-12-01

166

Frame Rate Considerations for Real-Time Abdominal Acoustic Radiation Force Impulse Imaging  

PubMed Central

With the advent of real-time Acoustic Radiation Force Impulse (ARFI) imaging, elevated frame rates are both desirable and relevant from a clinical perspective. However, fundamental limitations on frame rates are imposed by thermal safety concerns related to incident radiation force pulses. Abdominal ARFI imaging utilizes a curvilinear scanning geometry that results in markedly different tissue heating patterns than those previously studied for linear arrays or mechanically-translated concave transducers. Finite Element Method (FEM) models were used to simulate these tissue heating patterns and to analyze the impact of tissue heating on frame rates available for abdominal ARFI imaging. A perfusion model was implemented to account for cooling effects due to blood flow and frame rate limitations were evaluated in the presence of normal, reduced and negligible tissue perfusions. Conventional ARFI acquisition techniques were also compared to ARFI imaging with parallel receive tracking in terms of thermal efficiency. Additionally, thermocouple measurements of transducer face temperature increases were acquired to assess the frame rate limitations imposed by cumulative heating of the imaging array. Frame rates sufficient for many abdominal imaging applications were found to be safely achievable utilizing available ARFI imaging techniques.

Fahey, Brian J.; Palmeri, Mark L.; Trahey, Gregg E.

2008-01-01

167

Acoustic Radiation Force Impulse (ARFI) Imaging of Zebrafish Embryo by High-Frequency Coded Excitation Sequence  

PubMed Central

Acoustic radiation force impulse (ARFI) imaging has been developed as a non-invasive method for quantitative illustration of tissue stiffness or displacement. Conventional ARFI imaging (2–10 MHz) has been implemented in commercial scanners for illustrating elastic properties of several organs. The image resolution, however, is too coarse to study mechanical properties of micro-sized objects such as cells. This article thus presents a high-frequency coded excitation ARFI technique, with the ultimate goal of displaying elastic characteristics of cellular structures. Tissue mimicking phantoms and zebrafish embryos are imaged with a 100-MHz lithium niobate (LiNbO3) transducer, by cross-correlating tracked RF echoes with the reference. The phantom results show that the contrast of ARFI image (14 dB) with coded excitation is better than that of the conventional ARFI image (9 dB). The depths of penetration are 2.6 and 2.2 mm, respectively. The stiffness data of the zebrafish demonstrate that the envelope is harder than the embryo region. The temporal displacement change at the embryo and the chorion is as large as 36 and 3.6 ?m. Consequently, this high-frequency ARFI approach may serve as a remote palpation imaging tool that reveals viscoelastic properties of small biological samples.

Park, Jinhyoung; Lee, Jungwoo; Lau, Sien Ting; Lee, Changyang; Huang, Ying; Lien, Ching-Ling; Shung, K. Kirk

2011-01-01

168

Frame rate considerations for real-time abdominal acoustic radiation force impulse imaging.  

PubMed

With the advent of real-time Acoustic Radiation Force Impulse (ARFI) imaging, elevated frame rates are both desirable and relevant from a clinical perspective. However, fundamental limitations on frame rates are imposed by thermal safety concerns related to incident radiation force pulses. Abdominal ARFI imaging utilizes a curvilinear scanning geometry that results in markedly different tissue heating patterns than those previously studied for linear arrays or mechanically-translated concave transducers. Finite Element Method (FEM) models were used to simulate these tissue heating patterns and to analyze the impact of tissue heating on frame rates available for abdominal ARFI imaging. A perfusion model was implemented to account for cooling effects due to blood flow and frame rate limitations were evaluated in the presence of normal, reduced and negligible tissue perfusions. Conventional ARFI acquisition techniques were also compared to ARFI imaging with parallel receive tracking in terms of thermal efficiency. Additionally, thermocouple measurements of transducer face temperature increases were acquired to assess the frame rate limitations imposed by cumulative heating of the imaging array. Frame rates sufficient for many abdominal imaging applications were found to be safely achievable utilizing available ARFI imaging techniques. PMID:17521042

Fahey, Brian J; Palmeri, Mark L; Trahey, Gregg E

2006-10-01

169

Contrast in Intracardiac Acoustic Radiation Force Impulse Images of Radiofrequency Ablation Lesions  

PubMed Central

We have previously shown that intracardiac acoustic radiation force impulse (ARFI) imaging visualizes tissue stiffness changes caused by radiofrequency ablation (RFA). The objectives of this in vivo study were to (1) quantify measured ARFI-induced displacements in RFA lesion and unablated myocardium and (2) calculate the lesion contrast (C) and contrast-to-noise ratio (CNR) in two-dimensional ARFI and conventional intracardiac echo images. In eight canine subjects, an ARFI imaging-electroanatomical mapping system was used to map right atrial ablation lesion sites and guide the acquisition of ARFI images at these sites before and after ablation. Readers of the ARFI images identified lesion sites with high sensitivity (90.2%) and specificity (94.3%) and the average measured ARFI-induced displacements were higher at unablated sites (11.23 ± 1.71 ?m) than at ablated sites (6.06 ± 0.94 ?m). The average lesion C (0.29 ± 0.33) and CNR (1.83 ± 1.75) were significantly higher for ARFI images than for spatially registered conventional B-mode images (C = ?0.03 ± 0.28, CNR = 0.74 ± 0.68).

Eyerly, Stephanie A.; Bahnson, Tristram D.; Koontz, Jason I.; Bradway, David P.; Dumont, Douglas M.; Trahey, Gregg E.; Wolf, Patrick D.

2014-01-01

170

Image processing and data acquisition optimization for acoustic radiation force impulse imaging of in vivo breast masses  

NASA Astrophysics Data System (ADS)

Acoustic Radiation Force Impulse (ARFI) imaging utilizes brief, high-energy acoustic pulses to excite tissue and ultrasonic correlation based tracking methods to monitor the resulting tissue displacement, which reflects the relative mechanical properties of tissue (i.e. stiffer tissue displaces less). ARFI image contrast is optimized utilizing tightly focused radiation force excitations at multiple axial and lateral locations throughout a 2D field of view. In an ongoing, IRB approved, clinical study, suspicious breast lesions are interrogated in vivo via multi-focal-zone ARFI prior to undergoing core biopsy. A Siemens SONOLINE Antares (TM) scanner and VF10-5 probe were configured to acquire ARFI data from multiple focal-zones and lateral locations. Data was acquired in real-time, and processed off-line. Processing included: filtering, parametric data analysis, normalization and combination of the multiple focal-zone data, and automatic edge detection. ARFI sequences were designed with varying pushing pulse frequencies and intensities. Contrast to noise ratio was evaluated in a tissue mimicking phantom for lesions at different depths using the different pushing pulse sequences. For shallower lesions (depth=10mm), CNR was higher than for deeper lesions, and did not vary appreciably for the different push sequences. For deeper lesions (depth=20mm), CNR increased with increasing push pulse intensity and decreasing push pulse frequency. With the pushing pulse transmit intensity calibrated (in a homogeneous phantom) to achieve uniform displacement at all axial depths, in vivo results yielded poor SNR at depth and did not achieve overall uniform displacement. In vivo, image quality improved with increasing push pulse intensity. To date, 27 masses have been interrogated using multi-focal-zone ARFI and overall good structural agreement exists between B-mode and ARFI images. Normalization and blending facilitate image generation from ARFI interrogation using different intensities at different focal depths.

Sharma, Amy; Trahey, Gregg; Frinkley, Kristin; Soo, Mary Scott; Palmeri, Mark; Nightingale, Kathryn

2005-04-01

171

The Development and Potential of Acoustic Radiation Force Impulse (ARFI) Imaging for Carotid Artery Plaque Characterization  

PubMed Central

Stroke is the third leading cause of death and long-term disability in the U.S. Currently, surgical intervention decisions in asymptomatic patients are based upon the degree of carotid artery stenosis. While there is a clear benefit of endarterectomy for patients with severe (>70%) stenosis, in those with high/moderate (50–69%) stenosis the evidence is less clear. Evidence suggests ischemic stroke is associated less with calcified and fibrous plaques than with those containing softer tissue, especially when this it is accompanied by a thin fibrous cap. A reliable mechanism for the identification of individuals with atherosclerotic plaques which confer the highest risk for stroke is fundamental to the selection of patients for vascular interventions. Acoustic Radiation Force Impulse (ARFI) imaging is a new ultrasonic-based imaging method that characterizes the mechanical properties of tissue by measuring displacement resulting from applied short duration acoustic radiation force. These displacements provide information about the local mechanical properties of tissue and can differentiate between soft and hard areas. Because arterial walls, soft tissue, atheromas, and calcifications have a wide range in their stiffness properties, they represent excellent candidates for ARFI imaging. We present information from early phantom experiments and excised human limb studies to in vivo carotid artery scans and provide evidence for the ability of ARFI to provide high quality images which highlight mechanical differences in tissue stiffness not readily apparent in matched B-mode images. This allows ARFI to identify soft from hard plaques and differentiate characteristics associated with plaque vulnerability or stability.

Allen, Jason D.; Ham, Katherine L.; Dumont, Douglas M.; Sileshi, Bantayehu; Trahey, Gregg E.; Dahl, Jeremy J.

2012-01-01

172

Acoustic radiation force impulse imaging of vulnerable plaques: a finite element method parametric analysis.  

PubMed

Plaque rupture is the most common cause of complications such as stroke and coronary heart failure. Recent histopathological evidence suggests that several plaque features, including a large lipid core and a thin fibrous cap, are associated with plaques most at risk for rupture. Acoustic Radiation Force Impulse (ARFI) imaging, a recently developed ultrasound-based elasticity imaging technique, shows promise for imaging these features noninvasively. Clinically, this could be used to distinguish vulnerable plaques, for which surgical intervention may be required, from those less prone to rupture. In this study, a parametric analysis using Finite Element Method (FEM) models was performed to simulate ARFI imaging of five different carotid artery plaques across a wide range of material properties. It was demonstrated that ARFI imaging could resolve the softer lipid pool from the surrounding, stiffer media and fibrous cap and was most dependent upon the stiffness of the lipid pool component. Stress concentrations due to an ARFI excitation were located in the media and fibrous cap components. In all cases, the maximum Von Mises stress was<1.2 kPa. In comparing these results with others investigating plaque rupture, it is concluded that while the mechanisms may be different, the Von Mises stresses imposed by ARFI imaging are orders of magnitude lower than the stresses associated with blood pressure. PMID:23122224

Doherty, Joshua R; Dumont, Douglas M; Trahey, Gregg E; Palmeri, Mark L

2013-01-01

173

Density Change of an Oxidized Nuclear Graphite by Acoustic Microscopy and Image Processing  

SciTech Connect

The strong correlation between the density and the physical and mechanical properties of graphite suggests that the method of nondestructive density evaluation could be developed into a characterization technique of great value for the overall improvement of safety of graphite moderator reactors. In this study, the oxidation-induced density changes in nuclear graphite for VHTR were determined by a conventional destructive bulk density measurement method (BM), and by a new non-destructive method based on acoustic microscopy and image processing (AM). The results were compared in order to validate the applicability of the latter method. For a direct comparison of the results from both measurements, two specimens were prepared from a cylindrical graphite sample (1 inch diameter and 1 inch height, oxidized to 10% weight loss at 700 oC in air for 5 hours). The specimens were used for characterization by BM and AM methods, respectively. The results show that, even with a large standard deviation of the AM, the density changing trend from both methods appeared the same. Present observation may be attributed to the fact that AM images reflect characteristic density changes of the graphite sample through the acoustic impedance changes. This study demonstrates the possibility of using AM as a nondestructive technique for the evaluation of density changes in graphite when a database is prepared through a systematic series of experiments.

Chi, Se Hwan [Korea Atomic Energy Research Institute; Contescu, Cristian I [ORNL; Burchell, Timothy D [ORNL

2009-01-01

174

Local indentation modulus characterization of diamondlike carbon films by atomic force acoustic microscopy two contact resonance frequencies imaging technique  

SciTech Connect

Two contact resonance frequencies atomic force acoustic microscopy imaging technique has been used to evaluate local indentation modulus of a diamondlike carbon film deposited on a molybdenum foil by laser ablation from glassy carbon target. Acoustic images were obtained by measuring both first and second contact resonance frequency at each point of the scanned area, and then numerically evaluating local contact stiffness and reconstructing an indentation modulus bidimensional pattern. The wide difference of the indentation modulus values allows to detect the presence of residual glassy carbon agglomerates in the diamondlike carbon film.

Passeri, D.; Bettucci, A.; Germano, M.; Rossi, M.; Alippi, A.; Sessa, V.; Fiori, A.; Tamburri, E.; Terranova, M.L. [Dipartimento di Energetica, Universita di Roma 'La Sapienza', Via A. Scarpa 16, 00161 Rome (Italy); Dipartimento di Scienze e Tecnologie Chimiche, Universita di Roma 'Tor Vergata' and Micro and Nano-structured Systems Laboratory (MINASlab), Via della Ricerca Scientifica, 00133 Rome (Italy)

2006-03-20

175

Acoustic imaging in enclosed spaces: Analysis of room geometry modifications on the impulse response  

NASA Astrophysics Data System (ADS)

Sound propagation in enclosed spaces is characterized by reflections at the boundaries of the enclosure. Reflections can be wanted in the case when they support the direct sound or give a feeling of envelopment or they can be unwanted when they lead to echoes and colouration. When measuring multiple impulse responses in an enclosed space along an array the reflections can be mapped to the reflecting objects. Similar to seismic exploration, medical diagnostics, and underwater acoustics, an image of the reflecting objects is obtained in terms of reflected energy. The imaging process is based on inverse wave field extrapolation with the Kirchhoff-Helmholtz and Rayleigh integrals. The inverse of the imaging process recreates the measured impulse responses from the image and it allows one to remove or alter reflecting objects in the image and investigate their influence on the wave field in the enclosed space in a physically correct way. This can be verified by reimaging the altered wave field. Preliminary results from listening tests for the perceptual evaluation are presented. They indicate that the influence of a reflecting object can only be perceived in its close proximity. .

Kuster, M.; de Vries, D.; Hulsebos, E. M.; Gisolf, A.

2004-10-01

176

Passive element enriched photoacoustic computed tomography (PER PACT) for simultaneous imaging of acoustic propagation properties and light absorption.  

PubMed

We present a 'hybrid' imaging approach which can image both light absorption properties and acoustic transmission properties of an object in a two-dimensional slice using a computed tomography (CT) photoacoustic imager. The ultrasound transmission measurement method uses a strong optical absorber of small cross-section placed in the path of the light illuminating the sample. This absorber, which we call a passive element acts as a source of ultrasound. The interaction of ultrasound with the sample can be measured in transmission, using the same ultrasound detector used for photoacoustics. Such measurements are made at various angles around the sample in a CT approach. Images of the ultrasound propagation parameters, attenuation and speed of sound, can be reconstructed by inversion of a measurement model. We validate the method on specially designed phantoms and biological specimens. The obtained images are quantitative in terms of the shape, size, location, and acoustic properties of the examined heterogeneities. PMID:21369026

Jose, Jithin; Willemink, Rene G H; Resink, Steffen; Piras, Daniele; van Hespen, J C G; Slump, Cornelis H; Steenbergen, Wiendelt; van Leeuwen, Ton G; Manohar, Srirang

2011-01-31

177

Effect of MRI Acoustic Noise on Cerebral FDG Uptake in Simultaneous MR-PET Imaging  

PubMed Central

Integrated scanners capable of simultaneous PET and MRI data acquisition are now available for human use. Although the scanners’ manufacturers have made substantial efforts to understand and minimize the mutual electromagnetic interference between the two modalities, the potential physiological inference has not been evaluated. In this work, we have studied the influence of the acoustic noise produced by the MR gradients on brain FDG uptake in the Siemens MR-BrainPET prototype. While particular attention was paid to the primary auditory cortex (PAC), a brain-wide analysis was also performed. Methods The effects of the MR on the PET count rate and image quantification were first investigated in phantoms. Next, ten healthy volunteers underwent two simultaneous FDG-PET/MR scans in the supine position with the FDG injection occurring inside the MR-BrainPET, alternating between a “quiet” (control) environment in which no MR sequences were run during the FDG uptake phase (the first 40 minutes after radiotracer administration) and a “noisy” (test) case in which MR sequences were run for the entire time. Cortical and subcortical regions of interest (ROIs) were derived from the high-resolution morphological MR data using FreeSurfer. The changes in FDG uptake in the FreeSurfer-derived ROIs between the two conditions were analyzed from parametric and static PET images, and on a voxel-by-voxel basis using SPM8 and FreeSurfer. Results Only minimal to no electromagnetic interference was observed for most of the MR sequences tested, with a maximum drop in count rate of 1.5% and a maximum change in the measured activity of 1.1% in the corresponding images. The ROI-based analysis showed statistically significant increases in the right PAC in both the parametric (9.13±4.73%) and static (4.18±2.87%) images. SPM8 analysis showed no statistically significant clusters in any images when a p<0.05 (corrected) was used; however, a p<0.001 (uncorrected) resolved bilateral statistically significant clusters of increased FDG uptake in the area of the PAC for the parametric image (left: 8.37±1.55%, right: 8.20±1.17%), but only unilateral increase in the static image (left: 8.68±3.89%). Conclusion Although the operation of the BrainPET prototype is virtually unaffected by the MR scanner, the acoustic noise produced by the MR gradients causes a focal increase in FDG uptake in the PAC, which could affect the interpretation of pathological (or brain-activation related) changes in FDG uptake in this region, if the expected effects are of comparable amplitude.

Abolmaali, Nasreddin; Arabasz, Grae; Guimaraes, Alexander R.; Catana, Ciprian

2013-01-01

178

Shear wave elasticity imaging based on acoustic radiation force and optical detection.  

PubMed

Tissue elasticity is closely related to the velocity of shear waves within biologic tissue. Shear waves can be generated by an acoustic radiation force and tracked by, e.g., ultrasound or magnetic resonance imaging (MRI) measurements. This has been shown to be able to noninvasively map tissue elasticity in depth and has great potential in a wide range of clinical applications including cancer and cardiovascular diseases. In this study, a highly sensitive optical measurement technique is proposed as an alternative way to track shear waves generated by the acoustic radiation force. A charge coupled device (CCD) camera was used to capture diffuse photons from tissue mimicking phantoms illuminated by a laser source at 532 nm. CCD images were recorded at different delays after the transmission of an ultrasound burst and were processed to obtain the time of flight for the shear wave. A differential measurement scheme involving generation of shear waves at two different positions was used to improve the accuracy and spatial resolution of the system. The results from measurements on both homogeneous and heterogeneous phantoms were compared with measurements from other instruments and demonstrate the feasibility and accuracy of the technique for imaging and quantifying elasticity. The relative error in estimation of shear wave velocity can be as low as 3.3% with a spatial resolution of 2 mm, and increases to 8.8% with a spatial resolution of 1 mm for the medium stiffness phantom. The system is shown to be highly sensitive and is able to track shear waves propagating over several centimetres given the ultrasound excitation amplitude and the phantom material used in this study. It was also found that the reflection of shear waves from boundaries between regions with different elastic properties can cause significant bias in the estimation of elasticity, which also applies to other shear wave tracking techniques. This bias can be reduced at the expense of reduced spatial resolution. PMID:22749816

Cheng, Yi; Li, Rui; Li, Sinan; Dunsby, Christopher; Eckersley, Robert J; Elson, Daniel S; Tang, Meng-Xing

2012-09-01

179

A method for the frequency control in time-resolved two-dimensional gigahertz surface acoustic wave imaging  

NASA Astrophysics Data System (ADS)

We describe an extension of the time-resolved two-dimensional gigahertz surface acoustic wave imaging based on the optical pump-probe technique with periodic light source at a fixed repetition frequency. Usually such imaging measurement may generate and detect acoustic waves with their frequencies only at or near the integer multiples of the repetition frequency. Here we propose a method which utilizes the amplitude modulation of the excitation pulse train to modify the generation frequency free from the mentioned limitation, and allows for the first time the discrimination of the resulted upper- and lower-side-band frequency components in the detection. The validity of the method is demonstrated in a simple measurement on an isotropic glass plate covered by a metal thin film to extract the dispersion curves of the surface acoustic waves.

Kaneko, Shogo; Tomoda, Motonobu; Matsuda, Osamu

2014-01-01

180

Full-wave iterative image reconstruction in photoacoustic tomography with acoustically inhomogeneous media.  

PubMed

Existing approaches to image reconstruction in photoacoustic computed tomography (PACT) with acoustically heterogeneous media are limited to weakly varying media, are computationally burdensome, and/or cannot effectively mitigate the effects of measurement data incompleteness and noise. In this work, we develop and investigate a discrete imaging model for PACT that is based on the exact photoacoustic (PA) wave equation and facilitates the circumvention of these limitations. A key contribution of the work is the establishment of a procedure to implement a matched forward and backprojection operator pair associated with the discrete imaging model, which permits application of a wide-range of modern image reconstruction algorithms that can mitigate the effects of data incompleteness and noise. The forward and backprojection operators are based on the k-space pseudospectral method for computing numerical solutions to the PA wave equation in the time domain. The developed reconstruction methodology is investigated by use of both computer-simulated and experimental PACT measurement data. PMID:23529196

Huang, Chao; Wang, Kun; Nie, Liming; Wang, Lihong V; Anastasio, Mark A

2013-06-01

181

Acoustic radiation force impulse imaging of vulnerable plaques: a finite element method parametric analysis  

PubMed Central

Plaque rupture is the most common cause of complications such as stroke and coronary heart failure. Recent histopathological evidence suggests that several plaque features, including a large lipid core and a thin fibrous cap, are associated with plaques most at risk for rupture. Acoustic Radiation Force Impulse (ARFI) imaging, a recently developed ultrasound-based elasticity imaging technique, shows promise for imaging these features noninvasively. Clinically, this could be used to distinguish vulnerable plaques, for which surgical intervention may be required, from those less prone to rupture. In this study, a parametric analysis using Finite-Element Method (FEM) models was performed to simulate ARFI imaging of five different carotid artery plaques across a wide range of material properties. It was demonstrated that ARFI could resolve the softer lipid pool from the surrounding, stiffer media and fibrous cap and was most dependent upon the stiffness of the lipid pool component. Stress concentrations due to an ARFI excitation were located in the media and fibrous cap components. In all cases, the maximum Von Mises stress was < 1.2 kPa. In comparing these results with others investigating plaque rupture, it is concluded that while the mechanisms may be different, the Von Mises stresses imposed by ARFI are orders of magnitude lower than the stresses associated with blood pressure.

Doherty, Joshua R.; Dumont, Douglas M.; Trahey, Gregg E.; Palmeri, Mark L.

2012-01-01

182

Imaging of human tooth using ultrasound based chirp-coded nonlinear time reversal acoustics.  

PubMed

Human tooth imaging sonography is investigated experimentally with an acousto-optic noncoupling set-up based on the chirp-coded nonlinear time reversal acoustic concept. The complexity of the tooth internal structure (enamel-dentine interface, cracks between internal tubules) is analyzed by adapting the nonlinear elastic wave spectroscopy (NEWS) with the objective of the tomography of damage. Optimization of excitations using intrinsic symmetries, such as time reversal (TR) invariance, reciprocity, correlation properties are then proposed and implemented experimentally. The proposed medical application of this TR-NEWS approach is implemented on a third molar human tooth and constitutes an alternative of noncoupling echodentography techniques. A 10 MHz bandwidth ultrasonic instrumentation has been developed including a laser vibrometer and a 20 MHz contact piezoelectric transducer. The calibrated chirp-coded TR-NEWS imaging of the tooth is obtained using symmetrized excitations, pre- and post-signal processing, and the highly sensitive 14 bit resolution TR-NEWS instrumentation previously calibrated. Nonlinear signature coming from the symmetry properties is observed experimentally in the tooth using this bi-modal TR-NEWS imaging after and before the focusing induced by the time-compression process. The TR-NEWS polar B-scan of the tooth is described and suggested as a potential application for modern echodentography. It constitutes the basis of the self-consistent harmonic imaging sonography for monitoring cracks propagation in the dentine, responsible of human tooth structural health. PMID:21371732

Dos Santos, Serge; Prevorovsky, Zdenek

2011-08-01

183

SIMULTANEOUS BILATERAL REAL-TIME 3-D TRANSCRANIAL ULTRASOUND IMAGING AT 1 MHZ THROUGH POOR ACOUSTIC WINDOWS  

PubMed Central

Ultrasound imaging has been proposed as a rapid, portable alternative imaging modality to examine stroke patients in pre-hospital or emergency room settings. However, in performing transcranial ultrasound examinations, 8%–29% of patients in a general population may present with window failure, in which case it is not possible to acquire clinically useful sonographic information through the temporal bone acoustic window. In this work, we describe the technical considerations, design and fabrication of low-frequency (1.2 MHz), large aperture (25.3 mm) sparse matrix array transducers for 3-D imaging in the event of window failure. These transducers are integrated into a system for real-time 3-D bilateral transcranial imaging—the ultrasound brain helmet—and color flow imaging capabilities at 1.2 MHz are directly compared with arrays operating at 1.8 MHz in a flow phantom with attenuation comparable to the in vivo case. Contrast-enhanced imaging allowed visualization of arteries of the Circle of Willis in 5 of 5 subjects and 8 of 10 sides of the head despite probe placement outside of the acoustic window. Results suggest that this type of transducer may allow acquisition of useful images either in individuals with poor windows or outside of the temporal acoustic window in the field.

Lindsey, Brooks D.; Nicoletto, Heather A.; Bennett, Ellen R.; Laskowitz, Daniel T.; Smith, Stephen W.

2013-01-01

184

A novel application of time-reversed acoustics: Salt-dome flank imaging using walkaway VSP surveys  

Microsoft Academic Search

In this paper we present initial results of applying Time-Reversed Acoustics (TRA) technology to salt- dome flank, seismic imaging. We created a set of syn- thetic traces representing a multilevel, walkaway VSP for a model composed of a simplified Gulf of Mexico vertical-velocity gradient and an embedded salt dome. We first applied the concepts of TRA to the synthetic traces

Mark E. Willis; Rongrong Lu; Xander Campman; M. Nafi Toksöz; Yang Zhang; Maarten V. de Hoop

2006-01-01

185

Sharp estimates for the Neumann functions and applications to quantitative photo-acoustic imaging in inhomogeneous media  

NASA Astrophysics Data System (ADS)

We obtain sharp Lp and Hölder estimates for the Neumann function of the operator ????-ik on a bounded domain. We also obtain quantitative description of its singularity. We then apply these estimates to quantitative photo-acoustic imaging in inhomogeneous media. The problem is to reconstruct the optical absorption coefficient of a diametrically small anomaly from the absorbed energy density.

Ammari, Habib; Kang, Hyeonbae; Kim, Seick

186

Design and Numerical Evaluation of Off-Axis Aplanatic Straubel Mirror for Underwater Acoustic Imaging  

NASA Astrophysics Data System (ADS)

An aplanatic Straubel mirror was designed for underwater acoustic imaging. However, there was a problem in that incident sound waves coming into the aplanatic Straubel mirror were interrupted by a receiver array placed in front of the mirror. An off-axis Straubel mirror is proposed to solve this problem. In this study, an off-axis aplanatic Straubel mirror is designed and evaluated using numerical calculation to verify the feasibility of the off-axis design. Upon comparison of the off-axis and ordinary aplanatic Straubel mirrors, the off-axis mirror shows almost the same convergence property as the ordinary one when a receiver array exists. The off-axis aplanatic Straubel mirror is compared with an aplanatic Fresnel lens because this lens is not affected by the receiver. The results show that the off-axis mirror showed a smaller aberration than the aplanatic Fresnel lens at a wider angle of view.

Sato, Yuji; Mizutani, Koichi; Wakatsuki, Naoto; Nakamura, Toshiaki

2012-07-01

187

Measuring soft tissue elasticity by monitoring surface acoustic waves using image plane digital holography  

NASA Astrophysics Data System (ADS)

The detection of tumors in soft tissues, such as breast cancer, is important to achieve at the earliest stages of the disease to improve patient outcome. Tumors often exhibit a greater elastic modulus compared to normal tissues. In this paper, we report our first study to measure elastic properties of soft tissues by mapping the surface acoustic waves (SAWs) with image plane digital holography. The experimental results show that the SAW velocity is proportional to the square root of elastic modulus over a range from 3.7-122kPa in homogeneous tissue phantoms, consistent with Rayleigh wave theory. This technique also permits detection of the interface of two-layer phantoms 10mm deep under surface and the interface depth by quantifying the SAW dispersion.

Li, Shiguang; Oldenburg, Amy L.

2011-03-01

188

Imaging of Acoustically Coupled Oscillations Due to Flow Past a Shallow Cavity: Effect of Cavity Length Scale  

SciTech Connect

Flow-acoustic interactions due to fully turbulent inflow past a shallow axisymmetric cavity mounted in a pipe, which give rise to flow tones, are investigated using a technique of high-image-density particle image velocimetry in conjunction with unsteady pressure measurements. This imaging leads to patterns of velocity, vorticity, streamline topology, and hydrodynamic contributions to the acoustic power integral. Global instantaneous images, as well as time-averaged images, are evaluated to provide insight into the flow physics during tone generation. Emphasis is on the manner in which the streamwise length scale of the cavity alters the major features of the flow structure. These image-based approaches allow identification of regions of the unsteady shear layer that contribute to the instantaneous hydrodynamic component of the acoustic power, which is necessary to maintain a flow tone. In addition, combined image analysis and pressure measurements allow categorization of the instantaneous flow patterns that are associated with types of time traces and spectra of the fluctuating pressure. In contrast to consideration based solely on pressure spectra, it is demonstrated that locked-on tones may actually exhibit intermittent, non-phase-locked images, apparently due to low damping of the acoustic resonator. Locked-on flow tones (without modulation or intermittency), locked-on flow tones with modulation, and non-locked-on oscillations with short-term, highly coherent fluctuations are defined and represented by selected cases. Depending on which of these regimes occur, the time-averaged Q (quality)-factor and the dimensionless peak pressure are substantially altered.

P Oshkai; M Geveci; D Rockwell; M Pollack

2004-05-24

189

High-Performance Seismic Acoustic Imaging by Reverse-Time Migration on the Cell\\/B.E. Architecture  

Microsoft Academic Search

Reverse-Time Migration (RTM) is a state-of-the-art tech- nique in seismic acoustic imaging, because of the quality and integrity of the images it provides. Oil and gas com- panies trust RTM with crucial decisions on multi-million- dollar drilling investments. But RTM requires vastly more computational power than its predecessors, and this has somewhat hindered its practical success. On the other hand,

Mauricio Araya-Polo; F ´ elix Rubio; Mauricio Hanzich; Jos ´ e Mar ´ ia Cela; Daniele Paolo Scarpazza

190

Precisely shaped acoustic ablation of tumors utilizing steerable needle and 3D ultrasound image guidance  

NASA Astrophysics Data System (ADS)

Many recent studies have demonstrated the efficacy of interstitial ablative approaches for the treatment of hepatic tumors. Despite these promising results, current systems remain highly dependent on operator skill, and cannot treat many tumors because there is little control of the size and shape of the zone of necrosis, and no control over ablator trajectory within tissue once insertion has taken place. Additionally, tissue deformation and target motion make it extremely difficult to place the ablator device precisely into the target. Irregularly shaped target volumes typically require multiple insertions and several overlapping (thermal) lesions, which are even more challenging to accomplish in a precise, predictable, and timely manner without causing excessive damage to surrounding normal tissues. In answer to these problems, we have developed a steerable acoustic ablator called the ACUSITT with the ability of directional energy delivery to precisely shape the applied thermal dose . In this paper, we address image guidance for this device, proposing an innovative method for accurate tracking and tool registration with spatially-registered intra-operative three-dimensional US volumes, without relying on an external tracking device. This method is applied to guid-ance of the flexible, snake-like, lightweight, and inexpensive ACUSITT to facilitate precise placement of its ablator tip within the liver, with ablation monitoring via strain imaging. Recent advancements in interstitial high-power ultrasound applicators enable controllable and penetrating heating patterns which can be dynamically altered. This paper summarizes the design and development of the first synergistic system that integrates a novel steerable interstitial acoustic ablation device with a novel trackerless 3DUS guidance strategy.

Boctor, Emad M.; Stolka, Philipp; Kang, Hyun-Jae; Clarke, Clyde; Rucker, Caleb; Croom, Jordon; Burdette, E. Clif; Webster, Robert J., III

2010-03-01

191

An application of time-reversed acoustics to the imaging of a salt-dome flank  

NASA Astrophysics Data System (ADS)

We present results of applying the concept of time-reversed acoustics (TRA) to the imaging of a salt-dome flank in a v(z) medium. A simulated multi-level walk-away VSP survey with sources at the surface and receivers in the borehole can be sorted into an equivalent reverse VSP (RVSP) with effective downhole sources and surface receivers. We apply the TRA process to the RVSP traces and create a zero offset seismic section as if it had been collected from collocated downhole sources and receivers. This procedure effectively redatums the wavefield from the surface to the borehole, eliminating the need for any complicated processing. The redatummed traces are created by summing the autocorrelations of the traces in the RVSP common shot gather. Theory says that each shot gather should be from receivers which completely surround the source. From practical considerations, we only have available the RVSP common receivers on the earth's surface, so we obtain an approximate zero offset section. Even with this restriction, our example shows that the results are encouraging. The image of the salt dome flank is created from the redatummed traces using a standard post-stack depth migration algorithm. This image compares favorably with the salt dome flank model.

Willis, M. E.; Lu, R.; Campman, X.; Toksöz, N.; Zhang, Y.; de Hoop, M. V.

2005-12-01

192

Dynamic simulation of viscoelastic soft tissue in acoustic radiation force creep imaging.  

PubMed

Acoustic radiation force (ARF) creep imaging applies step ARF excitation to induce creep displacement of soft tissue, and the corresponding time-dependent responses are used to estimate soft tissue viscoelasticity or its contrast. Single degree of freedom (SDF) and homogeneous analytical models have been used to characterize soft tissue viscoelasticity in ARF creep imaging. The purpose of this study is to investigate the fundamental limitations of the commonly used SDF and homogeneous assumptions in ARF creep imaging. In this paper, finite element (FE) models are developed to simulate the dynamic behavior of viscoelastic soft tissue subjected to step ARF. Both homogeneous and heterogeneous models are studied with different soft tissue viscoelasticity and ARF configurations. The results indicate that the SDF model can provide good estimations for homogeneous soft tissue with high viscosity, but exhibits poor performance for low viscosity soft tissue. In addition, a smaller focal region of the ARF is desirable to reduce the estimation error with the SDF models. For heterogeneous media, the responses of the focal region are highly affected by the local heterogeneity, which results in deterioration of the effectiveness of the SDF and homogeneous simplifications. PMID:24975997

Zhao, Xiaodong; Pelegri, Assimina A

2014-09-01

193

Nearfield Acoustical Holography  

Microsoft Academic Search

Nearfield acoustical holography (NAH) is a method by which a set of acoustic pressure measurements at points located on a specific surface (called a hologram) can be used to image sources on vibrating surfaces on the acoustic field in three-dimensional space. NAH data are processed to take advantage of the evanescent wavefield to image sources that are separated less that

Sabih I. Hayek

2008-01-01

194

Intracardiac Acoustic Radiation Force Impulse (ARFI) and Shear Wave Imaging in Pigs with Focal Infarctions  

PubMed Central

Four pigs, three with focal infarctions in the apical intraventricular septum (IVS) and/or left ventricular free wall (LVFW), were imaged with an intracardiac echocardiography (ICE) transducer. Custom beam sequences were used to excite the myocardium with focused acoustic radiation force (ARF) impulses and image the subsequent tissue response. Tissue displacement in response to the ARF excitation was calculated with a phase-based estimator, and transverse wave magnitude and velocity were each estimated at every depth. The excitation sequence was repeated rapidly, either in the same location to generate 40 Hz M-Modes at a single steering angle, or with a modulated steering angle to synthesize 2-D displacement magnitude and shear wave velocity images at 17 points in the cardiac cycle. Both types of images were acquired from various views in the right and left ventricles, in and out of infarcted regions. In all animals, ARFI and SWEI estimates indicated diastolic relaxation and systolic contraction in non-infarcted tissues. The M-Mode sequences showed high beat-to-beat spatio-temporal repeatability of the measurements for each imaging plane. In views of noninfarcted tissue in the diseased animals, no significant elastic remodeling was indicated when compared to the control. Where available, views of infarcted tissue were compared to similar views from the control animal. In views of the LVFW, the infarcted tissue presented as stiff and non-contractile compared to the control. In a view of the IVS, no significant difference was seen between infarcted and healthy tissue, while in another view, a heterogeneous infarction was seen presenting itself as non-contractile in systole.

Hollender, Peter; Bradway, David; Wolf, Patrick; Goswami, Robi; Trahey, Gregg

2013-01-01

195

Spatially resolved acoustic spectroscopy for rapid imaging of material microstructure and grain orientation  

NASA Astrophysics Data System (ADS)

Measuring the grain structure of aerospace materials is very important to understand their mechanical properties and in-service performance. Spatially resolved acoustic spectroscopy is an acoustic technique utilizing surface acoustic waves to map the grain structure of a material. When combined with measurements in multiple acoustic propagation directions, the grain orientation can be obtained by fitting the velocity surface to a model. The new instrument presented here can take thousands of acoustic velocity measurements per second. The spatial and velocity resolution can be adjusted by simple modification to the system; this is discussed in detail by comparison of theoretical expectations with experimental data.

Smith, Richard J.; Li, Wenqi; Coulson, Jethro; Clark, Matt; Somekh, Michael G.; Sharples, Steve D.

2014-05-01

196

A view of the world through the bat's ear: the formation of acoustic images in echolocation.  

PubMed

Echolocating bats perceive objects as acoustic images derived from echoes of the ultrasonic sounds they emit. They can detect, track, identify, and intercept flying insects using sonar. Many species, such as the big brown bat, Eptesicus fuscus, emit frequency-modulated sonar sounds and perceive the distance to targets, or target range, from the delay of echoes. For Eptesicus, a point-target's image has a sharpness along the range axis that is determined by the acuity of echo-delay perception, which is about 10 ns under favorable conditions. The image as a whole has a fine range structure that corresponds to the cross-correlation function between emissions and echoes. A complex target- which has reflecting points, called "glints", located at slightly different distances and reflects echoes containing overlapping components with slightly different delays--is perceived in terms of its range profile. The separation of the glints along the range dimension is encoded by the shape of the echo spectrum created by interference between overlapping echo components. However, Eptesicus transforms the echo spectrum back into an estimate of the original delay separation of echo components. The bat thus converts spectral cues into elements of an image expressed in terms of range. The absolute range of the nearest glint is encoded by the arrival time of the earliest echo component, and the spectrally encoded range separation of additional glints is referred to this time-encoded reference range for the image as a whole. Each individual glint is represented by a cross-correlation function for its own echo component, the nearest of which is computed directly from arrival-time measurements while further ones are computed by transformation of the echo spectrum. The bat then sums the cross-correlation functions for multiple glints to form the entire image of the complex target. Range and shape are two distinct features of targets that are separately encoded by the bat's auditory system, but the bat perceives unitary images that require fusion of these features to create a synthetic psychological dimension of range. The bat's use of cross-correlation-like images reveals neural computations that achieve fusion of stimulus features and offers an example of high-level operations involved in the formation of perceptual "wholes". PMID:2691182

Simmons, J A

1989-11-01

197

The coordination chemistry and magnetism of some 3d-4f and 4f amino-polyalcohol compounds  

PubMed Central

Triethanolamine, teaH3, and diethanolamine, RdeaH2, 3d–4f and 4f compounds demonstrate an enormous variety in their structure and bonding. This review examines the synthetic strategies to these molecules and their magnetic properties, whilst trying to assess these ligands’ suitability towards new SMMs and magnetic refrigerants.

Sharples, Joseph W.; Collison, David

2014-01-01

198

Imaging velocity and attenuation anomalies in mining environments using Acoustic Emissions  

NASA Astrophysics Data System (ADS)

Imaging structural properties and monitoring fracturing processes in mining environments is of importance for mining exploitation. It is also helpful to characterize damages induced by mining activities, thus it is of primary interest for mining engineering and civil protection. Additionally, the development of improved monitoring and imaging methods is of great importance for salt deposits as potential reservoirs for CO2 sequestration. The analysis of Acoustic Emission (AE) and microseismicity data, which are routinely used in mining survey, is typically limited to estimate location of induced microcracks and seismicity. AE data will be here further analysed to obtain images of the seismic structure. We focus on an AE dataset recorded at the Morsleben salt mine, in Germany; the dataset contains more than 1 million events, recorded during a period of two months, with AE magnitudes spanning 5 units. Arrival times of first P and S onsets, as well as maximal amplitudes recorded for both seismic phases, are used to assess the seismic velocities and attenuation properties of the mining environment. Given the large size of the considered dataset, a spatial clustering of the events is first performed and a spatial homogeneous catalog of averaged "pseudoevents" is built. This new catalog is then used to provide first averaged images of the attenuation and velocity anomalies at specific depths. Results points to clear velocity and attenuation anomalies, which are correlated with the main structural features and the geometry of the salt body. The potential of the dataset for tomographic applications is investigated, both including synthetic simulations and considering real data. This study is funded by the project MINE, which is part of the R&D-Programme GEOTECHNOLOGIEN. The project MINE is funded by the German Ministry of Education and Research (BMBF), Grant of project BMBF03G0737.

Cesca, S.; Monna, S.; Kaiser, D.; Dahm, T.

2012-04-01

199

In vivo MR acoustic radiation force imaging in the porcine liver  

PubMed Central

Purpose: High intensity focused ultrasound (HIFU) in the abdomen can be sensitive to acoustic aberrations that can exist in the beam path of a single sonication. Having an accurate method to quickly visualize the transducer focus without damaging tissue could assist with executing the treatment plan accurately and predicting these changes and obstacles. By identifying these obstacles, MR acoustic radiation force imaging (MR-ARFI) provides a reliable method for visualizing the transducer focus quickly without damaging tissue and allows accurate execution of the treatment plan. Methods: MR-ARFI was used to view the HIFU focus, using a gated spin echo flyback readout-segmented echo-planar imaging sequence. HIFU spots in a phantom and in the livers of five live pigs under general anesthesia were created with a 550 kHz extracorporeal phased array transducer initially localized with a phase-dithered MR-tracking sequence to locate microcoils embedded in the transducer. MR-ARFI spots were visualized, observing the change of focal displacement and ease of steering. Finally, MR-ARFI was implemented as the principle liver HIFU calibration system, and MR-ARFI measurements of the focal location relative to the thermal ablation location in breath-hold and breathing experiments were performed. Results: Measuring focal displacement with MR-ARFI was achieved in the phantom and in vivo liver. In one in vivo experiment, where MR-ARFI images were acquired repeatedly at the same location with different powers, the displacement had a linear relationship with power [y?=?0.04x?+?0.83 ?m (R2?=?0.96)]. In another experiment, the displacement images depicted the electronic steering of the focus inside the liver. With the new calibration system, the target focal location before thermal ablation was successfully verified. The entire calibration protocol delivered 20.2 J of energy to the animal (compared to greater than 800 J for a test thermal ablation). ARFI displacement maps were compared with thermal ablations during seven breath-hold ablations. The error was 0.83?±?0.38 mm in the S?I direction and 0.99?±?0.45 mm in the L?R direction. For six spots in breathing ablations, the mean error in the nonrespiration direction was 1.02?±?0.89 mm. Conclusions: MR-ARFI has the potential to improve free-breathing plan execution accuracy compared to current calibration and acoustic beam adjustment practices. Gating the acquisition allows for visualization of the focal spot over the course of respiratory motion, while also being insensitive to motion effects that can complicate a thermal test spot. That MR-ARFI measures a mechanical property at the focus also makes it insensitive to high perfusion, of particular importance to highly perfused organs such as the liver.

Holbrook, Andrew B.; Ghanouni, Pejman; Santos, Juan M.; Medan, Yoav; Butts Pauly, Kim

2011-01-01

200

An electrochemical and high-speed imaging study of micropore decontamination by acoustic bubble entrapment.  

PubMed

Electrochemical and high-speed imaging techniques are used to study the abilities of ultrasonically-activated bubbles to clean out micropores. Cylindrical pores with dimensions (diameter × depth) of 500 ?m × 400 ?m (aspect ratio 0.8), 125 ?m × 350 ?m (aspect ratio 2.8) and 50 ?m × 200 ?m (aspect ratio 4.0) are fabricated in glass substrates. Each pore is contaminated by filling it with an electrochemically inactive blocking organic material (thickened methyl salicylate) before the substrate is placed in a solution containing an electroactive species (Fe(CN)6(3-)). An electrode is fabricated at the base of each pore and the Faradaic current is used to monitor the decontamination as a function of time. For the largest pore, decontamination driven by ultrasound (generated by a horn type transducer) and bulk fluid flow are compared. It is shown that ultrasound is much more effective than flow alone, and that bulk fluid flow at the rates used cannot decontaminate the pore completely, but that ultrasound can. In the case of the 125 ?m pore, high-speed imaging is used to elucidate the cleaning mechanisms involved in ultrasonic decontamination and reveals that acoustic bubble entrapment is a key feature. The smallest pore is used to explore the limits of decontamination and it is found that ultrasound is still effective at this size under the conditions employed. PMID:24477554

Offin, Douglas G; Birkin, Peter R; Leighton, Timothy G

2014-03-14

201

Ultra high resolution nonenhanced fast spin echo magnetic resonance imaging: Cost-effective screening for acoustic neuroma in patients with sudden sensorineural hearing loss  

Microsoft Academic Search

The financial burden for the evaluation of patients for acoustic neuroma in an otolaryngology practice is substantial. Patients with sudden sensorineural hearing loss represent a portion of that population seen with unilateral, asymmetric auditory symptoms who require investigation for acoustic neuroma. For these patients, gadolinium-enhanced magnetic resonance imaging is the diagnostic gold standard. Auditory brain stem response testing has been

ROBERT L. DANIELS; CLOUGH SHELTON; H. RIC HARNSBERGER

1998-01-01

202

Inferences of Particle Size and Composition From Video-like Images Based on Acoustic Data: Grotto Plume, Main Endeavor Field  

NASA Astrophysics Data System (ADS)

Optical and acoustic scattering from particles in a seafloor hydrothermal plume can be related if the particle properties and scattering mechanisms are known. We assume Rayleigh backscattering of sound and Mie forward scattering of light. We then use the particle concentrations implicit in the observed acoustic backscatter intensity to recreate the optical image a camera would see given a particular lighting level. The motivation for this study is to discover what information on particle size and composition in the buoyant plume can be inferred from a comparison of the calculated optical images (based on acoustic data) with actual video images from the acoustic acquisition cruise and the IMAX film "Volcanoes of the Deep Sea" (Stephen Low Productions, Inc.). Because the geologists, biologists and oceanographers involved in the study of seafloor hydrothermal plumes all "see" plumes in different ways, an additional motivation is to create more realistic plume images from the acoustic data. By using visualization techniques, with realistic lighting models, we can convert the plume image from mechanical waves (sound) to electromagnetic waves (light). The resulting image depends on assumptions about the particle size distribution and composition. Conversion of the volume scattering coefficients from Rayleigh to Mie scattering is accomplished by an extinction scale factor that depends on the wavelengths of light and sound and on the average particle size. We also make an adjustment to the scattered light based on the particles reflectivity (albedo) and color. We present a series of images of acoustic data for Grotto Plume, Main Endeavour Field (within the Endeavour ISS Site) using both realistic lighting models and traditional visualization techniques to investigate the dependence of the images on assumptions about particle composition and size. Sensitivity analysis suggests that the visibility of the buoyant plume increases as the intensity of supplied light increases, the particle size decreases, and the particle reflectivity increases. However, decreasing the particle size (and thus increasing the extinction scale factor) results in a wider, less defined plume and increases the relative importance of the acoustic background noise; the best fit of our calculated optical images to the character of actual video images of the bottom few meters of the plumes (the acoustic data volume is 55 m tall) suggests that average particle size is fairly large ( ˜1000 ? m) in the buoyant plume. This suggests that existing data on particle size distributions underestimates the average particle size; the best explanation is the breakup of aggregates of particles during collection and filtering of water samples (no in situ measurements exist). We also investigate the effects of particle color on plume color by using models based on data collected by Feely et al (1987), Walker and Baker (1988), and Mottl and McConachy (1990). Highly reflective particles result in result in sharper-edged plumes suggesting that pyrite (albedo ˜0.6) and chalcopyrite (albedo ˜0.3) are the dominant particle compositions. This study shows that plume particles in the buoyant plume are probably larger than previously suspected and a predominance of pyrite and chalcopyrite is necessary to explain the high reflectance of black smoker plumes.

Bemis, K. G.; Rona, P. A.; Santilli, K.; Dastur, J.; Silver, D.

2004-12-01

203

Image reconstruction in photoacoustic tomography with variable speed of sound using a higher-order geometrical acoustics approximation  

NASA Astrophysics Data System (ADS)

Previous research correcting for variable speed of sound in photoacoustic tomography (PAT) based on a generalized radon transform (GRT) model assumes first-order geometrical acoustics (GA) approximation. In the GRT model, the pressure is related to the optical absorption, in an acoustically inhomogeneous medium, through integration over nonspherical isochronous surfaces. Previous research based on the GRT model assumes that the path taken by acoustic rays is linear and neglects amplitude perturbations to the measured pressure. We have derived a higher-order GA expression that takes into account the first-order effect in the amplitude of the measured signal and higher-order perturbation to the travel times. The higher-order perturbation to travel time incorporates the effect of ray bending. Incorrect travel times can lead to image distortion and blurring. These corrections are expected to impact image quality and quantitative PAT. We have previously shown that travel-time corrections in 2-D suggest that perceivable differences in the isochronous surfaces can be seen when the second-order travel-time perturbations are taken into account with a 10% speed-of-sound variation. In this work, we develop iterative image reconstruction algorithms that incorporate this higher-order GA approximation assuming that the speed of sound map is known. We evaluate the effect of higher-order GA approximation on image quality and accuracy.

Modgil, Dimple; Anastasio, Mark A.; La Rivière, Patrick J.

2010-03-01

204

Time-averaged images and quantifications of seafloor hydrothermal plumes from acoustic imaging data: a case study at Grotto Vent, Endeavour Segment Seafloor Observatory  

NASA Astrophysics Data System (ADS)

Many simple models of plumes predict time-averaged behavior. Although instantaneous measurements of plumes are still useful, time-averaged measurements are more directly comparable. Averages of varying numbers of consecutive acoustic images are quantified and the results compared. The acoustic images of Grotto Vent in the Main Endeavour Vent Field were obtained during the VIP (Vents Imaging Pacific) 2000 cruise using the Simrad SM2000 sonar system mounted on ROV Jason. The acoustic images were calibrated, filtered and interpolated onto a uniform grid. The acoustic intensity is proportional to the particle load and herein referred to as such. For each horizontal slice, the summed mass, the area, the local maximum and the position of the local maximum were calculated within a threshold-bounded area. The summed mass, the local maximum (and its position) and the average radius (from the area) proved insensitive to the averaging process. A slight trend for the local maximum to decrease with the number of images averaged was observed. Variation of the local maximum in even these short time intervals may influence the results of averaging. The consistency of the summed mass with averaging variable numbers of images may relate to the conservation of mass by the plume, which would require the total mass at a height to be the same unless the mass supplied at the source changed. The distribution of particle load within the plume becomes progressively smoother as more consecutive images are averaged together. Averages of 1, 2, 5, and 10 images were compared. The three-dimensional pattern of the time-averaged particle load distribution suggests that the plume/chimney interface was about 10 m above the sonar system at approximately 20 m horizontal distance. Particle load decreases with distance from the plume centerline for all averages, but that decrease varies from irregular (single image) to smooth (10 images). For averages of 5-10 images, the distribution of particle load within the plume is approximately Gaussian on horizontal slices. The degree of misfit will be quantified by visual and numerical comparison. It is concluded that a minimal set of 5 consecutive images is required to produce an adequate time-averaged image. This time-averaged image of the plume shows a clear picture of the plume structure, which facilitates comparison with models.

Bemis, K. G.; Rona, P. A.; Jackson, D. R.; Jones, C.; Mitsuzawa, K.; Palmer, D.; Silver, D.; Gudlavalletti, R.

2001-12-01

205

High resolution imaging beyond the acoustic diffraction limit in deep tissue via ultrasound-switchable NIR fluorescence  

PubMed Central

Fluorescence imaging in deep tissue with high spatial resolution is highly desirable because it can provide details about tissue's structural, functional, and molecular information. Unfortunately, current fluorescence imaging techniques are limited either in penetration depth (microscopy) or spatial resolution (diffuse light based imaging) as a result of strong light scattering in deep tissue. To overcome this limitation, we developed an ultrasound-switchable fluorescence (USF) imaging technique whereby ultrasound was used to switch on/off the emission of near infrared (NIR) fluorophores. We synthesized and characterized unique NIR USF contrast agents. The excellent switching properties of these agents, combined with the sensitive USF imaging system developed in this study, enabled us to image fluorescent targets in deep tissue with spatial resolution beyond the acoustic diffraction limit.

Pei, Yanbo; Wei, Ming-Yuan; Cheng, Bingbing; Liu, Yuan; Xie, Zhiwei; Nguyen, Kytai; Yuan, Baohong

2014-01-01

206

High resolution imaging beyond the acoustic diffraction limit in deep tissue via ultrasound-switchable NIR fluorescence.  

PubMed

Fluorescence imaging in deep tissue with high spatial resolution is highly desirable because it can provide details about tissue's structural, functional, and molecular information. Unfortunately, current fluorescence imaging techniques are limited either in penetration depth (microscopy) or spatial resolution (diffuse light based imaging) as a result of strong light scattering in deep tissue. To overcome this limitation, we developed an ultrasound-switchable fluorescence (USF) imaging technique whereby ultrasound was used to switch on/off the emission of near infrared (NIR) fluorophores. We synthesized and characterized unique NIR USF contrast agents. The excellent switching properties of these agents, combined with the sensitive USF imaging system developed in this study, enabled us to image fluorescent targets in deep tissue with spatial resolution beyond the acoustic diffraction limit. PMID:24732947

Pei, Yanbo; Wei, Ming-Yuan; Cheng, Bingbing; Liu, Yuan; Xie, Zhiwei; Nguyen, Kytai; Yuan, Baohong

2014-01-01

207

Conventional US, US Elasticity Imaging, and Acoustic Radiation Force Impulse Imaging for Prediction of Malignancy in Thyroid Nodules.  

PubMed

Purpose To evaluate conventional ultrasonography (US), US elasticity imaging (EI), and acoustic radiation force impulse (ARFI) imaging in thyroid nodule malignancy prediction. Materials and Methods This prospective study was institutional review board approved; informed consent was obtained. Study included 375 patients (mean age, 51 years; range, 18-75 years) with 441 pathologically proven thyroid nodules. In 281 women (mean age, 50 years; range, 18-75 years) and 94 men (mean age, 53 years; range, 18-74 years), conventional US, EI, Virtual Touch tissue imaging (VTi; Siemens, Mountain View, Calif), and Virtual Touch tissue quantification (VTq; Siemens) of ARFI imaging were performed for each nodule. Multivariate logistic regression analysis was performed to assess 17 independent variables for malignancy prediction. Diagnostic performance was evaluated with receiver operating characteristic (ROC) curve analysis. Results There were 325 benign and 116 malignant nodules. Marked hypoechogenicity (odds ratio [OR]: 83.88; 95% confidence interval [CI]: 17.81, 394.99) was the strongest independent predictor for thyroid malignancy, followed by shape taller than wide (OR: 8.69; 95% CI: 2.87, 26.31), VTi (OR: 6.54; 95% CI: 3.61, 11.88), moderate hypoechogenicity (OR: 3.98; 95% CI: 1.13, 14.05), poorly defined margin (OR: 3.27; 95% CI: 1.22, 8.77), female sex (OR: 2.55; 95% CI: 1.33, 4.91), coarse background of surrounding thyroid tissue (OR: 2.01; 95% CI: 1.12, 3.62), and VTq (OR: 1.78; 95% CI: 1.28, 2.47) (all P < .05). EI was not significantly associated with thyroid malignancy (P = .855). Area under the ROC curve (Az) for VTq and VTi was higher than that with other significant independent variables. Az, sensitivity, and specificity were 0.91 (95% CI: 0.87, 0.94) and 0.86 (95% CI: 0.82, 0.90), 80% and 71.6%, and 93.8% and 83.4%, respectively, for VTi and VTq. VTq of at least 2.87 m/sec and VTi of at least grade IV were the best cutoff values for malignant thyroid nodules. Conclusion ARFI imaging is promising for malignant thyroid nodule prediction, with higher diagnostic performance than conventional US or EI. ARFI can be used to supplement conventional US to diagnose thyroid nodules in patients referred for surgery. © RSNA, 2014 Online supplemental material is available for this article. PMID:24689885

Xu, Jun-Mei; Xu, Xiao-Hong; Xu, Hui-Xiong; Zhang, Yi-Feng; Zhang, Jing; Guo, Le-Hang; Liu, Lin-Na; Liu, Chang; Zheng, Shu-Guang

2014-08-01

208

Quantitative enhancement of fatigue crack monitoring by imaging surface acoustic wave reflection in a space-cycle-load domain  

SciTech Connect

The surface wave acoustic method is applied to the in-situ monitoring of fatigue crack initiation and evolution on tension specimens. A small low-frequency periodic loading is also applied, resulting in a nonlinear modulation of reflected pulses. The acoustic wave reflections are collected for: each experimental cycle; a range of applied tension and modulation load levels; and a range of spatial propagation positions, and are presented in image form to aid pattern identification. Salient features of the image are then extracted and processed to evaluate the initiation time of the crack and its subsequent size evolution until sample failure. Additionally, a method for enhancing signal to noise ratio in Ti-6242 alloy samples is demonstrated.

Connolly, G. D.; Rokhlin, S. I. [Ohio State University, Edison Joining Technology Center, 1248 Arthur E Adams Drive, Columbus, OH 43221 (United States)

2011-06-23

209

Quantitative Enhancement of Fatigue Crack Monitoring by Imaging Surface Acoustic Wave Reflection in a Space-Cycle Domain  

NASA Astrophysics Data System (ADS)

The surface wave acoustic method is applied to the in-situ monitoring of fatigue crack initiation and evolution on tension specimens. A small low-frequency periodic loading is also applied, resulting in a nonlinear modulation of reflected pulses. The acoustic wave reflections are collected for: each experimental cycle; a range of applied tension and modulation load levels; and a range of spatial propagation positions, and are presented in image form to aid pattern identification. Salient features of the image are then extracted and processed to evaluate the initiation time of the crack and its subsequent size evolution until sample failure. Additionally, a method for enhancing signal to noise ratio in Ti-6242 alloy samples is demonstrated.

Connolly, G. D.; Rokhlin, S. I.

2011-06-01

210

Bats use a neuronally implemented computational acoustic model to form sonar images.  

PubMed

This paper reexamines neurophysiological results from echolocating big brown bats to propose a new perspective on FM biosonar processing in the auditory system. Individual auditory neurons are frequency-tuned and respond to brief, 2-10 ms FM sweeps with an average of one spike per sound to register their tuned frequencies, to detect echo arrival, or to register a local null in the echo spectrum. When initiated by the broadcast, these responses comprise a cascade of single spikes distributed across time in neurons tuned to different frequencies that persists for 30-50 ms, long after the sound has ended. Their progress mirrors the broadcast's propagation away from the bat and the return of echoes for distances out to 5-8 m. Each returning echo evokes a similar pattern of single spikes that coincide with ongoing responses to the broadcast to register the target's distance and shape. The hypothesis advanced here is that this flow of responses over time acts as an internal model of sonar acoustics that the bat executes using neuronal computations distributed across many neurons to accumulate a dynamic image of the bat's surroundings. PMID:22436892

Simmons, James A

2012-04-01

211

Optimization of acoustic emitted field of transducer array for ultrasound imaging.  

PubMed

A method is proposed to calculate the weight vector of a transducer array for ultrasound imaging to obtain a low-sidelobe transmitting beam pattern based on the near-field response vector. An optimization problem is established, and the second-order cone (SOC) algorithm is used to solve the problem to obtain the weight vector. The optimized acoustic emitted field of the transducer array is then calculated using the Field II program by applying the obtained weight vector to the array. The simulation results with a 64-element 26 MHz linear phased array show that the proposed method can be used to control the sidelobe of the near-field transmitting beam pattern of the transducer array and achieve a low-sidelobe level. The near-field sound pressure distribution of the transducer array using the proposed method focuses much better than that using the standard delay and sum (DAS) beamforming method. The sound energy is more concentrated using the proposed method. PMID:24212014

He, Zhengyao

2014-01-01

212

Apparatus for real-time acoustic imaging of Rayleigh-Bénard convection  

SciTech Connect

We have successfully designed, built and tested an experimental apparatus which is capable of providing the first real-time ultrasound images of Rayleigh-B\\'{e}nard convection in optically opaque fluids confined to large aspect ratio experimental cells. The apparatus employs a modified version of a commercially available ultrasound camera to capture images (30 frames per second) of flow patterns in a fluid undergoing Rayleigh Bénard convection. The apparatus was validated by observing convection rolls in 5cSt polydimethylsiloxane (PDMS) polymer fluid. Our first objective, after having built the apparatus, was to use it to study the sequence of transitions from diffusive to time--dependent heat transport in liquid mercury. The aim was to provide important information on pattern formation in the largely unexplored regime of very low Prandtl number fluids. Based on the theoretical stability diagram for liquid mercury, we anticipated that straight rolls should be stable over a range of Rayleigh numbers, between 1708 and approximately 1900. Though some of our power spectral densities were suggestive of the existence of weak convection, we have been unable to unambiguously visualize stable convection rolls above the theoretical onset of convection in liquid mercury. Currently, we are seeking ways to increase the sensitivity of our apparatus, such as (i) improving the acoustic impedance matching between our materials in the ultrasound path and (ii) reducing the noise level in our acoustic images due to turbulence and cavitation in the cooling fluids circulating above and below our experimental cell. If we are able to convincingly improve the sensitivity of our apparatus, and we still do not observe stable convection rolls in liquid mercury, then it may be the case that the theoretical stability diagram requires revision. In that case, either (i) straight rolls are not stable in a large aspect ratio cell at the Prandtl numbers associated with liquid mercury, or (ii) they are stable, but not in the region of the stability diagram which has been studied by this experimenter. Our second objective was to use the apparatus to study other optically opaque fluids. To this end, we have obtained the first ultrasound images of Rayleigh-Bénard convection in a ferrofluid (EFH1). This project has provided a vehicle for the scientific training of five undergraduate research assistants during the past four years. It allowed students at Wisconsin Lutheran College, a small undergraduate liberal arts college in Milwaukee, to become directly involved in a significant scientific project from its inception through publication of scientific results. The funding of this project has also strengthened the research and teaching infrastructure at the Wisconsin Lutheran College in three major ways. The project has funded the PI and his students in the design and construction of a major piece of scientific apparatus which is capable of performing novel studies of Rayleigh-Bénard convection in opaque fluids. With the acquisition of this apparatus, we are able to embark on a broad research program to study problems in pattern formation in alloys, ferro-fluids, opaque gels, and liquid metals under thermal or magnetic stresses. This project has allowed the PI to purchase auxiliary equipment necessary for establishing a fluid dynamics research laboratory at the College. And this project has served as an impetus for the College to invest in a new machine shop in the basement of the Science Building at the College in order to support this, and other, scientific projects at the College. The PI has presented work funded by this grant at physics and engineering colloquia at a nearby university and at the keynote presentation at an undergraduate research symposium at Wisconsin Lutheran College. Also, the work was featured in local magazine and newspaper articles, and is described on the PI's research webpage. Such scientific outreach serves to advance the cause of science by making it interesting and accessible to a wider audience, and to bring attention to the wor

Kuehn, Kerry, K.

2008-10-28

213

Pou4f1 and Pou4f2 Are Dispensable for the Long-Term Survival of Adult Retinal Ganglion Cells in Mice  

PubMed Central

Purpose To investigate the role of Pou4f1 and Pou4f2 in the survival of adult retinal ganglion cells (RGCs). Methods Conditional alleles of Pou4f1 and Pou4f2 were generated (Pou4f1loxP and Pou4f2loxP respectively) for the removal of Pou4f1 and Pou4f2 in adult retinas. A tamoxifen-inducible Cre was used to delete Pou4f1 and Pou4f2 in adult mice and retinal sections and flat mounts were subjected to immunohistochemistry to confirm the deletion of both alleles and to quantify the changes in the number of RGCs and other retinal neurons. To determine the effect of loss of Pou4f1 and Pou4f2 on RGC survival after axonal injury, controlled optic nerve crush (CONC) was performed and RGC death was assessed. Results Pou4f1 and Pou4f2 were ablated two weeks after tamoxifen treatment. Retinal interneurons and Müller glial cells are not affected by the ablation of Pou4f1 or Pou4f2 or both. Although the deletion of both Pou4f1 and Pou4f2 slightly delays the death of RGCs at 3 days post-CONC in adult mice, it does not affect the cell death progress afterwards. Moreoever, deletion of Pou4f1 or Pou4f2 or both has no impact on the long-term viability of RGCs at up to 6 months post-tamoxifen treatment. Conclusion Pou4f1 and Pou4f2 are involved in the acute response to damage to RGCs but are dispensable for the long-term survival of adult RGC in mice.

Huang, Liang; Hu, Fang; Xie, Xiaoling; Harder, Jeffery; Fernandes, Kimberly; Zeng, Xiang-yun; Libby, Richard; Gan, Lin

2014-01-01

214

Quantitative non-linear ultrasonic imaging of targets with significant acoustic impedance contrast--an experimental study.  

PubMed

This study deals with the reconstruction, from ultrasonic measured data, of the sound speed profile of a penetrable two-dimensional target of arbitrary cross-section embedded in an infinite medium. Green's theorem is used to obtain a domain integral representation of the acoustical scattered field, and a discrete formulation of the inverse problem is obtained using a moment method. An iterative non-linear algorithm minimizing the discrepancy between the measured and computed scattered fields is used to reconstruct the sound speed profile in the region of interest. The minimization process is performed using a conjugated-gradient method. An experimental study with significant acoustical impedance contrast targets immersed in water was performed. Images of the sound speed profile obtained by inversion of experimental data are presented. PMID:23927099

Guillermin, Régine; Lasaygues, Philippe; Rabau, Guy; Lefebvre, Jean-Pierre

2013-08-01

215

High-speed imaging, acoustic features, and aeroacoustic computations of jet noise from Strombolian (and Vulcanian) explosions  

NASA Astrophysics Data System (ADS)

imaging of explosive eruptions at Stromboli (Italy), Fuego (Guatemala), and Yasur (Vanuatu) volcanoes allowed visualization of pressure waves from seconds-long explosions. From the explosion jets, waves radiate with variable geometry, timing, and apparent direction and velocity. Both the explosion jets and their wave fields are replicated well by numerical simulations of supersonic jets impulsively released from a pressurized vessel. The scaled acoustic signal from one explosion at Stromboli displays a frequency pattern with an excellent match to those from the simulated jets. We conclude that both the observed waves and the audible sound from the explosions are jet noise, i.e., the typical acoustic field radiating from high-velocity jets. Volcanic jet noise was previously quantified only in the infrasonic emissions from large, sub-Plinian to Plinian eruptions. Our combined approach allows us to define the spatial and temporal evolution of audible jet noise from supersonic jets in small-scale volcanic eruptions.

Taddeucci, J.; Sesterhenn, J.; Scarlato, P.; Stampka, K.; Del Bello, E.; Pena Fernandez, J. J.; Gaudin, D.

2014-05-01

216

An acoustic pyrometer system for tomographic thermal imaging in power plant boilers  

Microsoft Academic Search

The paper presents an acoustic pyrometry method for the reconstruction of temperature maps inside power plant boilers. It is based on measuring times-of-flight of acoustic waves along a number of straight paths in a cross-section of the boiler; via an integral relationship, these times depend on the temperature of the gaseous medium along the paths. On this basis, 2D temperature

Mauro Bramanti; Emanuele A. Salerno; Anna Tonazzini; Sauro Pasini; Antonio Gray

1996-01-01

217

Density Functional Study of Structures and Electron Affinities of BrO4F/BrO4F?  

PubMed Central

The structures, electron affinities and bond dissociation energies of BrO4F/BrO4F? species have been investigated with five density functional theory (DFT) methods with DZP++ basis sets. The planar F-Br…O2…O2 complexes possess 3A? electronic state for neutral molecule and 4A? state for the corresponding anion. Three types of the neutral-anion energy separations are the adiabatic electron affinity (EAad), the vertical electron affinity (EAvert), and the vertical detachment energy (VDE). The EAad value predicted by B3LYP method is 4.52 eV. The bond dissociation energies De (BrO4F ? BrO4-mF + Om) (m = 1–4) and De? (BrO4F? ? BrO4-mF? + Om and BrO4F? ? BrO4-mF + Om?) are predicted. The adiabatic electron affinities (EAad) were predicted to be 4.52 eV for F-Br…O2…O2 (3A??4A?) (B3LYP method).

Gong, Liangfa; Xiong, Jieming; Wu, Xinmin; Qi, Chuansong; Li, Wei; Guo, Wenli

2009-01-01

218

Trigonal bipyramidal 5d-4f molecules with SMM behavior.  

PubMed

A family of trigonal bipyramidal (TBP) 5d-4f cyanide bridged aggregates were synthesized that exhibit slow relaxation of the magnetization below 4 K as indicated by a signal in the out-of-phase ac susceptibility data under zero field. PMID:24429464

Saber, Mohamed R; Dunbar, Kim R

2014-02-28

219

Application of pulse compression signal processing techniques to electromagnetic acoustic transducers for noncontact thickness measurements and imaging  

SciTech Connect

A pair of noncontact Electromagnetic Acoustic Transducers (EMATs) has been used for thickness measurements and imaging of metallic plates. This was performed using wide bandwidth EMATs and pulse-compression signal processing techniques, using chirp excitation. This gives a greatly improved signal-to-noise ratio for air-coupled experiments, increasing the speed of data acquisition. A numerical simulation of the technique has confirmed the performance. Experimental results indicate that it is possible to perform noncontact ultrasonic imaging and thickness gauging in a wide range of metal plates. An accuracy of up to 99% has been obtained for aluminum, brass, and copper samples. The resolution of the image obtained using the pulse compression approach was also improved compared to a transient pulse signal from conventional pulser(receiver). It is thus suggested that the combination of EMATs and pulse compression can lead to a wide range of online applications where fast time acquisition is required.

Ho, K.S.; Gan, T.H.; Billson, D.R.; Hutchins, D.A. [School of Engineering, University of Warwick, Coventry, CV4 7AL (United Kingdom)

2005-05-15

220

In vitro assessment of the relationship between acoustic properties and bone mass density of the calcaneus by comparison of ultrasound parametric imaging and quantitative computed tomography  

Microsoft Academic Search

This in vitro study aimed to add new experimental evidence to clarify the relation between acoustic properties of bone and bone mineral density (BMD) of the human calcaneus. Parametric images of normalized broadband ultrasonic attenuation (nBUA) and ultrasound bone velocity (UBV) were compared with quantitative computed tomography (QCT) images of the calcaneus. The experimental protocol was designed to control the

P. Laugier; P. Droin; A. M. Laval-Jeantet; G. Berger

1997-01-01

221

Quantitative assessment of acoustic intensity in the focused ultrasound field using hydrophone and infrared imaging.  

PubMed

With the popularity of ultrasound therapy in clinics, characterization of the acoustic field is important not only to the tolerability and efficiency of ablation, but also for treatment planning. A quantitative method was introduced to assess the intensity distribution of a focused ultrasound beam using a hydrophone and an infrared camera with no prior knowledge of the acoustic and thermal parameters of the absorber or the configuration of the array elements. This method was evaluated in both theoretical simulations and experimental measurements. A three-layer model was developed to calculate the acoustic field in the absorber, the absorbed acoustic energy during the sonication and the consequent temperature elevation. Experiments were carried out to measure the acoustic pressure with the hydrophone and the temperature elevation with the infrared camera. The percentage differences between the derived results and the simulation are <4.1% for on-axis intensity and <21.1% for -6-dB beam width at heating times up to 360 ms in the focal region of three phased-array ultrasound transducers using two different absorbers. The proposed method is an easy, quick and reliable approach to calibrating focused ultrasound transducers with satisfactory accuracy. PMID:23972377

Yu, Ying; Shen, Guofeng; Zhou, Yufeng; Bai, Jingfeng; Chen, Yazhu

2013-11-01

222

Acoustic radiation force impulse imaging for non-invasive assessment of liver fibrosis in chronic hepatitis B.  

PubMed

Acoustic radiation force impulse (ARFI) imaging is a novel ultrasound-based elastography method that is integrated in a conventional ultrasound machine. It might provide an alternative method to transient elastography for the noninvasive assessment of liver fibrosis. While previous studies have shown comparable diagnostic accuracy of ARFI to transient elastography in chronic hepatitis C, the aim of the present prospective multicenter study was to evaluate ARFI for the assessment of liver fibrosis in chronic hepatitis B. ARFI imaging involves the mechanical excitation of tissue using short-duration acoustic pulses to generate localized displacements in tissue. The displacements result in shear-wave propagation which is tracked using ultrasonic, correlation-based methods and recorded in m/s. In the present international prospective study, patients infected with chronic hepatitis B received ARFI imaging, blood tests and if available transient elastography. The results were compared to liver biopsy as reference method analysed by a central pathologist. In 92 of 114 patients, a comparison of ARFI with transient elastography was possible. ARFI imaging and transient elastography correlated significantly with histological fibrosis stage. The diagnostic accuracy expressed as areas under ROC curves for ARFI imaging and transient elastography was 0.75 and 0.83 for the diagnosis of significant fibrosis (F ? 2), 0.93 and 0.94 for the diagnosis of severe fibrosis (F ? 3), and 0.97 and 0.93 for the diagnosis of liver cirrhosis, respectively. No significant difference was found between ARFI and transient elastography. ARFI imaging is a reliable ultrasound-based method for the assessment of advanced stages of liver fibrosis in chronic hepatitis B. PMID:23490368

Friedrich-Rust, M; Buggisch, P; de Knegt, R J; Dries, V; Shi, Y; Matschenz, K; Schneider, M D; Herrmann, E; Petersen, J; Schulze, F; Zeuzem, S; Sarrazin, C

2013-04-01

223

Clinical feasibility study of combined opto-acoustic and ultrasonic imaging modality providing coregistered functional and anatomical maps of breast tumors  

NASA Astrophysics Data System (ADS)

We report on findings from the clinical feasibility study of the ImagioTM. Breast Imaging System, which acquires two-dimensional opto-acoustic (OA) images co-registered with conventional ultrasound using a specialized duplex hand-held probe. Dual-wavelength opto-acoustic technology is used to generate parametric maps based upon total hemoglobin and its oxygen saturation in breast tissues. This may provide functional diagnostic information pertaining to tumor metabolism and microvasculature, which is complementary to morphological information obtained with conventional gray-scale ultrasound. We present co-registered opto-acoustic and ultrasonic images of malignant and benign tumors from a recent clinical feasibility study. The clinical results illustrate that the technology may have the capability to improve the efficacy of breast tumor diagnosis. In doing so, it may have the potential to reduce biopsies and to characterize cancers that were not seen well with conventional gray-scale ultrasound alone.

Zalev, Jason; Clingman, Bryan; Smith, Remie J.; Herzog, Don; Miller, Tom; Stavros, A. Thomas; Ermilov, Sergey; Conjusteau, André; Tsyboulski, Dmitri; Oraevsky, Alexander A.; Kist, Kenneth; Dornbluth, N. C.; Otto, Pamela

2013-03-01

224

Acoustic profiles and images of the Palos Verdes margin: implications concerning deposition from the White's Point outfall  

NASA Astrophysics Data System (ADS)

Subbottom profiles and sidescan-sonar images collected on and around the Palos Verdes Shelf show a surficial deposit interpreted to contain effluent from the White's Point diffusers, as well as showing several geologic features that affect the deposit's distribution. The effluent-affected deposit is visible in high-resolution subbottom profiles on the shelf and the adjacent San Pedro basin slope to water depths of 170 m. It has a maximum thickness of 75 cm and was mapped acoustically over an area of 10.8 km 2, which encompasses a volume of about 3.2 million m 3. The deposit's basal reflector is acoustically distinct over most of the mapped area, implying that the deposit has not been extensively mixed across its base, perhaps being relatively free of reworking since its initial deposition. Nearshore, the basal reflector is weak and fades away toward land, which could result from syndepositional intermixing of coarse native sediment (particularly from the Portuguese Bend landslide) with effluent in the high-energy nearshore zone, or postdepositionally by physical (wave) or biological mixing across the interface. The geometry of the deposit implies that effluent is dispersed primarily in a northwesterly and seaward direction from the diffusers. Dispersal across the shelf break is in some places strongly affected by topography, particularly by submarine canyons. The deposit overlies stratified and unstratified Quaternary sediment, up to 30 m thick, that in turn overlies the irregular erosional surface of deformed Miocene bedrock that crops out in places on the shelf and upper basin slope. The effluent-affected deposit rests on potentially unstable landslide deposits on the San Pedro basin slope. The acoustic profiles and side-scan images show evidence for active and inactive vents, probably of hot water and gas, some of which are within the boundary of the effluent-affected sediment deposit and could disrupt it if seepage occurs.

Hampton, Monty A.; Karl, Herman A.; Murray, Christopher J.

2002-05-01

225

Acoustic profiles and images of the Palos Verdes margin: Implications concerning deposition from the White's Point outfall  

USGS Publications Warehouse

Subbottom profiles and sidescan-sonar images collected on and around the Palos Verdes Shelf show a surficial deposit interpreted to contain effluent from the White's Point diffusers, as well as showing several geologic features that affect the deposit's distribution. The effluent-affected deposit is visible in high-resolution subbottom profiles on the shelf and the adjacent San Pedro basin slope to water depths of 170 m. It has a maximum thickness of 75 cm and was mapped acoustically over an area of 10.8 km2, which encompasses a volume of about 3.2 million m3. The deposit's basal reflector is acoustically distinct over most of the mapped area. implying that the deposit has not been extensively mixed across its base, perhaps being relatively free of reworking since its initial deposition. Nearshore, the basal reflector is weak and fades away toward land, which could result from syndepositional intermixing of coarse native sediment (particularly from the Portuguese Bend landslide) with effluent in the high-energy nearshore zone, or postdepositionally by physical (wave) or biological mixing across the interface. The geometry of the deposit implies that effluent is dispersed primarily in a northwesterly and seaward direction from the diffusers. Dispersal across the shelf break is in some places strongly affected by topography, particularly by submarine canyons. The deposit overlies stratified and unstratified Quaternary sediment, up to 30m thick, that in turn overlies the irregular erosional surface of deformed Miocene bedrock that crops out in places on the shelf and upper basin slope. The effluent-affected deposit rests on potentially unstable landslide deposits on the San Pedro basin slope. The acoustic profiles and side-scan images show evidence for active and inactive vents, probably of hot water and gas, some of which are within the boundary of the effluent-affected sediment deposit and could disrupt it if seepage occurs. ?? 2002 Elsevier Science Ltd. All rights reserved.

Hampton, M. A.; Karl, H. A.; Murray, C. J.

2002-01-01

226

Remote acoustic imaging of the plume from a submarine spring in an arctic fjord.  

PubMed

Acoustic backscatter observations at 200 kilohertz were made of the buoyant plume from a submarine spring at a depth of 47 meters in Cambridge Fiord, Baffin Island. Vertical velocities of up to 37 centimeters per second are inferred from the ascent rates of discrete scattering structures in the plume. PMID:17782423

Hay, A E

1984-09-14

227

Ultrafast imaging of beamformed shear waves induced by the acoustic radiation force. Application to transient elastography  

Microsoft Academic Search

Several tissue characterization techniques based on acoustic radiation force have been proposed to remotely excite soft tissues with ultrasound. Recently, in transient elastography, an ultrafast echographic device was developed to follow the propagation inside soft tissues of very low frequency shear waves (?100 Hz). These waves were generated using a vibrating system located at the body surface. In this paper,

J. Bercoff; M. Tanter; S. Chaffai; M. Fink

2002-01-01

228

Noninvasive Ultrasound Imaging for Bone Quality Assessment Using Scanning Confocal Acoustic Diagnosis, ?CT, DXA Measurements, and Mechanical Testing  

NASA Astrophysics Data System (ADS)

Osteoporosis is a disease characterized by decreased bone mass and progressive deterioration of the microstructure, affecting both mineral density and bone's fragility. Current diagnoses are only measuring apparent bone mineral density (AppBMD). Using our newly developed scanning confocal acoustic diagnostic (SCAD) system, we evaluated the ability of quantitative ultrasound in noninvasively predicting bone's quantity and quality on 19 human cadaver calcanei. Results show that ultrasound attenuation image on intact calcaneus represents bone mass distribution. High correlation (R=0.82) exists between SCAD determined broadband ultrasound attenuation (BUA) and DXA determined AppBMD at the calcaneus, as well as in the AppBMD result at femoral neck (R=0.81). SCAD determined BUA and ultrasound velocity (UV) are highly correlated with the micro-CT and mechanical testing determined bone quantity and quality parameters. These results suggest that image-based quantitative ultrasound is able to identify ROI and predict both bone mass and strength.

Qin, Yi-Xian; Xia, Yi; Lin, Wei; Mittra, Erik; Rubin, Clint; Gruber, Barry

229

Electronic circular dichroism in the 4f-4f transitions of a series of cesium tetrakis (+)-3-heptafluorobutyrylcamphorate Ln(III) complexes.  

PubMed

For electronic circular dichroism in the 4f-4f transitions (4f-4f CD) of a series of nine tetrakis ((+)-3-heptafluorobutyrylcamphorato) Ln(III) complexes, ?-SAPR-8-C(4)(llll) Cs[Ln((+)-hfbc)(4)]·H(2)O (Cs-Ln = Cs-Pr, -Nd, -Sm, -Eu, -Dy, -Ho, -Er, -Tm, -Yb), the spectroscopic observables such as the dissymmetry factor g = ??/? values with the intensities (??) of the CD components and the molar absorption intensities (?) in the 4f-4f transitions between the (2S+1)L(J) levels are compared with each other to test the classification of the CD components in the relative order of the observables predicted in terms of the selection rule for 4f-4f transitions. The 4f-4f CD-based chiroptical spectra-structural relationship across the series of ?-SAPR-8-C(4)(llll) lanthanide(III) complexes is proposed: the signs of the 4f-4f CD or CPL in the hypersensitive transitions are related to the absolute configuration; Ln complexes with a negative CD component have the ?-configuration around Ln(III) and vice versa. PMID:22832476

Shirotani, Dai; Sato, Hisako; Yamanari, Kazuaki; Kaizaki, Sumio

2012-09-21

230

CYP4F2 genetic variant alters required warfarin dose  

PubMed Central

Warfarin is an effective, commonly prescribed anticoagulant used to treat and prevent thrombotic events. Because of historically high rates of drug-associated adverse events, warfarin remains underprescribed. Further, interindividual variability in therapeutic dose mandates frequent monitoring until target anticoagulation is achieved. Genetic polymorphisms involved in warfarin metabolism and sensitivity have been implicated in variability of dose. Here, we describe a novel variant that influences warfarin requirements. To identify additional genetic variants that contribute to warfarin requirements, screening of DNA variants in additional genes that code for drug-metabolizing enzymes and drug transport proteins was undertaken using the Affymetrix drug-metabolizing enzymes and transporters panel. A DNA variant (rs2108622; V433M) in cytochrome P450?4F2 (CYP4F2) was associated with warfarin dose in 3 independent white cohorts of patients stabilized on warfarin representing diverse geographic regions in the United States and accounted for a difference in warfarin dose of approximately 1 mg/day between CC and TT subjects. Genetic variation of CYP4F2 was associated with a clinically relevant effect on warfarin requirement.

Caldwell, Michael D.; Awad, Tarif; Johnson, Julie A.; Gage, Brian F.; Falkowski, Mat; Gardina, Paul; Hubbard, Jason; Turpaz, Yaron; Langaee, Taimour Y.; Eby, Charles; King, Cristi R.; Brower, Amy; Schmelzer, John R.; Glurich, Ingrid; Vidaillet, Humberto J.; Yale, Steven H.; Qi Zhang, Kai; Berg, Richard L.

2008-01-01

231

Multiscale monitoring of interface failure of brittle coating/ductile substrate systems: A non-destructive evaluation method combined digital image correlation with acoustic emission  

NASA Astrophysics Data System (ADS)

In this paper, we proposed a non-destructive evaluation method combined digital image correlation with acoustic emission techniques. The method was used to in situ monitor interface failure and internal damage of brittle coating/ductile substrate systems with different size scales. The results show that there is a good relationship between digital image correlation and acoustic emission signals, which can be applied to judge cracking formation and coating delamination and to determine fracture toughness of a thermal barrier coating system subjected to bending.

Mao, W. G.; Wu, D. J.; Yao, W. B.; Zhou, M.; Lu, C.

2011-10-01

232

Polytypism in wagnerite, Mg2PO4(F,OH)  

NASA Astrophysics Data System (ADS)

The Mg, Fe and Mn phosphates with formula Me2+_2PO_4(F,OH) belong to two groups which share the same fundamental monoclinic structure type, but in one of which the b parameter is doubled. Specifically, magniotriplite (Mg), zwieselite (Fe) and triplite (Mn) are F-dominant and have space group I2/a, with Z = 8, b_0 ? 6.5 Å, whereas wagnerite (Mg, F dominant), wolfeite (Fe, OH dominant) and triploidite (Mn, OH dominant) have space group P2_1/a, Z = 16 and b = 2 b_0 ? 13 Å. In I2/a magniotriplite, eight F atoms are distributed over two eightfold equipoints with 50% occupancy. Periodic ordering of the F atoms into each of these equipoint positions (say A and B), each alternately void and fully occupied along b, leads to a new, double cell with space group P2_1/a and a 2b_0 parameter, i.e. the wagnerite cell, in which the succession of the occupied F positions along b is ABAB (Tadini 1981). Ren et al. (2002) reported from granulite-facies rocks of East Antarctica a wagnerite "polymorph" structurally very close to wagnerite, but with space group Ia, b = 5b_0 ? 32 Å and Z = 40. We studied wagnerite crystals from granulite-facies rocks of central Australia (Vry and Cartwright 1994). CCD area-detector imaging revealed either 7b_0 ? 45 Å or 9b_0 ? 57 Å superstructures (Z = 56 and 72, respectively). The structure of the 9b_0 phase was refined in space group Ia to R = 6% from 11903 unique reflections. We show that wagnerite and the 5b_0, 7b_0 and 9b_0 phases share the same topological arrangement of cations and oxygen atoms, differ only by the periodic faulting of the A-B succession of the F atoms along b, and are all members of a polytypic series based on the magniotriplite cell (b_0). The relevant polytypes and F ordering schemes are wagnerite-a2bc (AB), wagnerite-a5bc (ABAAB), wagnerite-a7bc (ABAABAB) and wagnerite-a9bc (ABAABABAB). Reinvestigation of OH-rich wagnerite from Miregn (Central Alps) and of OH-rich to OH-dominant wagnerite from Dora-Maira (W. Alps) confirmed the original 2b polytype. The question arises whether the longer-period polytypes are not restricted to F-rich members, i.e. whether OH groups stabilize the most ordered configuration (2b) or, depending on the P and T conditions, other, completely different polymorphic structures that only exist for the Me2+_2PO_4(OH) members (cf. holtedahlite-satterlyite, althausite). Ren L., Grew E.S., Xiong M., Ma Z. (2002) GSA meeting, Denver, abstr. No. 234-8. Tadini C. (1981) Bull. Minéral. 104, 677-680. Vry J.K., Cartwright I. (1994) Contrib. Mineral. Petrol. 116, 78-91.

Chopin, C.; Armbruster, T.; Leyx, C.

2003-04-01

233

Defect characterization by acoustic holography. Volume 1: Imaging in field environments  

NASA Astrophysics Data System (ADS)

The results obtained when acoustic holographic (AH) techniques (also known as ultrasonic holography) were applied in a field environment to characterization of defects in pressure vessels are described. The production components contained natural or fabrication induced defects and the nonproduction specimens contained artificially induced defects. Seven types of components were evaluated: (1) production component thick plate base metal; (2) production component nozzle weld; (3) production component circle seam weld; (4) production component long seam weld; (5) nonproduction component two HSST thermal shock vessels; (6) nonproduction component acoustic emission pressure vessel; and (7) nonproduction component clad weld test block. The program developed a fairly large data base that includes interpreted AH imagery, destructive test photos, and the unprocessed holographic data base.

Holt, A.; Brophy, J.

1980-09-01

234

Electron acoustic imaging of Mn 50 Ni 28 Ga 22 ferromagnetic shape memory alloy  

Microsoft Academic Search

The novel ferromagnetic shape memory alloy Mn50Ni28Ga22 exhibits a single martensite phase with tetragonal structure at room temperature. Its martensite structure was investigated\\u000a by scanning electron acoustic microscopy. Stripe twin variants exist in every grain and exhibit the configurations of the\\u000a typical self-accommodation arrangement. The interfaces between twin variants are straight and clear. However, the magnetic\\u000a domain walls obtained by

H. Z. Song; Y. X. Li; H. R. Zeng; L. Ma; G. H. Wu; S. X. Hui; G. R. Li; Q. R. Yin

2008-01-01

235

Acoustic characterization and contrast imaging of microbubbles encapsulated by polymeric shells coated or filled with magnetic nanoparticles.  

PubMed

The combination of superparamagnetic iron oxide nanoparticles with polymeric air-filled microbubbles is used to produce two types of multimodal contrast agents to enhance medical ultrasound and magnetic resonance imaging. The nanoparticles are either covalently linked to the shell or physically entrapped into the shell. In this paper, the characterization of the acoustic properties (backscattered power, fracturing pressure, attenuation and dispersion of the ultrasonic wave) and ultrasound imaging of the two types of magnetic microbubbles are presented. In vitro B-mode images are generated using a medical ultrasound scanner by applying a nonconventional signal processing technique that is suitable to detect polymeric bubbles and based on the combination of multipulse excitation and chirp coding. Even if both types of microbubbles can be considered to be effective ultrasound contrast agents, the different structure of the shell loaded with nanoparticles has a pronounced effect on the echogenicity and the detection sensitivity of the imaging technique. The best results are obtained using microbubbles that are externally coated with nanoparticles. A backscattered power of 20?dB was achieved at lower concentration, and an increment of 8?dB in the contrast-to-tissue ratio was observed with respect to the more rigid microbubbles with particles entrapped into the shell. PMID:24180801

Sciallero, Claudia; Grishenkov, Dmitry; Kothapalli, Satya V V N; Oddo, Letizia; Trucco, Andrea

2013-11-01

236

Flow sorting and sequencing meadow fescue chromosome 4F.  

PubMed

The analysis of large genomes is hampered by a high proportion of repetitive DNA, which makes the assembly of short sequence reads difficult. This is also the case in meadow fescue (Festuca pratensis), which is known for good abiotic stress resistance and has been used in intergeneric hybridization with ryegrasses (Lolium spp.) to produce Festulolium cultivars. In this work, we describe a new approach to analyze the large genome of meadow fescue, which involves the reduction of sample complexity without compromising information content. This is achieved by dissecting the genome to smaller parts: individual chromosomes and groups of chromosomes. As the first step, we flow sorted chromosome 4F and sequenced it by Illumina with approximately 50× coverage. This provided, to our knowledge, the first insight into the composition of the fescue genome, enabled the construction of the virtual gene order of the chromosome, and facilitated detailed comparative analysis with the sequenced genomes of rice (Oryza sativa), Brachypodium distachyon, sorghum (Sorghum bicolor), and barley (Hordeum vulgare). Using GenomeZipper, we were able to confirm the collinearity of chromosome 4F with barley chromosome 4H and the long arm of chromosome 5H. Several new tandem repeats were identified and physically mapped using fluorescence in situ hybridization. They were found as robust cytogenetic markers for karyotyping of meadow fescue and ryegrass species and their hybrids. The ability to purify chromosome 4F opens the way for more efficient analysis of genomic loci on this chromosome underlying important traits, including freezing tolerance. Our results confirm that next-generation sequencing of flow-sorted chromosomes enables an overview of chromosome structure and evolution at a resolution never achieved before. PMID:24096412

Kopecký, David; Martis, Mihaela; ?íhalíková, Jarmila; H?ibová, Eva; Vrána, Jan; Bartoš, Jan; Kopecká, Jitka; Cattonaro, Federica; Sto?es, Št?pán; Novák, Petr; Neumann, Pavel; Macas, Ji?í; Šimková, Hana; Studer, Bruno; Asp, Torben; Baird, James H; Navrátil, Petr; Karafiátová, Miroslava; Kubaláková, Marie; Šafá?, Jan; Mayer, Klaus; Doležel, Jaroslav

2013-11-01

237

Detecting the Activation of a Self-Healing Mechanism in Concrete by Acoustic Emission and Digital Image Correlation  

PubMed Central

Autonomous crack healing in concrete is obtained when encapsulated healing agent is embedded into the material. Cracking damage in concrete elements ruptures the capsules and activates the healing process by healing agent release. Previously, the strength and stiffness recovery as well as the sealing efficiency after autonomous crack repair was well established. However, the mechanisms that trigger capsule breakage remain unknown. In parallel, the conditions under which the crack interacts with embedded capsules stay black-box. In this research, an experimental approach implementing an advanced optical and acoustic method sets up scopes to monitor and justify the crack formation and capsule breakage of concrete samples tested under three-point bending. Digital Image Correlation was used to visualize the crack opening. The optical information was the basis for an extensive and analytical study of the damage by Acoustic Emission analysis. The influence of embedding capsules on the concrete fracture process, the location of capsule damage, and the differentiation between emissions due to capsule rupture and crack formation are presented in this research. A profound observation of the capsules performance provides a clear view of the healing activation process.

Tsangouri, E.; Aggelis, D. G.; Van Tittelboom, K.; De Belie, N.; Van Hemelrijck, D.

2013-01-01

238

Detecting the activation of a self-healing mechanism in concrete by acoustic emission and digital image correlation.  

PubMed

Autonomous crack healing in concrete is obtained when encapsulated healing agent is embedded into the material. Cracking damage in concrete elements ruptures the capsules and activates the healing process by healing agent release. Previously, the strength and stiffness recovery as well as the sealing efficiency after autonomous crack repair was well established. However, the mechanisms that trigger capsule breakage remain unknown. In parallel, the conditions under which the crack interacts with embedded capsules stay black-box. In this research, an experimental approach implementing an advanced optical and acoustic method sets up scopes to monitor and justify the crack formation and capsule breakage of concrete samples tested under three-point bending. Digital Image Correlation was used to visualize the crack opening. The optical information was the basis for an extensive and analytical study of the damage by Acoustic Emission analysis. The influence of embedding capsules on the concrete fracture process, the location of capsule damage, and the differentiation between emissions due to capsule rupture and crack formation are presented in this research. A profound observation of the capsules performance provides a clear view of the healing activation process. PMID:24381518

Tsangouri, E; Aggelis, D G; Van Tittelboom, K; De Belie, N; Van Hemelrijck, D

2013-01-01

239

Hyperfine structure measurements in the ground states4 F 3\\/2,4 F 5\\/2 and4 F 7\\/2 of Ta181 with the atomic beam magnetic resonance method  

Microsoft Academic Search

Applying a recently developed evaporation technique for refractory elements the following results have been obtained for Ta181 in an atomic beam magnetic resonance experiment studying the hyperfine structure of 3 levels of the ground state multiplet4 F: 10050_2005_Article_BF01407256_TeX2GIFE1.gif begin{gathered} g_J (^4 F_{3\\/2} ) = 0.45024 (4) \\\\ Delta v (^4 F_{3\\/2} ;F = 5 leftrightarrow F = 4) = 1822.389

S. Büttgenbach; G. Meisel

1971-01-01

240

Optimal design of a transmit\\/receive system with a reflector and a transducer lens for long-range underwater acoustic imaging  

Microsoft Academic Search

As a transmitting\\/receiving system for long-range underwater acoustic imaging, the shape of a lens attached to the disk transducer, the shape of a relatively small reflector, and the transducer positioning are optimized so that a plane wave is generated at the plane bounded by the circularly symmetrical reflector edge. The actual field distribution on the aperture plane and the beam

Jong Taik Oh; Song Bai Park

1991-01-01

241

Compressive sensing beamforming based on covariance for acoustic imaging with noisy measurements.  

PubMed

Compressive sensing, a newly emerging method from information technology, is applied to array beamforming and associated acoustic applications. A compressive sensing beamforming method (CSB-II) is developed based on sampling covariance matrix, assuming spatially sparse and incoherent signals, and then examined using both simulations and aeroacoustic measurements. The simulation results clearly show that the proposed CSB-II method is robust to sensing noise. In addition, aeroacoustic tests of a landing gear model demonstrate the good performance in terms of resolution and sidelobe rejection. PMID:24181989

Zhong, Siyang; Wei, Qingkai; Huang, Xun

2013-11-01

242

Reducing the Impacts of Hydroelectric Dams on Juvenile Anadromous Fishes: Bioengineering Evaluations Using Acoustic Imaging in the Columbia River, USA  

SciTech Connect

Dams impact the survival of juvenile anadromous fishes by obstructing migration corridors, lowering water quality, delaying migrations, and entraining fish in turbine discharge. To reduce these impacts, structural and operational modifications to dams— such as voluntary spill discharge, turbine intake guidance screens, and surface flow outlets—are instituted. Over the last six years, we have used acoustic imaging technology to evaluate the effects of these modifications on fish behavior, passage rates, entrainment zones, and fish/flow relationships at hydroelectric projects on the Columbia River. The imaging technique has evolved from studies documenting simple movement patterns to automated tracking of images to merging and analysis with concurrent hydraulic data. This chapter chronicles this evolution and shows how the information gleaned from the scientific evaluations has been applied to improve passage conditions for juvenile salmonids. We present data from Bonneville and The Dalles dams that document fish behavior and entrainment zones at sluiceway outlets (14 to 142 m3/s), fish passage rates through a gap at a turbine intake screen, and the relationship between fish swimming effort and hydraulic conditions. Dam operators and fisheries managers have applied these data to support decisions on operational and structural changes to the dams for the benefit of anadromous fish populations in the Columbia River basin.

Johnson, Gary E.; Ploskey, Gene R.; Hedgepeth, J.; Khan, Fenton; Mueller, Robert P.; Nagy, William T.; Richmond, Marshall C.; Weiland, Mark A.

2008-07-29

243

Human cytochrome P450 4F3: structure, functions, and prospects.  

PubMed

Cytochrome P450 4F3 (CYP4F3), originally identified as one of the leukotriene B4 ?-hydroxylases, belongs to a CYP gene family that comprises several members, which participate in the metabolism of various endobiotics, as well as some xenobiotics. The CYP4F gene family is clustered in a 0.5-Mb stretch of genomic DNA on the p13 region of chromosome 19. Apart from the ?-hydroxylation of leukotriene B4 and prostaglandins, CYP4F3 is the main catalyst in the oxidation of fatty acid epoxides. CYP4F3 expression results from the synthesis of two distinct enzymes, CYP4F3A and CYP4F3B, which originate from the alternative splicing of a single pre-mRNA precursor molecule. Remarkably, the selection of either isoform is part of a tissue-specific control through which CYP3F3A is mostly expressed in leukocytes and CYP4F3B mostly in the liver. Recently, CYP4F3 single nucleotide polymorphisms have been incriminated in the onset of pathologies, including celiac or Crohn's diseases. Although much has been discovered in the regulation and function of CYP4F2, the closest CYP4F subfamily member, analyses of CYP4F3 enzymes lag somewhat behind in the field of our knowledge. In this short review, emphasis will be placed on the regulation and the functional roles of human CYP4F3. PMID:22706230

Corcos, Laurent; Lucas, Danièle; Le Jossic-Corcos, Catherine; Dréano, Yvonne; Simon, Brigitte; Plée-Gautier, Emmanuelle; Amet, Yolande; Salaün, Jean-Pierre

2012-01-01

244

Acoustic radiation force impulse imaging for assessing graft fibrosis after pediatric living donor liver transplantation: a pilot study.  

PubMed

Graft fibrosis is a common finding during protocol biopsy examinations after pediatric liver transplantation. We evaluated the clinical utility of liver stiffness measurements by acoustic radiation force impulse (ARFI) imaging, a novel ultrasound-based elastography method, for assessing graft fibrosis after pediatric living donor liver transplantation (LDLT). We performed 73 liver stiffness measurements by ARFI imaging in 65 pediatric LDLT recipients through the upper midline of the abdomen (midline value) and the right intercostal space (intercostal value) around the time of protocol biopsy examinations. Fifty-nine of these liver stiffness measurements could be compared with histopathological findings. Graft fibrosis was assessed according to the degrees of portal and pericellular fibrosis. Significant fibrosis, which was defined as F2 or worse portal fibrosis and/or moderate or worse pericellular fibrosis, was observed in 14 examinations, which had significantly higher midline (P = 0.005) and intercostal values (P < 0.001) than the others. Liver stiffness measurements by ARFI imaging significantly increased with increases in the portal and pericellular fibrosis grades. For the diagnosis of significant fibrosis, the areas under the receiver operating characteristic curve (AUROCs) were 0.760 (P = 0.005) and 0.849 (P < 0.001) for the midline and intercostal values, respectively. The optimal cutoff values were 1.30 and 1.39 m/second for midline and intercostal values, respectively. Slight but significant elevations were noted in the results of biochemical liver tests: serum levels of ?-glutamyltransferase showed the highest AUROC (0.809, P = 0.001) with an optimal cutoff value of 20 IU/L. In conclusion, liver stiffness measurements by ARFI imaging had good accuracy for diagnosing graft fibrosis after pediatric LDLT. The pericellular pattern of fibrosis was frequently observed after pediatric LDLT, and moderate pericellular fibrosis was detectable by ARFI imaging. PMID:23894066

Tomita, Hirofumi; Hoshino, Ken; Fuchimoto, Yasushi; Ebinuma, Hirotoshi; Ohkuma, Kiyoshi; Tanami, Yutaka; Du, Wenlin; Masugi, Yohei; Shimojima, Naoki; Fujino, Akihiro; Kano, Motohiro; Fujimura, Takumi; Ishihama, Hideo; Shimizu, Takahiro; Tanabe, Minoru; Saito, Hidetsugu; Sakamoto, Michiie; Hibi, Toshifumi; Kitagawa, Yuko; Kuroda, Tatsuo

2013-11-01

245

Studies of low-lying triplet states in 1,3-C4F6, c-C4F6 and 2-C4F6 by electron energy-loss spectroscopy and ab initio calculations  

NASA Astrophysics Data System (ADS)

This Letter reports on the first measurements of the lowest lying triplet states as studied by electron energy loss spectroscopy for C4F6 isomers, hexafluoro-1,3-butadiene (1,3-C4F6), hexafluorocyclobutene (c-C4F6) and hexafluoro-2-butyne (2-C4F6). This study has been performed at an incident electron energy of 30 eV, 30°, whilst sweeping the energy loss over the range 2.0-15.0 eV. The electronic state spectroscopy has been investigated and the assignments supported by multi-reference quantum chemical calculations. The transition to the steepest electronic excited potential energy curve, is suggested to be dominant for 2-C4F6, due to the large broadening in its energy profile.

Limão-Vieira, P.; Duflot, D.; Anzai, K.; Kato, H.; Hoshino, M.; Silva, F. Ferreira da; Mogi, D.; Tanioka, T.; Tanaka, H.

2013-06-01

246

ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS  

SciTech Connect

Three major goals were accomplished during this phase. First, a study was completed of the effects of stress-induced changes in anisotropic elastic moduli in sandstone. Second, a new method for measuring the anisotropic poroelastic moduli from acoustic data was developed. Third, a series of triaxial experiments were conducted on unconsolidated sands to identify pressure/stress conditions where liquefaction occurs under high confining pressures. Stress-induced changes in anisotropic Young's moduli and shear moduli were observed during deformational pathway experiments. A new method was made for the acquisition of compressional and shear wave velocities along a series of 3-dimensional raypaths through a core sample as it is subjected to deformation. Three different deformational pathway experiments were conducted. During the hydrostatic deformation experiment, little or no anisotropy was observed in either the Young's moduli or shear moduli. Significant deformational anisotropies were observed in both moduli during the uniaxial strain test and the triaxial compression experiment but each had a different nature. During the triaxial experiment the axial and lateral Young's moduli and shear moduli continued to diverge as load was applied. During the uniaxial strain experiment the anisotropy was ''locked in'' early in the loading phase but then remained steady as both the confining pressure and axial stress were applied. A new method for measuring anisotropic Biot's effective stress parameters has also been developed. The method involves measuring the compressional and shear wave velocities in the aforementioned acoustic velocity experiments while varying stress paths. For a stress-induced transversely isotropic medium the acoustic velocity data are utilized to calculate the five independent elastic stiffness components. Once the elastic stiffness components are determined these can be used to calculate the anisotropic Biot's effective stress parameters, {alpha}{sub v} and {alpha}{sub h}, using the equations of Abousleiman et al. (1996). A series of experiments have been conducted, on an initially inherently isotropic Berea sandstone rock sample, to dynamically determine these anisotropic Biot's parameters during deformational pathway experiments. Data acquired during hydrostatic, triaxial, and uniaxial strain pathway experiments indicates that Biot's effective stress parameter changes significantly if the applied stresses are not hydrostatic. Variations, as large as 20% between the axial (vertical) and lateral (horizontal) Biot's effective stress parameters, were observed in some experiments. A series of triaxial compression experiments have been conducted on unconsolidated sand (Oil Creek sand) to determine the pressure/stress conditions which would be favorable for liquefaction. Liquefaction of geopressured sands is thought to be one of the major causative mechanisms of damaging shallow water flows. The experiments were developed to determine if: (1) liquefaction could be made to occur in this particular sand at high confining pressures, and (2) the state of liquefication had the same nature at high pressure conditions typical of shallow water flows as it does in low confining pressure soil mechanics tests. A series of undrained triaxial experiments were successfully used to document that the Oil Creek sand could undergo liquefaction. The nature (i.e., the shape of the deformational pathway in mean pressure/shear stress space) was very similar to those observed in soil mechanics experiments. The undrained triaxial experiments also indicated that this sand would strain soften at relatively high confining pressures--a necessary precursor to liquefaction. These experiments serve as a starting point for a series of acoustic experiments to determine the signature of compressional and shear wave properties as the sand packs approach the state of liquefaction (and shallow water flows).

Thurman E. Scott, Jr., Ph.D.; Younane Abousleiman, Ph.D.; Musharraf Zaman, Ph.D., P.E.

2002-04-30

247

Pu 4f XPS spectra analysed in Anderson impurity model  

NASA Astrophysics Data System (ADS)

Pu metal displays a sequence of phases, ?, ?, ?, ?, which involve changes in the 5f electronic structure. In the sequence, opposite to expectations in conventional band theory, the volume/Pu atom increases and yet the measured valence band 5f width also increases^1. We report an analysis of the systematic changes in the structured 4f core level XPS spectra^2 using an Anderson impurity model for the 5f electrons and discuss the implications for understanding the phase diagram. ^1 L.E. Cox et al, Phys. Rev. B 46, 13571 (1992). ^2 J.W. Allen et al, J. Electron. Spectrosc. Relat. Phenom., to be published. Supported at LANL by the DoE and at UM by the USDOE under Contract No. DE-FG-02-90ER45416 and by the NSF under Grant No. DMR-94-23741.

Allen, J. W.; Cox, L. E.; Peek, J. M.

1996-03-01

248

An in vivo validation of the application of acoustic radiation force to enhance the diagnostic utility of molecular imaging using 3-d ultrasound.  

PubMed

For more than a decade, the application of acoustic radiation force (ARF) has been proposed as a mechanism to increase ultrasonic molecular imaging (MI) sensitivity in vivo. Presented herein is the first noninvasive in vivo validation of ARF-enhanced MI with an unmodified clinical system. First, an in vitro optical-acoustical setup was used to optimize system parameters and ensure sufficient microbubble translation when exposed to ARF. 3-D ARF-enhanced MI was then performed on 7 rat fibrosarcoma tumors using microbubbles targeted to ?(v)?? and nontargeted microbubbles. Low-amplitude (<25 kPa) 3-D ARF pulse sequences were tested and compared with passive targeting studies in the same animal. Our results demonstrate that a 78% increase in image intensity from targeted microbubbles can be achieved when using ARF relative to the passive targeting studies. Furthermore, ARF did not significantly increase image contrast when applied to nontargeted agents, suggesting that ARF did not increase nonspecific adhesion. PMID:22341052

Gessner, Ryan C; Streeter, Jason E; Kothadia, Roshni; Feingold, Steven; Dayton, Paul A

2012-04-01

249

Catalytic activity and isoform-specific inhibition of rat cytochrome p450 4F enzymes.  

PubMed

Arachidonic acid is omega-hydroxylated to 20-hydroxyeicosatetraenoic acid (20-HETE), which has effects on vasoactivity and renal tubular transport and has been implicated in the regulation of blood pressure. Cytochrome p450 (p450) 4A isoforms are generally considered the major arachidonic acid omega-hydroxylases; however, little is known about the role of rat CYP4F isoforms in 20-HETE formation. The rat CYP4F isoforms, CYP4F1, CYP4F4, CYP4F5, and CYP4F6, were heterologously expressed in Escherichia coli, and their substrate specificity in fatty acid metabolism was characterized. Substrate-binding assays indicated that leukotriene B(4) (LTB(4)) and arachidonic acid bound CYP4F1 and CYP4F4 in a type-I manner with a K(s) of 25 to 59 microM, and lauric acid bound CYP4F4 poorly. Reconstituted CYP4F1 and CYP4F4 catalyzed the omega-hydroxylation of LTB(4) with a K(m) of 24 and 31 microM, respectively, and CYP4F5 had minor activity in LTB(4) metabolism. Importantly, CYP4F1 and CYP4F4 catalyzed the omega-hydroxylation of arachidonic acid with an apparent k(cat) of 9 and 11 min(-1), respectively. Lauric acid was a poor substrate for all of the CYP4F isoforms, and CYP4F6 had no detectable fatty acid omega-hydroxylase activity. The p450 omega-hydroxylase inhibitors 17-octadecynoic acid, 10-undecynyl sulfate, and N-methylsulfonyl-12,12-dibromododec-11-enamide showed isoform-specific inhibition of CYP4F1- and CYP4F4-catalyzed omega-hydroxylation of arachidonic acid and potency differences between the CYP4A and CYP4F isoforms. These data support a significant role for CYP4F1 and CYP4F4 in the formation of 20-HETE and identify p450 inhibitors that can be used to understand the relative contribution of the CYP4A and CYP4F isoforms to renal 20-HETE formation. PMID:14634044

Xu, Fengyun; Falck, John R; Ortiz de Montellano, Paul R; Kroetz, Deanna L

2004-03-01

250

Development and applications of an acoustic package for deep-sea sub-bottom profiling and detailed seafloor imaging  

NASA Astrophysics Data System (ADS)

In the deep-sea geological survey, good survey results are difficult to obtain by a conventional surface-towed acoustic survey system, because the horizontal resolution is limited due to the long distance between the sensor and the target (seafloor). In order to improve the horizontal resolution, a deep-tow system, which tows the sensor in the vicinity of seafloor, is most practical, and many such systems have been developed and used until today. It is not easy, however, to carry out a high-density survey in a small area by maneuvering the towing body altitude sufficiently close to the seafloor with rugged topography. A ROV (Remotely Operated Vehicle) can be used to solve this problem. The ROV makes a high-density 2D survey feasible because of its maneuverability, although a long-distance survey is difficult with it. Accordingly, we have developed an acoustic survey system installed on a ROV. The system named DAIPACK (Deep-sea Acoustic Imaging Package) consists of (1) a deep-sea sub-bottom profiler and (2) a deep-sea sidescan sonar. (1) Deep-sea sub-bottom profiler A light-weight and compact sub-bottom profiler for shallow water was chosen to improve and repackage for the deep sea usage. The system is composed of three units; a transducer, an electronic unit and a notebook computer for system control and data acquisition. The source frequency is 10kHz. To convert the system for the deep sea, the transducer was exchanged for the deep sea model, and the electronic unit was improved accordingly. The electronic unit and the notebook computer were installed in a spherical pressure vessel. (2) Deep-sea sidescan sonar We remodeled a compact shallow sea sidescan sonar(water depth limitation is 30m ) into a deep sea one. This sidescan sonar is composed of a sonar towfish (transducers and an electronic unit ), a cable and a notebook computer (data processor). To accommodate in the deep water, the transducers were remodeled into a high pressure resistance type, and the electronic unit and the computer unit were stored in a spherical pressure vessel. The frequency output of the sidescan sonar is 330kHz, and the ranging distance is variable from 15m to 120m (one side).

Nishimura, Kiyokazu; Kisimoto, Kiyoyuki; Joshima, Masato; Arai, Kohsaku

251

Cytochrome P450-dependent catabolism of vitamin K: ?-hydroxylation catalyzed by human CYP4F2 and CYP4F11.  

PubMed

Vitamin K plays an essential role in many biological processes including blood clotting, maintenance of bone health, and inhibition of arterial calcification. A menaquinone form of vitamin K, MK4, is increasingly recognized for its key roles in mitochondrial electron transport, as a ligand for the nuclear receptor SXR, which controls the expression of genes involved in transport and metabolism of endo- and xenobiotics, and as a pharmacotherapeutic in the treatment of osteoporosis. Although cytochrome P450 (CYP) 4F2 activity is recognized as an important determinant of phylloquinone (K1) metabolism, the enzymes involved in menaquinone catabolism have not been studied previously. CYP4F2 and CYP4F11 were expressed and purified and found to be equally efficient as in vitro catalysts of MK4 ?-hydroxylation. CYP4F2, but not CYP4F11, catalyzed sequential metabolism of MK4 to the ?-acid without apparent release of the intermediate aldehyde. The ?-alcohol could also be metabolized to the acid by microsomal NAD(+)-dependent alcohol and aldehyde dehydrogenases. LC-MS/MS analysis of trypsinized human liver microsomes (using a surrogate peptide approach) revealed the mean concentrations of CYP4F2 and CYP4F11 to be 14.3 and 8.4 pmol/mg protein, respectively. Microsomal MK4 ?-hydroxylation activities correlated with the CYP4F2 V433M genotype but not the CYP4F11 D446N genotype. Collectively, these data expand the lexicon of vitamin K ?-hydroxylases to include the 'orphan' P450 CYP4F11 and identify a common variant, CYP4F2 (rs2108622), as a major pharmacogenetic variable influencing MK4 catabolism. PMID:24138531

Edson, Katheryne Z; Prasad, Bhagwat; Unadkat, Jashvant D; Suhara, Yoshitomo; Okano, Toshio; Guengerich, F Peter; Rettie, Allan E

2013-11-19

252

Acoustic radiation pressure: A ``phase contrast'' agent for x-ray phase contrast imaging  

Microsoft Academic Search

We show that the radiation pressure exerted by a beam of ultrasound can be used for contrast enhancement in high-resolution x-ray imaging of tissue and soft materials. Interfacial features of objects are highlighted as a result of both the displacement introduced by the ultrasound and the inherent sensitivity of x-ray phase contrast imaging to density variations. The potential of the

Claude J. Bailat; Theron J. Hamilton; Christoph Rose-Petruck; Gerald J. Diebold

2004-01-01

253

Acoustic radiation pressure: A “phase contrast” agent for x-ray phase contrast imaging  

Microsoft Academic Search

We show that the radiation pressure exerted by a beam of ultrasound can be used for contrast enhancement in high-resolution x-ray imaging of tissue and soft materials. Interfacial features of objects are highlighted as a result of both the displacement introduced by the ultrasound and the inherent sensitivity of x-ray phase contrast imaging to density variations. The potential of the

Claude J. Bailat; Theron J. Hamilton; Christoph Rose-Petruck; Gerald J. Diebold

2004-01-01

254

Nonlinear acoustic enhancement in photoacoustic imaging with wideband absorptive nanoemulsion beads  

NASA Astrophysics Data System (ADS)

A nanoemulsion contrast agent with a perfluorohexane core and optically absorptive gold nanospheres (GNSs) assembled on the surface, is presented to improve the specificity of photoacoustic (PA) molecular imaging in differentiating targeted cells or aberrant regions from heterogeneous background signals. Compared to distributed GNSs, clustered GNSs at the emulsion oil-water interface produce a red-shifted and broadened absorption spectrum, exhibiting fairly high absorption in the near-infrared region commonly used for deep tissue imaging. Above a certain laser irradiation fluence threshold, a phase transition creating a microbubble in the emulsion core leads to more than 10 times stronger PA signals compared with conventional thermal-expansion-induced PA signals. These signals are also strongly non-linear, as verified by a differential scheme using recorded PA images at different laser fluences. Assuming a linear relation between laser fluence and the PA signal amplitude, differential processing results in nearly perfect suppression of linear sources, but retains a significant residue for the non-linear nanoemulsion with more than 35 dB enhancement. This result demonstrates that contrast specificity can be improved using the nanoemulsion as a targeting agent in PA molecular imaging by suppressing all background signals related to a linear PA response. Furthermore, combined with a system providing simultaneous laser/ultrasound excitation, cavitation-generated bubbles have the potential to be a highly specific contrast agent for ultrasound molecular imaging and harmonic imaging, as well as a targeted means for noninvasive ultrasound-based therapies.

Wei, Chen-wei; Lombardo, Michael; Xia, Jinjun; Pelivanov, Ivan; Perez, Camilo; Larson-Smith, Kjersta; Matula, Thomas J.; Pozzo, Danilo; O'Donnell, Matthew

2014-03-01

255

Disruption of mouse cytochrome p450 4f14 (Cyp4f14 gene) causes severe perturbations in vitamin E metabolism.  

PubMed

Vitamin E is a family of naturally occurring and structurally related lipophilic antioxidants, one of which, ?-tocopherol (?-TOH), selectively accumulates in vertebrate tissues. The ?-hydroxylase cytochrome P450-4F2 (CYP4F2) is the only human enzyme shown to metabolize vitamin E. Using cDNA cloning, cell culture expression, and activity assays, we identified Cyp4f14 as a functional murine ortholog of CYP4F2. We then investigated the effect of Cyp4f14 deletion on vitamin E metabolism and status in vivo. Cyp4f14-null mice exhibited substrate-specific reductions in liver microsomal vitamin E-?-hydroxylase activity ranging from 93% (?-TOH) to 48% (?-tocotrienol). In vivo data obtained from metabolic cage studies showed whole-body reductions in metabolism of ?-TOH of 90% and of 68% for ?- and ?-TOH. This metabolic deficit in Cyp4f14(-/-) mice was partially offset by increased fecal excretion of nonmetabolized tocopherols and of novel ?-1- and ?-2-hydroxytocopherols. 12'-OH-?-TOH represented 41% of whole-body production of ?-TOH metabolites in Cyp4f14(-/-) mice fed a soybean oil diet. Despite these counterbalancing mechanisms, Cyp4f14-null mice fed this diet for 6 weeks hyper-accumulated ?-TOH (2-fold increase over wild-type littermates) in all tissues and appeared normal. We conclude that CYP4F14 is the major but not the only vitamin E-?-hydroxylase in mice. Its disruption significantly impairs whole-body vitamin E metabolism and alters the widely conserved phenotype of preferential tissue deposition of ?-TOH. This model animal and its derivatives will be valuable in determining the biological actions of specific tocopherols and tocotrienols in vivo. PMID:22665481

Bardowell, Sabrina A; Duan, Faping; Manor, Danny; Swanson, Joy E; Parker, Robert S

2012-07-27

256

The rare earth 4f hybridization with the GaN valence band  

NASA Astrophysics Data System (ADS)

The placement of the Gd, Er, and Yb 4f states within the GaN valence band has been explored by both experiment and theory. The 4d -- 4f photoemission resonances for various rare earth doped GaN thin films (RE = Gd, Er, Yb) provide an accurate depiction of the occupied 4f state placement within the GaN. The resonant photoemission show that the major Er and Gd rare earth 4f weight is at about 5-6 eV below the valence band maximum, similar to the 4f weights in the valence band of many other rare earth doped semiconductors. For Yb, there is very little resonant enhancement of the valence band of Yb doped GaN, consistent with a largely 4f^14-? occupancy. The placement of the rare earth 4f levels is in qualitative agreement with theoretical expectations.

Wang, Lu; Mei, Wai-Ning; McHale, Steve; McClory, John; Petrosky, James; Wu, J.; Palai, Ratnakar; Losovyj, Yaroslav; Dowben, Peter

2013-03-01

257

The thermodynamic properties of 4 f metal trifluorides  

NASA Astrophysics Data System (ADS)

The experimental low-temperature heat capacities of some solid 4 f metal trifluorides were used to reveal the trends in the behavior of variable parameters in the equation that described the lattice heat capacity component in the quasi-harmonic approximation for the whole series of LnF3 (Ln = La, … Lu) compounds. The results were used to describe the temperature dependences of heat capacity over the temperature range from 0 K to the melting point T m. The measured high-temperature enthalpy increments were used to determine corrections to the quasi-harmonic description of heat capacities at T > ˜0.5 T m. The reduced Gibbs energies were calculated over the temperature range 298.15 2000 K. The thermodynamic functions of LnF3 in the gaseous state were determined over the same temperature range in the rigid rotator-harmonic oscillator approximation. All calculations were performed taking into account excited electronic states whose energies did not exceed 10000 cm-1. The reliability of the thermodynamic functions obtained was proved by the convergence of the enthalpies of sublimation calculated by the second and third laws of thermodynamics from the experimental data on saturated vapor pressures. The complete set of the consistent thermodynamic properties of these compounds is described.

Chervonnyi, A. D.; Chervonnaya, N. A.

2007-10-01

258

Accessing 4f-states in single-molecule spintronics.  

PubMed

Magnetic molecules are potential functional units for molecular and supramolecular spintronic devices. However, their magnetic and electronic properties depend critically on their interaction with metallic electrodes. Charge transfer and hybridization modify the electronic structure and thereby influence or even quench the molecular magnetic moment. Yet, detection and manipulation of the molecular spin state by means of charge transport, that is, spintronic functionality, mandates a certain level of hybridization of the magnetic orbitals with electrode states. Here we show how a judicious choice of the molecular spin centres determines these critical molecule-electrode contact characteristics. In contrast to late lanthanide analogues, the 4f-orbitals of single bis(phthalocyaninato)-neodymium(III) molecules adsorbed on Cu(100) can be directly accessed by scanning tunnelling microscopy. Hence, they contribute to charge transport, whereas their magnetic moment is sustained as evident from comparing spectroscopic data with ab initio calculations. Our results showcase how tailoring molecular orbitals can yield all-electrically controlled spintronic device concepts. PMID:24061595

Fahrendorf, Sarah; Atodiresei, Nicolae; Besson, Claire; Caciuc, Vasile; Matthes, Frank; Blügel, Stefan; Kögerler, Paul; Bürgler, Daniel E; Schneider, Claus M

2013-01-01

259

Capacitive micromachined ultrasonic transducers: next-generation arrays for acoustic imaging?  

Microsoft Academic Search

Piezoelectric materials have dominated the ultrasonic transducer technology. Recently, capacitive micromachined ultrasonic transducers (CMUTs) have emerged as an alternative technology offering advantages such as wide bandwidth, ease of fabricating large arrays, and potential for integration with electronics. The aim of this paper is to demonstrate the viability of CMUTs for ultrasound imaging. We present the first pulse-echo phased array B-scan

Oincr Oralkan; A. Sanli Ergun; J. A. Johnson; M. Karaman; U. Demirci; K. Kaviani; T. H. Lee; B. T. Khuri-Yakub

2002-01-01

260

High Resolution X-Ray Phase Contrast Imaging with Acoustic Tissue- Selective Contrast Enhancement.  

National Technical Information Service (NTIS)

We show that ultrasound can be used for contrast enhancement in high- resolution x-ray imaging of tissue and soft materials. Interfacial features of objects are highlighted as a result of both the displacement introduced by the ultrasound and the inherent...

G. J. Diebold

2005-01-01

261

Combined acoustic-photoacoustic and fluorescence imaging catheter for the detection of the atherosclerotic plaque  

NASA Astrophysics Data System (ADS)

In industrialized countries, cardiovascular diseases remain the main cause of mortality. The detection of atherosclerosis and its associated plaque using imaging techniques allows studying the efficacy of new drugs in vivo. Intravascular ultrasound (IVUS) imaging has been demonstrated to be a powerful tool to uncover structural information of atherosclerotic plaques. Recently, intravascular photoacoustic (IVPA) has been combined with IVUS imaging to add functional and/or molecular information. The IVPA/IVUS combination has been demonstrated in phantoms and ex vivo tissues to provide relevant information about the composition of the plaque, as well as its vulnerability. In this work, we extend previous work by developing a combined IVPA/IVUS system using a rotating ultrasound transducer in a catheter to which an optical fiber is attached. In addition, a third modality was included through fluorescence detection in the same fiber at a distinct wavelength from PA, opening the door to complementary information using fluorescence activatable probes. Cylindrical silicon phantoms with inclusions containing fluorophores or ink were used to validate the system. Bleaching of the fluorophore by the pulsed laser used for photoacoustic was quantified. IVUS images were obtained continuously and used to co-register photoacoustic and fluorescence signals.

Abran, Maxime; Matteau-Pelletier, Carl; Zerouali-Boukhal, Karim; Tardif, Jean-Claude; Lesage, Frédéric

2011-02-01

262

Innovative acoustic reflection imaging techniques and application to clinical breast tomography  

NASA Astrophysics Data System (ADS)

Conventional ultrasound techniques use beam-formed, constant sound speed ray models for fast image reconstruction. However, these techniques are inadequate for the emerging new field of ultrasound tomography (UST). We present a new technique for reconstruction of reflection images from UST data. We have extended the planar Kirchhoff migration method used in geophysics, and combined it with sound speed and attenuation data obtained from the transmission signals to create reflection ultrasound images that are corrected for refractive and attenuative effects. The resulting techniques were applied to simulated numerical phantom data, physical phantom data and in-vivo breast data obtained with an experimental ring transducer prototype. Additionally, the ring transducer was customized to test compatibility with an existing ultrasound workstation. We were able to obtain independently recorded radio-frequency (RF) data for individual transmit-receive pair combinations for all 128 transducers. The signal data was then successfully reconstructed into reflection data using the Kirchhoff migration techniques. The results from the use of sound speed and attenuation corrections lead to significant improvements in image quality, particularly in dense tissues where the refractive and scattering effects are the greatest. The procedure was applied to a variety of breast densities and masses of different natures. The resulting reflection images successfully resolved boundaries and textures. The reflection characteristics of tomographic ultrasound maintain an indispensible position in the quantification of proper mass identification. The results of this project indicate the clinical significance of the invocation of properly compensated Kirchhoff based reconstruction method with the use of sound speed and attenuation parameters for the visualization and classification of masses and tissue.

Schmidt, Steve P.

263

Acoustic hemostasis  

NASA Astrophysics Data System (ADS)

Over the past several years, the Center for Industrial and Medical Ultrasound (CIMU) at the Applied Physics Laboratory in the University of Washington has undertaken a broad research program in the general area of High Intensity Focused Ultrasound (HIFU). Our principal emphasis has been on the use of HIFU to induce hemostasis; in particular, CIMU has sought to develop a small, lightweight, portable device that would use ultrasound for both imaging and therapy. Such a technology is needed because nearly 50% of combat casualty mortality results from exsanguinations, or uncontrolled bleeding. A similar percentage occurs for civilian death due to trauma. In this general review, a presentation of the general problem will be given, as well as our recent approaches to the development of an image-guided, transcutaneous, acoustic hemostasis device. [Work supported in part by the USAMRMC, ONR and the NIH.

Crum, L.; Andrew, M.; Bailey, M.; Beach, K.; Brayman, A.; Curra, F.; Kaczkowski, P.; Kargl, S.; Martin, R.; Vaezy, S.

2003-04-01

264

Structural relationships among LiNaMg[PO4]F and Na2M[PO4]F (M = Mn-Ni, and Mg), and the magnetic structure of LiNaNi[PO4]F.  

PubMed

The new compound LiNaMg[PO4]F has been synthesized by a wet chemical reaction route. Its crystal structure was determined from single-crystal X-ray diffraction data. LiNaMg[PO4]F crystallizes with the monoclinic pseudomerohedrally twinned LiNaNi[PO4]F structure, space group P2(1)/c, a = 6.772(4), b = 11.154(6), c = 5.021(3) Å, ? = 90.00(1)° and Z = 4. The structure contains [MgO3F]n chains made up of zigzag edge-sharing MgO4F2 octahedra. These chains are interlinked by PO4 tetrahedra forming 2D-Mg[PO4]F layers. The alkali metal atoms are well ordered in between these layers over two atomic positions. The use of group-subgroup transformation schemes in the Bärnighausen formalism enabled us to determine precise phase transition mechanisms from LiNaNi[PO4]F- to Na2M[PO4]F-type structures (M = Mn-Ni, and Mg) (see video clip 1 and 2). The crystal and magnetic structure and properties of the parent LiNaNi[PO4]F phase were also studied by magnetometry and neutron powder diffraction. Despite the rather long interlayer distance, d(min)(Ni(+2)-Ni(+2)) ~ 6.8 Å, the material develops a long-range magnetic order below 5 K. The magnetic structure can be viewed as antiferromagnetically coupled ferromagnetic layers with moments parallel to the b-axis. PMID:24276233

Ben Yahia, Hamdi; Shikano, Masahiro; Kobayashi, Hironori; Avdeev, Maxim; Liu, Samuel; Ling, Chris D

2014-02-01

265

Acoustic metafluids  

Microsoft Academic Search

Acoustic metafluids are defined as the class of fluids that allow one domain of fluid to acoustically mimic another, as exemplified by acoustic cloaks. It is shown that the most general class of acoustic metafluids are materials with anisotropic inertia and the elastic properties of what are known as pentamode materials. The derivation uses the notion of finite deformation to

Andrew N. Norris

2009-01-01

266

6s electron screening in isotope shifts of configurations 4f75d6s, 4f76s6d and 4f76s7d in europium  

NASA Astrophysics Data System (ADS)

In the experimental part of this work, measurement results of isotope shifts and the hyperfine structure of nine electronic levels in europium atoms, obtained using the laser induced fluorescence method, are presented. In the case of five levels, these results were obtained for the first time and have no counterparts in the literature. Most of the levels measured are classified as belonging to configuration 4f76s7d. From the results obtained, on the basis of the sharing rule and the wavefunctions for the levels investigated, known from the literature, isotope shifts for pure configurations 4f76s7d and 4f76p2 were determined for the first time using the semi-empirical method, and the isotope shift values for configurations 4f76s6d, 4f75d2 and 4f76s8s were verified. Wavefunction values at the nucleus for all three configurations and contributions from individual electrons s and p* were calculated ab initio with the use of programs MCHF and MCDF, and compared to experimental results of isotope shifts.

Furmann, B.; Stefanska, D.

2014-04-01

267

Signal/Image Processing of Acoustic Flaw Signatures for Detection and Localization  

SciTech Connect

The timely, nondestructive evaluation (NDE) of critical optics in high energy, pulsed laser experiments is a crucial analysis that must be performed for the experiment to be successful. Failure to detect flaws of critical sizes in vacuum-loaded optical windows can result in a catastrophic failure jeopardizing the safety of both personnel and costly equipment. We discuss the development of signal/image processing techniques to both detect critical flaws and locate their position on the window. The data measured from two Orthogonal arrays of narrow beamwidth ultrasonic transducers are preprocessed using a model-based scheme based on the Green's function of the medium providing individual channel signatures. These signatures are then transformed to the two-dimensional image space using a power-based estimator. A 2D-replicant is then constructed based on the underlying physics of the material along with the geometry of the window. Correlating the replicant with the enhanced power image leads to the optimal 2D-matched filter solution detecting and localizing the flaw. Controlled experimental results on machined flaws are discussed.

Candy, J V; Meyer, A W

2001-06-01

268

Very high-resolution seismo-acoustic imaging of seagrass meadows (Mediterranean Sea): Implications for carbon sink estimates  

NASA Astrophysics Data System (ADS)

Posidonia oceanica is a widespread coastal Mediterranean seagrass which accumulates in its subsurface large quantities of organic material derived from its roots, rhizomes and leaf sheaths embedded in sandy sediments. These organic deposits may be up to several meters thick as they accumulate over thousands of years forming the matte, whose high content in organic carbon plays a major role in the global ocean carbon cycle. In this study, very high-resolution seismo-acoustic methods were applied to image the subsurface features of a P. oceanica seagrass meadow at Portlligat (Cadaqués, Girona, Spain), in the NW-Mediterranean Sea. Our findings yield fresh insights into the settling of the P. oceanica meadow in the study area, and define with unprecedented detail the potential volume occupied by the matte. A strong reflector, located from 4.3 to 11.7 m depth, was recognized in several seismo-acoustic profiles as the substratum on which P. oceanica first settled in the study area. A 3D bathymetric model of this substratum allowed us to reconstruct the Portlligat palaeo-environment prior to the settling of P. oceanica, which corresponded to a shallow coastal setting protected from the open sea. A core drilled in the meadow at Portlligat revealed the presence of a 6 m thick dense matte composed of medium to coarse sandy sediments mixed with plant debris and bioclasts. Radiocarbon datings revealed a constant accretion rate of the matte of about 1.1 m/kyr. Gravelly bioclastic deposits observed at the base of the core correspond to the base of the matte and gave a date of 5616 +/- 46 Cal yr BP. For the first time, very high-resolution marine geophysical techniques allowed us to accurately define the volume occupied by P. oceanica matte, which in the study area reaches up to almost 220,000 +/- 17,400 m3. This result is an important step forward in our efforts to estimate the size of the carbon sink represented by P. oceanica meadows along the Mediterranean coasts significantly contributing to the biosphere carbon cycle.

Lo Iacono, Claudio; Mateo, Miguel Angel; Gràcia, Eulàlia; Guasch, Lluis; Carbonell, Ramon; Serrano, Laura; Serrano, Oscar; Dañobeitia, Juanjo

2008-09-01

269

Modifications of eukaryotic initiation factor 4F (eIF4F) in adult cardiocytes by adenoviral gene transfer: differential effects on eIF4F activity and total protein synthesis rates.  

PubMed

In adult feline cardiocytes, increases in eukaryotic initiation factor 4F (eIF4F) activity are correlated with accelerated rates of total protein synthesis produced in response to increased load. Adenoviral gene transfer was employed to increase either eIF4F complex formation or the phosphorylation of eIF4E on Ser-209. To simulate load,cardiocytes were electrically stimulated to contract (2 Hz,5 ms pulses). Non-stimulated cardiocytes were used as controls.Adenovirus-mediated overexpression of wild-type eIF4E increased the total eIF4E pool by 120-140% above endogenous levels after 24 h and produced a corresponding increase in eIF4F content.However, it did not accelerate total protein synthesis rates inquiescent cardiocytes; neither did it potentiate the increase produced by contraction. To modify the affinity of eIF4F, cardiocytes were infected with a mutant (eIF4E/W56F) with a decreased binding affinity for the mRNA cap. Overexpression of eIF4E/W56F increased the quantity of eIF4F but the rate of total protein synthesis was decreased inquiescent and contracting cardiocytes. Overexpression of a mutant that blocked eIF4E phosphorylation (eIF4E/S209A) increased the quantity ofeIF4F without any significant effect on total protein synthesis rates in quiescent or contracting cardiocytes. Overexpression of the eIF4Ekinase Mnk-1 increased eIF4E phosphorylation without a corresponding increase in eIF4F complex formation or in the rate of total protein synthesis. We conclude the following: (1) eIF4F assembly is increased by raising eIF4E levels via adenoviral gene transfer; (2) the capbinding affinity of eIF4F is a rate-limiting determinant for total protein synthesis rates; and (3) increases in the quantity of eIF4Falone or in eIF4E phosphorylation are not sufficient to accelerate total protein synthesis rates. PMID:11368785

Saghir, A N; Tuxworth, W J; Hagedorn, C H; McDermott, P J

2001-06-01

270

Modifications of eukaryotic initiation factor 4F (eIF4F) in adult cardiocytes by adenoviral gene transfer: differential effects on eIF4F activity and total protein synthesis rates.  

PubMed Central

In adult feline cardiocytes, increases in eukaryotic initiation factor 4F (eIF4F) activity are correlated with accelerated rates of total protein synthesis produced in response to increased load.Adenoviral gene transfer was employed to increase either eIF4F complex formation or the phosphorylation of eIF4E on Ser-209. To simulate load,cardiocytes were electrically stimulated to contract (2 Hz,5 ms pulses). Non-stimulated cardiocytes were used as controls.Adenovirus-mediated overexpression of wild-type eIF4E increased the total eIF4E pool by 120-140% above endogenous levels after 24 h and produced a corresponding increase in eIF4F content.However, it did not accelerate total protein synthesis rates inquiescent cardiocytes; neither did it potentiate the increase produced by contraction. To modify the affinity of eIF4F, cardiocytes were infected with a mutant (eIF4E/W56F) with a decreased binding affinity for the mRNA cap. Overexpression of eIF4E/W56F increased the quantity of eIF4F but the rate of total protein synthesis was decreased inquiescent and contracting cardiocytes. Overexpression of a mutant that blocked eIF4E phosphorylation (eIF4E/S209A) increased the quantity ofeIF4F without any significant effect on total protein synthesis rates in quiescent or contracting cardiocytes. Overexpression of the eIF4Ekinase Mnk-1 increased eIF4E phosphorylation without a corresponding increase in eIF4F complex formation or in the rate of total protein synthesis. We conclude the following: (1) eIF4F assembly is increased by raising eIF4E levels via adenoviral gene transfer; (2) the capbinding affinity of eIF4F is a rate-limiting determinant for total protein synthesis rates; and (3) increases in the quantity of eIF4Falone or in eIF4E phosphorylation are not sufficient to accelerate total protein synthesis rates.

Saghir, A N; Tuxworth , W J; Hagedorn, C H; McDermott, P J

2001-01-01

271

Time domain simulation of nonlinear acoustic beams generated by rectangular pistons with application to harmonic imaging  

NASA Astrophysics Data System (ADS)

A time-domain numerical code (the so-called Texas code) that solves the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation has been extended from an axis-symmetric coordinate system to a three-dimensional (3D) Cartesian coordinate system. The code accounts for diffraction (in the parabolic approximation), nonlinearity and absorption and dispersion associated with thermoviscous and relaxation processes. The 3D time domain code was shown to be in agreement with benchmark solutions for circular and rectangular sources, focused and unfocused beams, and linear and nonlinear propagation. The 3D code was used to model the nonlinear propagation of diagnostic ultrasound pulses through tissue. The prediction of the second-harmonic field was sensitive to the choice of frequency-dependent absorption: a frequency squared f2 dependence produced a second-harmonic field which peaked closer to the transducer and had a lower amplitude than that computed for an f1.1 dependence. In comparing spatial maps of the harmonics we found that the second harmonic had dramatically reduced amplitude in the near field and also lower amplitude side lobes in the focal region than the fundamental. These findings were consistent for both uniform and apodized sources and could be contributing factors in the improved imaging reported with clinical scanners using tissue harmonic imaging. .

Yang, Xinmai; Cleveland, Robin O.

2005-01-01

272

Time domain simulation of nonlinear acoustic beams generated by rectangular pistons with application to harmonic imaging.  

PubMed

A time-domain numerical code (the so-called Texas code) that solves the Khokhlov-Zabolotskaya-Kuznetsov (KZK) equation has been extended from an axis-symmetric coordinate system to a three-dimensional (3D) Cartesian coordinate system. The code accounts for diffraction (in the parabolic approximation), nonlinearity and absorption and dispersion associated with thermoviscous and relaxation processes. The 3D time domain code was shown to be in agreement with benchmark solutions for circular and rectangular sources, focused and unfocused beams, and linear and nonlinear propagation. The 3D code was used to model the nonlinear propagation of diagnostic ultrasound pulses through tissue. The prediction of the second-harmonic field was sensitive to the choice of frequency-dependent absorption: a frequency squared f2 dependence produced a second-harmonic field which peaked closer to the transducer and had a lower amplitude than that computed for an f1.1 dependence. In comparing spatial maps of the harmonics we found that the second harmonic had dramatically reduced amplitude in the near field and also lower amplitude side lobes in the focal region than the fundamental. These findings were consistent for both uniform and apodized sources and could be contributing factors in the improved imaging reported with clinical scanners using tissue harmonic imaging. PMID:15704404

Yang, Xinmai; Cleveland, Robin O

2005-01-01

273

Acoustic Radiation Force Impulse Imaging: A New Tool for the Diagnosis of Papillary Thyroid Microcarcinoma  

PubMed Central

Purpose. To evaluate the diagnostic performance of ARFI imaging in differentiating between benign and malignant thyroid nodules <1?cm. Materials and Methods. 173 pathologically proven thyroid nodules (77 benign, 96 malignant) in 157 patients were included in this study. Receiver-operating characteristic curve (ROC) analyses were performed to assess the diagnostic performance of conventional ultrasound (US) and ARFI imaging in papillary thyroid microcarcinoma (PTMC). The independent risk factors for predicting PTMC were evaluated. Results. The mean SWV value of benign and malignant thyroid nodules were 2.57 ± 0.79?m/s (range: 0.90–4.92?m/s) and 3.88 ± 2.24?m/s (range: 1.49–9.00?m/s) (P = 0.000). Az for VTI elastography score was higher than that for hypoechoic, absence of halo sign, and type III vascularity (P < 0.05). The optimal cut-offs for VTI elastography score and SWV were score 4 and 3.10?m/s. Gender, hypoechoic, taller than wide, VTI elastography score ? 4, and SWV > 3.10?m/s had been found to be independent risk factors for predicting PTMC. Conclusion. ARFI elastography can provide elasticity information of PTMC quantitatively (VTQ) and directly reflects the overall elastic properties (VTI). Gender, hypoechogenicity, taller than wide, VTI elastography score ? 4, and SWV > 3.10?m/s are independent risk factors for predicting PTMC. ARFI elastography seems to be a new tool for the diagnosis of PTMC.

Zhang, Yi-Feng; Xu, Jun-Mei; Zhang, Jing; Liu, Lin-Na; Xu, Xiao-Hong

2014-01-01

274

Acoustic performance of mesh compression paddles for a multimodality breast imaging system.  

PubMed

A system incorporating automated 3-D ultrasound and digital X-ray tomosynthesis is being developed for improved breast lesion detection and characterization. The goal of this work is to develop and test candidates for a dual-modality mesh compression paddle. A Computerized Imaging Reference Systems (Norfork, VA, USA) ultrasound phantom with tilted low-contrast cylindrical objects was used. Polyester mesh fabrics (1- and 2-mm spacing), a high-density polyethylene filament grid (Dyneema, DSM Dyneema, Stanley, NC, USA) and a solid polymethylpentene (TPX; Mitsui Plastics, Inc., White Plains, NY) paddle were compared with no overlying structures using a GE Logic 9 with M12L transducer. A viscous gel provided coupling. The phantom was scanned 10 times over 9 cm for each configuration. Image volumes were analyzed for signal strength, contrast and contrast-to-noise ratio. X-ray tests confirmed X-ray transparency for all materials. By all measures, both mesh fabrics outperformed TPX and Dyneema, and there were essentially no differences between 2-mm mesh and unobstructed configurations. PMID:24726203

LeCarpentier, Gerald L; Goodsitt, Mitchell M; Verweij, Sacha; Li, Jie; Padilla, Frederic R; Carson, Paul L

2014-07-01

275

A XANES study of LiVPO4F: a factor analysis approach.  

PubMed

Evolving factor analysis (EFA) of X-ray absorption near-edge spectroscopy (XANES) data is shown to be a useful tool to understand the phase relationships and compositional ranges of stability in the LiVPO4F-VPO4F system. EFA was used to calculate the concentration of phases versus state-of-charge in a lithium-ion battery and true XANES spectra. The results of EFA showed that, indeed, three phases were present during cycling of a LiVPO4F?Li cell: LiVPO4F, LixVPO4F, and VPO4F. In contrast to what was reported by others, the second phase was not a fixed composition with x = 0.67, but, instead, existed over a range of lithium stoichiometry, x = 0.25 to 0.80. EFA results also showed that the reactions leading to these phases are reversible. PMID:24407021

Piao, Ying; Qin, Yan; Ren, Yang; Heald, Steve M; Sun, Chengjun; Zhou, Dehua; Polzin, Bryant J; Trask, Steve E; Amine, Khalil; Wei, Yinjin; Chen, Gang; Bloom, Ira; Chen, Zonghai

2014-02-21

276

Acoustic radiation force impulse imaging: a new tool for the diagnosis of papillary thyroid microcarcinoma.  

PubMed

Purpose. To evaluate the diagnostic performance of ARFI imaging in differentiating between benign and malignant thyroid nodules <1?cm. Materials and Methods. 173 pathologically proven thyroid nodules (77 benign, 96 malignant) in 157 patients were included in this study. Receiver-operating characteristic curve (ROC) analyses were performed to assess the diagnostic performance of conventional ultrasound (US) and ARFI imaging in papillary thyroid microcarcinoma (PTMC). The independent risk factors for predicting PTMC were evaluated. Results. The mean SWV value of benign and malignant thyroid nodules were 2.57 ± 0.79?m/s (range: 0.90-4.92?m/s) and 3.88 ± 2.24?m/s (range: 1.49-9.00?m/s) (P = 0.000). Az for VTI elastography score was higher than that for hypoechoic, absence of halo sign, and type III vascularity (P < 0.05). The optimal cut-offs for VTI elastography score and SWV were score 4 and 3.10?m/s. Gender, hypoechoic, taller than wide, VTI elastography score ? 4, and SWV > 3.10?m/s had been found to be independent risk factors for predicting PTMC. Conclusion. ARFI elastography can provide elasticity information of PTMC quantitatively (VTQ) and directly reflects the overall elastic properties (VTI). Gender, hypoechogenicity, taller than wide, VTI elastography score ? 4, and SWV > 3.10?m/s are independent risk factors for predicting PTMC. ARFI elastography seems to be a new tool for the diagnosis of PTMC. PMID:25045673

Zhang, Yi-Feng; Liu, Chang; Xu, Hui-Xiong; Xu, Jun-Mei; Zhang, Jing; Guo, Le-Hang; Zheng, Shu-Guang; Liu, Lin-Na; Xu, Xiao-Hong

2014-01-01

277

Remote Underwater Laser Acoustic Source  

NASA Astrophysics Data System (ADS)

Through the use of nonlinear optical effects, an appropriately tailored laser pulse can propagate relatively long distances underwater at moderate intensity (up to distances on the order of the attenuation length, approximately 10 meters in sea water), then quickly converge to an intense focus within a few centimeters at a controlled location. Optical breakdown can then generate an acoustic pulse at this location. An array of laser-generated acoustic sources could comprise a large acoustic aperture sonar imaging system for locating mines, mapping sea floor topography, or identifying underwater structures. Previous experiments at NRL indicate that approx. 1 mJ of coupled laser energy will produce a 200 dB, microsecond-timescale acoustic pulse, a source level more than adequate for high resolution acoustic imaging applications. A combined experimental and theoretical research program at NRL aims to investigate intense underwater laser propagation and to develop techniques for a remote underwater laser acoustic source. Initial results will be presented.

Jones, T. G.; Ting, A.; Alexeev, I.; Briscoe, E.; Penano, J.; Sprangle, P.

2004-11-01

278

Acoustic metafluids  

Microsoft Academic Search

Acoustic metafluids are defined as the class of fluids that allow one domain\\u000aof fluid to acoustically mimic another, as exemplified by acoustic cloaks. It\\u000ais shown that the most general class of acoustic metafluids are materials with\\u000aanisotropic inertia and the elastic properties of what are known as pentamode\\u000amaterials. The derivation uses the notion of finite deformation to

Andrew N. Norris

2009-01-01

279

Evaluating the feasibility of acoustic radiation force impulse shear wave elasticity imaging of the uterine cervix with an intracavity array: a simulation study.  

PubMed

The uterine cervix softens, shortens, and dilates throughout pregnancy in response to progressive disorganization of its layered collagen microstructure. This process is an essential part of normal pregnancy, but premature changes are associated with preterm birth. Clinically, there are no reliable noninvasive methods to objectively measure cervical softening or assess cervical microstructure. The goal of these preliminary studies was to evaluate the feasibility of using an intracavity ultrasound array to generate acoustic radiation force impulse (ARFI) excitations in the uterine cervix through simulation, and to optimize the acoustic radiation force (ARF) excitation for shear wave elasticity imaging (SWEI) of the tissue stiffness. The cervix is a unique soft tissue target for SWEI because it has significantly greater acoustic attenuation (? = 1.3 to 2.0 dB·cm(-1)·MHz(-)1) than other soft tissues, and the pathology being studied tends to lead to an increase in tissue compliance, with healthy cervix being relatively stiff compared with other soft tissues (E ? 25 kPa). Additionally, the cervix can only be accessed in vivo using a transvaginal or catheter-based array, which places additional constraints on the excitation focal characteristics that can be used during SWEI. Finite element method (FEM) models of SWEI show that larger-aperture, catheter-based arrays can utilize excitation frequencies up to 7 MHz to generate adequate focal gain up to focal depths 10 to 15 mm deep, with higher frequencies suffering from excessive amounts of near-field acoustic attenuation. Using full-aperture excitations can yield ~40% increases in ARFI-induced displacements, but also restricts the depth of field of the excitation to ~0.5 mm, compared with 2 to 6 mm, which limits the range that can be used for shear wave characterization of the tissue. The center-frequency content of the shear wave particle velocity profiles ranges from 1.5 to 2.5 kHz, depending on the focal configuration and the stiffness of the material being imaged. Overall, SWEI is possible using catheter-based imaging arrays to generate adequate displacements in cervical tissue for shear wave imaging, although specific considerations must be made when optimizing these arrays for this shear wave imaging application. PMID:24081254

Palmeri, Mark L; Feltovich, Helen; Homyk, Andrew D; Carlson, Lindsey C; Hall, Timothy J

2013-10-01

280

Acoustic seal  

NASA Technical Reports Server (NTRS)

The invention relates to a sealing device having an acoustic resonator. The acoustic resonator is adapted to create acoustic waveforms to generate a sealing pressure barrier blocking fluid flow from a high pressure area to a lower pressure area. The sealing device permits noncontacting sealing operation. The sealing device may include a resonant-macrosonic-synthesis (RMS) resonator.

Steinetz, Bruce M. (Inventor)

2006-01-01

281

Acoustic Seal  

NASA Technical Reports Server (NTRS)

The invention relates to a sealing device having an acoustic resonator. The acoustic resonator is adapted to create acoustic waveforms to generate a sealing pressure barrier blocking fluid flow from a high pressure area to a lower pressure area. The sealing device permits noncontacting sealing operation. The sealing device may include a resonant-macrosonic-synthesis (RMS) resonator.

Steinetz, Bruce M. (Inventor)

2006-01-01

282

Significance of System L Amino Acid Transporter 1 (LAT-1) and 4F2 Heavy Chain (4F2hc) Expression in Human Developing Intestines  

PubMed Central

To clarify the significance of expression of system L amino acid transporter 1 (LAT1) and 4F2 heavy chain (4F2hc) in the developing intestine, immunohistochemical investigation and molecular analysis were performed in the human embryonic and/or fetal intestines, ranging from 28–30 days to 34–35 weeks gestation. The molecular analysis for the expression of LAT1 and 4F2hc mRNAs was done in the pure epithelial cell samples prepared after laser assisted microdissection. The immunoreactivities against LAT1 and 4F2hc were detected along the basolateral cell membrane of the primitive gut epithelium at 28–30 days gestation. According to advance in gestational age of up to 24–25 weeks gestation, the immunoreactivity of LAT1 was predominantly observed in the supranuclear cytplasmic localization with a granular or dot-like staining pattern. Up to 8–9 weeks gestation, the immunoreactivity of 4F2hc showed almost the same as that of LAT1. However, after the age of 12–13 weeks gestation, the immunoreactivity of 4F2hc was predominantly localized along the cell membrane of apical surface of the epithelial cells. No apical and linear membranous localization of LAT1 was observed until nearly 20 weeks gestation. In the late gestational stage, both the immunoreactivities against LAT1 and 4F2hc were localized along the apical surface of the epithelial cells. In conclusion, the expression of LAT1 and 4F2hc in early developing intestine suggests they have a more important role in cell proliferation rather than functional differentiation. The predominant cytoplasmic localization of LAT1 during mid-fetal life seems to be largely inactive as amino acid transporter. On the other hand, the apical and linear membranous co-localization of LAT1 and 4F2hc in the late fetal life suggests that these molecules may play a role as a functional amino acid transporter in the fetal intestinal epithelium.

Ohno, Chikara; Nakanishi, Yohko; Honma, Taku; Henmi, Akihiro; Sugitani, Masahiko; Kanai, Yoshikatsu; Nemoto, Norimichi

2009-01-01

283

Acoustic emission linear pulse holography  

DOEpatents

This device relates to the concept of and means for performing Acoustic Emission Linear Pulse Holography, which combines the advantages of linear holographic imaging and Acoustic Emission into a single non-destructive inspection system. This unique system produces a chronological, linear holographic image of a flaw by utilizing the acoustic energy emitted during crack growth. The innovation is the concept of utilizing the crack-generated acoustic emission energy to generate a chronological series of images of a growing crack by applying linear, pulse holographic processing to the acoustic emission data. The process is implemented by placing on a structure an array of piezoelectric sensors (typically 16 or 32 of them) near the defect location. A reference sensor is placed between the defect and the array.

Collins, H.D.; Busse, L.J.; Lemon, D.K.

1983-10-25

284

In vitro assessment of the relationship between acoustic properties and bone mass density of the calcaneus by comparison of ultrasound parametric imaging and quantitative computed tomography.  

PubMed

This in vitro study aimed to add new experimental evidence to clarify the relation between acoustic properties of bone and bone mineral density (BMD) of the human calcaneus. Parametric images of normalized broadband ultrasonic attenuation (nBUA) and ultrasound bone velocity (UBV) were compared with quantitative computed tomography (QCT) images of the calcaneus. The experimental protocol was designed to control the different potential sources of error in acoustic measurements, including the shape and thickness of the samples, intervening soft tissues and cortical bone, boundary effects, and variation in location of the regions of interest (ROIs) analyzed by ultrasound and X-ray. The present study was based on bone specimens from calcaneus removed from 15 cadavers (six male and nine female donors ranging from 69 to 89 years of age). Immersion ultrasonic measurements were performed in the through-thickness direction at normal incidence using a pair of focused broad-band 0.5-MHz transducers. QCT of the specimens was performed using standard 10-mm-thick slices with the Cann-Genant calibration standard. Identical, site-matched ROIs were selected for quantitative analysis on the three images. The pattern of acoustic parameters was similar to that of BMD with QCT. The relationships between nBUA and BMD (r2 = 0.75), between UBV and BMD (r2 = 0.88) and between nBUA and UBV (r2 = 0.84) were highly significant (p < 10(-4). From this study, it appears that ultrasound parameters as measured with current transmission techniques reflect mainly bone quantity and only reflect microarchitecture to a small extent and that BUA and UBV reflect the same bone property. PMID:9028541

Laugier, P; Droin, P; Laval-Jeantet, A M; Berger, G

1997-02-01

285

An In Vivo Validation of the Application of Acoustic Radiation Force to Enhance the Diagnostic Utility of Molecular Imaging Using 3D Ultrasound  

PubMed Central

For over a decade, the application of acoustic radiation force (ARF) has been proposed as a mechanism to increase ultrasonic molecular imaging (MI) sensitivity in vivo. Presented herein is the first noninvasive in vivo validation of ARF-enhanced MI with an unmodified clinical system. First, an in vitro optical-acoustical setup was used to optimize system parameters and ensure sufficient microbubble translation when exposed to ARF. 3D ARF-enhanced MI was then performed on 7 rat fibrosarcoma tumors using microbubbles targeted to ?v?3 and non-targeted microbubbles. Low-amplitude (< 25 kPa) 3D ARF pulse sequences were tested and compared to passive targeting studies in the same animal. Our results demonstrate that a 78% increase in image intensity from targeted microbubbles can be achieved when using ARF relative to the passive targeting studies. Furthermore, ARF did not significantly increase image contrast when applied to non-targeted agents, suggesting that ARF did not increase non-specific adhesion.

Gessner, Ryan C.; Streeter, Jason E.; Kothadia, Roshni; Feingold, Steven; Dayton, Paul A.

2012-01-01

286

Instrumentation for ocean acoustic tomography  

Microsoft Academic Search

A test ocean acoustic tomography experiment was conducted in the southern North Atlantic during 1981. Travel time variations of pulse-like signals transmitted between moored acoustic sources and receivers separated by hundreds of kilometers were used to image the intervening sound speed field. Intelligent sources, receivers, mooring positioning monitoring systems and precision time-keeping devices were developed specifically for this application. In

R. C. Spindel; P. F. Worcester; D. C. Webb; P. R. Boutin; K. R. Peal; A. M. Bradley

1982-01-01

287

Evaluating the Acoustic Effect of Over-the-Rotor Foam-Metal Liner Installed on a Low Speed Fan Using Virtual Rotating Microphone Imaging  

NASA Technical Reports Server (NTRS)

An in-duct beamforming technique for imaging rotating broadband fan sources has been used to evaluate the acoustic characteristics of a Foam-Metal Liner installed over-the-rotor of a low-speed fan. The NASA Glenn Research Center s Advanced Noise Control Fan was used as a test bed. A duct wall-mounted phased array consisting of several rings of microphones was employed. The data are mathematically resampled in the fan rotating reference frame and subsequently used in a conventional beamforming technique. The steering vectors for the beamforming technique are derived from annular duct modes, so that effects of reflections from the duct walls are reduced.

Sutliff, Daniel L.; Dougherty, Robert P.; Walker, Bruce E.

2010-01-01

288

Metastatic signet ring cell carcinoma presenting as a thyroid diffuse involvement: report of a case studied with Q-elastographic and acoustic radiation force impulse imaging features.  

PubMed

Metastatic carcinomas to the thyroid are rare in daily clinical practice. However, when encountered they represent a diagnostic challenge, since it is difficult to distinguish them from primary thyroid lesions, especially when occurring in patients with occult malignant history. Nevertheless, it is critical to differentiate a metastatic tumor from primary thyroid lesions, as the clinical management and the prognosis are different for the two entities. More recently, elastosonography opened new possibilities to ultrasound in different fields, such as thyroid nodule differentiation. Herein, we report a case of metastatic signet ring cell carcinoma to the thyroid studied with quantitative elastography and acoustic radiation force impulse imaging. PMID:24158087

Cantisani, Vito; Lodise, Pietro; Di Cosimo, Carla; Metere, Alessio; Chiesa, Carlo; Mancuso, Ester; Di Segni, Mattia; Fioravanti, Cristina; Di Rocco, Giorgio; Bernieri, Maria Giulia; Ricci, Paolo; Fierro, Giovanni; Giacomelli, Laura; Orsogna, Nicola; Redler, Adriano

2013-01-01

289

4F Decreases IRF5 Expression and Activation in Hearts of Tight Skin Mice  

PubMed Central

The apoAI mimetic 4F was designed to inhibit atherosclerosis by improving HDL. We reported that treating tight skin (Tsk?/+) mice, a model of systemic sclerosis (SSc), with 4F decreases inflammation and restores angiogenic potential in Tsk?/+ hearts. Interferon regulating factor 5 (IRF5) is important in autoimmunity and apoptosis in immune cells. However, no studies were performed investigating IRF5 in myocardium. We hypothesize that 4F differentially modulates IRF5 expression and activation in Tsk?/+ hearts. Posterior wall thickness was significantly increased in Tsk?/+ compared to C57Bl/6J (control) and Tsk?/+ mice with 4F treatment assessed by echoradiography highlighting reduction of fibrosis in 4F treated Tsk?/+ mice. IRF5 in heart lysates from control and Tsk/+ with and without 4F treatment (sc, 1 mg/kg/d, 6–8 weeks) was determined. Phosphoserine, ubiquitin, ubiquitin K63 on IRF5 were determined on immunoprecipitates of IRF5. Immunofluorescence and TUNEL assays in heart sections were used to determine positive nuclei for IRF5 and apoptosis, respectively. Fluorescence-labeled streptavidin (SA) was used to determine endothelial cell uptake of biotinylated 4F. SA-agarose pulldown and immunoblotting for IRF5 were used to determine 4F binding IRF5 in endothelial cell cytosolic fractions and to confirm biolayer interferometry studies. IRF5 levels in Tsk?/+ hearts were similar to control. 4F treatments decrease IRF5 in Tsk?/+ hearts and decrease phosphoserine and ubiquitin K63 but increase total ubiquitin on IRF5 in Tsk?/+ compared with levels on IRF5 in control hearts. 4F binds IRF5 by mechanisms favoring association over dissociation strong enough to pull down IRF5 from a mixture of endothelial cell cytosolic proteins. IRF5 positive nuclei and apoptotic cells in Tsk?/+ hearts were increased compared with controls. 4F treatments decreased both measurements in Tsk?/+ hearts. IRF5 activation in Tsk?/+ hearts is increased. 4F treatments decrease IRF5 expression and activation in Tsk?/+ hearts by a mechanism related to 4F’s ability to bind IRF5.

Xu, Hao; Krolikowski, John G.; Jones, Deron W.; Ge, Zhi-Dong; Pagel, Paul S.; Pritchard, Kirkwood A.; Weihrauch, Dorothee

2012-01-01

290

Vascular characterization of mice with endothelial expression of cytochrome P450 4F2.  

PubMed

Cytochrome P450 (CYP) 4A and 4F enzymes metabolize arachidonic acid to 20-hydroxyeicosatetraenoic acid (20-HETE). Although CYP4A-derived 20-HETE is known to have prohypertensive and proangiogenic properties, the effects of CYP4F-derived metabolites are not well characterized. To investigate the role of CYP4F2 in vascular disease, we generated mice with endothelial expression of human CYP4F2 (Tie2-CYP4F2-Tr). LC/MS/MS analysis revealed 2-foldincreases in 20-HETE levels in tissues and endothelial cells (ECs), relative to wild-type (WT) controls. Tie2-CYP4F2-Tr ECs demonstrated increases in growth (267.1±33.4 vs. 205.0±13% at 48 h) and tube formation (7.7±1.1 vs. 1.6±0.5 tubes/field) that were 20-HETE dependent and associated with up-regulation of prooxidant NADPH oxidase and proangiogenic VEGF. Increases in VEGF and NADPH oxidase levels were abrogated by inhibitors of NADPH oxidase and MAPK, respectively, suggesting the possibility of crosstalk between pathways. Interestingly, IL-6 levels in Tie2-CYP4F2-Tr mice (18.6±2.7 vs. 7.9±2.7 pg/ml) were up-regulated via NADPH oxidase- and 20-HETE-dependent mechanisms. Although Tie2-CYP4F2-Tr aortas displayed increased vasoconstriction, vasorelaxation and blood pressure were unchanged. Our findings indicate that human CYP4F2 significantly increases 20-HETE production, CYP4F2-derived 20-HETE mediates EC proliferation and angiogenesis via VEGF- and NADPH oxidase-dependent manners, and the Tie2-CYP4F2-Tr mouse is a novel model for examining the pathophysiological effects of CYP4F2-derived 20-HETE in the vasculature.-Cheng, J., Edin, M. L., Hoopes, S. L., Li, H., Bradbury, J. A., Graves, J. P., DeGraff, L. M., Lih, F. B., Garcia, V., Shaik, J. S. B., Tomer, K. B., Flake, G. P., Falck, J. R., Lee, C. R., Poloyac, S. M., Schwartzman, M. L., Zeldin, D. C. Vascular characterization of mice with endothelial expression of cytochrome P450 4F2. PMID:24668751

Cheng, Jennifer; Edin, Matthew L; Hoopes, Samantha L; Li, Hong; Bradbury, J Alyce; Graves, Joan P; DeGraff, Laura M; Lih, Fred B; Garcia, Victor; Shaik, Jafar Sadik B; Tomer, Kenneth B; Flake, Gordon P; Falck, John R; Lee, Craig R; Poloyac, Samuel M; Schwartzman, Michal L; Zeldin, Darryl C

2014-07-01

291

Evaluation of acoustic radiation force impulse imaging for determination of liver stiffness using transient elastography as a reference  

PubMed Central

AIM: To evaluate cut-off values and performance of acoustic radiation force impulse imaging (ARFI) using transient elastography [FibroScan© (FS)] as a reference. METHODS: Six hundred and six patients were enrolled in this study. All patients underwent liver stiffness measurement with FS (FS-LS) and ARFI (with shear wave velocity quantification; ARFI-SWV) and the performance of ARFI in comparison to FS was determined. Sixty-eight patients underwent liver biopsy. RESULTS: Significantly higher success rates for the determination of liver stiffness were found using ARFI as compared to FS [604/606 (99.7%) vs 482/606 (79.5%), P < 0.001]. ARFI-SWV correlated significantly with FS-LS (r = 0.920, P < 0.001). ARFI-SWV increased significantly with the stage of fibrosis (1.09 ± 0.13 m/s for patients with no significant fibrosis (FS-LS < 7.6 kPa); 1.46 ± 0.27 m/s for patients with significant liver fibrosis (7.6 < FS-LS ? 13.0 kPa); and 2.55 ± 0.77 m/s for patients with liver cirrhosis (FS-LS > 13.0 kPa)). ARFI-SWV cut-off values were identified for no significant fibrosis (1.29 m/s; sensitivity 91.4% and specificity 92.6%) and for liver cirrhosis (1.60 m/s; sensitivity 92.3% and specificity 96.5%). The optimal cut-off value for predicting liver fibrosis (F ? 2) was 1.32 m/s (sensitivity 87.0% and specificity 80.0%) and for liver cirrhosis (F4) 1.62 m/s (sensitivity 100% and specificity 85.7%), for patients who underwent liver biopsy. An excellent inter-and intraobserver reproducibility was observed for ARFI-SWV determinations. CONCLUSION: An ARFI-SWV cut-off value of 1.29 m/s seems to be optimal for patients with no significant liver fibrosis and 1.60 m/s for patients with liver cirrhosis.

Kircheis, Gerald; Sagir, Abdurrahman; Vogt, Christoph; vom Dahl, Stephan; Kubitz, Ralf; Haussinger, Dieter

2012-01-01

292

Regulation of Pattern Recognition Receptors by the Apolipoprotein A-I Mimetic Peptide 4F  

PubMed Central

Objective The apolipoprotein A-I (apoA-I) mimetic peptide 4F favors the differentiation of human monocytes to an anti-inflammatory phenotype and attenuates lipopolysaccharide (LPS)-induced inflammatory responses. We investigated effects of LPS on the Toll-like receptor (TLR) signaling pathway in 4F-differentiated monocyte-derived macrophages (MDMs). Methods and Results MDMs were pre-treated with 4F or vehicle for 7 days. 4F down-regulated cell surface TLRs (4, 5 and 6) as determined by flow cytometry. 4F attenuated the LPS-dependent up-regulation of genes encoding TLR1, 2 and 6 and genes of the MyD88-dependent (CD14, MyD88, TRAF6, IRAK4, and IKBKB) and MyD88-independent (IRF3, TBK1 and TRIF) pathways as determined by microarray analysis and qRT-PCR. Functional analyses of MDMs showed that 4F reduced LPS-dependent TLR4 recycling, phosphorylation of I?B?, activation and translocation of NF-?B and inhibited the secretion of TNF-? and IL-6 induced by LPS or lipoteichoic acid (LTA). These changes were associated with depletion of cellular cholesterol and caveolin, components of membrane lipid rafts. Conclusion These data suggest that disruption of rafts by 4F alters the assembly of TLR-ligand complexes in cell membranes and inhibits pro-inflammatory gene expression in MDMs, thus attenuating the responsiveness of macrophages to LPS.

White, C. Roger; Smythies, Lesley E.; Crossman, David K.; Palgunachari, Mayakonda N.; Anantharamaiah, G.M.; Datta, Geeta

2014-01-01

293

Diagnostics of Diatomic Carbon in High-Density C_4F8 Plasmas  

Microsoft Academic Search

Optical emission and laser-induced fluorescence (LIF) spectroscopy was applied to the diagnostics of diatomic carbon (C_2) molecules in low-pressure (~=10 mTorr) and high-density (n_e~=10^12 cm-3) C_4F8 plasmas generated by helicon wave discharges. Strong greenish emission from C2 (Swan band) was observed in visible optical emission spectrum from the C_4F8 plasmas. After the chamber was sufficiently seasoned by the C_4F8 plasmas,

C. Suzuki; K. Sasaki; K. Kadota

1997-01-01

294

Acoustic radiation force impulse (ARFI) imaging of preliminary mucosa associated lymphoid tissue (MALT) lymphoma in the breast: a case report  

PubMed Central

Primary lymphoma is a rare neoplasm in the breast accounting for between 0.04% and 0.5% of all malignant mammary tumors. The majority of cases lack typical features of breast malignancy or lymphoma, and likely to be misdiagnosed during daily clinical practice. In this report we describe a case of primary breast lymphoma assessed with acoustic radiation force impulse (ARFI) technology.

Chen, Jiexin; Jin, Zhanqiang; Deng, Dongli; Mao, Dongzhou; Li, Jianwen; Chen, Xiaodong; Ding, Hongfei

2013-01-01

295

Effectiveness of imaging seismic attenuation using visco-acoustic full waveform tomography: Examples from the Seattle Fault Zone and Northern Perth Basin  

NASA Astrophysics Data System (ADS)

Attenuation characterizes the decrease in amplitude of seismic waves as they propagate away from the source. A seismic wave propagating in the subsurface will suffer from two types of attenuation: Intrinsic attenuation and scattering attenuation. Scattering attenuation is due to small scale heterogeneity in the subsurface, whereas intrinsic attenuation arises from inelastic rock properties. Intrinsic attenuation can provide key information about the subsurface, which can be of value to the mining as well as the oil and gas industry. However, accurate imaging of intrinsic seismic attenuation using visco-acoustic full-waveform tomography is not straight forward. Attenuation models recovered by visco-acoustic waveform tomography are often contain contaminated by scattering effects as well as elastic mode conversion artefacts due to the inability of the visco-acoustic approximation to perfectly predict the amplitude of visco-elastic field data. The effect of scattering can be reduced if a velocity model with a high resolution is used. This usually necessitates a two-step inversion approach consisting of first recovering the velocity model and later, the attenuation model. In this study, we present a specific preconditioning of the data based on matching the amplitude variation with offset (AVO) of the field and modelled visco-acoustic data, and a specific inversion approach based on a sequential recovering of the seismic velocity and attenuation models using the visco-acoustic approximation. Our purpose is to improve the quality of the recovered attenuation model by decoupling the reconstruction of velocity and attenuation, thus reducing artefacts. We apply the method to two different areas: The Seattle Fault Zone in Puget Sound in the northwestern USA, using marine seismic reflection data from the Seismic Hazards investigation in Puget Sound (SHIPS) survey collected in 1998, and the Allanooka area within the Northern Perth Basin using high resolution seismic reflection data collected in 2010 for groundwater modelling. In the Allanooka area, we investigate the use of joint inversion of controlled source electromagnetic (CSEM) and seismic data to obtain a more accurate starting velocity model for full-waveform tomography, where the starting usable frequency for waveform tomography is relatively large. We assess the reliability of the results with a set of visco-elastic modelling tests.

Takam Takougang, E.; Calvert, A. J.

2012-12-01

296

28 CFR 55.8 - Relationship between section 4(f)(4) and section 203(c).  

Code of Federal Regulations, 2013 CFR

...IMPLEMENTATION OF THE PROVISIONS OF THE VOTING RIGHTS ACT REGARDING LANGUAGE MINORITY GROUPS Nature of Coverage § 55.8 Relationship...section 4(f)(4) and section 203(c) regarding minority language material and assistance are essentially identical....

2013-07-01

297

4f--5d transitions and polarizability of rare earth ions  

SciTech Connect

Simple and fairly general expressions for the contribution of 4f--5d transitions to the electric polarizability tensor of rare earth ions are derived on the basis of angular momentum theory. These expressions permit a quantitative calculation of the role of the 4f sublattice in the effects of circular and linear birefringence and dichroism. It is shown that the maximum contribution of 4f ions to the birefringence, including magnetic birefringence, may be as high as approx.10/sup -2/ when lambdaapprox.0.6 ..mu..m. As an illustration, a quantitative calculation of the contribution of 4f--5d transitions to the birefringence of orthoferrites DyFeO/sub 3/ and ErFeO/sub 3/ is carried out.

Moskvin, A.S.; Pleshchev, V.M.

1988-04-01

298

Impact of temperature on Na2 Sr(PO4)F:Eu3+ phosphor.  

PubMed

In this article, we report the synthesis of Na2 Sr1-x (PO4)F:Eux phosphor via a combustion method. The influence of different annealing temperatures on the photoluminescence properties was investigated. The phosphor was excited at both 254 and 393 nm. Na2 Sr1-x (PO4)F:Eux (3+) phosphors emit strong orange and red color at 593 and 612 nm, respectively, under both excitation wavelengths. Na2 Sr1-x (PO4)F:Eux (3+) phosphors annealed at 1050°C showed stronger emission intensity compared with 600, 900 and 1200°C. Moreover, Na2 Sr1-x (PO4)F:Eux (3+) phosphor was found to be more intense when compared with commercial Y2 O3:Eu(3+) phosphor. PMID:23853136

Shinde, K N; Pawade, V B; Dhoble, S J; Hakeem, A

2014-06-01

299

Investigations of electron attachment to the perfluorocarbon molecules c-C4F8, 2-C4F8, 1,3 C4F6, and c-C5F8  

NASA Astrophysics Data System (ADS)

Non-dissociative and dissociative electron attachment to a series of gas-phase perfluorocarbons (PFCs), namely octafluorocyclobutane, c-C4F8, octafluorobut-2-ene (perfluoro-2-butene), 2-C4F8, hexafluorobuta-1,3-diene (1,3 perfluorobutadiene), 1,3 C4F6, and octafluorocyclopentene (perfluorocyclopentene), c-C5F8, of importance to technological plasmas, have been investigated using two different, but complimentary, instruments available in Innsbruck over the electron energy range 0-20 eV. Anion yields as a function of electron energy have been recorded, with the positions and intensities of the electron attachment resonances being determined. One of these instruments is a double focusing sector field mass spectrometer (VG-ZAB-2SEQ), which has been used for measurements requiring high sensitivity and for obtaining accurate relative anion yields. It has also been used to determine the electron detachment lifetimes of the parent anions under various accelerating voltages, and these results are also presented. The second instrument (CELIA) is a trochoidal electron monochromator coupled to a quadrupole mass filter with a pulse counting system for detecting product anionic species. This provides a much higher energy resolution than the VG-ZAB, which makes it a better instrument to investigate narrow energy resonances close to 0 eV. The results of anion yields, peak positions and the relative intensities presented in this paper are compared with previous data of electron attachment to the above PFCs, including investigations by Professor Eugen Illenberger.

Feil, Stefan; Märk, Tilmann D.; Mauracher, Andreas; Scheier, Paul; Mayhew, Chris A.

2008-11-01

300

Web Ecology: Recycling HTML Pages as XML Documents Using W4F  

Microsoft Academic Search

In this paper we present the World-Wide Web Wrapper Factory(W4F), a Java toolkit to generate wrappers for Webdata sources. Some key features of W4F are an expressivelanguage to extract information from HTML pages in astructured way, a mapping to export it as XML documentsand some visual tools to assist the user during wrapper creation.Moreover, the entire description of wrappers is

Arnaud Sahuguet; Fabien Azavant

1999-01-01

301

Unprecedented nitronyl nitroxide bridged 3d-4f complexes: structure and magnetic properties.  

PubMed

Two novel 2p-3d-4f compounds, {Ln(hfac)3[Cu(hfac)2]3(NITPhPyrim)2} [Ln = Gd (1), Dy (2)], have been obtained by reacting phenyl pyrimidyl nitronyl nitroxide with Cu(hfac)2 and Ln(hfac)3. These two compounds are the first examples of two-dimensional 3d-4f complexes bridged by nitronyl nitroxide radicals. Overall ferromagnetic behaviors were observed in both compounds. PMID:24151811

Zhu, Mei; Li, Yun-Gai; Ma, Yue; Li, Li-Cun; Liao, Dai-Zheng

2013-11-01

302

LiVPO 4F: A new active material for safe lithium-ion batteries  

Microsoft Academic Search

In this paper, we report the latest findings for the new lithium vanadium fluorophosphate cathode material, LiVPO4F. High quality samples have been prepared using a carbothermal reduction approach and extensive electrochemical and DSC measurements have been performed. In graphite based lithium-ion cells, the LiVPO4F demonstrates reversible specific capacity behavior approaching theoretical. The lithium-ion system operates with an average discharge voltage

R. K. B. Gover; P. Burns; A. Bryan; M. Y. Saidi; J. L. Swoyer; J. Barker

2006-01-01

303

A comparison between ZnO films doped with 3d and 4f magnetic ions  

Microsoft Academic Search

We present electrical and magnetic properties of ZnO films doped with 3d (Mn) and 4f (Gd or Nd) magnetic ions grown on a-plane Al2O3 substrates. Both for films doped with 3d magnetic ions and for films doped with 4f magnetic ions, Hall investigations revealed that the carrier concentration decreases and the resistivity increases with increasing the oxygen partial pressure during

Mariana Ungureanu; Heidemarie Schmidt; Holger von Wenckstern; Holger Hochmuth; Michael Lorenz; Marius Grundmann; Marian Fecioru-Morariu; Gernot Güntherodt

2007-01-01

304

A rail system for circular synthetic aperture sonar imaging and acoustic target strength measurements: design/operation/preliminary results.  

PubMed

A 22 m diameter circular rail, outfitted with a mobile sonar tower trolley, was designed, fabricated, instrumented with underwater acoustic transducers, and assembled on a 1.5 m thick sand layer at the bottom of a large freshwater pool to carry out sonar design and target scattering response studies. The mobile sonar tower translates along the rail via a drive motor controlled by customized LabVIEW software. The rail system is modular and assembly consists of separately deploying eight circular arc sections, measuring a nominal center radius of 11 m and 8.64 m arc length each, and having divers connect them together in the underwater environment. The system enables full scale measurements on targets of interest with 0.1° angular resolution over a complete 360° aperture, without disrupting target setup, and affording a level of control over target environment conditions and noise sources unachievable in standard field measurements. In recent use, the mobile cart carrying an instrumented sonar tower was translated along the rail in 720 equal position increments and acoustic backscatter data were acquired at each position. In addition, this system can accommodate both broadband monostatic and bistatic scattering measurements on targets of interest, allowing capture of target signature phenomena under diverse configurations to address current scientific and technical issues encountered in mine countermeasure and unexploded ordnance applications. In the work discussed here, the circular rail apparatus is used for acoustic backscatter testing, but this system also has the capacity to facilitate the acquisition of magnetic and optical sensor data from targets of interest. A brief description of the system design and operation will be presented along with preliminary processed results for data acquired from acoustic measurements conducted at the Naval Surface Warfare Center, Panama City Division Test Pond Facility. [Work Supported by the U.S. Office of Naval Research and The Strategic Environmental Research and Development Program.]. PMID:24517797

Kennedy, J L; Marston, T M; Lee, K; Lopes, J L; Lim, R

2014-01-01

305

A rail system for circular synthetic aperture sonar imaging and acoustic target strength measurements: Design/operation/preliminary results  

NASA Astrophysics Data System (ADS)

A 22 m diameter circular rail, outfitted with a mobile sonar tower trolley, was designed, fabricated, instrumented with underwater acoustic transducers, and assembled on a 1.5 m thick sand layer at the bottom of a large freshwater pool to carry out sonar design and target scattering response studies. The mobile sonar tower translates along the rail via a drive motor controlled by customized LabVIEW software. The rail system is modular and assembly consists of separately deploying eight circular arc sections, measuring a nominal center radius of 11 m and 8.64 m arc length each, and having divers connect them together in the underwater environment. The system enables full scale measurements on targets of interest with 0.1° angular resolution over a complete 360° aperture, without disrupting target setup, and affording a level of control over target environment conditions and noise sources unachievable in standard field measurements. In recent use, the mobile cart carrying an instrumented sonar tower was translated along the rail in 720 equal position increments and acoustic backscatter data were acquired at each position. In addition, this system can accommodate both broadband monostatic and bistatic scattering measurements on targets of interest, allowing capture of target signature phenomena under diverse configurations to address current scientific and technical issues encountered in mine countermeasure and unexploded ordnance applications. In the work discussed here, the circular rail apparatus is used for acoustic backscatter testing, but this system also has the capacity to facilitate the acquisition of magnetic and optical sensor data from targets of interest. A brief description of the system design and operation will be presented along with preliminary processed results for data acquired from acoustic measurements conducted at the Naval Surface Warfare Center, Panama City Division Test Pond Facility. [Work Supported by the U.S. Office of Naval Research and The Strategic Environmental Research and Development Program.

Kennedy, J. L.; Marston, T. M.; Lee, K.; Lopes, J. L.; Lim, R.

2014-01-01

306

Subsurface 3D high-resolution fault imaging: An example from the Kamishiro fault in Lake Aoki obtained by acoustic exploration, central Japan  

NASA Astrophysics Data System (ADS)

To visualize 3D inland geologic structure associated with active faulting, one uses high-cost multiple seismic reflection profiles. Here we fortunately face an unusual case: a large lake across one of the most active faults allows us to use acoustic exploration to visualize the subsurface deformation as the 3D high-resolution images. We investigated the Kamishiro fault, which is a northern part of the Itoigawa-Shizuoka tectonic line active fault system (ISTL), to reveal its Holocene activity. Lake Aoki, which is a natural dam reservoir bonded by an old landslide mass located in the city of Omachi, Nagano Prefecture, hides a 30-meter-high N-S striking fault scarp. On the lake, we employed a 10-KHz acoustic sonar equipment which maximum resolution for the images is 5 cm and which maximum depth of acoustic penetration is 20 m. We cruised the 51 transverse lines which interval and length are 25 m and 900 m on average. The entire profile set covers ~ 1.5 km x 1.5 km area and provides us not only the detailed fault traces ever mapped but also multiple paleoseismic event horizons in the deformed lacustrine strata. We found three major fault traces (F1, F2, and F3 from west to east), one of which (F2) corresponds to the previously mapped the N-S striking fault scarp that separates the major basin (west) and shallow sub-basin (east). A newly identified fault (F1) coincides with a steep sub-lake cliff that bounds the western margin of the major basin. These two faults (F1 and F2) are bifurcated from the north coast of the lake to the south and bear the major basin as a pull-apart basin structure. On the sub-basin, strata under a 500-meter-long topographic bulge also show evidence of the recent reverse faulting. Such an imaged complex fault system that strike-slip faults and a reverse fault coexist would cast a new view over the common knowledge of tectonic framework for the future earthquake potential on the ISTL.

Haraguchi, T.; Yoshinaga, Y.; Toda, S.

2006-12-01

307

Calculation of the 4f1 ? 4f05d1 transitions in Ce3+-doped systems by Ligand Field Density Functional Theory  

NASA Astrophysics Data System (ADS)

We present a recipe for the calculation of the optical properties of Ce3+-doped systems. The model implies the use of ligand field phenomenology in conjunction with Density Functional Theory (DFT). The particular procedures enable the reliable prediction of the 4f1 ? 4f05d1 transitions in Cs2NaYCl6:Ce3+. The analysis of the doping of Ce3+ into the host is accomplished by band structure calculations. The calculated multiplet energy levels are in agreement with the experimental observation, the outlined treatment being, to the best of our knowledge, unprecedented clear and conclusive application of DFT for the rather complex problems of structure and spectroscopy of cerium-doped systems.

Ramanantoanina, Harry; Urland, Werner; García-Fuente, Amador; Cimpoesu, Fanica; Daul, Claude

2013-11-01

308

Visualization of Acoustic Waves Propagating within a Single Anisotropic Crystalline Plate.  

National Technical Information Service (NTIS)

We present a hybrid acoustic imaging system to directly visualize acoustic waves propagating within a single anisotropic crystalline plate. A high frequency acoustic point focus lens was used to form a small point source within the plate. A laser interfer...

C. Miyasaka J. T. Sadler K. L. Telschow R. G. Maev

2007-01-01

309

Association of 1347 G/A cytochrome P450 4F2 (CYP4F2) gene variant with hypertension and stroke.  

PubMed

Genetic variants of cytochrome P450 4F2 (CYP4F2) gene have been suggested to be risk factors for hypertension, cardiovascular diseases and stroke. In the present case-control study we investigated the association of 1347 G/A polymorphism (rs2108622) in the 11th exon region of CYP4F2 gene with hypertension, ischemic stroke and stroke subtypes classified according to TOAST (Trial of Org 10172 in Acute Stroke Treatment) classification. Five hundred and seven stroke patients (hypertensives: normotensives = 279:228) and four hundred and eighty seven, age and sex matched controls (males: females = 356:131) (hypertensives: normotensives = 148:339) were involved in the study. The genotypes were determined by PCR-RFLP technique. Genotypes were confirmed by subjecting the PCR products to sequencing. Significant difference was observed in the genotypic distribution and allelic frequency between the stroke patients and healthy controls. AA genotype and A allele associated significantly with stroke and hypertension [P = 0.009; OR = 1.59 (95% CI = 1.119-2.283) and P = 0.010; OR = 1.26 (95% CI = 1.056-1.502); P = 0.01; OR = 1.58 (95% CI = 1.11-2.272) and P = 0.010; OR = 1.25(95% CI = 1.054-1.504) respectively]. A stepwise logistic regression analysis confirmed these findings. To establish that this polymorphism is associated with stroke independent of hypertension; we compared stroke patients without hypertension with normotensive controls. Significant difference was observed in genotypic distribution and allelic frequency between the two groups (P = 0.001 and 0.002 respectively). Evaluating the association of this polymorphism with stroke subtypes we found significant associations with cardioembolic stroke (P < 0.001). In conclusion our study suggests that 1347A allele of CYP4F2 gene is an important risk factor for hypertension and ischemic stroke. PMID:21625857

Munshi, Anjana; Sharma, Vandana; Kaul, Subhash; Al-Hazzani, Amal; Alshatwi, Ali A; Shafi, Gowhar; Koppula, Rajeshwar; Mallemoggala, Sai Babu; Jyothy, A

2012-02-01

310

P4F-6 On the Potential of Combined ARFI and Elastography to Improve Differentiation of Material Structure in Viscoelastic Tissue  

Microsoft Academic Search

Acoustic radiation force imaging methods distinguish tissue structure and composition by monitoring tissue responses to applied radiation force excitations. Applying Voigt and Kelvin viscoelastic tissue models, we present a new radiation force technique - monitored steady-state excitation and recovery (MSSER) imaging - that tracks both steady-state displacement during prolonged force application and transient response following force cessation to estimate tissue

F. William Mauldin; Olgha B. Davis; Mansoor A. Haider; Elizabeth G. Loboa; T. Wayne Pfeiler; Caterina M. Gallippi

2007-01-01

311

The use of acoustic microscopy for biological tissue characterization.  

PubMed

A system of transmission raster acoustic microscope with an ultrasound frequency of 450 MHz has been designed to investigate biological tissues and comparative analysis of their optical and acoustic images. The possibility of obtaining the contrast acoustic images of nonfixed, nonstained biological tissues and viscoelasticity measurements in microscale was demonstrated. PMID:3310355

Kolosov, O V; Levin, V M; Mayev, R G; Senjushkina, T A

1987-08-01

312

Isomer effects on the total cross section for electron scattering from C4F6 molecules  

NASA Astrophysics Data System (ADS)

The absolute total cross section (TCS) for electron scattering from hexafluoro-1,3-butadiene (1,3-C4F6) was obtained in a transmission experiment for electron impact energies from 0.6 to 370 eV. The TCS energy function has two pronounced enhancements separated by a deep minimum located near 2.6 eV: a low-energy hump around 1 eV and a dominant very broad enhancement centred near 30 eV. The 1,3-C4F6 TCS results are compared with the data for hexafluoro-2-butyne (2-C4F6) and the influence of the structural differences on the electron-scattering TCS for isomers of the C4F6 molecule (isomeric effect) is explicitly indicated. The most pronounced role of the molecular geometry on the magnitude and shape of the TCS energy dependence is observed at the lowest energies studied. Above 40 eV the TCSs for both isomers are close to each other. Some conformities of TCSs within a series of perfluorocarbons (C2F4, 1,3-C4F6, C6F6) as well as in a series of their hydrocarbon counterparts (C2H4, 1,3-C4H6, C6H6) are also pointed out and discussed.

Szmytkowski, Czeslaw; Kwitnewski, Stanislaw

2003-12-01

313

Music Acoustics  

NSDL National Science Digital Library

The Music Acoustics Web site is maintained by the University of New South Wales School of Physics. General topics covered include what a decibel is, what interference beats are, what a sound spectrum is, what acoustic impedance is, and others. Specific instrument questions are also answered, such as waves in strings, flute and clarinet acoustics, Helmholz resonance, and pipes and harmonics. This very interesting site, with its many illustrations and animations, along with its easily-read text, answers all the questions you�ve ever had on the physics of music and many of the ones you never knew you wanted to ask.

2007-11-06

314

Acoustic window  

NASA Astrophysics Data System (ADS)

A cost-effective, producible improved apparatus for and method of fabricating a transducer acoustic window for a marine environment has acceptable acoustic energy transmitting properties and appropriate mechanical properties to withstand the rigors associated with varying velocities of flowing water, fluctuating temperatures, changing ambient pressures, the abuse attendant operations, etc., that are routinely encountered during a prolonged deployment. The acoustic window has a cast CONAP 1556 polyurethane window portion that extends over a hull opening and on a bearing surface rim about the opening. A number of equidistantly, circumferentially spaced stainless steel inserts are molded in the cast polyurethane window portion.

Bullat, David M.; Bradshaw, Philip C.; Brown, Jay C.

1994-01-01

315

Revealing, identifying, and assessing flaws in operating equipment by the acoustic emission image recognition method under strong background noise condition  

NASA Astrophysics Data System (ADS)

The analysis has shown that high pressure and high temperature piping in fossil and nuclear power plants suffer from unexpected and rarely predictable failures. To guarantee operational safety and to prevent failures authors have performed the complex investigations and have created Quantitative Acoustic Emission NDI technology for revealing, identifying and assessing flaws in equipment operated under strong background noise condition. These enabled: Overall inspection of the piping operated under stress, temperature, pressure, steam flow and loading, variation. Locating suspected zones and zones of flaw development with low J-integral value and the great variation of the dynamic range of flaws danger level. Identification of flaw types and their danger level. Detection of defective components in service prior to shut down. The continuous and the burst Acoustic Emission (AE) were used in combination as an information tool. As result, the significant number of flaws such as creep at stage 3a-3b, closed-edge micro-cracks, systems of randomly dispersed pores and inclusions, plastic deformation development around them, or/and individual micro-cracking were revealed, identified and assessed in 50 operating high energy piping. The findings and assessing flaw danger level obtained by QAE NDI were confirmed by independent NDI methods as TOFD, X-ray, replication, metallurgical investigations, etc. The findings and assessing flaw danger level obtained by QAE NDI were confirmed by independent NDI methods such as TOFD, X-ray, replication, metallurgical investigations, etc

Muravin, Gregory; Muravin, Boris; Lezvisky, Ludmila

2004-05-01

316

Acoustic images of the submarine fan system of the northern Kumano Basin obtained during the experimental dives of the Deep Sea AUV URASHIMA  

NASA Astrophysics Data System (ADS)

Autonomous underwater vehicles (AUVs) present the important advantage of being able to approach the seafloor more closely than surface vessel surveys can. To collect bathymetric data, bottom material information, and sub-surface images, multibeam echosounder, sidescan sonar (SSS) and subbottom profiler (SBP) equipment mounted on an AUV are powerful tools. The 3000m class AUV URASHIMA was developed by the Japan Agency for Marine-Earth Science and Technology (JAMSTEC). After finishing the engineering development and examination phase of a fuel-cell system used for the vehicle's power supply system, a renovated lithium-ion battery power system was installed in URASHIMA. The AUV was redeployed from its prior engineering tasks to scientific use. Various scientific instruments were loaded on the vehicle, and experimental dives for science-oriented missions conducted from 2006. During the experimental cruise of 2007, high-resolution acoustic images were obtained by SSS and SBP on the URASHIMA around the northern Kumano Basin off Japan's Kii Peninsula. The map of backscatter intensity data revealed many debris objects, and SBP images revealed the subsurface structure around the north-eastern end of our study area. These features suggest a structure related to the formation of the latest submarine fan. However, a strong reflection layer exists below ~20ms below the seafloor in the south-western area, which we interpret as a denudation feature, now covered with younger surface sediments. We continue to improve the vehicle's performance, and expect that many fruitful results will be obtained using URASHIMA.

Kasaya, Takafumi; Kanamatsu, Toshiya; Sawa, Takao; Kinosita, Masataka; Tukioka, Satoshi; Yamamoto, Fujio

2011-02-01

317

System and method to create three-dimensional images of non-linear acoustic properties in a region remote from a borehole  

DOEpatents

In some aspects of the disclosure, a method for creating three-dimensional images of non-linear properties and the compressional to shear velocity ratio in a region remote from a borehole using a conveyed logging tool is disclosed. In some aspects, the method includes arranging a first source in the borehole and generating a steered beam of elastic energy at a first frequency; arranging a second source in the borehole and generating a steerable beam of elastic energy at a second frequency, such that the steerable beam at the first frequency and the steerable beam at the second frequency intercept at a location away from the borehole; receiving at the borehole by a sensor a third elastic wave, created by a three wave mixing process, with a frequency equal to a difference between the first and second frequencies and a direction of propagation towards the borehole; determining a location of a three wave mixing region based on the arrangement of the first and second sources and on properties of the third wave signal; and creating three-dimensional images of the non-linear properties using data recorded by repeating the generating, receiving and determining at a plurality of azimuths, inclinations and longitudinal locations within the borehole. The method is additionally used to generate three dimensional images of the ratio of compressional to shear acoustic velocity of the same volume surrounding the borehole.

Vu, Cung; Nihei, Kurt T.; Schmitt, Denis P.; Skelt, Christopher; Johnson, Paul A.; Guyer, Robert; TenCate, James A.; Le Bas, Pierre-Yves

2013-01-01

318

The 4f-5d luminescence transitions in cerium-doped LuF3  

NASA Astrophysics Data System (ADS)

Emission and excitation spectra of the Ce3+ ion in LuF3 single crystal were measured at 77?K. The broad bands observed in these spectra were attributed to the parity-allowed electric-dipole 4f???5d transitions within Ce3+ ion. No zero-phonon lines were observed, which is indicative of a strong electron-phonon coupling in this host. It is shown that Ce3+ 5d excited configuration splits into five crystal-field components in LuF3. The influence of the crystalline environment on the position of the lowest Ce3+ 5d level is investigated. The energy of the lowest level of the 4fN-15d excited configuration was predicted for all the trivalent rare earth ions embedded in LuF3. Positions of crystal field spitting levels of 4fN-15d configuration relative to the host electronic bands were discussed.

Guerbous, L.; Krachni, O.

319

A Mössbauer spectroscopy study of polyol synthesized tavorite LiFeSO4F  

NASA Astrophysics Data System (ADS)

The tavorite polymorph of LiFeSO4F has attracted considerable attention as a cathode material for lithium ion batteries due to interesting structural and electrochemical characteristics. For the analysis of such iron-based electrode materials, Mössbauer spectroscopy has become an important and highly useful tool. In this work, we perform a detailed Mössbauer study of pristine tavorite LiFeSO4F prepared by an optimized synthesis in tetraethylene glycol as reaction media. In contrast to many reported results, we demonstrate the use of an asymmetric fitting model for the inner doublet of the spectrum, which is coupled to the structural properties of the compound. Moreover, we discuss a new approach of ascribing the Fe2 + -doublets to the two distinct crystallographic iron sites of tavorite LiFeSO4F by comparing the Mössbauer signal intensities with the expected f-factors for the corresponding iron atom.

Sobkowiak, Adam; Ericsson, Tore; Edström, Kristina; Gustafsson, Torbjörn; Björefors, Fredrik; Häggström, Lennart

2014-04-01

320

Underwater Acoustics.  

ERIC Educational Resources Information Center

Summarizes the history of underwater acoustics and describes related research studies and teaching activities at the University of Birmingham (England). Also includes research studies on transducer design and mathematical techniques. (SK)

Creasey, D. J.

1981-01-01

321

Functional and morphological characterization of 4F7+ spleen accessory dendritic cells.  

PubMed

Recently we have reported on the production of the mAb 4F7. This recognizes a molecule that is upregulated on dermal and epidermal dendritic cells after application of contact allergen. Furthermore, this antibody detects an antigen on spleen and lymph node dendritic cells. In this study, we characterize 4F7+ spleen dendritic cells and show that the mAb recognizes in situ few labeled cells in the white pulp of the spleen and approximately 1% of spleen single cell suspensions as evidenced by cell enrichment, immunoperoxidase staining and FACS analysis. Immunohistological characterization of the cells with mAbs revealed the expression of class II, class I MHC antigens, 33D1, CD11c, ICAM-1, and CD45 molecules. After enrichment and cultivation for approximately 3 days, these cells showed no adherent properties. The capacity of 4F7+ spleen dendritic cells to activate allogeneic T cells in the primary mixed lymphocyte reaction was similar to freshly isolated Ia+ Langerhans cells. With regard to the induction of a proliferative response of CD4+ naive T cells that were incubated with concanavalin A or anti-CD3 mAb, 4F7+ spleen dendritic cells were two to three times more potent than spleen microphages and B cells. Furthermore, 4F7+ cells efficiently stimulated the antigen dependent proliferation of a T helper cell line. The mAb 4F7 will be useful for the purification of dendritic cells and for functional and molecular biological studies. PMID:8347556

Mohamadzadeh, M; Jonuleit, H; Kolde, G; Pavlidou, A; Schmitt, E; Knop, J

1993-06-01

322

Structure of Some 4f Rare Earth Liquid Metals — A Charged Hard Sphere Approach  

NASA Astrophysics Data System (ADS)

A well-established pseodopotential is used to study the structure of some 4f rare earth liquid metals (Ce, Pr, Eu, Gd, Tb, and Yb). The structure factor S(q), pair distribution function g(r), interatomic distance r1, and coordination number n1 are calculated using Charged Hard Sphere (CHS) reference system. To introduce the exchange and correlation effects, the local field correction due to Sarkar et al. (S) is applied. The present investigation is successful in generating the structural information of Ce, Pr, Eu, Gd, Tb, and Yb 4f rare earth liquid metals.

P. B., Thakor; P. N., Gajjar; A. R., Jani

2006-08-01

323

Proton cyclotron echoes at 3fH and 4fH resonances  

NASA Astrophysics Data System (ADS)

A new class of proton cyclotron echoes observed on topside sounder ionograms is presented; these echoes occur at frequencies above the electron plasma frequency and at the third and fourth harmonics of the electron cyclotron frequency, 3fH and 4fH. Some features are noted such as the dependence on low dip angle values. It is suggested that the 3fH and 4fH proton cyclotron echoes may be generated by wave-particle interaction between the electrostatic waves and the protons that are both energized by the dipole antenna on Alouette II, ISIS I, or ISIS II.

Chen, G. M.; Horita, R. E.

1991-02-01

324

Syntheses and NMR study of 4f-spin-free electron-doped copper oxides  

Microsoft Academic Search

All the electron-doped high-Tc oxides discovered so far inevitably contain lanthanides, whose 4f-spin fluctuation hides all the NMR information on the superconductivity. The new copper oxide superconductor (La1-yYy)2-xCexCuO4 with T'-type structure, which is free from 4f-spins has been successfully synthesized. Obtained compounds showed a nearly zero electric field gradient(EFG) at Cu site, which demonstrates that the doped carrier is electronic.

Masatsugu Fukunaga; Takayuki Goto; Kazuya Miyagawa; Tetsuo Fukase

1994-01-01

325

Synthesis and spectral investigations of Mn(II) ions doped NaCaAlPO4F3 phosphor  

NASA Astrophysics Data System (ADS)

Mn(II) ions doped NaCaAlPO4F3 phosphor was synthesized by using solid state reaction method. The prepared sample was characterized by various spectroscopic techniques such as powder XRD, SEM with EDS, Optical absorption, electron paramagnetic resonance (EPR) and photoluminescence. From powder XRD, the average crystallite size was calculated about 46 nm. SEM images showed the irregular shaped entities present in the sample. Optical absorption spectrum gave the absorption bands in UV-VIS region which are the characteristic of Mn(II) ions in octahedral symmetry. The room temperature EPR spectrum exhibited a six weak hyperfine splitting lines centered at g = 2.0. Photoluminescence spectrum showed the emission peaks in visible region, from yellow to red with an excitation wavelength of 465 nm. From the emission spectral data, the CIE chromaticity coordinates were also calculated as (x = 0.661, y = 0.338).

Pushpa Manjari, V.; Rama Krishna, Ch.; Muntaz Begum, Sk.; Ravikumar, R. V. S. S. N.

2014-01-01

326

Acoustic metamaterial design and applications  

Microsoft Academic Search

The explosion of interest in metamaterials is due to the dramatically increased manipulation ability over light as well as sound waves. This material research was stimulated by the opportunity to develop an artificial media with negative refractive index and the application in superlens which allows super-resolution imaging. High-resolution acoustic imaging techniques are the essential tools for nondestructive testing and medical

Shu Zhang

2010-01-01

327

Temperature dependent magnetic structure of lithium delithiated LixFeSO4F (x = 0, 1) by Mössbauer spectroscopy  

NASA Astrophysics Data System (ADS)

Recently, lithium iron sulfate compounds have been highly considered for a positive electrode material for lithium ion batteries. In this work, LiFeSO4F and the fully delithiated FeSO4F were prepared by the ionothermal process and chemical oxidation reaction method. The LixFeSO4F (x = 0, 1) samples show the triclinic structure with P-1 space group. In the case of delithiated FeSO4F, changes in lattice parameters were observed due to the disappearance of the Li site while maintaining the triclinic structure. Temperature-dependent magnetic susceptibility curves show the antiferromagnetic (AFM) structure with the ordering temperature of 28 K for LiFeSO4F and 99 K for FeSO4F. Also, temperature-dependent Mössbauer spectra of LiFeSO4F below TN were fitted with two-sets of eight Lorentzian indicating the existence of two different types of Fe2+ ions due to the different hyperfine and electric quadrupole interactions. With the lithium delithiated, the Fe3+ iron ions in FeSO4F exhibit two-sets of six-line patterns due to the electron transfer in FeO4F2 site by lithium delithiation. These suggest that the different AFM ordering in LixFeSO4F can be originated from the Fe2+/Fe3+ magnetic ions with different charge distributions and spin contributions.

Lee, In Kyu; Wook Hyun, Sung; Kouh, Taejoon; Shim, In-Bo; Sung Kim, Chul

2012-04-01

328

Energy position of 4f levels in rare-earth metals  

Microsoft Academic Search

The energy position of the occupied and unoccupied 4f levels relative to the Fermi energy is studied for the rare-earth metals. This is done by treating the excited state as an impurity in an otherwise perfect crystal. This picture is first considered in the complete screening approximation. In this approximation thermochemical data can be used directly to give energy values

Börje Johansson

1979-01-01

329

From serendipitous assembly to controlled synthesis of 3d-4f single-molecule magnets.  

PubMed

Learning from serendipitous assembly, we have prepared a new family of designed 3d-4f Mn6Ln complexes. The dynamics of relaxation of the magnetization via alternating-current magnetic susceptibility for the new Mn6Ln complexes 1 (Ln = La), 2 (Ln = Tb), and 4 (Ln = Dy) have been studied down to 0.2 K. PMID:24853637

Ledezma-Gairaud, M; Grangel, L; Aromí, G; Fujisawa, T; Yamaguchi, A; Sumiyama, A; Sañudo, E C

2014-06-16

330

Structural and electrochemical properties of lithium vanadium fluorophosphate, LiVPO 4F  

NASA Astrophysics Data System (ADS)

The electroactive lithium vanadium fluorophosphate phase, LiVPO 4F ( P1¯, a = 5.1687(2) Å, b = 5.3062(2) Å, c = 7.5031(3) Å, ? = 66.856(2)°, ? = 67.004(2)°, ? = 81.583(2)° and cell volume = 174.21(1) Å 3) has been synthesized by a two-step reaction scheme based on a carbothermal reduction (CTR) process. High-resolution electrochemical measurements reveal a structured voltage response for the lithium extraction process while the lithium insertion process proceeds via a two-phase reaction mechanism centered at around 4.2 V versus Li. Performance evaluation of a graphite||LiVPO 4F lithium-ion cell indicates an average discharge voltage of 4.06 V coupled to an initial material utilization for the LiVPO 4F of around 123 mAh g -1. Long-term cycling of this lithium-ion system demonstrates good capacity retention over the first 300 cycles. Based on the available data we believe the LiVPO 4F offers considerable promise as a viable cathode replacement for LiCoO 2.

Barker, J.; Gover, R. K. B.; Burns, P.; Bryan, A.; Saidi, M. Y.; Swoyer, J. L.

331

CYP4F2 genetic polymorphisms are associated with coronary heart disease in a Chinese population  

PubMed Central

Background To explore the relationship between CYP4F2 gene polymorphism and coronary heart disease (CHD) in a Chinese Han population. Methods We selected 440 CHD patients and 440 control subjects to perform a case - control study. Four SNPs (rs2108622, rs3093100, rs3093105 and rs3093135) in CYP4F2 gene were genotyped using polymerase chain reaction - restriction fragment length polymorphism (PCR - RFLP) methods. The genotype and haplotype distributions were compared between the case and the control group. Results We found both rs2108622 and rs3093105 in CYP4F2 gene were associated with the risk for CHD (P <0.01). Haplotype analysis indicated that GGGT haplotype consisted by rs2108622-rs3093100-rs3093105-rs3093135 was associated with CHD risk (OR?=?4.367, 95% CI: 2.241?~?8.510; P?4F2 gene polymorphisms were associated with the risk of CHD in Chinese population.

2014-01-01

332

A preliminary engineering design of intravascular dual-frequency transducers for contrast-enhanced acoustic angiography and molecular imaging.  

PubMed

Current intravascular ultrasound (IVUS) probes are not optimized for contrast detection because of their design for high-frequency fundamental-mode imaging. However, data from transcutaneous contrast imaging suggests the possibility of utilizing contrast ultrasound for molecular imaging or vasa vasorum assessment to further elucidate atherosclerotic plaque deposition. This paper presents the design, fabrication, and characterization of a small-aperture (0.6 × 3 mm) IVUS probe optimized for high-frequency contrast imaging. The design utilizes a dual-frequency (6.5 MHz/30 MHz) transducer arrangement for exciting microbubbles at low frequencies (near their resonance) and detecting their broadband harmonics at high frequencies, minimizing detected tissue backscatter. The prototype probe is able to generate nonlinear microbubble response with more than 1.2 MPa of rarefractional pressure (mechanical index: 0.48) at 6.5 MHz, and is also able to detect microbubble response with a broadband receiving element (center frequency: 30 MHz, ¿6-dB fractional bandwidth: 58.6%). Nonlinear super-harmonics from microbubbles flowing through a 200-¿m-diameter micro-tube were clearly detected with a signal-to-noise ratio higher than 12 dB. Preliminary phantom imaging at the fundamental frequency (30 MHz) and dual-frequency super-harmonic imaging results suggest the promise of small aperture, dual-frequency IVUS transducers for contrast-enhanced IVUS imaging. PMID:24801226

Ma, Jianguo; Martin, K; Dayton, Paul; Jiang, Xiaoning

2014-05-01

333

A Preliminary Engineering Design of Intravascular Dual-Frequency Transducers for Contrast-Enhanced Acoustic Angiography and Molecular Imaging  

PubMed Central

Current intravascular ultrasound (IVUS) probes are not optimized for contrast detection because of their design for high-frequency fundamental-mode imaging. However, data from transcutaneous contrast imaging suggests the possibility of utilizing contrast ultrasound for molecular imaging or vasa vasorum assessment to further elucidate atherosclerotic plaque deposition. This paper presents the design, fabrication, and characterization of a small-aperture (0.6 × 3 mm) IVUS probe optimized for high-frequency contrast imaging. The design utilizes a dual-frequency (6.5 MHz/30 MHz) transducer arrangement for exciting microbubbles at low frequencies (near their resonance) and detecting their broadband harmonics at high frequencies, minimizing detected tissue backscatter. The prototype probe is able to generate nonlinear microbubble response with more than 1.2 MPa of rarefractional pressure (mechanical index: 0.48) at 6.5 MHz, and is also able to detect microbubble response with a broadband receiving element (center frequency: 30 MHz, ?6-dB fractional bandwidth: 58.6%). Nonlinear super-harmonics from microbubbles flowing through a 200-?m-diameter micro-tube were clearly detected with a signal-to-noise ratio higher than 12 dB. Preliminary phantom imaging at the fundamental frequency (30 MHz) and dual-frequency super-harmonic imaging results suggest the promise of small aperture, dual-frequency IVUS transducers for contrast-enhanced IVUS imaging.

Ma, Jianguo; Martin, K. Heath; Dayton, Paul A.; Jiang, Xiaoning

2014-01-01

334

The Possibility of Gain among the 5D-4F Transitions of the Rare Earth Ions  

NASA Astrophysics Data System (ADS)

Although a wealth of information exists on the 4f-4f transitions of rare earth ions doped into solid-state materials, relatively little research exists on the 5d -4f transitions present in the same materials. We have studied the 5d-4f transitions of three rare-earth ions in a variety of materials in an attempt to evaluate the potential of the 5d-4f transition as a laser transition. We have measured the pump-probe spectrum of Sm ^{2+}:CaF_2 over a wide spectral region in order to characterize a material known to lase on a 5d-4f transition. We then measured comparable pump-probe spectra for Sm^ {2+} in SrF_2 and SrCl_2. This provided us with a systematic look at the excited state and its dependence on the host material. In addition to investigating divalent samarium, we have investigated other rare-earth ion doped systems similar in nature to known laser systems. Divalent europium, being a neighbor of samarium on the periodic table, has a very similar electronic configuration. Historically, europium has been recognized as an efficient fluorescent material, but has not demonstrated gain in any solid state host. We measured the pump-probe spectrum of divalent europium over a wide spectral region in CaF_2, SrF_2, SrCl_2, and LiCaAlF_6 in order to better understand the nature of the excited states and to evaluate whether it is possible for Eu^ {2+} to exhibit gain in any host medium. Among the trivalent rare earths, two elements, cerium and neodymium, have been demonstrated to lase. We chose expand upon current knowledge of 5d-4f transitions in the trivalent RE ions by studying trivalent praseodymium in CaF_2, SrF_2, BaF_2, BaY_2 F_8, and LiYF_4. Pr^{3+} seemed to be a reasonable candidate for gain, in part because it lies on the periodic table between the two elements which exhibit gain as trivalent ions in solid state media. The recent availability of non-linear crystals with Pu transparency made it possible to pump the ion using the fifth harmonic of Nd:YAG (213 nm).

Lawson, Janice Kay

335

Time reversed acoustics techniques for elastic imaging in reverberant and nonreverberant media: An experimental study of the chaotic cavity transducer concept  

NASA Astrophysics Data System (ADS)

In view of emerging imaging technologies based on the combination of Time Reversed Acoustics (TRA) with Nonlinear Elastic Wave Spectroscopy (NEWS) for the detection and localization of micro-damage in solids, we have investigated the benefits of chirped source signal excitation, inverse filtering techniques, and the implementation of chaotic cavity transducers to improve the quality of energy focusing, especially for weakly reverberant media. Chaotic cavity transducer focusing is defined as the hardware-software combination of a piezoelectric ceramic glued on a cavity of chaotic shape on the one hand with the reciprocal Time Reversal (or Inverse Filter) technique on the other hand. Experimental data for reverberant and nonreverberant composite plates show that the use of chirps, inverse filtering and chaotic cavity transducers significantly enhances the focusing process, and enables focusing in a nonreverberant medium using only one transducer. As a potential exploitation, the application of the chaotic cavity transducer concept for synthetic imaging is examined, revealing several properties similar to phased arrays.

van Damme, Bart; van den Abeele, Koen; Li, Yifeng; Matar, Olivier Bou

2011-05-01

336

The acoustic lens design and in vivo use of a multifunctional catheter combining intracardiac ultrasound imaging and electrophysiology sensing  

Microsoft Academic Search

A multifunctional 9F intracardiac imaging and electrophysiology mapping catheter was developed and tested to help guide diagnostic and therapeutic intracardiac electrophysiology (EP) procedures. The catheter tip includes a 7.25-MHz, 64-element, side-looking phased array for high resolution sector scanning. Multiple electrophysiology mapping sensors were mounted as ring electrodes near the array for electrocardiographic synchronization of ultrasound images. The catheter array elevation

Douglas N. Stephens; Jonathan Cannata; Ruibin Liu; Jian Zhong Zhao; K. K. Shung; Hien Nguyen; R. Chia; A. Dentinger; D. Wildes; K. E. Thomenius; A. Mahajan; K. Shivkumar; Kang Kim; M. O'Donnell; David Sahn

2008-01-01

337

Convergence of temporal and spectral information into acoustic images of complex sonar targets perceived by the echolocating bat, Eptesicus fuscus  

Microsoft Academic Search

Summary 1.FM echolocating bats (Eptesicus fuscus) were trained to discriminate between a two-component complex target and a one-component simple target simulated by electronically-returned echoes in a series of experiments that explore the composition of the image of the two-component target. In Experiment I, echoes for each target were presented sequentially, and the bats had to compare a stored image of

James A. Simmons; Cynthia F. Moss; Michael Ferragamo

1990-01-01

338

Ion energy distribution and optical measurements in high-density, inductively coupled C4F6 discharges  

NASA Astrophysics Data System (ADS)

Hexafluoro-1,3 butadiene (C4F6) is a potential etching gas with a very low global warming potential for the manufacturing of semiconductors, unlike commonly used fluorocarbon gases such as CF4 and c-C4F8. We report ion energy distributions, relative ion intensities and absolute total ion current densities measured at the edge of an inductively coupled gaseous electronics conference radio-frequency reference cell for discharges generated in pure C4F6 and C4F6:Ar mixtures. In addition, the ratio of radical densities relative to CF measured using submillimeter absorption spectroscopy and optical emission spectroscopy measurements are presented. These measurements of the C4F6 plasmas were made for several different gas pressures (0.67, 1.33, and 2.66 Pa) and gas mixture ratios (25%, 50%, 75%, and 100% C4F6 volume fractions).

Benck, Eric C.; Goyette, Amanda; Wang, Yicheng

2003-08-01

339

Acoustic Inversion in Optoacoustic Tomography: A Review  

PubMed Central

Optoacoustic tomography enables volumetric imaging with optical contrast in biological tissue at depths beyond the optical mean free path by the use of optical excitation and acoustic detection. The hybrid nature of optoacoustic tomography gives rise to two distinct inverse problems: The optical inverse problem, related to the propagation of the excitation light in tissue, and the acoustic inverse problem, which deals with the propagation and detection of the generated acoustic waves. Since the two inverse problems have different physical underpinnings and are governed by different types of equations, they are often treated independently as unrelated problems. From an imaging standpoint, the acoustic inverse problem relates to forming an image from the measured acoustic data, whereas the optical inverse problem relates to quantifying the formed image. This review focuses on the acoustic aspects of optoacoustic tomography, specifically acoustic reconstruction algorithms and imaging-system practicalities. As these two aspects are intimately linked, and no silver bullet exists in the path towards high-performance imaging, we adopt a holistic approach in our review and discuss the many links between the two aspects. Four classes of reconstruction algorithms are reviewed: time-domain (so called back-projection) formulae, frequency-domain formulae, time-reversal algorithms, and model-based algorithms. These algorithms are discussed in the context of the various acoustic detectors and detection surfaces which are commonly used in experimental studies. We further discuss the effects of non-ideal imaging scenarios on the quality of reconstruction and review methods that can mitigate these effects. Namely, we consider the cases of finite detector aperture, limited-view tomography, spatial under-sampling of the acoustic signals, and acoustic heterogeneities and losses.

Rosenthal, Amir; Ntziachristos, Vasilis; Razansky, Daniel

2013-01-01

340

Decay mechanisms of the 4d core hole through the 4d-4f resonance in dysprosium  

NASA Astrophysics Data System (ADS)

Soft x-ray emission through the 4d-4f resonance of Dy2O3 is studied with monochromatic photon excitation. The different soft x-ray emission processes are compared and it is found that inelastic scattering due to 4f inner-shell excitation and resonant elastic scattering are the strongest emission processes followed by inelastic scattering due to 5p-4f net transitions. The nonresonant emission occurring for excitation energies above the 4d-4f resonance is an extremely weak process. The measurements are in good agreement with our calculations.

Moewes, A.; Grush, M. M.; Callcott, T. A.; Ederer, D. L.

1999-12-01

341

Characterization of Core Samples from a Hardened Crust Layer in Tank 4F  

SciTech Connect

Waste removal operations in Tank 4F are scheduled to begin in late 2005 to provide material for Sludge Batch 5. Mining/probing operations to support installation of submersible mixer pumps encountered a hard layer of material at {approx}45'' to 50'' from the bottom of the tank. Attempts at penetrating the hard layer using a manual mining tool in several different risers were not successful. A core-sampling tool was used to obtain samples of the hard crust layer in Tank 4F for characterization. Three 12'' core samples and a dip sample of the supernate near the surface of the hard layer were sent to Savannah River National Laboratory (SRNL) for characterization. X-ray Diffraction (XRD) results for the crystalline solids from both sample FTF-434 and FTF-435 identifies the major component of both samples as Burkeite (Na{sub 6}(CO{sub 3})(SO{sub 4}){sub 2}). All of the other data collected on the crystalline solids from the Tank 4F core samples support this conclusion. The conditions in Tank 4F for the last twenty years have been ideal for Burkeite formation. The tank has been largely undisturbed with a tank temperature consistently above 30 C, a carbonate to sulfate molar ratio in the supernate conducive to Burkeite formation, and slow evaporation of the supernate phase. Thermodynamic modeling and the results of a Burkeite solubility test confirm that a ratio of 1:1:12 for the volumes of Burkeite solids, supernate, and inhibited water will dissolve all of the Burkeite. These ratios could be used to remove the 6'' layer of Burkeite from Tank 4F with no mixing. However, the thermodynamic modeling and the solubility test neglect the sludge layer beneath the Burkeite crust in Tank 4F. Settled sludge in Savannah River Site (SRS) high-level waste tanks usually contains greater than 75% interstitial supernate by volume. If the supernate in the sludge layer should mix into the solution used to dissolve the Burkeite, significantly more inhibited water would be needed to dissolve the Burkeite layer. Additionally, the average thickness of the Burkeite layer across the diameter of the tank may be thicker or thinner than the 6'' assumed for modeling purposes. The 6'' thickness assumed for the Burkeite layer was based on the 6'' plug of solids found in one core sample. An average thickness greater than 6'' would increase the amount of water needed to dissolve the Burkeite.

Hay, M. L.

2005-09-28

342

Acoustic Characterization of Mesoscale Objects  

SciTech Connect

This report describes the science and engineering performed to provide state-of-the-art acoustic capabilities for nondestructively characterizing mesoscale (millimeter-sized) objects--allowing micrometer resolution over the objects entire volume. Materials and structures used in mesoscale objects necessitate the use of (1) GHz acoustic frequencies and (2) non-contacting laser generation and detection of acoustic waves. This effort demonstrated that acoustic methods at gigahertz frequencies have the necessary penetration depth and spatial resolution to effectively detect density discontinuities, gaps, and delaminations. A prototype laser-based ultrasonic system was designed and built. The system uses a micro-chip laser for excitation of broadband ultrasonic waves with frequency components reaching 1.0 GHz, and a path-stabilized Michelson interferometer for detection. The proof-of-concept for mesoscale characterization is demonstrated by imaging a micro-fabricated etched pattern in a 70 {micro}m thick silicon wafer.

Chinn, D; Huber, R; Chambers, D; Cole, G; Balogun, O; Spicer, J; Murray, T

2007-03-13

343

Acoustic Neuroma  

MedlinePLUS

... weakness. He feels great and is very active. "My perspective now," he says, "is to help others in the decision-making process and to champion Gamma Knife radiosurgery for acoustic neuromas as the standard treatment with microsurgery as an adjunctive or alternative option."

344

Acoustic accelerometers  

Microsoft Academic Search

The characteristics of a number of recently developed acoustic accelerometers are discussed. The accelerometers discussed employ resonant vibrating elements, such as piezoelectric crystals and micromechanical cantilever beams containing either a piezoelectric capacitor, a piezoresistive circuit, or a SAW oscillator. Other accelerometers discussed employ a force rebalance technique using closed-loop servo electronics. Accelerometer sensitivities are limited by weight and frequency response

M. Edward Motamedi

1987-01-01

345

Characterization of acoustically forced swirl flame dynamics  

Microsoft Academic Search

Lean premixed combustors are highly susceptible to combustion instabilities, caused by the coupling between heat release fluctuations and combustor acoustics. In order to predict the conditions under which these instabilities occur and their limit cycle amplitudes, understanding of the amplitude dependent response of the flame to acoustic excitation is required. This study presents an analysis of phase-locked OH PLIF images

Sai Kumar Thumuluru; Tim Lieuwen

2009-01-01

346

Smart Cooling Technology Utilizing Acoustic Streaming  

Microsoft Academic Search

Acoustic streaming induced by longitudinal vibration at 30 kHz is visualized with particle imaging velocimetry (PIV). To gauge an increase in the velocity of air flow due to acoustic streaming, the velocity of air flow in a gap between the heat source and ultrasonic vibrator is measured using PIV. The ultrasonic wave propagating into air in the gap creates steady-state

Dong-Ryul Lee; Byoung-Gook Loh

2007-01-01

347

Optical absorption and NMR spectroscopic studies on paramagnetic neodymium(III) complexes with ?-diketone and heterocyclic amines. The environment effect on 4f-4f hypersensitive transitions  

NASA Astrophysics Data System (ADS)

The optical absorption spectra of [Nd(acac) 3(H 2O) 2]·H 2O, [Nd(acac) 3bpy] and [Nd(acac) 3phen(H 2O) 2] (where acac = acetylacetone, bpy = 2,2'-bipyridyl and phen = 1,10-phenanthroline) complexes in the visible region, in a series of non-aqueous solvents (methanol, ethanol, isopropanol, chloroform, acetonitrile, pyridine, nitrobenzene and dimethylsulphoxide) have been analyzed. The transition 4G 5/2 ? 4I 9/2 (Nd-VI) located near the middle of the visible region (17,500 cm -1) is hypersensitive. Its behavior is in sharp contrast to many other typically weak and consistently unvaried, normal 4f-4f transitions. The oscillator strength of this transition for the chelate as well as its adducts with phen and bpy in any of the solvent employed is larger than the oscillator strength of Nd 3+ aqua-ion. It is most intense in pyridine for all the complexes studied and, therefore, pyridine is the most effective in promoting f-f spectral intensity. The band shape and oscillator strength of the hypersensitive transitions display pronounced changes as compared to Nd 3+ aqua-ion. The band shapes of the hypersensitive transitions show remarkable changes on passing from aqueous solution to various non-aqueous solutions, which is the result of change in the environment about the Nd(III) ion in the various solutions and suggests change in the environment about the Nd(III) ion in the various solutions and suggests coordination of solvent molecule(s), in some cases. A comparative account of hypersensitivity in the present complexes with those of other adducts of Nd(?-diketoenolate) 3 with heterocyclic amines is discussed. The NMR signals of heterocyclic amines have been shifted to high fields while the resonances due to acetylacetone moiety have moved to low fields. The paramagnetic shift in the complexes is dipolar in nature.

Ansari, A. A.; Irfanullah, M.; Iftikhar, K.

2007-08-01

348

TOPICAL REVIEW: Acoustic cloaking and transformation acoustics  

Microsoft Academic Search

In this review, we give a brief introduction to the application of the new technique of transformation acoustics, which draws on a correspondence between coordinate transformation and material properties. The technique is formulated for both acoustic waves and linear liquid surface waves. Some interesting conceptual devices can be designed for manipulating acoustic waves. For example, we can design acoustic cloaks

Huanyang Chen; C. T. Chan

2010-01-01

349

Mutation in transcription factor POU4F3 associated with inherited progressive hearing loss in humans.  

PubMed

The molecular basis for autosomal dominant progressive nonsyndromic hearing loss in an Israeli Jewish family, Family H, has been determined. Linkage analysis placed this deafness locus, DFNA15, on chromosome 5q31. The human homolog of mouse Pou4f3, a member of the POU-domain family of transcription factors whose targeted inactivation causes profound deafness in mice, was physically mapped to the 25-centimorgan DFNA15-linked region. An 8-base pair deletion in the POU homeodomain of human POU4F3 was identified in Family H. A truncated protein presumably impairs high-affinity binding of this transcription factor in a dominant negative fashion, leading to progressive hearing loss. PMID:9506947

Vahava, O; Morell, R; Lynch, E D; Weiss, S; Kagan, M E; Ahituv, N; Morrow, J E; Lee, M K; Skvorak, A B; Morton, C C; Blumenfeld, A; Frydman, M; Friedman, T B; King, M C; Avraham, K B

1998-03-20

350

Cytochrome P450 4F2 polymorphism in patients with liver cirrhosis.  

PubMed

1297C/T polymorphism of CYP4F2 gene was studied in 108 patients with chronic liver diseases. No significant correlation with predisposition to rapid liver cirrhosis was revealed without consideration for cirrhosis etiology (OR=0.93, 95% CI=0.28-2.99, p=0.885). In patients with viral cirrhosis, a tendency to association of 1297T allele genotypes with rapid cirrhosis development was found (OR=6.0, 95% CI=0.28-382.64, p=0.222). At the same time, CYP4F2 1297T allele was associated with mild (Child-Pugh class A-B) cirrhosis (OR=2.9, p=0.044). PMID:24319743

Vavilin, V A; Nepomnyashchikh, D L; Shchepotina, E G; Karavaeva, Yu Yu; Makarova, S I; Vinogradova, E V; Kudryashov, A V; Nokhrina, Zh V; Lyakhovich, V V

2013-12-01

351

Investigations on Pva:. NH4F: ZrO2 Composite Polymer Electrolytes  

NASA Astrophysics Data System (ADS)

Composite polymer electrolytes have been prepared using Poly (vinyl alcohol), ammonium fluoride, nanofiller ZrO2 by solution casting technique. The amorphous nature of the composite polymer electrolyte has been confirmed by XRD analysis. FTIR analysis confirms the complex formation among the polymer, salt and nanofiller. The maximum ionic conductivity for 85 PVA:15 NH4F has been found to be 6.9 × 10-6 Scm-1 at ambient temperature. In the present work, the addition of 2 mol% nanofilller ZrO2 to the electrolyte 85PVA:15NH4F enhances the conductivity to 3.4 × 10-5 Scm-1. The temperature dependence of the conductivity of composite polymer electrolytes obeys Arrhenius relation. In the modulus spectra, there is a long tail at low frequencies which is an evidence for large capacitance associated with the electrodes. In the high frequency region, ?'(?) value saturates and giving rise to the dielectric constant of the material.

Radha, K. P.; Selvasekarapandian, S.; Karthikeyan, S.; Sanjeeviraja, C.

2013-07-01

352

4f-5f heterotrimetallic complexes exhibiting electrochemical and magnetic communication.  

PubMed

Novel 4f-5f complexes of U(IV) and Th(IV) with Yb have been prepared using a terpyridyl-functionalized ketimide linking group. These 4f-5f heterotrimetallic complexes (C5Me5)2An[-N=C(CH2C6H5)(tpyYb(C5Me5)2)]2 (where An = Th, U) exist in Yb(II/III) valence equilibria and exhibit rich electrochemical behavior consistent with electronic coupling between the actinide and Yb(II/III)tpy*- moieties. The magnetic response of the uranium complex, studied qualitatively using a subtraction method, is indicative of a coupled magnetic state between the U(IV) and Yb(III)tpy*- groups at low temperatures. Both the electrochemical and magnetic data are in agreement and are consistent with differences in participation of the actinide valence orbitals in the ketimide bonding. PMID:16478158

Schelter, Eric J; Veauthier, Jacqueline M; Thompson, Joe D; Scott, Brian L; John, Kevin D; Morris, David E; Kiplinger, Jaqueline L

2006-02-22

353

Anomalous duality of 4f electrons in filled skutterudite CeOs4Sb12.  

PubMed

We study the electronic structure of the filled skutterudite CeOs4Sb12 using photoemission spectroscopy (PES). Soft x-ray excited Ce 3d-4f resonant PES confirms the existence of Ce 4f states at the Fermi level (EF). Temperature dependent high-resolution laser-PES spectra reveal a pseudogap formation around EF, which can be explained in terms of the hybridization gap. Simultaneously, a sharp feature is formed just above EF with decreasing temperature. The heavy-fermion-like specific heat is attributed to the occupation of this feature. The results identify the origin of the anomalous coexistence of heavy-fermion and pseudogap behavior in terms of a symmetry dependent hybridization. PMID:19257374

Matsunami, M; Eguchi, R; Kiss, T; Horiba, K; Chainani, A; Taguchi, M; Yamamoto, K; Togashi, T; Watanabe, S; Wang, X-Y; Chen, C-T; Senba, Y; Ohashi, H; Sugawara, H; Sato, H; Harima, H; Shin, S

2009-01-23

354

High-nuclearity 3d-4f clusters as enhanced magnetic coolers and molecular magnets.  

PubMed

Four 52-metal-ion 3d-4f cluster complexes featuring a common core of Ln(42)M(10) (Ln = Gd(3+), Dy(3+); M = Co(2+/3+), Ni(2+)) were obtained through self-assembly of the metal ions templated by mixed anions (ClO(4)(-) and CO(3)(2-)). Magnetic studies revealed that the Gd(42)Co(10) and Gd(42)Ni(10) clusters exhibit the largest magnetocaloric effect (MCE) among any known 3d-4f complexes. Replacement of Gd(3+) ions with anisotropic Dy(3+) ions caused significant changes in the magnetic behavior of the clusters; both Dy(42)Co(10) and Dy(42)Ni(10) displayed slow relaxation of the magnetization. PMID:22313167

Peng, Jun-Bo; Zhang, Qian-Chong; Kong, Xiang-Jian; Zheng, Yan-Zhen; Ren, Yan-Ping; Long, La-Sheng; Huang, Rong-Bin; Zheng, Lan-Sun; Zheng, Zhiping

2012-02-22

355

Structure of Some 4f Rare Earth Liquid Metals — A Charged Hard Sphere Approach  

Microsoft Academic Search

A well-established pseodopotential is used to study the structure of some 4f rare earth liquid metals (Ce, Pr, Eu, Gd, Tb, and Yb). The structure factor S(q), pair distribution function g(r), interatomic distance r1, and coordination number n1 are calculated using Charged Hard Sphere (CHS) reference system. To introduce the exchange and correlation effects, the local field correction due to

P. B. Thakor; P. N. Gajjar; A. R. Jani

2006-01-01

356

4f binding-energy shifts of the light-actinide dioxides and tetrafluorides  

Microsoft Academic Search

With our measurements of the 4f binding energies of NpF4 and PuF4, values for all the light-actinide dioxides and tetrafluorides (Th-Pu, except Pa) are available. In spite of the fact that the electronegativities of these elements are nearly constant, the chemical shifts for each series show a regular increase, relative to the metals. Using the results of previously reported band-structure

L. E. Cox; J. D. Farr

1989-01-01

357

Tunable interplay between 3d and 4f electrons in Co-doped iron pnictides  

NASA Astrophysics Data System (ADS)

We study the interplay of 3d and 4f electrons in the iron pnictides CeFe1-xCoxAsO and GdFe1-yCoyAsO, which correspond to two very different cases of 4f-magnetic moment. Both CeFeAsO and GdFeAsO undergo a spin-density-wave (SDW) transition associated with Fe 3d electrons at high temperatures, which is rapidly suppressed by Fe/Co substitution. Superconductivity appears in a narrow doping range: 0.054f electrons form an antiferromagnetic (AFM) order at low temperatures over the entire doping range and Co 3d electrons are ferromagnetically ordered on the Co-rich side; the Curie temperature reaches TCCo? 75 K at x=1 and y=1. In the Ce compounds, the Néel temperature TNCe increases upon suppressing the SDW transition of Fe and then remains nearly unchanged with further increasing Co concentration up to x?0.8 (TNCe? 4 K). Furthermore, evidence of Co-induced polarization on Ce moments is observed on the Co-rich side. In the Gd compounds, the two magnetic species of Gd and Co are coupled antiferromagnetically to give rise to ferrimagnetic behavior in the magnetic susceptibility on the Co-rich side. For 0.7?y<1.0, the system undergoes a possible magnetic reorientation below the Néel temperature of Gd (TNGd). Our results suggest that the effects of both electron hybridizations and magnetic exchange coupling between the 3d-4f electrons give rise to a rich phase diagram in the rare-earth iron pnictides.

Shang, T.; Yang, L.; Chen, Y.; Cornell, N.; Ronning, F.; Zhang, J. L.; Jiao, L.; Chen, Y. H.; Chen, J.; Howard, A.; Dai, J.; Thompson, J. D.; Zakhidov, A.; Salamon, M. B.; Yuan, H. Q.

2013-02-01

358

Anomalous ordered phase in 4f 2-based heavy electron PrFe 4P 12  

Microsoft Academic Search

Recent study on the anomalous ordered state (ODS) in filled-skutterudite PrFe4P12 is presented, where the existence of a rare 4f2-based heavy electron (HE) state outside ODS has been experimentally confirmed recently. From specific heat measurements, it is found that the HE behavior is largely suppressed in ODS. The Pr nuclear Schottky contribution strongly indicates that ODS is non-magnetic, most probably

Yuji Aoki; Takahiro Namiki; Tatsuma D Matsuda; Hitoshi Sugawara; Hideyuki Sato

2002-01-01

359

4f spin density in the reentrant ferromagnet SmMn2Ge2  

NASA Astrophysics Data System (ADS)

The spin contribution to the magnetic moment in SmMn2Ge2 has been measured by magnetic Compton scattering in both the low- and high-temperature ferromagnetic phases. At low temperature, the Sm site is shown to possess a large 4f spin moment of 3.4+/-0.1?B, aligned antiparallel to the total magnetic moment. At high temperature, the data show conclusively that ordered magnetic moments are present on the samarium site.

McCarthy, J. E.; Duffy, J. A.; Detlefs, C.; Cooper, M. J.; Canfield, P. C.

2000-09-01

360

Long-term tropospheric trend of octafluorocyclobutane (c-C4F8 or PFC-318)  

NASA Astrophysics Data System (ADS)

Air samples collected at Cape Grim, Tasmania between 1978 and 2008 and during a series of more recent aircraft sampling programmes have been analysed to determine the atmospheric abundance and trend of octafluorocyclobutane (c-C4F8 or PFC-318). c-C4F8 has an atmospheric lifetime in excess of 3000 yr and a global warming potential (GWP) of 10 300 (100 yr time horizon), making it one of the most potent greenhouse gases detected in the atmosphere to date. The abundance of c-C4F8 in the Southern Hemisphere has risen from 0.35 ppt in 1978 to 1.2 ppt in 2010, and is currently increasing at a rate of around 0.03 ppt yr-1. It is the third most abundant perfluorocarbon (PFC) in the present day atmosphere, behind CF4 (~75 ppt) and C2F6 (~4 ppt). Although a number of potential sources of c-C4F8 have been reported, including the electronics and semi-conductor industries, there remains a large discrepancy in the atmospheric budget. Using a 2-D global model to derive top-down global emissions based on the Cape Grim measurements yields a recent (2007) emission rate of around 1.1 Gg yr-1 and a cumulative emission up to and including 2007 of 38.1 Gg. Emissions reported on the EDGAR emissions database for the period 1986-2005 represent less than 1% of the top-down emissions for the same period, which suggests there is a large unaccounted for source of this compound. It is also apparent that the magnitude of this source has varied considerably over the past 30 yr, declining sharply in the late 1980s before increasing again in the mid-1990s.

Oram, D. E.; Mani, F. S.; Laube, J. C.; Newland, M. J.; Reeves, C. E.; Sturges, W. T.; Penkett, S. A.; Brenninkmeijer, C. A. M.; Röckmann, T.; Fraser, P. J.

2012-01-01

361

Piezoelectrically driven vertical cavity acoustic transducers for the convective transport and rapid detection of DNA and protein binding to DNA microarrays with SPR imaging--a parametric study.  

PubMed

Mixing within the microdomain is limited because convective mixing cannot be achieved since diffusion dominates as the main form of transport. Hence microassays can take on the order of 1 to 72 h, without the aid of a passive or active mixer to shorten the time of transport of a target molecule to a probe (Lai et al., 2004). Liu et al. (2002, 2003) developed a low cost cavitation microstreaming based mixer which is easy to implement and use, but no comprehensive study has been done to optimize such a mixer for various applications. We present a study of the effects of various frequencies and cavity parameters on mixing using dye and surface based assays with protein, DNA, and nanoparticles to obtain an optimum mixing frequency and configuration for a wide range of assay applications. We present a novel method to monitor real time binding using surface plasmon resonance imaging (SPRI) coupled with a vertical cavity acoustic transducer (VCAT) micromixer for various biomolecule surface assays. The combination of VCAT and SPRI allows assay signal saturation within one minute while conserving reagent volume. The kinetic rate constant for adsorption (k(a)) and desorption (k(d)) as well as the limit of detection (LOD) of 5 nM for the DNA duplex formation are reported using this VCAT micromixer. PMID:22503031

Okabe, Yuka; Chen, Yulin; Purohit, Rishi; Corn, Robert M; Lee, Abraham P

2012-05-15

362

REVIEW ARTICLE: Band structure theory of magnetism in 3d-4f compounds  

NASA Astrophysics Data System (ADS)

The band structure theory of magnetism in 3d-4f compounds is reviewed. Among the open-shell electrons, a hierarchy of interactions is present which governs the intrinsic magnetic properties of these materials. Density functional theory (DFT) is an appropriate tool to describe and quantitatively investigate both ground state properties and model interaction parameters, which are necessary to calculate the temperature-dependent behaviour. The cornerstones of the DFT are explicitly sketched, as well as recent developments needed to cope with the treatment of localized 4f and itinerant 3d magnetism in one and the same framework. This includes the open-core scheme, self-interaction corrected DFT, relativistic DFT, and orbital polarization. On this basis, the exchange coupling among itinerant and localized states can be understood, together with the size of Curie temperature and ground state spin and orbital magnetic moments. Finally, the problem of magnetocrystalline anisotropy is addressed, concerning both the band and the 4f crystal field contribution.

Richter, Manuel

1998-05-01

363

Recent Advances in 1-3 Piezoelectric Polymer Composite Transducer Technology for AUV\\/UUV Acoustic Imaging Applications  

Microsoft Academic Search

Over the past 5 years, the use of 1-3 piezoelectric polymer composite has been studied under various U.S. Navy-funded transducer research programs. As a transduction material, the 1-3 piezoelectric composite offers many advantages for autonomous undersea vehicles\\/unmanned undersea vehicle (AUV\\/UUV) imaging array construction. Broad bandwidth, high transmit\\/receive response, low cost of fabrication, mechanical ruggedness, and the ability to form conformal

Kim C. Benjamin

2002-01-01

364

Visualization of protease activity in vivo using an activatable photo-acoustic imaging probe based on CuS nanoparticles.  

PubMed

Herein, we for the first time report a novel activatable photoacoustic (PA) imaging nano-probe for in vivo detection of cancer-related matrix metalloproteinases (MMPs). A black hole quencher 3 (BHQ3) which absorbs red light is conjugated to near-infrared (NIR)-absorbing copper sulfide (CuS) nanoparticles via a MMP-cleavable peptide linker. The obtained CuS-peptide-BHQ3 (CPQ) nano-probe exhibits two distinctive absorption peaks at 630 nm and 930 nm. Inside the tumor microenvironment where MMPs present, the MMP-sensitive peptide would be cleaved, releasing BHQ3 from the CuS nanoparticles, the former of which as a small molecule is then rapidly cleared out from the tumor, whereas the latter of which as large nanoparticles would retain inside the tumor for a much longer period of time. As the result, the PA signal at 680 nm which is contributed by BHQ3 would be quickly diminished while that at 930 nm would be largely retained. The PA signal ratio of 680 nm / 930 nm could thus serve as an in vivo indicator of MMPs activity inside the tumor. Our work presents a novel strategy of in vivo sensing of MMPs based on PA imaging, which should offer remarkably improved detection depth compared with traditional optical imaging techniques. PMID:24465271

Yang, Kai; Zhu, Lei; Nie, Liming; Sun, Xiaolian; Cheng, Liang; Wu, Chenxi; Niu, Gang; Chen, Xiaoyuan; Liu, Zhuang

2014-01-01

365

Acoustic transducer for acoustic microscopy  

DOEpatents

A shear acoustic transducer-lens system in which a shear polarized piezoelectric material excites shear polarized waves at one end of a buffer rod having a lens at the other end which excites longitudinal waves in a coupling medium by mode conversion at selected locations on the lens.

Khuri-Yakub, Butrus T. (Palo Alto, CA); Chou, Ching H. (Palo Alto, CA)

1990-01-01

366

Non-intrusive telemetry applications in the oilsands: from visible light and x-ray video to acoustic imaging and spectroscopy  

NASA Astrophysics Data System (ADS)

While the production, transport and refining of oils from the oilsands of Alberta, and comparable resources elsewhere is performed at industrial scales, numerous technical and technological challenges and opportunities persist due to the ill defined nature of the resource. For example, bitumen and heavy oil comprise multiple bulk phases, self-organizing constituents at the microscale (liquid crystals) and the nano scale. There are no quantitative measures available at the molecular level. Non-intrusive telemetry is providing promising paths toward solutions, be they enabling technologies targeting process design, development or optimization, or more prosaic process control or process monitoring applications. Operation examples include automated large object and poor quality ore during mining, and monitoring the thickness and location of oil water interfacial zones within separation vessels. These applications involve real-time video image processing. X-ray transmission video imaging is used to enumerate organic phases present within a vessel, and to detect individual phase volumes, densities and elemental compositions. This is an enabling technology that provides phase equilibrium and phase composition data for production and refining process development, and fluid property myth debunking. A high-resolution two-dimensional acoustic mapping technique now at the proof of concept stage is expected to provide simultaneous fluid flow and fluid composition data within porous inorganic media. Again this is an enabling technology targeting visualization of diverse oil production process fundamentals at the pore scale. Far infrared spectroscopy coupled with detailed quantum mechanical calculations, may provide characteristic molecular motifs and intermolecular association data required for fluid characterization and process modeling. X-ray scattering (SAXS/WAXS/USAXS) provides characteristic supramolecular structure information that impacts fluid rheology and process fouling. The intent of this contribution is to present some of the challenges and to provide an introduction grounded in current work on non-intrusive telemetry applications - from a mine or reservoir to a refinery!

Shaw, John M.

2013-06-01

367

Imaging feedback for histotripsy by characterizing dynamics of acoustic radiation force impulse (ARFI)-induced shear waves excited in a treated volume.  

PubMed

Our previous study indicated that shear waves decay and propagate at a lower speed as they propagate into a tissue volume mechanically fractionated by histotripsy. In this paper, we hypothesize that the change in the shear dynamics is related to the degree of tissue fractionation, and can be used to predict histotripsy treatment outcomes. To test this hypothesis, lesions with different degrees of tissue fractionation were created in agar-graphite tissue phantoms and ex vivo kidneys with increasing numbers of therapy pulses, from 0 to 2000 pulses per treatment location. The therapy pulses were 3-cycle 750-kHz focused ultrasound delivered at a peak negative/positive pressure of 17/108 MPa and a repetition rate of 50 Hz. The shear waves were excited by acoustic radiation force impulse (ARFI) focused at the center of the lesion. The spatial and temporal behavior of the propagating shear waves was measured with ultrasound plane wave imaging. The temporal displacement profile at a lateral location 10 mm offset to the shear excitation region was detected with M-mode imaging. The decay and delay of the shear waves were quantitatively characterized on the temporal displacement profile. Results showed significant changes in two characteristics on the temporal displacement profile: the peak-to-peak displacement decayed exponentially with increasing numbers of therapy pulses; the relative time-to-peak displacement increased with increasing numbers of therapy pulses, and appeared to saturate at higher numbers of pulses. Correspondingly, the degree of tissues fractionation, as indicated by the percentage of structurally intact cell nuclei, decreased exponentially with increasing numbers of therapy pulses. Strong linear correlations were found between the two characteristics and the degree of tissue fractionation. These results suggest that the characteristics of the shear temporal displacement profile may provide useful feedback information regarding the treatment outcomes. PMID:24960703

Wang, Tzu-Yin; Hall, Timothy; Xu, Zhen; Fowlkes, J; Cain, Charles

2014-07-01

368

Implementation and Comparison of Acoustic Travel-Time Measurement Procedures for the Helioseismic and Magnetic Imager Time-Distance Helioseismology Pipeline  

NASA Technical Reports Server (NTRS)

The Helioseismic and Magnetic Imager (HMI) instrument on board the Solar Dynamics Observatory (SDO) satellite is designed to produce high-resolution Doppler velocity maps of oscillations at the solar surface with high temporal cadence. To take advantage of these high-quality oscillation data, a time-distance helioseismology pipeline has been implemented at the Joint Science Operations Center (JSOC) at Stanford University. The aim of this pipeline is to generate maps of acoustic travel times from oscillations on the solar surface, and to infer subsurface 3D flow velocities and sound-speed perturbations. The wave travel times are measured from cross covariances of the observed solar oscillation signals. For implementation into the pipeline we have investigated three different travel-time definitions developed in time-distance helioseismology: a Gabor wavelet fitting (Kosovichev and Duvall, 1997), a minimization relative to a reference cross-covariance function (Gizon and Birch, 2002), and a linearized version of the minimization method (Gizon and Birch, 2004). Using Doppler velocity data from the Michelson Doppler Imager (MDI) instrument on board SOHO, we tested and compared these definitions for the mean and difference travel-time perturbations measured from reciprocal signals. Although all three procedures return similar travel times in a quiet Sun region, the method of Gizon and Birch (2004) gives travel times that are significantly different from the others in a magnetic (active) region. Thus, for the pipeline implementation we chose the procedures of Kosovichev and Duvall (1997) and Gizon and Birch (2002). We investigated the relationships among these three travel-time definitions, their sensitivities to fitting parameters, and estimated the random errors they produce

Couvidat, S.; Zhao, J.; Birch, A. C.; Kosovichev, A. G.; Duvall, T. L., Jr.; Parchevsky, K.; Scherrer, P. H.

2009-01-01

369

Implementation and Comparison of Acoustic Travel-Time Measurement Procedures for the Solar Dynamics Observatory/Helioseismic and Magnetic Imager Time - Distance Helioseismology Pipeline  

NASA Astrophysics Data System (ADS)

The Helioseismic and Magnetic Imager (HMI) instrument onboard the Solar Dynamics Observatory (SDO) satellite is designed to produce high-resolution Doppler-velocity maps of oscillations at the solar surface with high temporal cadence. To take advantage of these high-quality oscillation data, a time - distance helioseismology pipeline (Zhao et al., Solar Phys. submitted, 2010) has been implemented at the Joint Science Operations Center (JSOC) at Stanford University. The aim of this pipeline is to generate maps of acoustic travel times from oscillations on the solar surface, and to infer subsurface 3D flow velocities and sound-speed perturbations. The wave travel times are measured from cross-covariances of the observed solar oscillation signals. For implementation into the pipeline we have investigated three different travel-time definitions developed in time - distance helioseismology: a Gabor-wavelet fitting (Kosovichev and Duvall, SCORE’96: Solar Convection and Oscillations and Their Relationship, ASSL, Dordrecht, 241, 1997), a minimization relative to a reference cross-covariance function (Gizon and Birch, Astrophys. J. 571, 966, 2002), and a linearized version of the minimization method (Gizon and Birch, Astrophys. J. 614, 472, 2004). Using Doppler-velocity data from the Michelson Doppler Imager (MDI) instrument onboard SOHO, we tested and compared these definitions for the mean and difference travel-time perturbations measured from reciprocal signals. Although all three procedures return similar travel times in a quiet-Sun region, the method of Gizon and Birch ( Astrophys. J. 614, 472, 2004) gives travel times that are significantly different from the others in a magnetic (active) region. Thus, for the pipeline implementation we chose the procedures of Kosovichev and Duvall ( SCORE’96: Solar Convection and Oscillations and Their Relationship, ASSL, Dordrecht, 241, 1997) and Gizon and Birch ( Astrophys. J. 571, 966, 2002). We investigated the relationships among these three travel-time definitions, their sensitivities to fitting parameters, and estimated the random errors that they produce.

Couvidat, S.; Zhao, J.; Birch, A. C.; Kosovichev, A. G.; Duvall, T. L.; Parchevsky, K.; Scherrer, P. H.

2012-01-01

370

Measurement of acoustic streaming using magnetic resonance.  

PubMed

Magnetic resonance imaging (MRI) has been used to explore acoustic streaming caused in water under ultrasonic exposure conditions similar to those used for diagnostic applications. Streaming was established in an enclosed tube with acoustically transparent end windows, using a pulsed, weakly-focused transducer of acoustic frequency 3.5 MHz. Phase-detection MRI was used to image and quantify streaming profiles in the region of the acoustic focus. Acoustic powers in the range 0.4 mW to 100 mW were used. The sensitivity of the technique enabled streaming velocities down to 0. 1 mm s(-1) to be measured, generated by acoustic power less than 1 mW. In addition, acoustic streaming generated within open meshes with minimum pore dimensions of 3.0 mm and 2.0 mm was measured. The flow velocity in the coarser mesh reached 0.9 mm s(-1) at 95 mW total acoustic power. These observations demonstrate that acoustic streaming is probably a much more general phenomenon in diagnostic ultrasound (ultrasound) than previously recognised. The combination of magnetic resonance and ultrasound shows promise as a diagnostic method for the differentiation of cystic lesions in vivo, and for their characterisation, with sensitivity significantly greater than using ultrasound alone. PMID:10722922

Starritt, H C; Hoad, C L; Duck, F A; Nassiri, D K; Summers, I R; Vennart, W

2000-02-01

371

Acoustic Tooth Cleaner  

NASA Technical Reports Server (NTRS)

Acoustically-energized water jet aids in plaque breakdown. Acoustic Wand includes acoustic transducer 1/4 wave plate, and tapered cone. Together elements energize solution of water containing mild abrasive injected into mouth to help prevent calculous buildup.

Heyman, J. S.

1984-01-01

372

Ketoconazole increases fingolimod blood levels in a drug interaction via CYP4F2 inhibition.  

PubMed

The sphingosine-1-phosphate receptor modulator fingolimod is predominantly hydroxylated by cytochrome CYP4F2. In vitro experiments showed that ketoconazole significantly inhibited the oxidative metabolism of fingolimod by human liver microsomes and by recombinant CYP4F2. The authors used ketoconazole as a putative CYP4F2 inhibitor to quantify its influence on fingolimod pharmacokinetics in healthy subjects. In a 2-period, single-sequence, crossover study, 22 healthy subjects received a single 5-mg dose of fingolimod in period 1. In period 2, subjects received ketoconazole 200 mg twice daily for 9 days and a single 5-mg dose of fingolimod coadministered on the 4th day of ketoconazole treatment. Ketoconazole did not affect fingolimod t(max) or half-life, but there was a weak average increase in C(max) of 1.22-fold (90% confidence interval, 1.15-1.30). The AUC over the 5 days of ketoconazole coadministration increased 1.40-fold (1.31-1.50), and the full AUC to infinity increased 1.71-fold (1.53-1.91). The AUC of the active metabolite fingolimod-phosphate was increased to a similar extent by 1.67-fold (1.50-1.85). Ketoconazole predose plasma levels were not altered by fingolimod. The magnitude of this interaction suggests that a proactive dose reduction of fingolimod is not necessary when adding ketoconazole to a fingolimod regimen. The clinician, however, should be aware of this interaction and bear in mind the possibility of a fingolimod dose reduction based on clinical monitoring. PMID:19118083

Kovarik, John M; Dole, Kiran; Riviere, Gilles-Jacques; Pommier, Francoise; Maton, Steve; Jin, Yi; Lasseter, Kenneth C; Schmouder, Robert L

2009-02-01

373

Statins increase cytochrome P450 4F3-mediated eicosanoids production in human liver cells: a PXR dependent mechanism.  

PubMed

In the present study, the ability of lovastatin, a competitive inhibitor of HMG-CoA reductase, to regulate the gene expression and function of Cytochrome P450 4F3B (CYP4F3B) was examined in the well differentiated HepaRG human hepatoma cell line. Statins induced CYP4F3B mRNA, protein and the production of 20-hydroxyeicosatetraenoic acid (20-HETE), a product of arachidonic acid metabolism and a peroxisome proliferator activated receptor (PPAR) ligand. This response was not dependent on cholesterol shortage or on sterol regulatory element binding protein activation. By both a pharmacological and a siRNA approaches, we demonstrated that recruitment of the Pregnane X Receptor (PXR) was required to mediate CYP4F3 induction by lovastatin. Furthermore, the CYP4F3 gene promoter was transcriptionally activated by PXR, and responded to lovastatin. Finally, the expression of fatty acid-responsive genes was increased in response to the statin or 20-HETE in a CYP4F3-dependent way. We propose that metabolites produced by CYP4F3 could modulate lipid metabolism in response to lovastatin. These results suggest the existence of a novel pathway, operating in liver cells, through which statins could lower lipid levels. PMID:22634049

Plée-Gautier, Emmanuelle; Antoun, Joseph; Goulitquer, Sophie; Le Jossic-Corcos, Catherine; Simon, Brigitte; Amet, Yolande; Salaün, Jean-Pierre; Corcos, Laurent

2012-08-15

374

Pu 4f XPS spectra analyzed in the Anderson impurity model  

NASA Astrophysics Data System (ADS)

X-ray photoemission spectra of the ?, ?, ?, and ? phases of Pu have been analyzed using the Gunnarsson-Schönhammer implementation of the Anderson impurity model. Changes in the relative spectral weights of the two features representing mixed f 5 and f 6 final states are in reasonable agreement with the model's predictions. The Coulomb terms, Uff and Ufc, are quite consistent with those derived from atomic and LDA calculations. Multiplet structure, which agrees with atomic calculations for 4f 135f 5, strongly suggests 5f localization in the final state.

Cox, L. E.; Peek, J. M.; Allen, J. W.

1999-01-01

375

4-[F-18]fluoroproline: A potential tracer for collagen synthesis. Radiosynthesis and biological evaluation  

SciTech Connect

Proline is an important constituent of the structural protein collagen. It has been shown that its fluorinated analogs (2S,4S)- and particularly (2S,4R)-4-fluoroproline are also incorporated into collagen (Gottlieb et al., Biochemistry (1965), 4: 2507). 4-[F-18]fluoroproline is therefore a potential probe for studying abnormal collagen synthesis e. g. in tumors, lung fibrosis and liver cirrhosis. We have evaluated the two diastereomeric forms using a transplantable osteosarcoma in mice as an in vivo model for elevated collagen synthesis, and a MCF 7 mamma carcinoma cell line for monolayer incubation studies.

Hamacher, K. [Institut fuer Nuklearchemie, KFA Juelich (Germany); Herz, M.; Truckenbrodt, R. [Nuklearmedizinische Klinik der TU Muenchen (Germany)] [and others

1996-05-01

376

Structural and electrochemical properties of lithium vanadium fluorophosphate, LiVPO 4F  

Microsoft Academic Search

The electroactive lithium vanadium fluorophosphate phase, LiVPO4F (P1¯, a=5.1687(2)Å, b=5.3062(2)Å, c=7.5031(3)Å, ?=66.856(2)°, ?=67.004(2)°, ?=81.583(2)° and cell volume=174.21(1)Å3) has been synthesized by a two-step reaction scheme based on a carbothermal reduction (CTR) process. High-resolution electrochemical measurements reveal a structured voltage response for the lithium extraction process while the lithium insertion process proceeds via a two-phase reaction mechanism centered at around 4.2V

J. Barker; R. K. B. Gover; P. Burns; A. Bryan; M. Y. Saidi; J. L. Swoyer

2005-01-01

377

XeCl laser pumped iodine laser using t-C4F9I  

NASA Technical Reports Server (NTRS)

An iodine photodissociation laser using t-C4F9I as the active material was pumped by an XeCl laser. An iodine laser output energy of 3 mJ with pulse duration of 25 ns was obtained when the pumping pulse energy was 80 mJ, the iodide pressure was 70 torr, and the reflectance of the output mirror was 85 percent. The high pumping efficiency and low threshold pump power achieved in this experiment are attributable to the high absorption cross section at the pump laser wavelength (308 nm) of the iodide used.

Hwang, In Heon; Han, Kwang S.

1989-01-01

378

XeCl laser pumped iodine laser using t-C4F9I  

NASA Technical Reports Server (NTRS)

An iodine photodissociation laser using t-C4F9I as the active material was pumped by a XeCl laser. An iodine laser output energy of 3 mJ with pulse duration of 25 ns was obtained when the pumping pulse energy was 80 mJ, the iodine pressure was 70 torr, and the reflectance of the output mirror was 85 percent. The high pumping efficiency and low threshold pump power achieved in this experiment are attributable to the high absorption cross section at the pump laser wavelength (308 nm) of the iodide used.

Hwang, In Heon; Han, Kwang S.; Lee, Ja H.

1989-01-01

379

Variable temperature optoacoustic studies of 4f-states of neodymium in oxide phases  

SciTech Connect

An apparatus for recording high sensitivity photoacoustic spectra from strongly light scattering samples has been constructed and tested at temperatures from 4 to 295K. The apparatus is suitable for use with air- or moisture-sensitive samples or radioactive samples requiring containment. Unlike an earlier ambient temperature photoacoustic study on Nd{sub 2}O{sub 3}, the photoacoustic bands observed from high purity Nd{sub 2}O{sub 3} in the present work agree well with the Stark components of 4f states of Nd{sup 3+} in A-type Nd{sub 2}O{sub 3} as assigned by Caro, Derouet, and Beaury.

Beitz, J.V.; Hinaus, B.M. [Argonne National Lab., IL (United States); Huang, Jin [Wisconsin Univ., Madison, WI (United States). Dept. of Physics and Astronomy

1993-09-01

380

Acoustic radiation force impulse imaging with Virtual Touch(TM) tissue quantification: mean shear wave velocity of malignant and benign breast masses  

PubMed Central

Acoustic radiation force impulse imaging (ARFI) with Virtual Touch™ tissue quantification (VTTQ) enables the determination of shear wave velocity (SWV) in meters per second (m/s). The aim of our study was to describe the mean SWV in normal breast tissue and various breast masses. We performed measurements of SWV with ARFI VTTQ in 145 breast masses (57 malignant, 88 benign) and in the adjacent breast parenchyma and adipose tissue. The mean SWV as well as the rate of successful measurements were analyzed. The difference between adipose tissue and parenchyma was statistically significant (3.05 versus 3.65 m/s) (P < 0.001). Focusing on breast masses, numerous measurements exceeded the upper limit of possible measurement (?9.10 m/s, indicated as “X.XX m/s”). Nevertheless, the difference between the malignant and benign masses was statistically significant (8.38 ± 1.99 m/s versus 5.39 ± 2.95 m/s) (P < 0.001). The best diagnostic accuracy (75.9%) was achieved when the cutoff point for malignancy was set to 9.10 m/s in ARFI VTTQ. This implies that the SWV was regarded as suspicious when the upper limit of possible measurement was exceeded and the machine returned the value X.XX m/s. In conclusion, ARFI VTTQ is a feasible method for measurement of SWV in a region of interest. Furthermore, we propose the event of a highly elevated SWV as a significant criterion for malignancy. However, the method is technically not yet fully developed, and the problem of unsuccessful measurements must still be solved.

Wojcinski, Sebastian; Brandhorst, Kathrin; Sadigh, Gelareh; Hillemanns, Peter; Degenhardt, Friedrich

2013-01-01

381

Imaging transverse isotropic properties of muscle by monitoring acoustic radiation force induced shear waves using a 2-D matrix ultrasound array.  

PubMed

A 2-D matrix ultrasound array is used to monitor acoustic radiation force impulse (ARFI) induced shear wave propagation in 3-D in excised canine muscle. From a single acquisition, both the shear wave phase and group velocity can be calculated to estimate the shear wave speed (SWS) along and across the fibers, as well as the fiber orientation in 3-D. The true fiber orientation found using the 3-D radon transform on B-mode volumes of the muscle was used to verify the fiber direction estimated from shear wave data. For the simplified imaging case when the ARFI push can be oriented perpendicular to the fibers, the error in estimating the fiber orientation using phase and group velocity measurements was 3.5 ± 2.6° and 3.4 ± 1.4° (mean ± standard deviation), respectively, over six acquisitions in different muscle samples. For the more general case when the push is oblique to the fibers, the angle between the push and the fibers is found using the dominant orientation of the shear wave displacement magnitude. In 30 acquisitions on six different muscle samples with oblique push angles up to 40°, the error in the estimated fiber orientation using phase and group velocity measurements was 5.4 ± 2.9° and 5.3 ± 3.2°, respectively, after estimating and accounting for the additional unknown push angle. Either the phase or group velocity measurements can be used to estimate fiber orientation and SWS along and across the fibers. Although it is possible to perform these measurements when the push is not perpendicular to the fibers, highly oblique push angles induce lower shear wave amplitudes which can cause inaccurate SWS measurements. PMID:23686942

Wang, Michael; Byram, Brett; Palmeri, Mark; Rouze, Ned; Nightingale, Kathryn

2013-09-01

382

Explaining extended linear features observed in remote sonar images of the New Jersey continental shelf break during Acoustic Clutter Experiments in 2001 and 2003  

NASA Astrophysics Data System (ADS)

Prominent acoustic clutter forming a lineated feature spanning more than 10 km has been repeatedly observed in long-range sonar imagery acquired during the Acoustic Clutter Experiments in 2001 and 2003. The lineated feature appears on the continental shelf near the shelf break for downslope sonar positions. It is hypothesized that this lineated feature is caused by scattering from fish shoals, seafloor slopes, or subbottom geology such as the R-reflector. A range-dependent reverberation and scattering model using the parabolic equation [Ratilal et al., J. Acoust. Soc. Am. 114, 2302 (2003)] is employed to test these various hypotheses by model-data comparison using high resolution bathymetry, subbottom profiles, and fish density data acquired in support of the long-range acoustic measurements.

Lee, Sunwoong; Ratilal, Purnima; Makris, Nicholas C.

2001-05-01

383

Air-coupled acoustic thermography for in-situ evaluation  

NASA Technical Reports Server (NTRS)

Acoustic thermography uses a housing configured for thermal, acoustic and infrared radiation shielding. For in-situ applications, the housing has an open side adapted to be sealingly coupled to a surface region of a structure such that an enclosed chamber filled with air is defined. One or more acoustic sources are positioned to direct acoustic waves through the air in the enclosed chamber and towards the surface region. To activate and control each acoustic source, a pulsed signal is applied thereto. An infrared imager focused on the surface region detects a thermal image of the surface region. A data capture device records the thermal image in synchronicity with each pulse of the pulsed signal such that a time series of thermal images is generated. For enhanced sensitivity and/or repeatability, sound and/or vibrations at the surface region can be used in feedback control of the pulsed signal applied to the acoustic sources.

Zalameda, Joseph N. (Inventor); Winfree, William P. (Inventor); Yost, William T. (Inventor)

2010-01-01

384

Anisotropic metamaterials for full control of acoustic waves.  

PubMed

We study a class of acoustic metamaterials formed by layers of perforated plates and producing negative refraction and backward propagation of sound. A slab of such material is shown to act as a perfect acoustic lens, yielding images with subwavelength resolution over large distances. Our study constitutes a nontrivial extension of similar concepts from optics to acoustics, capable of sustaining negative refraction over extended angular ranges, with potential application to enhanced imaging for medical and detection purposes, acoustofluidics, and sonochemistry. PMID:22540586

Christensen, Johan; García de Abajo, F Javier

2012-03-23

385

Anisotropic Metamaterials for Full Control of Acoustic Waves  

NASA Astrophysics Data System (ADS)

We study a class of acoustic metamaterials formed by layers of perforated plates and producing negative refraction and backward propagation of sound. A slab of such material is shown to act as a perfect acoustic lens, yielding images with subwavelength resolution over large distances. Our study constitutes a nontrivial extension of similar concepts from optics to acoustics, capable of sustaining negative refraction over extended angular ranges, with potential application to enhanced imaging for medical and detection purposes, acoustofluidics, and sonochemistry.

Christensen, Johan; de Abajo, F. Javier García

2012-03-01

386

Panel acoustic contribution analysis.  

PubMed

Formulations are derived to analyze the relative panel acoustic contributions of a vibrating structure. The essence of this analysis is to correlate the acoustic power flow from each panel to the radiated acoustic pressure at any field point. The acoustic power is obtained by integrating the normal component of the surface acoustic intensity, which is the product of the surface acoustic pressure and normal surface velocity reconstructed by using the Helmholtz equation least squares based nearfield acoustical holography, over each panel. The significance of this methodology is that it enables one to analyze and rank relative acoustic contributions of individual panels of a complex vibrating structure to acoustic radiation anywhere in the field based on a single set of the acoustic pressures measured in the near field. Moreover, this approach is valid for both interior and exterior regions. Examples of using this method to analyze and rank the relative acoustic contributions of a scaled vehicle cabin are demonstrated. PMID:23363099

Wu, Sean F; Natarajan, Logesh Kumar

2013-02-01

387

Azide interaction with 4f and 5f ions in aqueous solutions. I. Trivalent ions  

SciTech Connect

Solvent extraction and UV, Raman, and NMR spectroscopic studies were carried out on trivalent actinide and lanthanide aqueous azido complexes. Unlike trivalent d transition ions (..beta../sub 11/ approx. = 10/sup 5/) 5f and 4f aqueous azido complexes are weak (..beta../sub 11/ approx. = 2.5 for neodymium azide complexes (Nd(N/sub 3/)/sup 2 +/)), but the trivalent actinides exhibit formation constants 1 order of magnitude higher than the lanthanides. All the spectroscopic methods indicate that we are dealing with inner-sphere complexes and actinide-lanthanide differences must be attributed to higher covalent contributions in the 5f azides. /sup 15/N NMR combined with /sup 1/H NMR served to investigate the azide binding properties. With the trivalent 5f and 4f ions the binding occurs by one of the terminal nitrogen atoms. The M-N bond distance is close to 2.75 A. The lanthanide(III)-(linear azide) moieties are bent with a bond angle close to 135/sup 0/, unlike the homologous linear thiocyanate complexes. 7 figures, 4 tables.

Musikas, C. (Centre d'Etudes Nucleaires de Fontenay-aux-Roses, France); Cuillerdier, C.; Livet, J.; Forchioni, A.; Chachaty, C.

1983-08-31

388

Optical alignment of pixelated 4f optical system using multiplexed filter.  

PubMed

Novel optical alignment techniques to perform precise alignment of a typical pixelated 4f optical system are presented in this paper. These techniques use optical multiplexed matched filters, which were designed using a simple, efficient iterative optimization algorithm, known as direct binary search. Three alignment challenges are identified: positioning, focusing, and magnification. The first two alignments were performed using the optical multiplexed matched filtering technique, and the last one was performed using a new optical arrangement. Experimental results of the new alignment techniques and a simple optical pattern recognition problem to demonstrate the benefits of the new alignment techniques are also presented. Two pixelated, electrically addressed spatial light modulators (128 × 128 pixels and one pixel width is 80 ?m) were used to represent the input and filter planes. The results clearly show that the new alignment techniques allow the 4f system to be aligned to a precision of 80 ?m in the x-y direction and 0.716 mm in the z direction. PMID:24216742

Manivannan, N; Neil, M A A; Balachandran, W

2013-11-10

389

Treatment of 4f states of the rare earths: The case study of TbN  

NASA Astrophysics Data System (ADS)

The lattice constant, bulk modulus, and shear constant of TbN are calculated by means of density functional theory (DFT) in the local density approximation (LDA) and generalized gradient approximation (GGA), with 4f states treated as valence electrons or core electrons. In addition, local Coulomb repulsions U are treated both statically as in the LDA+U approach and dynamically as in the dynamical mean-field theory in the Hubbard-I approximation. It is shown that all methods, except DFT-LDA with 4f electrons treated as either valence states, produce lattice constants and bulk moduli in good agreement with experiment. In the LDA+U approach multiple minima are found, and we focus on the competition between a state with cubic symmetry and a state obtained from atomic Hund's rules. We find the state with cubic symmetry to be 0.59 eV lower in energy than the Hund's rules state, while the opposite was obtained in previous literature. The shear constant is shown to be rather sensitive to the theoretical method used, and the Hund's rules state obtained in LDA+U is found to be unstable towards tetragonal shear. As to the magnetism, we find that the calculation based on the Hubbard-I approximation reproduces observations with the best accuracy. Finally, the spectral properties of TbN are discussed, together with the general applicability of the different methods in describing rare-earth elements and compounds.

Peters, L.; Di Marco, I.; Thunström, P.; Katsnelson, M. I.; Kirilyuk, A.; Eriksson, O.

2014-05-01

390

Relevance of NH4F in acid digestion before ICP-MS analysis.  

PubMed

In order to implement a simpler, less expensive and more safe sample dissolution procedure, we have substituted the HF-HClO(4) mixture by NH(4)F. By testing three certified reference materials, lichen 336, basalt BE-N, soil 7, it was found that the three-reagents digestion without HF and HClO(4) (HNO(3)+H(2)O(2)+NH(4)F was used) was very effective for the pretreatment of ICP-MS measurement. The comparison was based on the measurement results and their uncertainties. All are reference material for amount contents of different trace elements. The accuracy and precision of the developed method were tested by replicate analyses of reference samples of established element contents. The accuracy of the data as well as detection limits (LODs) vary among elements but are usually very good (accuracy better than 8%, LODs usually below 1 microg/g in solids). ICP-MS capabilities enable us to determine routinely 13 and 16 minor and trace elements in basalt and soil. PMID:18804658

Mariet, Clarisse; Belhadj, Oulfa; Leroy, Stéphanie; Carrot, Francine; Métrich, Nicole

2008-10-19

391

Behavior of nickel anode in CsF-NH4F-HF melts  

NASA Astrophysics Data System (ADS)

The chemical composition and the electrochemical properties of the oxide layer formed on a nickel anode in molten CsF-NH4F-4HF at 50 and 100 C were studied. Nickel compounds of high oxidation state such as NiF4, Ni3O4, and Ni2O3 were formed on the anode at potentials more positive than 3 V vs. the hydrogen evolution potential in the melt. NiO(1+x) (0 less than x less than 0.5), especially Ni3O4, was conductive and electrochemically active in contrast with the passive layer of divalent compounds (NiO and NiF2) formed at low potentials. It is estimated that these layers are less than several tens of angstroms thick depending on the polarization potentials and the time of electrolysis. It is also estimated that the thickness of these layers formed in molten CsF-NH4F-4HF-4HF containing water is larger than that formed in a well-dehydrated melt.

Tasaka, Akimasa; Miki, Keiji; Ohashi, Toshitaka; Yamaguchi, Shin-Ichi; Kanemaru, Muneaki; Iwanaga, Naruyuki; Aritsuka, Makoto

1994-06-01

392

Li 2B 3O 4F 3, a new lithium-rich fluorooxoborate  

NASA Astrophysics Data System (ADS)

The new lithium fluorooxoborate, Li 2B 3O 4F 3, is obtained by a solid state reaction from LiBO 2 and LiBF 4 at 553 K and crystallizes in the acentric orthorhombic space group P2 12 12 1 (no. 19) with the cell parameters a=4.8915(9), b=8.734(2), and c=12.301(2) Å. Chains of fluorinated boroxine rings along the b axis consists of BO 3 triangles and BO 2F 2 as well as BO 3F tetrahedra. Mobile lithium ions are compensating the negative charge of the anionic chain, in which the fourfold coordinated boron atoms bear a negative formal charge. Annealing Li 2B 3O 4F 3 at temperatures above 573 K leads to conversion into Li 2B 6O 9F 2. The title compound is an ionic conductor with the highest ion conductivity among the hitherto know lithium fluorooxoborates, with conductivities of 1.6×10 -9 and 1.8×10 -8 S cm -1 at 473 and 523 K, respectively.