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1

Design and characterization of acoustic 4f imaging system by using an optical microring ultrasound detector  

PubMed Central

We propose an acoustic 4f imaging system by using a pair of acoustic lens and an optical microring ultrasound detector (OMUD). The system was designed to have a long range imaging, and the signal strength was enhanced by a factor of ?13 by using an acryl-based acoustic lens at an imaging distance of close to 10 cm. The acoustic signal had a broadband and high frequency spectrum for a given focal distance owing to the unique characteristic of the OMUD. The imaging was obtained without using any reconstruction algorithms. Several performances of the designed system have been investigated by using photo-acoustic microspheres (301 ?m in diameter) which are excited by pulsed laser beam. The resolution of images were compared, which consist of full frequency spectrum and harmonic frequency components. With high frequency (10 MHz and 15 MHz), the images showed consistently better resolutions (440 ?m and 370 ?m) for the microsphere. Frequency analysis of a time-domain signal waveform showed that the signal spectrum of the current system extends up to 20 MHz.

Baac, Hyoung Won; Ling, Tao; Guo, L. Jay

2010-01-01

2

Design and characterization of acoustic 4f imaging system by using an optical microring ultrasound detector.  

PubMed

We propose an acoustic 4f imaging system by using a pair of acoustic lens and an optical microring ultrasound detector (OMUD). The system was designed to have a long range imaging, and the signal strength was enhanced by a factor of ?13 by using an acryl-based acoustic lens at an imaging distance of close to 10 cm. The acoustic signal had a broadband and high frequency spectrum for a given focal distance owing to the unique characteristic of the OMUD. The imaging was obtained without using any reconstruction algorithms. Several performances of the designed system have been investigated by using photo-acoustic microspheres (301 ?m in diameter) which are excited by pulsed laser beam. The resolution of images were compared, which consist of full frequency spectrum and harmonic frequency components. With high frequency (10 MHz and 15 MHz), the images showed consistently better resolutions (440 ?m and 370 ?m) for the microsphere. Frequency analysis of a time-domain signal waveform showed that the signal spectrum of the current system extends up to 20 MHz. PMID:20336169

Baac, Hyoung Won; Ling, Tao; Guo, L Jay

2010-02-01

3

Design and characterization of acoustic 4f imaging system by using an optical microring ultrasound detector  

NASA Astrophysics Data System (ADS)

We propose an acoustic 4f imaging system by using a pair of acoustic lens and an optical microring ultrasound detector (OMUD). The system was designed to have a long range imaging, and the signal strength was enhanced by a factor of ~13 by using an acryl-based acoustic lens at an imaging distance of close to 10 cm. The acoustic signal had a broadband and high frequency spectrum for a given focal distance owing to the unique characteristic of the OMUD. The imaging was obtained without using any reconstruction algorithms. Several performances of the designed system have been investigated by using photo-acoustic microspheres (301 ?m in diameter) which are excited by pulsed laser beam. The resolution of images were compared, which consist of full frequency spectrum and harmonic frequency components. With high frequency (10 MHz and 15 MHz), the images showed consistently better resolutions (440 ?m and 370 ?m) for the microsphere. Frequency analysis of a time-domain signal waveform showed that the signal spectrum of the current system extends up to 20 MHz.

Baac, Hyoung Won; Ling, Tao; Guo, L. Jay

2010-02-01

4

Image formation in electron thermoelastic acoustic microscopy  

Microsoft Academic Search

The theory of electron beam acoustic imaging with acoustic wave generation through the thermoelastic effect, or electron thermoelastic acoustic microscopy, has been developed in three dimensions. Images are created through two separate processes: acoustic wave (vibration) generation and acoustic wave transmission. Acoustic wave generation through the thermoelastic effect depends on the material’s thermal and elastic properties. Images based on these

W. L. Holstein

1985-01-01

5

Acoustic image-processing software  

NASA Astrophysics Data System (ADS)

Several algorithims that display, enhance and analyze side-scan sonar images of the seafloor, have been developed by the University of Washington, Seattle, as part of an Office of Naval Research funded program in acoustic image analysis. One of these programs, PORTAL, is a small (less than 100K) image display and enhancement program that can run on MS-DOS computers with VGA boards. This program is now available in the public domain for general use in acoustic image processing.PORTAL is designed to display side-scan sonar data that is stored in most standard formats, including SeaMARC I, II, 150 and GLORIA data. (See image.) In addition to the “standard” formats, PORTAL has a module “front end” that allows the user to modify the program to accept other image formats. In addition to side-scan sonar data, the program can also display digital optical images from scanners and “framegrabbers,” gridded bathymetry data from Sea Beam and other sources, and potential field (magnetics/gravity) data. While limited in image analysis capability, the program allows image enhancement by histogram manipulation, and basic filtering operations, including multistage filtering. PORTAL can print reasonably high-quality images on Postscript laser printers and lower-quality images on non-Postscript printers with HP Laserjet emulation. Images suitable only for index sheets are also possible on dot matrix printers.

6

Acoustic waves in medical imaging and diagnostics.  

PubMed

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. Beginning in the 1990s, there started to emerge numerous acoustic imaging modalities based on the use of a different mode of acoustic wave: shear waves. Imaging with these waves was shown to provide very useful and very different information about the biological tissue being examined. We discuss the 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 is presented. We discuss the potential for future shear wave imaging applications. PMID:23643056

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

2013-04-30

7

Acoustical Imaging of Individual Microbubbles  

NASA Astrophysics Data System (ADS)

This paper describes an acoustical approach for imaging the behavior of individual microbubbles in ultrasound fields. The experimental set-up includes a tank where small concentrations of encapsulated microbubbles are suspended in distilled water. When insonified by a programmable transmitter (TX), each microbubble is pushed away by the US radiation force to an extent which depends on its size and composition as well as on the TX parameters. For each transmitted ultrasound burst, the RF echo-signals backscattered by microbubbles over the ROI are processed in a high-speed digital board. The acquired data is used to produce two real-time displays. Tests performed in different experimental conditions clearly show bubbles accelerating in the focal region and moving slower elsewhere. It is seen in particular that all velocities measured for a full population of microbubbles are lower than- or equal to- the maximum velocities predicted for resonating bubbles. Finally, the destruction of a bubble is identified by a sudden interruption of the corresponding trace in the M-mode display. By controlling the TX parameters and monitoring the bubble movements, information about their dimension and elastic features can be obtained

Guidi, F.; Vos, H. J.; Nicchi, F.; Boni, E.; Tortoli, P.

8

Acoustic imaging of thermally fractured rock  

Microsoft Academic Search

Recent proposals for the disposal of nuclear waste in granitic rock have generated interest in thermally induced fracturing of the rock formations. For these reasons, a program of research has been undertaken in the laboratory to image thermal fracturing using concurrent ultrasonic tomographic imaging and acoustic emission (AE) location. In these experiments, a cartridge heater was used to cycle the

D. P. Jansen; D. A. Hutchins; R. P. Young

1991-01-01

9

Combined photoacoustic and magneto-acoustic imaging.  

PubMed

Ultrasound is a widely used modality with excellent spatial resolution, low cost, portability, reliability and safety. In clinical practice and in the biomedical field, molecular ultrasound-based imaging techniques are desired to visualize tissue pathologies, such as cancer. In this paper, we present an advanced imaging technique - combined photoacoustic and magneto-acoustic imaging - capable of visualizing the anatomical, functional and biomechanical properties of tissues or organs. The experiments to test the combined imaging technique were performed using dual, nanoparticle-based contrast agents that exhibit the desired optical and magnetic properties. The results of our study demonstrate the feasibility of the combined photoacoustic and magneto-acoustic imaging that takes the advantages of each imaging techniques and provides high sensitivity, reliable contrast and good penetrating depth. Therefore, the developed imaging technique can be used in wide range of biomedical and clinical application. PMID:19964846

Qu, Min; Mallidi, Srivalleesha; Mehrmohammadi, Mohammad; Ma, Li Leo; Johnston, Keith P; Sokolov, Konstantin; Emelianov, Stanislav

2009-01-01

10

Imaging of acoustic waves in sand  

NASA Astrophysics Data System (ADS)

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 accommodated 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 at 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 A.; Telschow, Ken L.; Watson, Scott M.

2003-12-01

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 imaging with a moving acoustic lens.  

PubMed

The acoustic lens is a high-resolution, forward-looking sonar for three dimensional (3-D) underwater imaging. We discuss processing the lens data for recreating and visualizing the scene. Acoustical imaging, compared to optical imaging, is sparse and low resolution. To achieve higher resolution, we obtain a denser sample by mounting the lens on a moving platform and passing over the scene. This introduces the problem of data fusion from multiple overlapping views for scene formation, which we discuss. We also discuss the improvements in object reconstruction by combining data from several passes over an object. We present algorithms for pass registration and show that this process can be done with enough accuracy to improve the image and provide greater detail about the object. The results of in-water experiments show the degree to which size and shape can be obtained under (nearly) ideal conditions. PMID:18267382

Kamgar-Parsi, B; Rosenblum, L J; Belcher, E O

1998-01-01

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

Imaging Tissue Mechanical Properties Using Impulsive Acoustic Radiation Force  

Microsoft Academic Search

Acoustic radiation force impulse (ARFI) imaging utilizes brief, high energy, focused acoustic pulses to generate radiation force in tissue, and conventional diagnostic ultrasound methods to detect the resulting tissue displacements in order to image the relative mechanical properties of tissue. Parametric images of maximum displacement, the time the tissue takes to reach its peak displacement, and tissue recovery time provide

Mary Scott Soo; Mark Palmeri; Kathryn Nightingale; Amy Congdon; Kristin Frinkley; Gregg E. Trahey

2004-01-01

15

Development of passive acoustic imaging for large heat transfer components  

SciTech Connect

A passive acoustic imaging system for acoustic source location with no restriction on source character is being developed for thermal-hydraulic components. The system is particularly useful in locating continuous or quasi-continuous acoustic emission sources such as leaks in steam generators or rapid rattling of tubes in steam generators. In the imaging system to be described, acoustic signals that emanate outward from the source, through the medium, are detected by an array of low-frequency accelerometers. These time domain functions are combined with a mesh mapping algorithm to produce a spatial image showing the location and intensity of the noise source.

Claytor, T.N.; Greene, D.A.

1985-01-01

16

Acoustic thoracic images for transmitted glottal sounds.  

PubMed

Sound transmission has been of interest for many years in an attempt to study the structure of the lung and different researches have shown that artificial sounds produce a lateralization of sound information at the thoracic surface. Most of these studies have use non-simultaneous recording and input sounds introduced at the mouth or other thoracic points. In this paper, we present acoustic thoracic images, for transmitted glottal sounds, formed by a multichannel system with an array of 5x5 microphones. The study was done using 4 healthy subjects and 4 subjects having diffuse interstitial pneumonia. In both groups of subjects, it was found that the thorax behaves as a lowpass filter depending on the physical properties of its components, and that the transmitted acoustic thoracic imaging (TATHI) could reflect such properties. In most of the healthy subjects right to left asymmetries and heterogeneous apical to basal distribution were found. In patients the lateral dominance was lost and an intensity increment in the frequency band of 300 to 600 Hz was revealed. We conclude that TATHI permits to observe easily the spatial extension of the disease through sound transmission. PMID:18002746

Charleston-Villalobos, S; González-Camarena, R; Chi-Lem, G; Aljama-Corrales, T

2007-01-01

17

Interpreting Underwater Acoustic Images of the Upper Ocean Boundary Layer  

ERIC Educational Resources Information Center

|A challenging task in physical studies of the upper ocean using underwater sound is the interpretation of high-resolution acoustic images. This paper covers a number of basic concepts necessary for undergraduate and postgraduate students to identify the most distinctive features of the images, providing a link with the acoustic signatures of…

Ulloa, Marco J.

2007-01-01

18

Adjustable acoustic knife edge for anisotropic and dark-field acoustic imaging  

NASA Astrophysics Data System (ADS)

A new effective method for acoustic anisotropy and dark-field imaging in reflection ultrasonic focusing devices is proposed. Part of the spherical acoustic wave propagating to and coming from the object is stopped by an ultrasonically opaque acoustic knife edge (AKE) set at the aperture plane of the focusing lens or transducer. This method can be easily applied to commercially available focusing systems and allows optimization of the setup for the microscopic study of various objects.

Kolosov, Oleg; Yamanaka, Kazushi

1994-01-01

19

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

20

Reproducibility of dynamically represented acoustic lung images from healthy individuals  

PubMed Central

Background and aim: Acoustic lung imaging offers a unique method for visualising the lung. This study was designed to demonstrate reproducibility of acoustic lung images recorded from healthy individuals at different time points and to assess intra- and inter-rater agreement in the assessment of dynamically represented acoustic lung images. Methods: Recordings from 29 healthy volunteers were made on three separate occasions using vibration response imaging. Reproducibility was measured using quantitative, computerised assessment of vibration energy. Dynamically represented acoustic lung images were scored by six blinded raters. Results: Quantitative measurement of acoustic recordings was highly reproducible with an intraclass correlation score of 0.86 (very good agreement). Intraclass correlations for inter-rater agreement and reproducibility were 0.61 (good agreement) and 0.86 (very good agreement), respectively. There was no significant difference found between the six raters at any time point. Raters ranged from 88% to 95% in their ability to identically evaluate the different features of the same image presented to them blinded on two separate occasions. Conclusion: Acoustic lung imaging is reproducible in healthy individuals. Graphic representation of lung images can be interpreted with a high degree of accuracy by the same and by different reviewers.

Maher, T M; Gat, M; Allen, D; Devaraj, A; Wells, A U; Geddes, D M

2008-01-01

21

Adjustable Acoustic Knife Edge for Anisotropic and Dark-Field Acoustic Imaging  

NASA Astrophysics Data System (ADS)

A new effective method for acoustic anisotropy and dark-field imaging in reflection ultrasonic focusing devices is proposed. Part of the spherical acoustic wave propagating to and coming from the object is stopped by an ultrasonically opaque acoustic knife edge (AKE) set at the aperture plane of the focusing lens or transducer. This AKE provides the focusing device with directional sensitivity and the capacity for dark-field imaging. Sensitivity of the AKE system to the elastic anisotropy of the leaky surface acoustic wave (LSAW) velocity was demonstrated using an X-cut LiNbO3 crystal. Dark-field imaging of cracks in Si3N4 ceramics and the structure of carbon fiber-reinforced plastic (FRP) was performed. This method can be easily applied to commercially available focusing systems and allows optimization of the setup for the microscopic study of various objects.

Kolosov, Oleg; Yamanaka, Kazushi

1994-01-01

22

Image reconstruction in optoacoustic tomography for dispersive acoustic media  

NASA Astrophysics Data System (ADS)

Conventional image reconstruction methods for optoacoustic tomography (OAT) assume an idealized, nondispersive acoustic medium. However, the linear attenuation coefficient and the phase velocity of acoustic waves propagating in soft tissue depend on temporal frequency and satisfy a known dispersion law. These frequency-dependent effects are incorporated into an optoacoustic wave equation, and a corresponding reconstruction method for OAT is developed. The improvement in image fidelity that can be achieved over conventional reconstruction methods is demonstrated by use of computer-simulation studies.

La Rivière, Patrick J.; Zhang, Jin; Anastasio, Mark A.

2006-03-01

23

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

24

Phase retrieval via spatial light modulator phase modulation in 4f optical setup: numerical inverse imaging with sparse regularization for phase and amplitude.  

PubMed

The 4f optical setup is considered with a wave field modulation by a spatial light modulator located in the focal plane of the first lens. Phase as well as amplitude of the wave field are reconstructed from noisy multiple-intensity observations. The reconstruction is optimal due to a constrained maximum likelihood formulation of the problem. The proposed algorithm is iterative with decoupling of the inverse of the forward propagation of the wave field and the filtering of phase and amplitude. The sparse modeling of phase and amplitude enables the advanced high-accuracy filtering and sharp imaging of the complex-valued wave field. Artifacts typical for the conventional algorithms (wiggles, ringing, waves, etc.) and attributed to optical diffraction can be suppressed by the proposed algorithm. PMID:22218357

Katkovnik, Vladimir; Astola, Jaakko

2012-01-01

25

Optical Bragg imaging of acoustic fields after reflection.  

PubMed

Bragg diffraction of x-rays occurs when the rays interact with a crystalline lattice at the appropriate angle. Bragg diffraction of visible light occurs when the light interacts at the Bragg angle with an ultrasonic field of the appropriate frequency. (The spacing between acoustic condensations and rarefactions acts like the planes in an atomic lattice.) If a beam of light is Bragg diffracted by an ultrasonic beam that previously has passed through an object, an image of the structure of the object is made visible in the diffraction field of the optical beam since there is a one-to-one mapping of the ultrasonic field onto the diffraction order. In many acoustic Bragg imaging applications, the sound field must pass through the object which is to be imaged. Ultrasonic attenuation at the very high acoustic frequencies needed for Bragg imaging (typically approximately 25-30 MHz) severely limits the nondestructive testing (NDT) applications of traditional acoustic Bragg imaging. In this paper, a reflection-based application of acoustic Bragg imaging is discussed which may have useful industrial and biomedical NDT applications. PMID:20550246

Declercq, Nico F; McPherson, Michael S; Breazeale, Mack A; Teklu, Alem A

2010-06-01

26

Acoustic imaging in a water filled metallic pipe  

SciTech Connect

A method is described for the imaging of the interior of a water filled metallic pipe using acoustical techniques. The apparatus consists of an array of 20 acoustic transducers mounted circumferentially around the pipe. Each transducer is pulsed in sequence, and the echos resulting from bubbles in the interior are digitized and processed by a computer to generate an image. The electronic control and digitizing system and the software processing of the echo signals are described. The performance of the apparatus is illustrated by the imaging of simulated bubbles consisting of thin walled glass spheres suspended in the pipe.

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

1985-02-01

27

High-Speed Vortex Wind Velocity Imaging by Acoustic Tomography  

Microsoft Academic Search

\\u000a A technique for monitoring strong vortex wind fields is highly desired due to the rapid development of global warming. Vortex\\u000a wind velocity imaging using an acoustic travel time tomography technique was developed to meet this need. The method can be\\u000a implemented with a small number of parallel facing pairs of acoustic transmitters\\/receivers from just a single illumination\\u000a view direction, so

H. Li; T. Ueki; K. Hayashi; A. Yamada

28

Non-destructive acoustic micro imaging of package seals  

Microsoft Academic Search

Seals, which close a medical or pharmaceutical package, are designed to maintain its contents in a sterile condition until use. Imperfections in the seals can allow bacteria or other contaminants to reach the contents, with potentially dangerous consequences. The technology of acoustic micro imaging, which has become widely used in the microelectronics industry, has recently demonstrated its ability to image

Tom Adams

2000-01-01

29

Transient OH* Chemiluminescence Imaging of Acoustically Coupled Fuel Droplet Combustion  

NASA Astrophysics Data System (ADS)

This study focuses on combustion of liquid fuel droplets during exposure to external acoustic disturbances generated as standing waves within a closed acoustic waveguide. During such acoustic excitation, the mean flame orientation is observed to be dependent on the droplet's location relative to the pressure node (PN), and is consistent with the sign of a theoretical acoustic acceleration acting on the burning system. Yet experimentally estimated acoustic accelerations, measured from the degree of mean flame deflection, differ substantially in a quantitative sense from those predicted by theory.ootnotetextTanabe, et al., Proc. Comb. Inst., 2000 Phase-locked OH* chemiluminescence imaging reveals a deflected flame which oscillates in position relative to the droplet, with the largest degree of oscillation near the PN. A range of acoustic forcing frequencies and droplet locations are used to investigate flame movement over multiple acoustic cycles. The degree of flame oscillation, mean flame deflection angle, and fuel droplet burning rate all correlate with one another for different relative positions of the droplet.

Wegener, Jeffrey; Sevilla, Cristhian; Smolke, Jennifer; Sung, Aaron; Chen, Kelvin; Smith, Owen; Karagozian, Ann

2011-11-01

30

Laser Imaging of Airborne Acoustic Emission by Nonlinear Defects  

NASA Astrophysics Data System (ADS)

Strongly nonlinear vibrations of near-surface fractured defects driven by an elastic wave radiate acoustic energy into adjacent air in a wide frequency range. The variations of pressure in the emitted airborne waves change the refractive index of air thus providing an acoustooptic interaction with a collimated laser beam. Such an air-coupled vibrometry (ACV) is proposed for detecting and imaging of acoustic radiation of nonlinear spectral components by cracked defects. The photoelastic relation in air is used to derive induced phase modulation of laser light in the heterodyne interferometer setup. The sensitivity of the scanning ACV to different spatial components of the acoustic radiation is analyzed. The animated airborne emission patterns are visualized for the higher harmonic and frequency mixing fields radiated by planar defects. The results confirm a high localization of the nonlinear acoustic emission around the defects and complicated directivity patterns appreciably different from those observed for fundamental frequencies.

Solodov, Igor; Döring, Daniel; Busse, Gerd

2008-06-01

31

Acoustic Angiography: A New Imaging Modality for Assessing Microvasculature Architecture  

PubMed Central

The purpose of this paper is to provide the biomedical imaging community with details of a new high resolution contrast imaging approach referred to as “acoustic angiography.” Through the use of dual-frequency ultrasound transducer technology, images acquired with this approach possess both high resolution and a high contrast-to-tissue ratio, which enables the visualization of microvascular architecture without significant contribution from background tissues. Additionally, volumetric vessel-tissue integration can be visualized by using b-mode overlays acquired with the same probe. We present a brief technical overview of how the images are acquired, followed by several examples of images of both healthy and diseased tissue volumes. 3D images from alternate modalities often used in preclinical imaging, contrast-enhanced micro-CT and photoacoustics, are also included to provide a perspective on how acoustic angiography has qualitatively similar capabilities to these other techniques. These preliminary images provide visually compelling evidence to suggest that acoustic angiography may serve as a powerful new tool in preclinical and future clinical imaging.

Gessner, Ryan C.; Frederick, C. Brandon; Foster, F. Stuart; Dayton, Paul A.

2013-01-01

32

Improved acoustic scattering model for medical imaging  

NASA Astrophysics Data System (ADS)

In this work a model for acoustic backscatter from a three-dimensional medium having high acoustic contrast is presented. The Fourier transform of the scattered pressure amplitude is expressed as the solution of the Helmholtz integral equation. The solution is sought in terms of a perturbation expansion in powers of varepsilon ksp2, where k is the acoustic wavenumber and varepsilon is the acoustic contrast of the scatterer. The medium is ensonified by a broadband pressure pulse. It is shown that the limitation that varepsilon ksp2 be small in magnitude can be overcome by recasting the perturbation sequence as a rational fraction using Pade approximants. The resulting solution form allows for an accurate representation of the pressure and allows the frequency poles in the scattering amplitude to be modeled. The Pade approximant based procedure is used to obtain the time response function of the pressure at the transducer. The magnitude of the compressibility contrast is shown, using an exact formulation, to have a direct impact on multiple scattering in the impulse response of a sphere. Results are given for the scattered pressure in a phantom medium using a model that incorporates features of the tissue medium, and the scanning procedure. Fourier domain subsampling is used to reduce the number of samples by 75%. Multiple scattering is demonstrated for a simulated tissue phantom. The magnitude of the multiple scattering for a spherical scatterer inside a homogeneous host medium is shown to depend on the magnitude of the compressibility contrast. The spherical inclusion produces echoes whose temporal separation is directly related to the distance between the acoustic interfaces. For a randomly inhomogeneous host medium, echoes produced by the sphere are less distinct. This is due to echoes produced by scattering from multiple acoustic interfaces within the medium. As much of the literature has only used the first two terms of the Neumann series perturbation expansion, based on the weak scattering assumption, we feel that our work extends the capabilities of previous research. This is based on the observance of multiple scattering within A-scans that use higher order Neumann terms.

Kozloff, Anthony Charles

33

Epipolar geometry of opti-acoustic stereo imaging.  

PubMed

Optical and acoustic cameras are suitable imaging systems to inspect underwater structures, both in regular maintenance and security operations. Despite high resolution, optical systems have limited visibility range when deployed in turbid waters. In contrast, the new generation of high-frequency (MHz) acoustic cameras can provide images with enhanced target details in highly turbid waters, though their range is reduced by one to two orders of magnitude compared to traditional low-/midfrequency (10s-100s KHz) sonar systems. It is conceivable that an effective inspection strategy is the deployment of both optical and acoustic cameras on a submersible platform, to enable target imaging in a range of turbidity conditions. Under this scenario and where visibility allows, registration of the images from both cameras arranged in binocular stereo configuration provides valuable scene information that cannot be readily recovered from each sensor alone. We explore and derive the constraint equations for the epipolar geometry and stereo triangulation in utilizing these two sensing modalities with different projection models. Theoretical results supported by computer simulations show that an opti-acoustic stereo imaging system outperforms a traditional binocular vision with optical cameras, particularly for increasing target distance and (or) turbidity. PMID:17699922

Negahdaripour, Shahriar

2007-10-01

34

Application of acoustic reflection tomography to sonar imaging.  

PubMed

Computer-aided tomography is a technique for providing a two-dimensional cross-sectional view of a three-dimensional object through the digital processing of many one-dimensional views (or projections) taken at different look directions. In acoustic reflection tomography, insonifying the object and then recording the backscattered signal provides the projection information for a given look direction (or aspect angle). Processing the projection information for all possible aspect angles enables an image to be reconstructed that represents the two-dimensional spatial distribution of the object's acoustic reflectivity function when projected on the imaging plane. The shape of an idealized object, which is an elliptical cylinder, is reconstructed by applying standard backprojection, Radon transform inversion (using both convolution and filtered backprojections), and direct Fourier inversion to simulated projection data. The relative merits of the various reconstruction algorithms are assessed and the resulting shape estimates compared. For bandpass sonar data, however, the wave number components of the acoustic reflectivity function that are outside the passband are absent. This leads to the consideration of image reconstruction for bandpass data. Tomographic image reconstruction is applied to real data collected with an ultra-wideband sonar transducer to form high-resolution acoustic images of various underwater objects when the sonar and object are widely separated. PMID:15957762

Ferguson, Brian G; Wyber, Ron J

2005-05-01

35

Acoustic imaging of underground storage tank wastes  

SciTech Connect

Acoustics is a potential tool to determine the properties of high level wastes stored in Underground Storage Tanks. Some acoustic properties were successfully measured by a limited demonstration conducted in 114-TX. This accomplishment provides the basis for expanded efforts to qualify techniques which depend on the acoustic properties of tank wastes. This work is being sponsored by the Department of Energy under the Office of Science and Technology. In FY-1994, limited Tank Waste Remediation Systems EM-30 support was available at Hanford and Los Alamos National Laboratory. The Massachusetts Institute of Technology (MIT) and Earth Resources Laboratory (ERL) were engaged for analysis support, and Elohi Geophysics, Inc. for seismic testing services. Westinghouse-Hanford Company provided the testing and training, supplied the special engineering and safety analysis equipment and procedures, and provided the trained operators for the actual tank operations. On 11/9/94, limited in-tank tests were successfully conducted in tank 114-TX. This stabilized Single Shell Tank was reported as containing 16.8 feet of waste, the lower 6.28 feet of which contained interstitial liquid. Testing was conducted over the lower 12 feet, between two Liquid Observation Wells thirty feet apart. The ``quick-look`` data was reviewed on-site by MIT and Elohi.

Mech, S.J.

1995-09-01

36

Imaging and detection of mines from acoustic measurements  

NASA Astrophysics Data System (ADS)

A laboratory-scale acoustic experiment is described where a buried target, a hockey puck cut in half, is shallowly buried in a sand box. To avoid the need for source and receiver coupling to the host sand, an acoustic wave is generated in the subsurface by a pulsed laser suspended above the air-sand interface. Similarly, an airborne microphone is suspended above this interface and moved in unison with the laser. After some pre-processing of the data, reflections for the target, although weak, could clearly be identified. While the existence and location of the target can be determined by inspection of the data, its unique shape can not. Since target discrimination is important in mine detection, a 3D imaging algorithm was applied to the acquired acoustic data. This algorithm yielded a reconstructed image where the shape of the target was resolved.

Witten, Alan J.; Dimarzio, Charles A.; Li, Wen; McKnight, Stephen W.

1999-08-01

37

Harbor shield program update: Underwater acoustic imaging of moving vessels  

Microsoft Academic Search

Battelle and Naval Undersea Warfare Center (NUWC) Division Newport have developed a maritime security system called Harbor Shield, which can acoustically image the underhull of a vessel from a fixed location to detect potential threats while the vessel is underway. US Immigration and Customs Enforcement dive teams and other security personnel have recovered parasitic drug smuggling devices attached to hulls,

Rich Granger; Lynn Faulkner; Eric Rabe; Donald Steinbrecher

2011-01-01

38

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

39

Acoustic property measurements in a photoacoustic imager  

NASA Astrophysics Data System (ADS)

Photoacoustics is a hybrid imaging technique that combines the contrast available to optical imaging with the resolution that is possessed by ultrasound imaging. The technique is based on generating ultrasound from absorbing structures in tissue using pulsed light. In photoacoustic (PA) computerized tomography (CT) imaging, reconstruction of the optical absorption in a subject, is performed for example by filtered backprojection. The backprojection is performed along circular paths in image space instead of along straight lines as in X-ray CT imaging. To achieve this, the speed-of-sound through the subject is usually assumed constant. An unsuitable speed-of-sound can degrade resolution and contrast. We discuss here a method of actually measuring the speed-of- sound distribution using ultrasound transmission through the subject under photoacoustic investigation. This is achieved in a simple approach that does not require any additional ultrasound transmitter. The method uses a passive element (carbon fiber) that is placed in the imager in the path of the illumination which generates ultrasound by the photoacoustic effect and behaves as an ultrasound source. Measuring the time-of-flight of this ultrasound transient by the same detector used for conventional photoacoustics, allows a speed-of-sound image to be reconstructed. This concept is validated on phantoms.

Willemink, René G. H.; Manohar, Srirang; Slump, Cornelis H.; van der Heijden, Ferdi; van Leeuwen, Ton

2007-07-01

40

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

41

Opti-Acoustic Stereo Imaging: On System Calibration and 3-D Target Reconstruction  

Microsoft Academic Search

Utilization of an acoustic camera for range measurements is a key advantage for 3-D shape recovery of underwater targets by opti-acoustic stereo imaging, where the associated epipolar geometry of optical and acoustic image correspondences can be described in terms of conic sections. In this paper, we propose methods for system calibration and 3-D scene reconstruction by maximum likelihood estimation from

Shahriar Negahdaripour; Hicham Sekkati; Hamed Pirsiavash

2009-01-01

42

Opti-Acoustic Stereo Imaging, System Calibration and 3-D Reconstruction  

Microsoft Academic Search

Utilization of an acoustic camera for range measure- ments is a key advantage for 3-D shape recovery of under- water targets by opti-acoustic stereo imaging, where the as- sociated epipolar geometry of optical and acoustic image correspondences can be described in terms of conic sec- tions. In this paper, we propose methods for system cali- bration and 3-D scene reconstruction

Shahriar Negahdaripour; Hicham Sekkati; Hamed Pirsiavash

2007-01-01

43

Designable hybrid sonic crystals for transportation and division of acoustic images  

NASA Astrophysics Data System (ADS)

Conventional sonic crystal (SC) imaging devices can focus acoustic waves from an input source into only one image but not multi-images. Furthermore, the position of formed image cannot be designed at will. In this paper, we propose the hybrid SC imaging devices to achieve multi-images from one-source input along with the designable image positions. The proposed hybrid devices can image acoustic waves radiated both from point source and Gaussian beam, which is different from conventional SC imaging devices that only applies to point source. The multi-functional hybrid sonic crystal will have extensive application in the manipulation of acoustic images.

He, Zhaojian; Deng, Ke; Zhao, Heping; Li, Xiaochun

2012-12-01

44

Optical and opto-acoustic imaging.  

PubMed

 Since the inception of the microscope, optical imaging is serving the biological discovery for more than four centuries. With the recent emergence of methods appropriate for in vivo staining, such as bioluminescence, fluorescent molecular probes, and proteins, as well as nanoparticle-based targeted agents, significant attention has been shifted toward in vivo interrogations of different dynamic biological processes at the molecular level. This progress has been largely supported by the development of advanced optical tomographic imaging technologies suitable for obtaining volumetric visualization of biomarker distributions in small animals at a whole-body or whole-organ scale, an imaging frontier that is not accessible by the existing tissue-sectioning microscopic techniques due to intensive light scattering beyond the depth of a few hundred microns. Biomedical optoacoustics has also emerged in the recent decade as a powerful tool for high-resolution visualization of optical contrast, overcoming a variety of longstanding limitations imposed by light scattering in deep tissues. By detecting tiny sound vibrations, resulting from selective absorption of light at multiple wavelengths, multispectral optoacoustic tomography methods can now "hear color" in three dimensions, i.e., deliver volumetric spectrally enriched (color) images from deep living tissues at high spatial resolution and in real time. These new-found imaging abilities directly relate to preclinical screening applications in animal models and are foreseen to significantly impact clinical decision making as well. PMID:23179880

Ntziachristos, Vasilis; Razansky, Daniel

2013-01-01

45

Automated synthesis of 11beta-methoxy-4,16alpha-[16alpha-(18)F]difluoroestradiol (4F-M[(18)F]FES) for estrogen receptor imaging by positron emission tomography.  

PubMed

Addition of both a 4-fluoro and 11beta-methoxy group onto 16alpha-[(18)F]fluoroestradiol ([(18)F]FES) yields 11beta-methoxy-4,16alpha-[16alpha-(18)F]difluoroestradiol (4F-M[(18)F]FES) with potential improved properties for positron emission tomography (PET) imaging of estrogen receptor densities in breast cancer patients. In order to provide 4F-M[(18)F]FES as a radiopharmaceutical for clinical trials, we developed an automated synthesis procedure using 3-O-methoxymethyl-11beta-methoxy-4-fluoro-16,17-O-sulfuryl-16-epiestriol as precursor. The radio synthesis involves stereoselective opening of the protected cyclic sulfone precursor via nucleophilic fluorination with [(18)F]fluoride in acetonitrile. After removal of the protecting ether and 17beta-sulphate groups by rapid hydrolysis in acidic ethanol and subsequent reversed-phase HPLC purification, the pure 4F-M[(18)F]FES was obtained as a sterile physiological saline solution in 45-50% radiochemical yield (decay corrected). The radiochemical purity of the final product was >98% and the effective specific activity (ESA) of 4F-M[(18)F]FES prepared under optimized conditions was >15,000 Ci/mmol. The total preparation time was 110+/-5 min and the product was shown to be stable for at least 6 h. PMID:17499736

Ahmed, Naseem; Langlois, Rejean; Rodrigue, Serge; Bénard, François; van Lier, Johan E

2007-05-01

46

Subwavelength imaging through spoof surface acoustic waves on a two-dimensional structured rigid surface  

NASA Astrophysics Data System (ADS)

We demonstrate that acoustic subwavelength imaging can be realized through the spoof surface acoustic waves on the surface phononic crystal which is composed of borehole arrays with square lattice in a rigid plate. The dispersion property of the spoof surface acoustic waves on the two-dimensional textured rigid plate is analyzed theoretically. By utilizing the broad flat equifrequency contour of the spoof surface acoustic waves, a subwavelength image with full width at half maximum of 0.14 ? has been obtained both numerically and experimentally. We believe that such work can bring potential applications in the design of acoustic imaging and focusing devices.

Jia, Han; Lu, Minghui; Wang, Qingcui; Bao, Ming; Li, Xiaodong

2013-09-01

47

A method of imaging viscoelastic parameters with acoustic radiation force.  

PubMed

Acoustic radiation force has been proposed as a method of interrogating the mechanical properties of tissue. One simple approach applies a series of focused ultrasonic pulses to generate an acoustic radiation force, then processes the echoes returned from these pulses to estimate the radiation-force-induced displacement as a function of time. This process can be repeated at a number of locations to acquire data for image formation. In previous work we have formed images of tissue stiffness by depicting the maximum displacement induced at each tissue location after a finite period of insonification. While these maximum displacement images are able to differentiate materials of disparate mechanical properties, they exploit only a fraction of the information available. In this paper we show that the time-displacement curves acquired from tissue mimicking phantoms exhibit a viscoelastic response which is accurately described by the Voigt model. We describe how the viscous and elastic parameters of this model may be determined from experimental data. Finally, we show phantom images that depict not only the maximum local displacement, but also the viscous and elastic model parameters. These images offer complementary information about the target. PMID:10870702

Walker, W F; Fernandez, F J; Negron, L A

2000-06-01

48

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

49

Image of nonlinear structures of heterogeneous media using the second harmonic in scanning acoustical microscope  

Microsoft Academic Search

Scanning acoustic microscopy (SAM) images are created on the basis of sound reflection from sharp overfall of acoustical impedance. For that reason any internal structural components and inclusions with similar impedance values will be resolved with certain difficulties. In such particular cases, acoustical nonlinear phenomena could provide very important additional information. Interface between two media at certain conditions can be

Fedar M. Severin; Brian O'Neill; Roman Gr. Maev

2000-01-01

50

11 Acoustic Imaging Techniques for Characterization of Corrosion, Corrosion Protective Coatings, and Surface Cracks  

Microsoft Academic Search

Acoustic (ultrasonic) inspection is among the most widely used NDE techniques. Ultrasonic techniques have proven to foster early detection of defects and enhance the understanding of failure processes. Acoustic imaging techniques and for instance Scanning Acoustic Microscopy (SAM) provides very detailed information about material defects with high spatial and depth resolution. It enables studying elastic properties, characterization of interfaces and

J. Hoffmann; S. Sathish; E. B. Shell; S. Fassbender; N. Meyendorf

51

Experimental analysis of wheel\\/rail noise by near field acoustical imaging  

Microsoft Academic Search

In this paper a near field acoustical imaging method applied to the localization and analysis of rolling noise sources on a wheel of a railway tracked vehicle is presented. This method consists in using an acoustical plane microphone array (mounted on the vehicle), which may be moved depending on the wheel\\/rail part being investigated. A space-frequency processing of the acoustical

P. Wetta; B. Beguet; E. Parent de Curzon

1988-01-01

52

Acoustic Radiation Force Impulse Imaging for Differentiation of Thyroid Nodules  

PubMed Central

Background Acoustic Radiation Force Impulse (ARFI)-Imaging is an ultrasound-based elastography method enabling quantitative measurement of tissue stiffness. The aim of the present study was to evaluate sensitivity and specificity of ARFI-imaging for differentiation of thyroid nodules and to compare it to the well evaluated qualitative real-time elastography (RTE). Methods ARFI-imaging involves the mechanical excitation of tissue using acoustic pulses to generate localized displacements resulting in shear-wave propagation which is tracked using correlation-based methods and recorded in m/s. Inclusion criteria were: nodules ?5 mm, and cytological/histological assessment. All patients received conventional ultrasound, real-time elastography (RTE) and ARFI-imaging. Results One-hundred-fifty-eight nodules in 138 patients were available for analysis. One-hundred-thirty-seven nodules were benign on cytology/histology, and twenty-one nodules were malignant. The median velocity of ARFI-imaging in the healthy thyroid tissue, as well as in benign and malignant thyroid nodules was 1.76 m/s, 1.90 m/s, and 2.69 m/s, respectively. While no significant difference in median velocity was found between healthy thyroid tissue and benign thyroid nodules, a significant difference was found between malignant thyroid nodules on the one hand and healthy thyroid tissue (p?=?0.0019) or benign thyroid nodules (p?=?0.0039) on the other hand. No significant difference of diagnostic accuracy for the diagnosis of malignant thyroid nodules was found between RTE and ARFI-imaging (0.74 vs. 0.69, p?=?0.54). The combination of RTE with ARFI did not improve diagnostic accuracy. Conclusions ARFI can be used as an additional tool in the diagnostic work up of thyroid nodules with high negative predictive value and comparable results to RTE.

Bojunga, Joerg; Dauth, Nina; Berner, Christian; Meyer, Gesine; Holzer, Katharina; Voelkl, Lisa; Herrmann, Eva; Schroeter, Hartmut; Zeuzem, Stefan; Friedrich-Rust, Mireen

2012-01-01

53

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.

54

Long range acoustic imaging of the continental shelf environment: the Acoustic Clutter Reconnaissance Experiment 2001.  

PubMed

An active sonar system is used to image wide areas of the continental shelf environment by long-range echo sounding at low frequency. The bistatic system, deployed in the STRATAFORM area south of Long Island in April-May of 2001, imaged a large number of prominent clutter events over ranges spanning tens of kilometers in near real time. Roughly 3000 waveforms were transmitted into the water column. Wide-area acoustic images of the ocean environment were generated in near real time for each transmission. Between roughly 10 to more than 100 discrete and localized scatterers were registered for each image. This amounts to a total of at least 30000 scattering events that could be confused with those from submerged vehicles over the period of the experiment. Bathymetric relief in the STRATAFORM area is extremely benign, with slopes typically less than 0.5 degrees according to high resolution (30 m sampled) bathymetric data. Most of the clutter occurs in regions where the bathymetry is locally level and does not coregister with seafloor features. No statistically significant difference is found in the frequency of occurrence per unit area of repeatable clutter inside versus outside of areas occupied by subsurface river channels. PMID:15898642

Ratilal, Purnima; Lai, Yisan; Symonds, Deanelle T; Ruhlmann, Lilimar A; Preston, John R; Scheer, Edward K; Garr, Michael T; Holland, Charles W; Goff, John A; Makris, Nicholas C

2005-04-01

55

Acoustic imaging of underground storage tank wastes: A feasibility study. Final report  

Microsoft Academic Search

The objectives for this underground storage tank (UST) imaging investigation are: (1) to assess the feasibility of using acoustic methods in UST wastes, if shown to be feasible, develop and assess imaging strategies; (2) to assess the validity of using chemical simulants for the development of acoustic methods and equipment. This investigation examined the velocity of surrogates, both salt cake

R. Turpening; Z. Zhu; C. Caravana; J. Matarese; W. Turpening

1995-01-01

56

Acoustical imaging of spheres above a reflecting surface  

NASA Astrophysics Data System (ADS)

An analytical study using the MUSIC method of subspace imaging is presented for the case of spheres above a reflecting boundary. The field scattered from the spheres and the reflecting boundary is calculated analytically, neglecting interactions between spheres. The singular value decomposition of the response matrix is calculated and the singular vectors divided into signal and noise subspaces. Images showing the estimated sphere locations are obtained by backpropagating the noise vectors using either the free space Green's function or the Green's function that incorporates reflections from the boundary. We show that the latter Green's function improves imaging performance after applying a normalization that compensates for the interference between direct and reflected fields. We also show that the best images are attained in some cases when the number of singular vectors in the signal subspace exceeds the number of spheres. This is consistent with previous analysis showing multiple eigenvalues of the time reversal operator for spherical scatterers [Chambers and Gautesen, J. Acoust. Soc. Am. 109 (2001)]. [Work performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.

Chambers, David; Berryman, James

2003-04-01

57

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

58

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

59

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

60

Theoretical investigation of scanning electron-acoustic imaging  

NASA Astrophysics Data System (ADS)

A 1-D theoretical analysis of the electron-acoustic signal excited in a solid sample by a modulated electron beam is given. An explicit expression for the temperature distribution is found using the thermal wave equation. Then, a theoretical analysis of the thermo-acoustic signals in the sample is carried out by solving the displacement field equation. Numerical calculation of the electron-acoustic signals on the modulation frequency, the thermal conductivity and elastic properties of the sample are given.

Gao, C.-M.; Zhang, S.-Y.; Zhang, Z.-N.; Qian, S.-G.

2005-06-01

61

Negative refraction induced acoustic concentrator and the effects of scattering cancellation, imaging, and mirage  

NASA Astrophysics Data System (ADS)

We present a three-dimensional acoustic concentrator capable of significantly enhancing the sound intensity in the compressive region with scattering cancellation, imaging, and mirage effects. The concentrator shell is built by isotropic gradient negative-index materials, which together with an exterior host medium slab constructs a pair of complementary media. The enhancement factor, which can approach infinity by tuning the geometric parameters, is always much higher than that of a traditional concentrator made by positive-index materials with the same size. The acoustic scattering theory is applied to derive the pressure field distribution of the concentrator, which is consistent with the numerical full-wave simulations. The inherent acoustic impedance match at the interfaces of the shell as well as the inverse processes of “negative refraction—progressive curvature—negative refraction” for arbitrary sound rays can exactly cancel the scattering of the concentrator. In addition, the concentrator shell can also function as an acoustic spherical magnifying superlens, which produces a perfect image with the same shape, with bigger geometric and acoustic parameters located at a shifted position. Then some acoustic mirages are observed whereby the waves radiated from (scattered by) an object located in the center region may seem to be radiated from (scattered by) its image. Based on the mirage effect, we further propose an intriguing acoustic transformer which can transform the sound scattering pattern of one object into another object at will with arbitrary geometric, acoustic, and location parameters.

Wei, Qi; Cheng, Ying; Liu, Xiao-jun

2012-07-01

62

A Microcomputer-Based Digital Data Acquisition Controller for a Computer Aided Acoustic Imaging System.  

National Technical Information Service (NTIS)

This thesis describes the design and construction of a microcomputer based controller for an ultrasonic acoustic imaging system. The INTEL 8748 single chip microcomputer was utilized and the associated hardware and software for the system are described in...

R. A. Colton

1979-01-01

63

Comparative sonographic appearance of nephroliths and associated acoustic shadowing artifacts in conventional vs. spatial compound imaging.  

PubMed

Spatial compound sonography improves visualization of tissue details and allows clearer delineation of structural margins. Improved image clarity is due to reduced speckling artifact; however, other types of acoustic shadowing artifacts may be unchanged or variably altered when conventional and spatial compound sonographic images are compared. Because intrarenal distal shadowing artifacts in conventional sonographic images are oftentimes the first or only evidence that a nephroliths is present, we compared the appearance and associated artifacts of nephroliths examined with both imaging modes. Consensus evaluation by two evaluators confirmed differences in appearance of nephroliths based on imaging mode. Nephroliths with conventional imaging mode were less hyperechoic and had better margin delineation while nephroliths were more hyperechoic and had less distinct margins with spatial compound imaging mode. Distal acoustic shadowing artifacts were present in 43% of spatial compound imaging mode vs. 86% of conventional imaging mode. When present in both imaging modes, intensity of these artifacts was weaker and the distance traveled was shorter in spatial compound imaging mode. Multiple diverging acoustic shadowing artifacts originating from a single source, the nephroliths were occasionally noted in spatial compound but not conventional imaging mode. These results demonstrate that the absence of distal acoustic shadowing cannot be used to exclude the presence of a nephrolith in dogs and cats. Optimal diagnosis of nephroliths, margin delineation, and visualization of the distal renal parenchyma requires paired radiography and sonography, and alternating between sonographic imaging modes is therefore suggested. PMID:22168895

Heng, Hock Gan; Rohleder, Jacob J; Pressler, Barrak M

64

ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS  

SciTech Connect

The research during this project has concentrated on developing a correlation between rock deformation mechanisms and their acoustic velocity signature. This has included investigating: (1) the acoustic signature of drained and undrained unconsolidated sands, (2) the acoustic emission signature of deforming high porosity rocks (in comparison to their low porosity high strength counterparts), (3) the effects of deformation on anisotropic elastic and poroelastic moduli, and (4) the acoustic tomographic imaging of damage development in rocks. Each of these four areas involve triaxial experimental testing of weak porous rocks or unconsolidated sand and involves measuring acoustic properties. The research is directed at determining the seismic velocity signature of damaged rocks so that 3-D or 4-D seismic imaging can be utilized to image rock damage. These four areas of study are described in the report: (1) Triaxial compression experiments have been conducted on unconsolidated Oil Creek sand at high confining pressures. (2) Initial experiments on measuring the acoustic emission activity from deforming high porosity Danian chalk were accomplished and these indicate that the AE activity was of a very low amplitude. (3) A series of triaxial compression experiments were conducted to investigate the effects of induced stress on the anisotropy developed in dynamic elastic and poroelastic parameters in rocks. (4) Tomographic acoustic imaging was utilized to image the internal damage in a deforming porous limestone sample. Results indicate that the deformation damage in rocks induced during laboratory experimentation can be imaged tomographically in the laboratory. By extension the results also indicate that 4-D seismic imaging of a reservoir may become a powerful tool for imaging reservoir deformation (including imaging compaction and subsidence) and for imaging zones where drilling operation may encounter hazardous shallow water flows.

Thurman E. Scott, Jr.; Younane Abousleiman

2004-04-01

65

Biosonar acoustic images for target localization and classification by bats  

NASA Astrophysics Data System (ADS)

Echolocating bats use sonar to guide interception of insects, recognize objects by shape, and even track prey in clutter. Broadcasts of the big brown bat are 0.5 to 20 ms FM signals in the 20-100 kHz ultrasonic band. Insects consist of several reflecting glints, each equivalent in cross- section to a small sphere of 2 mm to 2 cm radius, while clutter is typically composed of numerous glints distributed over a large volume. The bats' signals extend in space for many target lengths, while ka values for each glint are 0.5 to 30 across the broadcast band. Bats perceive acoustic images having echo delay as their primary dimension, and space is perceived in terms of the distribution of target glints in range. Range disparities between the ears provide two 'looks' at each target from slightly different locations as well as information about azimuth. The bats auditory system encodes the FM sweeps of broadcasts and echoes as linear-period spectrograms with integration-times of 300-400 micrometers . Bats nevertheless perceive individual glints in targets for echo-delay separations well inside the integration-time window. Deconvolution is achieved by spectrogram correlation in the time domain and spectral shape transformation in the frequency-domain, with all output evidently being displayed in the time domina. Neural responses in the bat's auditory system seem limited in time precision to 20-50 micrometers at best and 300 microsecond(s) to 3 ms in a broader sample, and stimulus phase is thought to be lost for frequencies above 1-3 kHz. Yet bats perceive echo delay with an accuracy of 10-15 ns and have two-echo resolution of about 2 microsecond(s) . Moreover, bats perceive echo phase-shifts as the correctly corresponding shifts in echo delay. Successive images are subtracted to enhance perception of shape from multiple 'looks', and echo phase is an integral part of this critical process. Utterly novel time-scale magnification appears in the bat's neural responses to ultrasonic broadcasts and echoes, with time-stretch factors of roughly 10 to 100 that account for the bat's mysteriously high temporal acuity. Bats reconstruct time-domain features of FM broadcasts and echoes in a compact, distributed format that incorporates delay, phase, glint separation, and inter-ear delay differences along the same image dimension.

Simmons, James A.

1997-07-01

66

Acoustic micro-Doppler radar for human gait imaging.  

PubMed

A portable acoustic micro-Doppler radar system for the acquisition of human gait signatures in indoor and outdoor environments is reported. Signals from an accelerometer attached to the leg support the identification of the components in the measured micro-Doppler signature. The acoustic micro-Doppler system described in this paper is simpler and offers advantages over the widely used electromagnetic wave micro-Doppler radars. PMID:17407918

Zhang, Zhaonian; Pouliquen, Philippe O; Waxman, Allen; Andreou, Andreas G

2007-03-01

67

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

68

Modeling Hemodynamic Responses in Auditory Cortex at 1.5T Using Variable Duration Imaging Acoustic Noise  

PubMed Central

A confound for functional magnetic resonance imaging (fMRI), especially for auditory studies, is the presence of imaging acoustic noise generated mainly as a byproduct of rapid gradient switching during volume acquisition and to a lesser extent, the radio-frequency transmit. This work utilized a novel pulse sequence to present actual imaging acoustic noise for characterization of the induced hemodynamic responses and assessment of linearity in the primary auditory cortex with respect to noise duration. Results show that responses to brief duration (46ms) imaging acoustic noise is highly nonlinear while responses to longer duration (>1s) imaging acoustic noise becomes approximately linear, with the right primary auditory cortex exhibiting a higher degree of nonlinearity than the left for the investigated noise durations. This study also assessed the spatial extent of activation induced by imaging acoustic noise, showing that the use of modeled responses (specific to imaging acoustic noise) as the reference waveform revealed additional activations in the auditory cortex not observed with a canonical gamma variate reference waveform, suggesting an improvement in detection sensitivity for imaging acoustic noise-induced activity. Longer duration (1.5s) imaging acoustic noise was observed to induce activity that expanded outwards from Heschl’s gyrus to cover the superior temporal gyrus as well as parts of the middle temporal gyrus and insula, potentially affecting higher level acoustic processing.

Hu, Shuowen; Olulade, Olumide; Gonzalez, Javier Castillo; Santos, Joseph; Kim, Sungeun; Tamer, Gregory G.; Luh, Wen-Ming; Talavage, Thomas M.

2009-01-01

69

Noise immunity analysis of neuron-like algorithms in acoustic image processing  

SciTech Connect

There exists the problem of pre-selection of the most noise-immune algorithms (including the neuron-like ones) when acoustic signals are processed in subwater acoustic vision systems. A software version is considered for choosing the parameters in the acoustic image processing algorithms which improve the noise immunity of the decision-making process. It is shown that the processing modes with improved noise immunity can be chosen in model experiments associated with threshold changes in the neuron-like transformation algorithms.

Gorsky, S.M.; Kurzenin, E.B.; Khil`ko, A.I.; Yakhno, V.G. [Institute of Physics, Nizhny Novgorod (Russian Federation)

1995-03-01

70

Spatially resolved acoustic spectroscopy for fast noncontact imaging of material microstructure.  

PubMed

We have developed a noncontact and nondestructive technique that uses laser-generated and detected surface acoustic waves to rapidly determine the local acoustic velocity, in order to map the microstructure of multi-grained materials. Optical fringes excite surface waves at a fixed frequency, and the generation efficiency is determined by how closely the fringe spacing matches the acoustic wavelength in the excitation region. Images of titanium alloys are presented, acquired using the technique. Methods to improve the current lateral resolution of 0.8mm are discussed, and the ability to measure velocity change to an accuracy of one part in 3300 is experimentally demonstrated. PMID:19529442

Sharples, Steve D; Clark, Matthew; Somekh, Mike G

2006-10-30

71

COMPARISON OF ACOUSTIC AND ELECTRICAL IMAGE LOGS FROM THE COSO GEOTHERMAL FIELD, CA  

Microsoft Academic Search

Electrical and acoustic image logs collected from well 58A-10 in crystalline rock on the eastern margin of the Coso Geothermal Field, CA, reveal different populations of planar structures intersecting the borehole. Electrical image logs appear to be sensitive to variations in mineralogy, porosity, and fluid content that highlight both natural fractures and rock fabrics. These fabric elements account for about

NICHOLAS C. DAVATZES; STEVE HICKMAN

72

Acoustic imaging in bat sonar: Echolocation signals and the evolution of echolocation  

Microsoft Academic Search

Echolocating bats behave as though they perceive the crosscorrelation functions between their sonar transmissions and echoes as images of targets, at least with respect to perception of target range, horizontal direction, and shape. These data imply that bats use a multi-dimensional acoustic imaging system for echolocation with broadband, usually frequencymodulated signals. The perceptual structure of the echolocation signals used by

James A. Simmons; Roger A. Stein

1980-01-01

73

Acoustic imaging of hydrothermal plumes, East Pacific Rise, 21°N, 109°W  

NASA Astrophysics Data System (ADS)

We report the first observations based on acoustic imaging of large-scale structure and time variability of buoyant plumes emanating from black smoker-type seafloor hot springs. Three-dimensional plume reconstructions were made from a digital data set of acoustic backscattering information recorded on a prototype submersible-mounted sonar system. The acoustic images of two adjacent black smokers depict volume and show zones of flow organization (meters to tens of meters) in the lower 40 m of the buoyant plumes. The two plumes coalesce, bend in the prevailing current, exhibit short-term (minutes) variation in cross section, and rapid (seconds) turbulent eddy variations at small scales (< 1 m). The plume imaging system is being developed for determination of plume dynamics, flux determinations when combined with chemical and thermal measurements, and long-term monitoring of the activity of seafloor hydrothermal fields.

Rona, P. A.; Palmer, D. R.; Jones, C.; Chayes, D. A.; Czarnecki, M.; Carey, E. W.; Guerrero, J. C.

1991-12-01

74

Image Processing for AN Amplitude and Phase Acoustic Microscope  

Microsoft Academic Search

We have built a scanning acoustic microscope (SAM) operating in the 3 to 10 MHz range that measures both amplitude and phase reliably and accurately. It has been primarily used in non-destructive evaluation (NDE) of machined parts, composite materials, etc. for the presence of cracks, voids, and delaminations. Most SAMs measure amplitude only; by measuring phase as well, we can

Paul Andrew Reinholdtsen

1989-01-01

75

The application of acoustic radiation force for molecular imaging and drug delivery  

NASA Astrophysics Data System (ADS)

Acoustic radiation force is exerted on objects in an acoustic field. By optimizing acoustic parameters to maximize this force, ultrasound contrast agents can be manipulated and concentrated with an acoustic field. This technique can be used to enhance molecular imaging and drug delivery. Ultrasonic molecular imaging employs contrast agents such as microbubbles, nanoparticles, or liposomes coated with ligands specific for receptors expressed on cells at sites of angiogenesis, inflammation, or thrombus. Concentration of these highly echogenic contrast agents at a target site enhances the ultrasound signal received from that site, promoting ultrasonic detection and analysis of disease states. It is demonstrated that acoustic radiation force can be used to displace targeted contrast agents to a vessel wall, greatly increasing the number of agents binding to available surface receptors. Radiation force can also be used for microparticle-carrier based drug delivery. Acoustically active drug-carrier vehicles can be concentrated with radiation force, and then disrupted with high-intensity ultrasound bursts, resulting in local delivery of the therapeutic agent. This talk will discuss simulations and experimental results demonstrating these applications.

Dayton, Paul A.; Ferrara, Katherine W.

2005-04-01

76

The Prototype of Microwave-Induced Thermo-Acoustic Tomography Imaging by Time Reversal Mirror  

Microsoft Academic Search

Microwave-Induced Thermo-Acoustic Tomography (MITAT) is a promising technique in biologic tissue imaging. It has predominant advantages in both contrast and resolution compared with conventional microwave or ultrasound imaging system for malignant tumors. In this paper, an integrated prototype MITAT system is briefly introduced. And Time Reversal Mirror (TRM) imaging technique based on Pseudo-Spectrum Time Domain (PSTD) is also first time

G. P. Chen; W. B. Yu; Z. Q. Zhao; Z. P. Nie; Q. H. Liu

2008-01-01

77

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

78

Acoustical holographic recording with coherent optical read-out and image processing  

NASA Astrophysics Data System (ADS)

New acoustic holographic wave memory devices have been designed for real-time in-situ recording applications. The basic operating principles of these devices and experimental results through the use of some of the prototypes of the devices are presented. Recording media used in the device include thermoplastic resin, Crisco vegetable oil, and Wilson corn oil. In addition, nonlinear coherent optical image processing techniques including equidensitometry, A-D conversion, and pseudo-color, all based on the new contact screen technique, are discussed with regard to the enhancement of the normally poor-resolved acoustical holographic images.

Liu, H. K.

1980-10-01

79

Phase-sensitive imaging of tissue acoustic vibrations using spectrally encoded interferometry.  

PubMed

Acoustic vibrations in tissue are often difficult to image, requiring high-speed scanning, high sensitivity and nanometer-scale axial resolution. Here we use spectrally encoded interferometry to measure the vibration pattern of two-dimensional surfaces, including the skin of a volunteer, at nanometric resolution, without the need for rapid lateral scanning and with no prior knowledge of the driving acoustic waveform. Our results demonstrate the feasibility of this technique for measuring tissue biomechanics using simple and compact imaging probes. PMID:24105515

Ilgayev, Ovadia; Yelin, Dvir

2013-08-26

80

An image method for a sphere in an acoustic waveguide  

NASA Astrophysics Data System (ADS)

The scattering of acoustic waves by a sphere in a shallow ocean waveguide is investigated. Expressions for the scattered waves are given. Numerical values for a quantity called the far-field form function for various depths are presented in graphical forms. Also we investigate the unknown body problem in a waveguide. The Rayleigh conjecture states that every point on an illuminated body radiates sound from that point as if the point lies on its tangent sphere. This conjecture is the cornerstone of the intersecting canonical body approximation (ICBA) for solving the unknown body inverse problem. Therefore, the use of the ICBA requires that an analytical solution be known exterior to the sphere in the waveguide, which leads us to analytically compute the exterior solution for a sphere between two parallel plates. A least-squares matching of theoretical acoustic fields against the measured, scattered field permits a reconstruction of the unknown object.

Lee, Doo-Sung; Gilbert, R. P.

2012-05-01

81

Characterization of interfacial thermal resistance by acoustic micrography imaging  

Microsoft Academic Search

In high-power electronics modules, the heat generated by the power devices is transferred to the ambient environment by attaching a heat spreader to the semiconductor package to ensure efficient thermal management. Typical attachment materials introduce interfaces and\\/or interlayers of finite thickness. Using a scanning acoustic microscope (SAM), a non-destructive inspection tool, we can detect the cracks, voiding, porosity, coplanarity and

Shatil Haque; Guo-Quan Lu; J. Goings; J. Sigmund

2000-01-01

82

A combined microphone and camera calibration technique with application to acoustic imaging.  

PubMed

We present a calibration technique for an acoustic imaging microphone array, combined with a digital camera. Computer vision and acoustic time of arrival data are used to obtain microphone coordinates in the camera reference frame. Our new method allows acoustic maps to be plotted onto the camera images without the need for additional camera alignment or calibration. Microphones and cameras may be placed in an ad-hoc arrangement and, after calibration, the coordinates of the microphones are known in the reference frame of a camera in the array. No prior knowledge of microphone positions, inter-microphone spacings, or air temperature is required. This technique is applied to a spherical microphone array and a mean difference of 3 mm was obtained between the coordinates obtained with this calibration technique and those measured using a precision mechanical method. PMID:23797248

Legg, Mathew; Bradley, Stuart

2013-06-17

83

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

84

Constant-beamwidth and constant-powerwidth wideband robust Capon beamformers for acoustic imaging  

NASA Astrophysics Data System (ADS)

The standard Capon beamformer (SCB) is sensitive to the mismatch between the assumed and actual array steering vector, which occurs often in practice. Recently a robust Capon beamformer (RCB) was proposed by extending the SCB to the case of uncertain array steering vectors. In certain applications such as acoustic imaging, it is desirable that the beamwidth is constant across the frequency bins. This prevents future corrections for different frequencies and contributes to consistent sound pressure level (SPL) estimation, which means that for an acoustic wideband monopole source with a flat spectrum the acoustic image for each frequency bin stays the same. However, the beamwidth of RCB decreases with frequency, which can lead to inconsistent imaging results across the frequencies. In this paper two beamformers are proposed, namely a constant-beamwidth robust Capon beamformer (CBRCB) and a constant-powerwidth robust Capon beamformer (CPRCB), as extensions of RCB for consistent wideband acoustic imaging. Both CBRCB and CPRCB are more robust against array steering vector errors and finite sample size problems than SCB and have better resolution and interference suppression capability than data-independent beamformers. Moreover, they both can be efficiently implemented. The effectiveness of CBRCB and CPRCB is demonstrated via a number of simulated and experimental examples.

Wang, Zhisong; Li, Jian; Stoica, Petre; Nishida, Toshikazu; Sheplak, Mark

2004-09-01

85

Observation of damage evolution in polymer bonded explosives using acoustic emission and digital image correlation  

Microsoft Academic Search

The Acoustic Emission (AE) and Digital Image Correlation (DIC) methods have been combined to measure and evaluate the damage evolution of Polymer Bonded Explosives (PBXs) under uniaxial compression. The global damage evolution was measured by AE and the local (spatial) distribution of damage observed by DIC. It was found that a Dominant Localization Band (DLB) plays a key role in

Xian Wang; Shaopeng Ma; Yingtao Zhao; Zhongbin Zhou; Pengwan Chen

2011-01-01

86

MR acoustic radiation force imaging: In vivo comparison to ultrasound motion tracking  

PubMed Central

MR acoustic radiation force (ARF) imaging was developed for measuring tissue elastic properties using focused ultrasound to deliver a localized tissue motion. In this study, an imaging ultrasound transducer was mounted on the focused ultrasound transducer and ultrasound motion tracking was performed simultaneously to MR ARF imaging to validate the measurement results. In vivo studies on rabbit thigh muscle were performed and results showed a general agreement between the two modalities (slope=0.96 and R2=0.67). The temporal information by the ultrasound measurement indicates that the parameters in MR ARF imaging should be optimized according to the tissue type, acoustic power, and envelope and frequency of the ARF modulation.

Huang, Yuexi; Curiel, Laura; Kukic, Aleksandra; Plewes, Donald B.; Chopra, Rajiv; Hynynen, Kullervo

2009-01-01

87

High range resolution medical acoustic vascular imaging with frequency domain interferometry.  

PubMed

For high range resolution acoustic vascular imaging we apply frequency domain interferometry and Capon method to a few frames of in-phase and quadrature (IQ) data acquired by a commercial ultrasonographic device. To suit the adaptive beamforming algorithm to medical acoustic imaging we employ three techniques; frequency averaging, whitening, and pseudo-double RF data conversion. The proposed method detected two couples of boundaries 0.26 and 0.19 mm apart using a single frame and two frames of IQ data, respectively, where each couple of boundaries is indistinguishable from a single boundary utilizing B-mode images. Further this algorithm could depict a swine femoral artery with higher range resolution than conventional B-mode imaging. These results indicate the potential of the proposed method for the range resolution improvement in ultrasonography, originating the progress in detection of vessel stenosis. PMID:21096063

Taki, Hirofumi; Taki, Kousuke; Sakamoto, Takuya; Yamakawa, Makoto; Shiina, Tsuyoshi; Sato, Toru

2010-01-01

88

Electromagnetic-Acoustic Modeling of Fields Induced by Gradient Pulses in Diffusion Tensor Magnetic Resonance Imaging  

NASA Astrophysics Data System (ADS)

Diffusion tensor magnetic resonance imaging (DT-MRI) has recently gained popularity because of its capabilities in axonography of the central nervous system. Fast imaging sequences are used to reduce motion induced distortion effects on the diffusion signal, resulting in low signal levels, loud acoustic noise, and occasional peripheral nerve stimulation. Eddy current induced by diffusion gradient pulses is also a challenge to DT-MRI. Magnetic field associated with the eddy current is a major source of artifacts in scanner images. This paper introduces a finite element modeling of electromagnetic and acoustic fields in DT-MRI sequences. The analysis involves three dimensional modeling of the scanner and its interaction with pulses applied to gradient coils. Efficient modeling of induced fields is essential in optimizing parameter settings and improving performance of this imaging modality.

Elshafiey, I.; Melapudi, V. R.; Udpa, L.

2006-03-01

89

Acoustic imaging of underground storage tank wastes: A feasibility study. Final report  

SciTech Connect

The objectives for this underground storage tank (UST) imaging investigation are: (1) to assess the feasibility of using acoustic methods in UST wastes, if shown to be feasible, develop and assess imaging strategies; (2) to assess the validity of using chemical simulants for the development of acoustic methods and equipment. This investigation examined the velocity of surrogates, both salt cake and sludge surrogates. In addition collected seismic cross well data in a real tank (114-TX) on the Hanford Reservation. Lastly, drawing on the knowledge of the simulants and the estimates of the velocities of the waste in tank 114-TX the authors generated a hypothetical model of waste in a tank and showed that non-linear travel time tomographic imaging would faithfully image that stratigraphy.

Turpening, R.; Zhu, Z.; Caravana, C.; Matarese, J. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Earth Resources Lab.; Turpening, W. [Elohi Geophysical, Inc., Houston, TX (United States)

1995-12-31

90

An acoustic charge transport imager for high definition television applications  

NASA Astrophysics Data System (ADS)

The progress during the third six month period of the project is presented. This includes both experimental and theoretical work on the acoustic charge transport (ACT) portion of the chip, the theoretical program modeling of the avalanche photodiode (APD) and the charge overflow transistor, and the materials growth and fabrication part of the program. Among other results from a comprehensive experimental study, it was found that the use of a ZnO thin film piezoelectric overlay can reduce the RF power consumption of a typical ACT device from 28 dBm to 8 dBm.

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

1993-05-01

91

Synchronization of Infrared Imaging with Acoustic Emission for Depth Measurement of Discrete Failure Events in Composites  

NASA Astrophysics Data System (ADS)

Infrared (IR) imaging together with acoustic emission (AE) sensing are employed to follow the progression to failure of graphite epoxy test panels under dynamic loading. Acoustic emission generated by fiber breaks and matrix cracks define the ``zero'' time for surface observation by an IR camera of the deep heat source from that event. The AE clock and IR clock must be synchronized. The timing of the surface event relative to ``zero'' permits the calculation of its depth. The position and depth of the IR events can then be related to crack evolution and modeling for failure prediction.

Knight, B.; Ringermacher, H. I.; Li, Jian; Plotnikov, Y. A.; Aksel, Gulperi; Howard, D. R.; Thompson, J. L.

2007-03-01

92

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

93

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

94

Epipolar Geometry of Opti-Acoustic Stereo Imaging  

Microsoft Academic Search

Optical and sonar cameras are suitable imaging systems for inspecting underwater structures, both in regular maintenance and security operations. Despite their high resolution, optical systems have limited visibility range when deployed in turbid waters. In contrast, the new generation of high-frequency (MHz) forward-scan sonar cameras can provide images with enhanced target details in highly turbid waters though their range is

Shahriar Negahdaripour

2007-01-01

95

Synthetic aperture acoustic imaging of canonical targets with a 2-15 kHz linear FM chirp  

NASA Astrophysics Data System (ADS)

Synthetic aperture image reconstruction applied to outdoor acoustic recordings is presented. Acoustic imaging is an alternate method having several military relevant advantages such as being immune to RF jamming, superior spatial resolution, capable of standoff side and forward-looking scanning, and relatively low cost, weight and size when compared to 0.5 - 3 GHz ground penetrating radar technologies. Synthetic aperture acoustic imaging is similar to synthetic aperture radar, but more akin to synthetic aperture sonar technologies owing to the nature of longitudinal or compressive wave propagation in the surrounding acoustic medium. The system's transceiver is a quasi mono-static microphone and audio speaker pair mounted on a rail 5meters in length. Received data sampling rate is 80 kHz with a 2- 15 kHz Linear Frequency Modulated (LFM) chirp, with a pulse repetition frequency (PRF) of 10 Hz and an inter-pulse period (IPP) of 50 milliseconds. Targets are positioned within the acoustic scene at slant range of two to ten meters on grass, dirt or gravel surfaces, and with and without intervening metallic chain link fencing. Acoustic image reconstruction results in means for literal interpretation and quantifiable analyses. A rudimentary technique characterizes acoustic scatter at the ground surfaces. Targets within the acoustic scene are first digitally spotlighted and further processed, providing frequency and aspect angle dependent signature information.

Vignola, Joseph F.; Judge, John A.; Good, Chelsea E.; Bishop, Steven S.; Gugino, Peter M.; Soumekh, Mehrdad

2011-05-01

96

Internal wave effects on high-frequency acoustic propagation to horizontal arrays-experiment and implications to imaging  

Microsoft Academic Search

An experiment was carried out over a nine day period from August 18 to 27, 1996 to examine acoustic wave propagation in random media at frequencies applicable to synthetic aperture sonar. The objective was to test experimentally the hypothesized imaging effects of variations in the sound speed along two different acoustic paths as put forth by F.S. Henyey et al.

Kevin L. Williams; Frank S. Henyey; Daniel Rouseff; Stephen A. Reynolds; Terry E. Ewart

2001-01-01

97

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

98

ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS  

SciTech Connect

During this phase of the project the research team concentrated on acquisition of acoustic emission data from the high porosity rock samples. The initial experiments indicated that the acoustic emission activity from high porosity Danian chalk were of a very low amplitude. Even though the sample underwent yielding and significant plastic deformation the sample did not generate significant AE activity. This was somewhat surprising. These initial results call into question the validity of attempting to locate AE activity in this weak rock type. As a result the testing program was slightly altered to include measuring the acoustic emission activity from many of the rock types listed in the research program. The preliminary experimental results indicate that AE activity in the sandstones is much higher than in the carbonate rocks (i.e., the chalks and limestones). This observation may be particularly important for planning microseismic imaging of reservoir rocks in the field environment. The preliminary results suggest that microseismic imaging of reservoir rock from acoustic emission activity generated from matrix deformation (during compaction and subsidence) would be extremely difficult to accomplish.

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

2001-01-31

99

Evaluation of Acoustic Anisotropy to Image Defects in Weld Metal by Ultrasonic Phased Array  

NASA Astrophysics Data System (ADS)

An ultrasonic phased array (PA) does not work well in some weld metals owing to the strong acoustic anisotropy. However, the analysis of anisotropy for the compensation of the shift of the defect image in the PA has not been performed. In this study, we compared the results of imaging a slit in a Ni-based weld metal, commercially available as Inconel alloy 600, in an experiment and in simulations using the analytical solution of group velocity or the finite-difference time-domain (FDTD) method. As a result, we succeeded in reproducing the shift and broadening of the defect image obtained in an experiment by the simulations.

Shintaku, Yohei; Ohara, Yoshikazu; Yamanaka, Kazushi

2011-09-01

100

SAW-CTD (Surface Acoustic Wave-Charge Trasfer Devices) Serial to Parallel Imager and Waveform Recorder.  

National Technical Information Service (NTIS)

A device for the high speed recording of photon images and nonrepetitive electrical waveforms which comprises a waveform recorder wherein surface acoustic waves excited in a can be GaAs, not layered piezoelectric-insulator-semiconductor layered structure ...

R. R. Whitlock N. A. Papanicolaou

1985-01-01

101

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 non-transparent 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.; Leskovar, B.; Turko, B.T.

1984-02-01

102

An Objective Focussing Measure for Acoustically Obtained Images  

NASA Astrophysics Data System (ADS)

In scientific literature many parameters of an image sharpness can be defined, that can be used for the evaluation of display energy concentration (EC). This paper proposes a new, simple approach to EC quantitative evaluation in spectrograms, which are used for the analysis and visualization of sonar signals. The presented approach of the global-image EC measure was developed to the evaluation of EC in arbitrary direction (or at an arbitrary angle) and along an arbitrary path that is contained within the displayed area. The proposed measures were used to establish optimum spectrograph parameters, subject to high EC in images, in particular the type and width of the window. Moreover, the paper defines the marginal EC distributions that can be used in sonar signal detection as a support to the main detector.

Czarnecki, Krzysztof; Moszy?ski, Marek; Rojewski, Miros?aw

103

Photoacoustic imaging in attenuating acoustic media based on strongly causal models  

NASA Astrophysics Data System (ADS)

In this paper we derive time reversal imaging functionals for two strongly causal acoustic attenuation models, which have been proposed recently. The time reversal techniques are based on recently proposed ideas of Ammari et al for the thermo-viscous wave equation. Here and there an asymptotic analysis provides reconstruction functionals from first order corrections for the attenuating effect. In addition, we present a novel approach for higher order corrections.

Kalimeris, Konstantinos; Scherzer, Otmar

2013-11-01

104

Near-Field Imaging with Sound: An Acoustic STM Model  

ERIC Educational Resources Information Center

|The invention of scanning tunneling microscopy (STM) 30 years ago opened up a visual window to the nano-world and sparked off a bunch of new methods for investigating and controlling matter and its transformations at the atomic and molecular level. However, an adequate theoretical understanding of the method is demanding; STM images can be…

Euler, Manfred

2012-01-01

105

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

106

Singular value spectra of transmission mode acoustic time reversal imaging  

NASA Astrophysics Data System (ADS)

We have formalized the theory of transmission mode time reversal imaging for arbitrary transducer geometry. Although it is not possible to implement such a system in practice, we have shown that transmission mode time reversal imaging is achievable a posteriori from the scattered field time series as measured at the receivers. We apply this theory to studying the singular value spectra of objects buried in the ground. We provide simulated finite-difference time-domain (FDTD) examples designed to model the case of geophysical vertical seismic profiling in which a series of sources are excited on the surface and the scattered fields are measured on a chain of receivers in a bore hole. A single, non-point scatterer can have multiple singular values dependent upon the scatterer's physical properties. We study the relationship between the singular value spectra and these physical properties.

Lehman, Sean K.; Devaney, Anthony J.

2002-05-01

107

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

108

Elastography of soft materials and tissues by holographic imaging of surface acoustic waves.  

PubMed

We use optical interferometry to capture coherent surface acoustic waves for elastographic imaging. An inverse method is employed to convert multi-frequency data into an elastic depth profile. Using this method, we image elastic properties over a 55 mm range with <5 mm resolution. For relevance to breast cancer detection, we employ a tissue phantom with a tumor-like inclusion. Holographic elastography is also shown to be well-behaved in ex vivo tissue, revealing the subsurface position of a bone. Because digital holography can assess waves over a wide surface area, this constitutes a flexible new platform for large volume and non-invasive elastography. PMID:23038528

Mohan, Karan D; Oldenburg, Amy L

2012-08-13

109

ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS  

SciTech Connect

During the sixth quarter of this research project the research team developed a method and the experimental procedures for acquiring the data needed for ultrasonic tomography of rock core samples under triaxial stress conditions as outlined in Task 10. Traditional triaxial compression experiments, where compressional and shear wave velocities are measured, provide little or no information about the internal spatial distribution of mechanical damage within the sample. The velocities measured between platen-to-platen or sensor-to-sensor reflects an averaging of all the velocities occurring along that particular raypath across the boundaries of the rock. The research team is attempting to develop and refine a laboratory equivalent of seismic tomography for use on rock samples deformed under triaxial stress conditions. Seismic tomography, utilized for example in crosswell tomography, allows an imaging of the velocities within a discrete zone within the rock. Ultrasonic or acoustic tomography is essentially the extension of that field technology applied to rock samples deforming in the laboratory at high pressures. This report outlines the technical steps and procedures for developing this technology for use on weak, soft chalk samples. Laboratory tests indicate that the chalk samples exhibit major changes in compressional and shear wave velocities during compaction. Since chalk is the rock type responsible for the severe subsidence and compaction in the North Sea it was selected for the first efforts at tomographic imaging of soft rocks. Field evidence from the North Sea suggests that compaction, which has resulted in over 30 feet of subsidence to date, is heterogeneously distributed within the reservoir. The research team will attempt to image this very process in chalk samples. The initial tomographic studies (Scott et al., 1994a,b; 1998) were accomplished on well cemented, competent rocks such as Berea sandstone. The extension of the technology to weaker samples is more difficult but potentially much more rewarding. The chalk, since it is a weak material, also attenuates wave propagation more than other rock types. Three different types of sensors were considered (and tested) for the tomographic imaging project: 600 KHz PZT, 1 MHz PZT, and PVDF film sensors. 600 KHz PZT crystals were selected because they generated a sufficiently high amplitude pulse to propagate across the damaged chalk. A number of different configurations were considered for placement of the acoustic arrays. It was decided after preliminary testing that the most optimum arrangement of the acoustic sensors was to place three arrays of sensors, with each array containing twenty sensors, around the sample. There would be two horizontal arrays to tomographically image two circular cross-sectional planes through the rock core sample. A third array would be vertically oriented to provide a vertical cross-sectional view of the sample. A total of 260 acoustic raypaths would be shot and acquired in the horizontal acoustic array to create each horizontal tomographic image. The sensors can be used as both acoustic sources or as acoustic each of the 10 pulsers to the 10 receivers.

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

2002-11-18

110

ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS  

SciTech Connect

During the seven quarter of the project the research team analyzed some of the acoustic velocity data and rock deformation data. The goal is to create a series of ''deformation-velocity maps'' which can outline the types of rock deformational mechanisms which can occur at high pressures and then associate those with specific compressional or shear wave velocity signatures. During this quarter, we began to analyze both the acoustical and deformational properties of the various rock types. Some of the preliminary velocity data from the Danian chalk will be presented in this report. This rock type was selected for the initial efforts as it will be used in the tomographic imaging study outlined in Task 10. This is one of the more important rock types in the study as the Danian chalk is thought to represent an excellent analog to the Ekofisk chalk that has caused so many problems in the North Sea. Some of the preliminary acoustic velocity data obtained during this phase of the project indicates that during pore collapse and compaction of this chalk, the acoustic velocities can change by as much as 200 m/s. Theoretically, this significant velocity change should be detectable during repeated successive 3-D seismic images. In addition, research continues with an analysis of the unconsolidated sand samples at high confining pressures obtained in Task 9. The analysis of the results indicate that sands with 10% volume of fines can undergo liquefaction at lower stress conditions than sand samples which do not have fines added. This liquefaction and/or sand flow is similar to ''shallow water'' flows observed during drilling in the offshore Gulf of Mexico.

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

2002-11-18

111

Novel Acoustic Radiation Force Impulse Imaging Methods for Visualization of Rapidly Moving Tissue  

PubMed Central

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.

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

2010-01-01

112

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

113

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

114

Defect avoidance in a 3-D heterogeneous sensor [acoustic\\/seismic\\/active pixel\\/IR imaging sensor array  

Microsoft Academic Search

A 3D heterogeneous sensor using a stacked chip is investigated. Optical active pixel sensor (APS) and IR bolometer detectors are combined to create a multispectral pixel for aligned color and infrared imaging. An acoustic and seismic micromachined sensor array obtains sound spectral and directional information. For the optical\\/IR imagers, fault tolerant APS cells and software methods are used for defect

Glenn H. Chapman; Vijay Jain; Shekhar Bhansali

2004-01-01

115

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

116

Distribution and height of methane bubble plumes on the Cascadia Margin characterized by acoustic imaging  

NASA Astrophysics Data System (ADS)

Submersible investigations of the Cascadia accretionary complex have identified localized venting of methane gas bubbles in association with gas hydrate occurrence. Acoustic profiles of these bubble plumes in the water column in the vicinity of Hydrate Ridge offshore Oregon provide new constraints on the spatial distribution of these gas vents and the fate of the gas in the water column. The gas vent sites remained active over the span of two years, but varied dramatically on time scales of a few hours. All plumes emanated from local topographic highs near the summit of ridge structures. The acoustic images of the bubble plumes in the water column disappear at water depths between 500 to 460 m, independent of the seafloor depth. This coincides with the predicted depth of the gas hydrate stability boundary of 510 to 490 m, suggesting that the presence of a hydrate skin on the bubble surface prevents them from rapid dissolution. The upper limit of the acoustic bubble plumes at 460 m suggests that dissolution of the residual bubbles is relatively rapid above the hydrate stability zone.

Heeschen, Katja U.; Tréhu, Anne M.; Collier, Robert W.; Suess, Erwin; Rehder, Gregor

2003-06-01

117

Contribution of the supraglottic larynx to the vocal product: imaging and acoustic analysis  

NASA Astrophysics Data System (ADS)

Horizontal supraglottic laryngectomy is a surgical procedure to remove a mass lesion located in the region of the pharynx superior to the true vocal folds. In contrast to full or partial laryngectomy, patients who undergo horizontal supraglottic laryngectomy often present with little or nor involvement to the true vocal folds. This population provides an opportunity to examine the acoustic consequences of altering the pharynx while sparing the laryngeal sound source. Acoustic and magnetic resonance imaging (MRI) data were acquired in a group of four patients before and after supraglottic laryngectomy. Acoustic measures included the identification of vocal tract resonances and the fundamental frequency of the vocal fold vibration. 3D reconstruction of the pharyngeal portion of each subjects' vocal tract were made from MRIs taken during phonation and volume measures were obtained. These measures reveal a variable, but often dramatic difference in the surgically-altered area of the pharynx and changes in the formant frequencies of the vowel/i/post surgically. In some cases the presence of the tumor created a deviation from the expected formant values pre-operatively with post-operative values approaching normal. Patients who also underwent radiation treatment post surgically tended to have greater constriction in the pharyngeal area of the vocal tract.

Gracco, L. Carol

1996-04-01

118

Acoustic radiation force impulse (ARFI) imaging of zebrafish embryo by high-frequency coded excitation sequence.  

PubMed

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 (LiNbO?) 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. PMID:22101757

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

2011-11-19

119

Compton scattering studies of 4f ferromagnetism  

NASA Astrophysics Data System (ADS)

Ferromagnetism can be studied in Compton scattering experiments, which use high-energy, elliptically polarised synchrotron radiation. The basis of the method and its interpretation in terms of site-specific moments will be explained and illustrated by a series of examples of archetypal compounds. For example, the hexaborides exhibit a wide range of electronic properties. Data will be presented for the heavy Fermion system CeB6 and the controversial ferromagnet Ca1-xLaxB6. Undoped CeB6 exhibits a delocalised spin moment, more characteristic of the 5d than the 4f orbital. Whereas the magnetism in the Ca1-xLaxB6 system has been suggested to be an extrinsic effect arising from iron contamination, our data indicate that the magnetism is intrinsic and inconsistent with what would be expected for an iron 3d moment. This supports the proposal that this system is, indeed, a weak itinerant ferromagnet. In Ru2SrGdCu208, we observe a combination of Gd 4f, Gd 5d and Ru 4d moments and the 5d moment appears to flip orientation below the Néel temperature.

Cooper, M. J.; Duffy, J. A.; Banfield, Z. F.; Bebb, A. M.; Blaauw, L.; Shenton-Taylor, C.; Steer, C.; Taylor, J. W.

2006-11-01

120

A novel imaging technique based on the spatial coherence of backscattered waves: demonstration in the presence of acoustical clutter  

NASA Astrophysics Data System (ADS)

In the last 20 years, the number of suboptimal and inadequate ultrasound exams has increased. This trend has been linked to the increasing population of overweight and obese individuals. The primary causes of image degradation in these individuals are often attributed to phase aberration and clutter. Phase aberration degrades image quality by distorting the transmitted and received pressure waves, while clutter degrades image quality by introducing incoherent acoustical interference into the received pressure wavefront. Although significant research efforts have pursued the correction of image degradation due to phase aberration, few efforts have characterized or corrected image degradation due to clutter. We have developed a novel imaging technique that is capable of differentiating ultrasonic signals corrupted by acoustical interference. The technique, named short-lag spatial coherence (SLSC) imaging, is based on the spatial coherence of the received ultrasonic wavefront at small spatial distances across the transducer aperture. We demonstrate comparative B-mode and SLSC images using full-wave simulations that include the effects of clutter and show that SLSC imaging generates contrast-to-noise ratios (CNR) and signal-to-noise ratios (SNR) that are significantly better than B-mode imaging under noise-free conditions. In the presence of noise, SLSC imaging significantly outperforms conventional B-mode imaging in all image quality metrics. We demonstrate the use of SLSC imaging in vivo and compare B-mode and SLSC images of human thyroid and liver.

Dahl, Jeremy J.; Pinton, Gianmarco F.; Lediju, Muyinatu; Trahey, Gregg E.

2011-03-01

121

Improving the resolution of three-dimensional acoustic imaging with planar phased arrays  

NASA Astrophysics Data System (ADS)

This paper examines and compares two methods of improving the quality of three-dimensional beamforming with phased microphone arrays. The intended application is the detection of aerodynamic noise sources on wind turbines. Both methods employ Fourier based deconvolution. The first method involves a transformation of coordinates that tends to make the response to a point source, the point spread function, more shift invariant. The result is a significant improvement in sound source imaging in the transformed coordinate system. However, the inverse transformation to Cartesian coordinates introduces range dependent resolution limitations because of the irregular distribution of the focal points. The second method combines the transformation of coordinates with an alternative scanning technique. This method can be used in near field three-dimensional acoustic imaging to produce maps free of sidelobes and with constant resolution. The robustness of the proposed methods is validated both with computer simulations and experimentally.

Xenaki, Angeliki; Jacobsen, Finn; Fernandez-Grande, Efren

2012-04-01

122

Noncontact photoacoustic imaging achieved by using a low-coherence interferometer as the acoustic detector.  

PubMed

We report on a noncontact photoacoustic imaging (PAI) technique in which a low-coherence interferometer [(LCI), optical coherence tomography (OCT) hardware] is utilized as the acoustic detector. A synchronization approach is used to lock the LCI system at its highly sensitive region for photoacoustic detection. The technique is experimentally verified by the imaging of a scattering phantom embedded with hairs and the blood vessels within a mouse ear in vitro. The system's axial and lateral resolutions are evaluated at 60 and 30??m, respectively. The experimental results indicate that PAI in a noncontact detection mode is possible with high resolution and high bandwidth. The proposed approach lends itself to a natural integration of PAI with OCT, rather than a combination of two separate and independent systems. PMID:22002357

Wang, Yi; Li, Chunhui; Wang, Ruikang K

2011-10-15

123

X-ray imaging of the surface acoustic wave propagation in La3Ga5SiO14 crystal  

NASA Astrophysics Data System (ADS)

Direct imaging of a 10 ?m surface acoustic wave (SAW) propagation in a La3Ga5SiO14 crystal was obtained on the European Synchrotron Radiation Facility (ESRF) synchrotron radiation source in the sagittal diffraction geometry using the Talbot effect. Imaging of the SAW wave field with the period 10 ?m was observed at a distance corresponding to the half of the Talbot distance. It is shown that the presence of the growth banding in the crystal does not influence the propagation of acoustic wave-fields in the crystal nor does it cause a distortion of the SAW wave front.

Roshchupkin, Dmitry; Ortega, Luc; Snigirev, Anatolii; Snigireva, Iraida

2013-10-01

124

Acoustic radiation force impulse and supersonic shear imaging versus transient elastography for liver fibrosis assessment.  

PubMed

Our study compared three elastographic methods-transient elastography (TE), acoustic radiation force impulse (ARFI) imaging and supersonic shear imaging (SSI)-with respect to the feasibility of their use in liver fibrosis evaluation. We also compared the performance of ARFI imaging and SSI, with TE as the reference method. The study included 332 patients, with or without hepatopathies, in which liver stiffness was evaluated using TE, ARFI and SSI. Reliable measurements were defined as a median value of 10 (TE, ARFI imaging) or 5 (SSI) liver stiffness measurements with a success rate ?60% and an interquartile range interval <30%. A significantly higher percentage of reliable measurements were obtained using ARFI than by using TE and SSI: 92.1% versus 72.2% (p < 0.0001) and 92.1% versus 71.3% (p < 0.0001). Higher body mass index and older age were significantly associated with inability to obtain reliable measurements of liver stiffness using TE and SSI. In 55.4% of patients, reliable liver stiffness measurements were obtained using all three elastographic methods, and ARFI imaging and TE were similarly accurate in diagnosing significant fibrosis and cirrhosis, with TE as the reference method. PMID:23932281

Sporea, Ioan; Bota, Simona; Jurchis, Ana; Sirli, Roxana; Gr?dinaru-Tasc?u, Oana; Popescu, Alina; Ratiu, Iulia; Szilaski, Milana

2013-08-09

125

Algorithms for image restoration from acoustic-optical tunable-filter multispectral sensors  

NASA Astrophysics Data System (ADS)

Multispectral sensing with acoustic-optical tunable filters (AOTFs) offers several advantages for the automated recognition of targets and classification of terrain features. High spectral resolution, real-time selection of the wavelength, and dual polarization are among the chief advantages. AOTFs employed in an imaging sensor usually involve a shifting of the spatial image on the focal plane as the wavelength is sampled. This results in a misregistered data hypercube where selected spectral images are not aligned spatially. This can severely limit the sensor's application if not accounted for and rectified. An edged-based routine operating on data taken with the Real-Time Multispectral Sensor (RTMS), an imaging AOTF sensor produced by the Jet Propulsion Laboratory, will be described and demonstrated in this paper. The method is completely general and is capable of removing misregistration for any reason (e.g. platform jitter) not only for AOTF-induced misregistration. This paper will also provide examples of image classification within several scenes collected by RTMS during tower data collection. The basis for the classification is spectral and/or polarization characteristics of the targets and scenes.

Noren, Keith; Loyd, Jody; Elgin, Douglas; Kerstiens, Bernard

1998-07-01

126

ACOUSTICAL IMAGING AND MECHANICAL PROPERTIES OF SOFT ROCK AND MARINE SEDIMENTS  

SciTech Connect

The oil and gas industry has encountered significant problems in the production of oil and gas from weak rocks (such as chalks and limestones) and from unconsolidated sand formations. Problems include subsidence, compaction, sand production, and catastrophic shallow water sand flows during deep water drilling. Together these cost the petroleum industry hundreds of millions of dollars annually. The goals of this first quarterly report is to document the progress on the project to provide data on the acoustic imaging and mechanical properties of soft rock and marine sediments. The project is intended to determine the geophysical (acoustic velocities) rock properties of weak, poorly cemented rocks and unconsolidated sands. In some cases these weak formations can create problems for reservoir engineers. For example, it cost Phillips Petroleum 1 billion dollars to repair of offshore production facilities damaged during the unexpected subsidence and compaction of the Ekofisk Field in the North Sea (Sulak 1991). Another example is the problem of shallow water flows (SWF) occurring in sands just below the seafloor encountered during deep water drilling operations. In these cases the unconsolidated sands uncontrollably flow up around the annulus of the borehole resulting in loss of the drill casing. The $150 million dollar loss of the Ursa development project in the U.S. Gulf Coast resulted from an uncontrolled SWF (Furlow 1998a,b; 1999a,b). The first three tasks outlined in the work plan are: (1) obtain rock samples, (2) construct new acoustic platens, (3) calibrate and test the equipment. These have been completed as scheduled. Rock Mechanics Institute researchers at the University of Oklahoma have obtained eight different types of samples for the experimental program. These include: (a) Danian Chalk, (b) Cordoba Cream Limestone, (c) Indiana Limestone, (d) Ekofisk Chalk, (e) Oil Creek Sandstone, (f) unconsolidated Oil Creek sand, and (g) unconsolidated Brazos river sand. These weak rocks and sands are intended to represent analogs to the formations that present oil and gas engineers with problems during oil and gas production and drilling operations. A series of new axial acoustic sensors have been constructed (and tested) to allow measurement of compressional and shear wave velocities during high pressure triaxial tests on these weak rock and sand samples. In addition, equipment to be utilized over the next 18 months of the project have tested and calibrated. These include the load frames, triaxial pressure cells, pressure sensors, load cells, extensometers, and oscilloscopes have been calibrated and tested. The multichannel acoustic emission and acoustic pulse transmission systems have also been tested. Graduate research assistant, research faculty, and the laboratory technician have begun Tasks 4 and 5 which involve preparing the sand samples and rock samples for testing. The construction of the lateral acoustic sensors has also been started during this quarter as outlined in the project timeline. With the equipment having been tested and calibrated, and the samples now being prepared, the experiments are on schedule to be started in April, 2001.

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

2001-04-01

127

Evaluation of real-time acoustical holography for breast imaging and biopsy guidance  

NASA Astrophysics Data System (ADS)

Ultrasound is an attractive modality for adjunctive characterization of certain breast lesions, but it is not considered specific for cancer and it is not recommended for screening. An imaging technique remarkably different from pulse-echo ultrasound, termed Optical SonographyTM (Advanced Diagnostics, Inc.), uses the through-transmission signal. The method was applied to breast examinations in 41 asymptomatic and symptomatic women ranging in age from 18 to 83 years to evaluate this imaging modality for detection and characterization of breast disease and normal tissue. This approach uses coherent sound and coherent light to produce real-time, large field-of-view images with pronounced edge definition in soft tissues of the body. The system patient interface was modified to improve coupling to the breast and bring the chest wall to within 3 cm of the sound beam. System resolution (full width half maximum of the line-spread function) was 0.5 mm for a swept-frequency beam centered at 2.7 MHz. Resolution degrades slightly in the periphery of the very large 15.2-cm field of view. Dynamic range of the reconstructed 'raw' images (no post processing) was 3000:1. Included in the study population were women with dense parenchyma, palpable ductal carcinoma in situ with negative mammography, superficial and deep fibroadenomas, and calcifications. Successful breast imaging was performed in 40 of 41 women. These images were then compared with images generated using conventional X-ray mammography and pulse-echo ultrasound. Margins of lesions and internal textures were particularly well defined and provided substantial contrast to fatty and dense parenchyma. In two malignant lesions, Optical SonographyTM appeared to approximate more closely tumor extent compared to mammography than pulse-echo sonography. These preliminary studies indicate the method has unique potential for detecting, differentiating, and guiding the biopsy of breast lesions using real-time acoustical holography.

Lehman, Constance D.; Andre, Michael P.; Fecht, Barbara A.; Johansen, Jennifer M.; Shelby, Ronald L.; Shelby, Jerod O.

1999-05-01

128

Microbubble Evolution due to Acoustic Droplet Vaporization: Observation via Ultra-High Speed Imaging  

NASA Astrophysics Data System (ADS)

A potential therapy for cancer, gas embolotherapy, is being researched. It involves selective, acoustic vaporization of liquid PFC droplets (encapsulated by albumin shells) into gas bubbles that can lodge in the nearby vasculature to achieve occlusion of blood flow and ``starvation'' of the tumor. The shape evolution of microbubbles due to acoustic droplet vaporization in a 120-micron flow tube at room temperature was imaged via a 8-channel, 16-frames ultra-high-speed camera, at rates of several million frames per second. Initial droplet size ranges from 0.05 to 0.95 times tube diameter D. The bubbles followed an elliptical evolution more closely than a circular evolution. Depending on the initial droplet size, bubbles of two- to six-fold diameters were produced within a few microseconds. Growth-collapse cycles were observed in cases where the albumin shell was broken completely. For large droplets, internal phase change events could be observed. When small droplets were lined up in close proximity, coalescence was achieved for dual as well as multiple droplets. The experimental results show general consensus with a computational model by Ye & Bull (2004) and a detailed comparison would be worthwhile.

Wong, Zheng Zheng; Kripfgans, Oliver; Fowlkes, J. Brian; Bull, Joseph

2008-11-01

129

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

130

ee4f?-A program for e+e--->4f,4f? with nonzero fermion masses  

NASA Astrophysics Data System (ADS)

A computer program ee4f? for calculating cross-sections of any four fermion final state of e+e--annihilation at high energy and the corresponding bremsstrahlung reaction that is possible in the framework of the Standard Model is presented. As the fermion masses are arbitrary, the cross-sections for channels that do not contain e+ and/or e- in the final state can be computed without any collinear cut, the on-shell top quark production can be studied and the Higgs boson exchange can be incorporated in a consistent way. The program can be used as a Monte Carlo generator of unweighted events as well. Program summary Title of program: ee4f? Version: 1.0 (February 2004) Catalogue identifier: ADTQ Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADTQ Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions: none Computers: all Operating systems: Unix/Linux Programming language used: FORTRAN 90 CPC Program Library subprograms used: RANLUX, ACPR RANLUX 79 (1994) 111-a random number generator Memory required to execute with typical data: 4.0 Mb No. of bits in a word: 32 No. of bytes in distributed program, including test data, etc.: 364490 No. of lines in distributed program, including test data, etc.: 45278 Distribution format: tar gzip file Nature of physical problem: Description of all e+e--->4 fermions and corresponding bremsstrahlung reactions that are possible in the Standard Model (SM) to lowest order and with nonzero fermion masses at center of mass energies typical for next generation linear colliders. Such reactions are relevant, typically, for W-pair or intermediate mass Higgs boson production and decay. Method of solution: Matrix elements are calculated with the helicity amplitude method. The phase space integration is performed numerically utilizing a multi-channel Monte Carlo method. Restrictions on complexity of the problem: No higher order effects are taken into account, except for assuming the fine structure constant and the strong coupling at the appropriate scale and partial summation of those one particle irreducible loop corrections which are inducing the (fixed) finite widths of unstable particles. Typical running time: The running time depends strongly on a selected channel and desired precision of the result. The results of the appended test run have been obtained on a 800 MHz Pentium III processor with the use of Absoft FORTRAN 90 compiler in about 9 minutes. In order to obtain a precision level below one per mile a few million calls to the integrand are required. This results in less than one hour running time for the fastest channel e+e--->???¯????¯? and more than 100 hours running time for the slowest channel e+e--->e+e-e+e-. However, the typical running time for channels that are relevant for the W-pair or Higgs boson production is several hours.

Kolodziej, Karol; Jegerlehner, Fred

2004-05-01

131

Invariant correlation filter with linear phase coefficient holographic realization in 4-F correlator  

NASA Astrophysics Data System (ADS)

Realization of distortion invariant correlation filters in optical image correlators open possibilities for object identification with remarkably high computational capabilities. Application of the linear phase coefficient composite filter (LPCCF) is attractive for recognition of binary edged images. We use methods of digital holographic synthesis to realize LPCCF in a coherent 4-F correlator as a computer-generated amplitude holographic filter. A high resolution spatial light modulator (SLM) has to be implemented for such a filter representation. Transparency limitations of high frame rate and high resolution SLM's and its effect on recognition performance of holographic filter in the 4-F correlator are discussed in the given paper.

Evtikhiev, Nickolay N.; Starikov, Sergey N.; Shaulskiy, Dmitriy V.; Starikov, Rostislav S.; Zlokazov, Evgeny Yu.

2011-06-01

132

High-Resolution Acoustic-Radiation-Force-Impulse Imaging for Assessing Corneal Sclerosis  

PubMed Central

In ophthalmology, detecting the biomechanical properties of the cornea can provide valuable information about various corneal pathologies, including keratoconus and the phototoxic effects of ultraviolet radiation on the cornea. Also, the mechanical properties of the cornea can be used to evaluate the recovery from corneal refractive surgeries. Therefore, noninvasive and high-resolution estimation of the stiffness distribution in the cornea is important in ophthalmic diagnosis. The present study established a method for high-resolution acoustic-radiation-force-impulse (ARFI) imaging based on a dual-frequency confocal transducer in order to obtain a relative stiffness map, which was used to assess corneal sclerosis. An 11-MHz pushing element was used to induce localized displacements of tissue, which were monitored by a 48-MHz imaging element. Since the tissue displacements are directly correlated with the tissue elastic properties, the stiffness distribution in a tiny region of the cornea can be found by a mechanical B/D scan. The experimental system was verified using tissue-mimicking phantoms that included different geometric structures. Ex vivo cornea experiments were carried out using fresh porcine eyeballs. Corneas with localized sclerosis were created artificially by the injection of a formalin solution. The phantom experiments showed that the distributions of stiffness within different phantoms can be recognized clearly using ARFI imaging, and the measured lateral and axial resolutions of this imaging system were 177 and 153 ?m, respectively. The ex vivo experimental results from ARFI imaging showed that a tiny region of localized sclerosis in the cornea could be distinguished. All of the obtained results demonstrate that high-resolution ARFI imaging has considerable potential for the clinical diagnosis of corneal sclerosis.

Shih, Cho-Chiang; Zhou, Qifa; Shung, K. Kirk

2013-01-01

133

Near-Field Acoustical Imaging using Lateral Bending Mode of Atomic Force Microscope Cantilevers  

NASA Astrophysics Data System (ADS)

Scanning probe microscopy techniques enable one to investigate surface properties such as contact stiffness and friction between the probe tip and a sample with nm resolution. So far the bending and the torsional eigenmodes of an atomic force microscope cantilever have been used to image variations of elasticity and shear elasticity, respectively. Such images are near-field images with the resolution given by the contact radius typically between 10 nm and 50 nm. We show that the flexural modes of a cantilever oscillating in the width direction and parallel to the sample surface can also be used for imaging. Additional to the dominant in-plane component of the oscillation, the lateral modes exhibit a vertical component as well, provided there is an asymmetry in the cross-section of the cantilever or in its suspension. The out-of-plane deflection renders the lateral modes detectable by the optical position sensors used in atomic force microscopes. We studied cracks which were generated by Vickers indents, in submicro- and nanocrystalline ZrO2. Images of the lateral contact stiffness were obtained by vibrating the cantilever close to a contact-resonance frequency. A change in contact stiffness causes a shift of the resonant frequency and hence a change of the cantilever vibration amplitude. The lateral contact-stiffness images close to the crack faces display a contrast that we attribute to altered elastic properties indicating a process zone. This could be caused by a stress-induced phase transformation during crack propagation. Using the contact mode of an atomic force microscope, we measured the crack-opening displacement as a function of distance from the crack tip, and we determined the crack-tip toughness Ktip. Furthermore, K1c was inferred from the length of radial cracks of Vickers indents that were measured using classical scanning acoustic microscopy

Caron, A.; Rabe, U.; Rödel, J.; Arnold, W.

134

Digital image processing of sectorial oscillations for acoustically levitated drops and surface tension measurement  

NASA Astrophysics Data System (ADS)

A type of non-axisymmetric oscillations of acoustically levitated drops is excited by modulating the ultrasound field at proper frequencies. These oscillations are recorded by a high speed camera and analyzed with a digital image processing method. They are demonstrated to be the third mode sectorial oscillations, and their frequencies are found to decrease with the increase of equatorial radius of the drops, which can be described by a modified Rayleigh equation. These oscillations decay exponentially after the cessation of ultrasound field modulation. The decaying rates agree reasonably with Lamb's prediction. The rotating rate of the drops accompanying the shape oscillations is found to be less than 1.5 rounds per second. The surface tension of aqueous ethanol has been measured according to the modified Rayleigh equation. The results agree well with previous reports, which demonstrates the possible application of this kind of sectorial oscillations in noncontact measurement of liquid surface tension.

Shen, Changle; Xie, Wenjun; Wei, Bingbo

2010-12-01

135

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

136

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

137

A Spinal Cord Window Chamber Model for In Vivo Longitudinal Multimodal Optical and Acoustic Imaging in a Murine Model  

PubMed Central

In vivo and direct imaging of the murine spinal cord and its vasculature using multimodal (optical and acoustic) imaging techniques could significantly advance preclinical studies of the spinal cord. Such intrinsically high resolution and complementary imaging technologies could provide a powerful means of quantitatively monitoring changes in anatomy, structure, physiology and function of the living cord over time after traumatic injury, onset of disease, or therapeutic intervention. However, longitudinal in vivo imaging of the intact spinal cord in rodent models has been challenging, requiring repeated surgeries to expose the cord for imaging or sacrifice of animals at various time points for ex vivo tissue analysis. To address these limitations, we have developed an implantable spinal cord window chamber (SCWC) device and procedures in mice for repeated multimodal intravital microscopic imaging of the cord and its vasculature in situ. We present methodology for using our SCWC to achieve spatially co-registered optical-acoustic imaging performed serially for up to four weeks, without damaging the cord or induction of locomotor deficits in implanted animals. To demonstrate the feasibility, we used the SCWC model to study the response of the normal spinal cord vasculature to ionizing radiation over time using white light and fluorescence microscopy combined with optical coherence tomography (OCT) in vivo. In vivo power Doppler ultrasound and photoacoustics were used to directly visualize the cord and vascular structures and to measure hemoglobin oxygen saturation through the complete spinal cord, respectively. The model was also used for intravital imaging of spinal micrometastases resulting from primary brain tumor using fluorescence and bioluminescence imaging. Our SCWC model overcomes previous in vivo imaging challenges, and our data provide evidence of the broader utility of hybridized optical-acoustic imaging methods for obtaining multiparametric and rich imaging data sets, including over extended periods, for preclinical in vivo spinal cord research.

Maeda, Azusa; Conroy, Leigh; McMullen, Jesse D.; Silver, Jason I.; Stapleton, Shawn; Vitkin, Alex; Lindsay, Patricia; Burrell, Kelly; Zadeh, Gelareh; Fehlings, Michael G.; DaCosta, Ralph S.

2013-01-01

138

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

139

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

140

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

141

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

142

Experimental results for a prototype 3-D acoustic imaging system using an ultra-sparse planar array  

NASA Astrophysics Data System (ADS)

A handheld high resolution sonar has been under development to provide Navy Divers with a 3-D acoustic imaging system for mine reconnaissance. An ultra-sparse planar array, consisting of 121 1 mm x1 mm, 2 MHz elements, was fabricated to provide 3-D acoustic images. The array was 10 cm x10 cm. A full array at this frequency with elements at half-wavelength spacing would consist of 16384 elements. The first phase of testing of the planar array was completed in September 2001 with the characterization of the array in the NUWC Acoustic Test Facility (ATF). The center frequency was 2 MHz with a 667 kHz bandwidth. A system-level technology demonstration will be conducted in July 2002 with a real-time beamformer and near real-time 3-D imaging software. The demonstration phase consists of imaging simple targets at a range of 3 m in the ATF. Experimental results obtained will be reported on. [Work supported by the Defense Applied Research Project Agency, Advance Technology Office, Dr. Theo Kooij, Program Manager.

Impagliazzo, John M.; Chiang, Alice M.; Broadstone, Steven R.

2002-11-01

143

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

144

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

145

Acoustical Imaging Using a Leaky Wave Transducer Composed of a Piezoelectric Ceramic Plate and an Acryl Plate  

NASA Astrophysics Data System (ADS)

An interdigital transducer (IDT) for leaky waves in a layered substrate composed of a piezoelectric ceramic thin plate and an acryl plate is incorporated into a C-mode acoustical imaging system. The transducer performance in the layered structure is described from the viewpoint of ultrasound radiation at an interface between an acryl plate and a water layer. The leaky wave transducer has frequency-dependent radiation angles, corresponding to the leaky wave velocity, under multiple operation modes. The bulk wave direction in a test sample via the longitudinal wave in the water layer is easily controlled by frequency change. A reflection type C-mode acoustical imaging system is successfully demonstrated for nondestructive testing.

Toda, Kohji; Motegi, Kenji

1995-05-01

146

Methods for Acoustic Holography and Acoustic Measurements.  

National Technical Information Service (NTIS)

A novel 'four step acoustical holographic imaging system' is described and several means to implement it are theoretically and experimentally analyzed. The 'holographic sound image converter,' consisting of an optical 'holographic interferometer' and an a...

W. K. Fischer

1973-01-01

147

Data-driven inversion\\/depth imaging derived from approximations to one-dimensional inverse acoustic scattering  

Microsoft Academic Search

This paper presents a new mathematical framework based on inverse scattering for the estimation of the scattering potential and its nature of a one-dimensional acoustic layered medium from single scattering data. Given the Born potential associated with constant-velocity imaging of the single scattering data, a closed-form implicit expression for the scattering potential is derived in the WKBJ and eikonal approximations.

Lasse Amundsen; Arne Reitan; Hans Kr Helgesen; Børge Arntsen

2005-01-01

148

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:24092093

He, Zhengyao

2013-01-01

149

NMR imaging system with reduced cryogenic losses and reduced acoustic noise  

US Patent & Trademark Office Database

A magnetic resonance imaging system having an exterior cryogenic enclosure containing a device for creating an intense main magnetic field in a usable interior tunnel space an RF exciter, a set of solenoid gradient windings in a cylindrical space around the interior tunnel space and electronic control circuits. The cryogenic enclosure includes an interior cylindrical space vacuum at room temperature having the set of windings therein, at least one thermal screen in a temperature range of 20.degree. K to 80.degree. K, a cold box below 5.degree. K, and a former supporting the exciter for creating an intense main magnetic field. To reduce acoustic noise and cryogenic losses, an additional envelope is between the set of windings and the vacuum enclosure, the additional envelope being of a conductive material having electrical resistivity at least 7.times.10.sup.-8 .OMEGA.m and having a characteristic frequency no more than the characteristic frequencies of each of the other components of the exterior cryogenic enclosure.

Aubert; Guy (Poitiers, FR)

2013-04-02

150

Acoustic radiation force impulse imaging of the mechanical properties of arteries: in vivo and ex vivo results.  

PubMed

We present results of a pilot study of ex vivo and in vivo acoustic radiation force impulse (ARFI) imaging demonstrating measurements of the mechanical properties of the carotid and popliteal arteries. The results were obtained on a modified commercial scanner, providing coregistered B-mode and color Doppler images. 2D and 1D through time images are formed from the measurements of tissues' response to very brief and localized applications of radiation force. The images show good correlation with B-mode and, in ex vivo studies, pathology-based characterizations of vessel geometry and plaque stiffness. In vivo measurements of arterial response during both systole and diastole are presented. We address implementation issues and discuss potential applications of this new vascular imaging method. PMID:15550320

Trahey, Gregg E; Palmeri, Mark L; Bentley, Rex C; Nightingale, Kathryn R

2004-09-01

151

4f electron delocalization and volume collapse in praseodymium metal  

SciTech Connect

We study the pressure evolution of the 4f electrons in elemental praseodymium metal compressed through several crystallographic phases, including the large volume-collapse transition at 20 GPa. Using resonant x-ray emission, we directly and quantitatively measure the development of multiple electronic configurations with differing 4f occupation numbers, the key quantum observable related to the delocalization of the strongly correlated 4f electrons. These results provide a high-fidelity test of prior predictions by dynamical mean-field theory, and support the hypothesis of a strong connection between electronic and structural degrees of freedom at the volume-collapse transition.

Bradley, Joseph A.; Moore, Kevin T.; Lipp, Magnus J.; Mattern, Brian A.; Pacold, Joseph I.; Seidler, Gerald T.; Chow, Paul; Rod, Eric; Xiao, Yuming; Evans, William J. (UWASH); (LLNL); (CIW)

2012-04-17

152

MINACE filter realization as computer generated hologram for 4-f correlator  

NASA Astrophysics Data System (ADS)

Optical correlators are well known to be perspective for real time image recognition. Application of distortion invariant filters (DIF) provides image recognition with increased speed of correlation image matching. Minimum noise and correlation energy filters (MINACE filters) provide good recognition in the case of gray-scale input images. These filters possess a good mathematical basis and can be efficiently implemented in digital processing systems or in hybrid opto-digital correlators at a high rate. This paper is subjected to synthesis and realization of MINACE filters for 4-f correlator as computer generated holograms (holographic filters).

Evtikhiev, Nikolay N.; Shaulskiy, Dmitriy V.; Zlokazov, Evgeny Y.; Starikov, Rostislav S.

2013-03-01

153

Structural, magnetic, and energetic properties of Na2FePO4F, Li2FePO4F, NaFePO4F, and LiFePO4F from ab initio calculations  

NASA Astrophysics Data System (ADS)

In this paper, we report on Na2FePO4F and Li2FePO4F, which are materials that are used as cathodes in batteries, using density functional theory with the LDA, LDA+U, GGA, or GGA+U approximations. Specifically, we study their crystal structure, electronic structure, and magnetic properties and provide similar information about the intermediate compounds LiFePO4F and NaFePO4F. Finally, the intercalation voltages of the corresponding batteries are calculated using various exchange-correlation approximations and conclusions are drawn about which one is the most suitable to use for the study of this class of materials.

Ramzan, M.; Lebègue, S.; Larsson, P.; Ahuja, R.

2009-08-01

154

Magnetic structure and properties of NaFeSO4F and NaCoSO4F  

NASA Astrophysics Data System (ADS)

NaFeSO4F and NaCoSO4F crystallize in the maxwellite crystal structure and consist of one-dimensional chains of corner-sharing MO4F2 octahedra linked together through F atoms sitting in a trans configuration with respect to each other. Magnetic susceptibility measurements and low-temperature powder neutron diffraction indicate that both the Fe- and Co-based phases establish G-type antiferromagnetic ground states below 36 and 29 K, respectively. We discuss the obtained magnetic structure in the context of the local anisotropy of the two magnetic ions.

Melot, B. C.; Rousse, G.; Chotard, J.-N.; Kemei, M. C.; Rodríguez-Carvajal, J.; Tarascon, J.-M.

2012-03-01

155

An analysis and retrofit of the acoustics at Image Creators Health and Beauty Salon  

NASA Astrophysics Data System (ADS)

This paper discusses the analysis and retrofit of the acoustics in a high-volume beauty salon in Severna Park, MD. The major issues in what was designed to be a serene environment are reverberation times of 1-1.68 s in the mid- to upper-frequency range. Employee and customer complaints include heightened stress, vocal strain, headaches, and poor intelligibility. Existing analysis and acoustical retrofit solutions will be demonstrated.

Ellis, Donna

2002-11-01

156

An analysis and retrofit of the acoustics at Image Creators Health and Beauty Salon  

Microsoft Academic Search

This paper discusses the analysis and retrofit of the acoustics in a high-volume beauty salon in Severna Park, MD. The major issues in what was designed to be a serene environment are reverberation times of 1-1.68 s in the mid- to upper-frequency range. Employee and customer complaints include heightened stress, vocal strain, headaches, and poor intelligibility. Existing analysis and acoustical

Donna Ellis

2002-01-01

157

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

158

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

2013-08-22

159

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

160

Redetermination of durangite, NaAl(AsO4)F  

PubMed Central

The crystal structure of durangite, ideally NaAl(AsO4)F (chemical name sodium aluminium arsenate fluoride), has been determined previously [Kokkoros (1938). Z. Kristallogr. 99, 38–49] using Weissenberg film data without reporting displacement parameters of atoms or a reliability factor. This study reports the redetermination of the structure of durangite using single-crystal X-ray diffraction data from a natural sample with composition (Na0.95Li0.05)(Al0.91Fe3+ 0.07Mn3+ 0.02)(AsO4)(F0.73(OH)0.27) from the type locality, the Barranca mine, Coneto de Comonfort, Durango, Mexico. Durangite is isostructural with minerals of the titanite group in the space group C2/c. Its structure is characterized by kinked chains of corner-sharing AlO4F2 octa­hedra parallel to the c axis. These chains are cross-linked by isolated AsO4 tetra­hedra, forming a three-dimensional framework. The Na+ cation (site symmetry 2) occupies the inter­stitial sites and is coordinated by one F? and six O2? anions. The AlO4F2 octa­hedron has symmetry -1; it is flattened, with the Al—F bond length [1.8457?(4)?Å] shorter than the Al—O bond lengths [1.8913?(8) and 1.9002?(9)?Å]. Examination of the Raman spectra for arsenate minerals in the titanite group reveals that the position of the band originating from the As—O symmetric stretching vibrations shifts to lower wavenumbers from durangite, maxwellite [ideally NaFe(AsO4)F], to tilasite [CaMg(AsO4)F].

Downs, Gordon W.; Yang, Betty N.; Thompson, Richard M.; Wenz, Michelle D.; Andrade, Marcelo B.

2012-01-01

161

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

162

Distribution and height of methane bubble plumes on the Cascadia Margin characterized by acoustic imaging  

Microsoft Academic Search

Submersible investigations of the Cascadia accretionary complex have identified localized venting of methane gas bubbles in association with gas hydrate occurrence. Acoustic profiles of these bubble plumes in the water column in the vicinity of Hydrate Ridge offshore Oregon provide new constraints on the spatial distribution of these gas vents and the fate of the gas in the water column.

Katja U. Heeschen; Anne M. Tréhu; Robert W. Collier; Erwin Suess; Gregor Rehder

2003-01-01

163

Distribution and height of methane bubble plumes on the Cascadia Margin characterized by acoustic imaging  

Microsoft Academic Search

(1) Submersible investigations of the Cascadia accretionary complex have identified localized venting of methane gas bubbles in association with gas hydrate occurrence. Acoustic profiles of these bubble plumes in the water column in the vicinity of Hydrate Ridge offshore Oregon provide new constraints on the spatial distribution of these gas vents and the fate of the gas in the water

Katja U. Heeschen; Anne M. Trehu; Robert W. Collier

2003-01-01

164

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

165

Acoustic imaging of underwater embedded objects: signal simulation for three-dimensional sonar instrumentation  

Microsoft Academic Search

This paper presents a method able to emulate the signals received by a sonar system exploring a submerged environment. The simulation of the response of an underwater scene insonified by a wideband pulse has been based on the reproduction of the interactions of the acoustic field with a buried object, with the seabed surface, and with the sediment volume. The

Maria Palmese; Andrea Trucco

2006-01-01

166

Internal Auditory Canal Involvement of Acoustic Neuromas: Surgical Correlates to Magnetic Resonance Imaging Findings  

Microsoft Academic Search

Objective: Factors that play a role in the selection of surgical approach for acoustic neuromas include patient health and age, size of tumor, hearing status, and location of tumor in the internal auditory canal (IAC) and the cerebellopontine angle. Deep extension into the IAC makes hearing preservation ex- tremely difficult when a retrosigmoid craniotomy is used, and the best approach

Samuel H. Selesnick; Janez Rebol; Linda A. Heier; Jeffrey B. Wise; Philip H. Gutin; Michael H. Lavyne

2001-01-01

167

Detection of imaging acoustic signals for synchronizing a commercial ultrasound imager with a high intensity focused ultrasound therapy system  

Microsoft Academic Search

Transcutaneous surgical procedures performed with a high intensity focused ultrasound (HIFU) therapy system can be monitored in real-time with an ultrasound imaging system if the HIFU is gated appropriately. Without synchronization, gated or continuous HIFU saturates the imaging system and interference occludes the image. If a gating signal is synchronized with the imaging cycle from any commercial imager, the location

Neil R. Owen; Michael R. Bailey; Peter J. Kaczkowski; Wayne Kreider; Lawrence A. Crum

2004-01-01

168

Plant Cap-binding Complexes Eukaryotic Initiation Factors eIF4F and eIFISO4F  

PubMed Central

The initiation of translation in eukaryotes requires a suite of eIFs that include the cap-binding complex, eIF4F. eIF4F is comprised of the subunits eIF4G and eIF4E and often the helicase, eIF4A. The eIF4G subunit serves as an assembly point for other initiation factors, whereas eIF4E binds to the 7-methyl guanosine cap of mRNA. Plants have an isozyme form of eIF4F (eIFiso4F) with comparable subunits, eIFiso4E and eIFiso4G. Plant eIF4A is very loosely associated with the plant cap-binding complexes. The specificity of interaction of the individual subunits of the two complexes was previously unknown. To address this issue, mixed complexes (eIF4E-eIFiso4G or eIFiso4E-eIF4G) were expressed and purified from Escherichia coli for biochemical analysis. The activity of the mixed complexes in in vitro translation assays correlated with the large subunit of the respective correct complex. These results suggest that the eIF4G or eIFiso4G subunits influence translational efficiency more than the cap-binding subunits. The translation assays also showed varying responses of the mRNA templates to eIF4F or eIFiso4F, suggesting that some level of mRNA discrimination is possible. The dissociation constants for the correct complexes have KD values in the subnanomolar range, whereas the mixed complexes were found to have KD values in the ?10 nm range. Displacement assays showed that the correct binding partner readily displaces the incorrect binding partner in a manner consistent with the difference in KD values. These results show molecular specificity for the formation of plant eIF4F and eIFiso4F complexes and suggest a role in mRNA discrimination during initiation of translation.

Mayberry, Laura K.; Allen, M. Leah; Nitka, Kelley R.; Campbell, Lara; Murphy, Patricia A.; Browning, Karen S.

2011-01-01

169

77 FR 42802 - Section 4(f) Policy Paper  

Federal Register 2010, 2011, 2012, 2013

...of the Section 4(f) process was created and added as an appendix. Finally...documentation might include the reasons why the historic site was not eligible for the NR. Question...property, the fact that the resource was created with TEA funding would not...

2012-07-20

170

Novel MEMS microshell transducer arrays for high-resolution underwater acoustic imaging applications  

Microsoft Academic Search

Presents the design, fabrication process and experimental acoustic test data for a novel MEMS-based 2-D ferroelectric ultrasound microshell transducer array. A new 3-D-micromachining technique is used to fabricate a MEMS microshell structure that acts as an ultrasound transducer in the 1-5 MHz range. A rounded sacrificial carbon structure generated by a two-step photo-resist reflow and pyrolysis process provides the shape

Mark J. Mescher; Ken Houston; Jon J. Bernstein; Greg A. Kirkos; Jinrong Cheng; L. E. Cross

2002-01-01

171

Imaging surface acoustic waves on GaAs by X-ray diffraction techniques  

Microsoft Academic Search

Surface acoustic waves (SAWs) are excited on the GaAs (001) surface by using interdigital transducers, designed for frequencies of up to 900 MHz. The emitted surface phonons with wave-lengths down to 3.5 ?m are visualized and characterized by combined x-ray diffraction techniques. By increasing the amplitude of the SAW, high resolution x-ray diffraction profiles show up to 12 phonon-induced satellite

W. Sauer; M. Streibl; T. H. Metzger; A. G. C. Haubrich; S. Manus; A. Wixforth; J. Peisl; A. Mazuelas; J. Haertwig; J. Baruchel

1999-01-01

172

An image processing approach for aircraft flight parameter estimation using the acoustical Lloyd's mirror effect  

Microsoft Academic Search

A time-frequency analysis of the output of an acoustic sensor located above the ground during the transit of an aircraft shows an interference (or fringe) pattern on the time-frequency plane. This interference pattern, referred to as the Lloyd's mirror effect, is caused by the temporal variations of the constructive\\/destructive interference frequencies of the direct and ground-reflected aircraft sound fields at

Kam W. Lo; Stuart W. Perry; Brian G. Ferguson

1999-01-01

173

Comparison of scanning acoustic microscopy and histology images in characterizing surface irregularities among engineered human oral mucosal tissues.  

PubMed

Acoustic microscopy was used to monitor an ex vivo produced oral mucosal equivalent (EVPOME) developed on acellular cadaveric dermis (AlloDerm®). As seeded cells adhered and grew, they filled in and smoothed out the surface irregularities, followed by the production of a keratinized protective outermost layer. If noninvasive in vitro ultrasonic monitoring of these cellular changes could be developed, then tissue cultivation could be adjusted in-process to account for biologic variations in the development of these stratified cell layers. Cultured keratinocytes (from freshly obtained oral mucosa) were harvested and seeded onto AlloDerm® coated with human type IV collagen and cultured 11 days. EVPOMEs were imaged on the 11th day post-seeding using a scanning acoustic microscope (SAM) that consists of a single-element transducer: 61 MHz center frequency, 32 MHz bandwidth, 1.52 f-number. The specimen surface was determined by thresholding the magnitude of the signal at the first axial incidence of a value safely above noise: 20-40 dB above the signal for the water and 2-dimensional (2-D) ultrasonic images were created using confocal image reconstruction. A known area from each micrograph was divided into 12-40 even segments and examined for surface irregularities. These irregularities were quantified and one-way analysis of variance (ANOVA) and linear regression analysis were performed to correlate the surface profiles for both the AlloDerm® and EVPOME specimens imaged by SAM. Histology micrographs of the AlloDerm® and EVPOME specimens were also prepared and examined for surface irregularities. Unseeded AlloDerm® averaged seven to nine surface changes per 400 ?m. The number of changes in surface irregularities decreased to two to three per 400 ?m on the mature EVPOMEs. The numbers of surface irregularities between the unseeded AlloDerm® vs. developing EVPOME are similar for both histology and SAM 2-D B-scan images. For the EVPOME 2-D B-scan micrographs produced by SAM, the decrease in surface irregularities is indicative of the stratified epithelium formed by seeded oral keratinocytes; verified in the histology images between the AlloDerm® and EVPOME. A near 1:1 linear correlation shows the similarities between the two imaging modalities. SAM demonstrates its ability to discern the cell development and differentiation occurring on the EVPOME devices. Unlike histology, SAM measurements are noninvasive and can be used to monitor tissue graft development without damaging any cells/tissues. PMID:21871704

Winterroth, Frank; Hollman, Kyle W; Kuo, Shiuhyang; Izumi, Kenji; Feinberg, Stephen E; Hollister, Scott J; Fowlkes, J Brian

2011-08-25

174

The eIF4F and eIFiso4F Complexes of Plants: An Evolutionary Perspective  

PubMed Central

Translation initiation in eukaryotes requires a number of initiation factors to recruit the assembled ribosome to mRNA. The eIF4F complex plays a key role in initiation and is a common target point for regulation of protein synthesis. Most work on the translation machinery of plants to date has focused on flowering plants, which have both the eIF4F complex (eIF4E and eIF4G) as well as the plant-specific eIFiso4F complex (eIFiso4E and eIFiso4G). The increasing availability of plant genome sequence data has made it possible to trace the evolutionary history of these two complexes in plants, leading to several interesting discoveries. eIFiso4G is conserved throughout plants, while eIFiso4E only appears with the evolution of flowering plants. The eIF4G N-terminus, which has been difficult to annotate, appears to be well conserved throughout the plant lineage and contains two motifs of unknown function. Comparison of eIFiso4G and eIF4G sequence data suggests conserved features unique to eIFiso4G and eIF4G proteins. These findings have answered some questions about the evolutionary history of the two eIF4F complexes of plants, while raising new ones.

Patrick, Ryan M.; Browning, Karen S.

2012-01-01

175

Characterization of a broadband all-optical ultrasound transducer-from optical and acoustical properties to imaging.  

PubMed

A broadband all-optical ultrasound transducer has been designed, fabricated, and evaluated for high- frequency ultrasound imaging. The device consists of a 2-D gold nanostructure imprinted on top of a glass substrate, followed by a 3 microm PDMS layer and a 30 nm gold layer. A laser pulse at the resonance wavelength of the gold nanostructure is focused onto the surface for ultrasound generation, while the gold nanostructure, together with the 30 nm thick gold layer and the PDMS layer in between, forms an etalon for ultrasound detection, which uses a CW laser at a wavelength far from resonance as the probing beam. The center frequency of a pulse-echo signal recorded in the far field of the transducer is 40 MHz with -6 dB bandwidth of 57 MHz. The signal to noise ratio (SNR) from a 70 microm diameter transmit element combined with a 20 microm diameter receive element probing a near perfect reflector positioned 1.5 mm from the transducer surface is more than 10 dB and has the potential to be improved by at least another 40 dB. A high-frequency ultrasound array has been emulated using multiple measurements from the transducer while mechanically scanning an imaging target. Characterization of the device's optical and acoustical properties, as well as preliminary imaging results, strongly suggest that all-optical ultrasound transducers can be used to build high-frequency arrays for real-time high-resolution ultrasound imaging. PMID:18986929

Hou, Yang; Kim, Jin-Sung; Huang, Sheng-Wen; Ashkenazi, S; Guo, L J; O'Donnell, M

2008-08-01

176

Characterization of a Broadband All-Optical Ultrasound Transducer--From Optical and Acoustical Properties to Imaging  

PubMed Central

A broadband all-optical ultrasound transducer has been designed, fabricated, and evaluated for high-frequency ultrasound imaging. The device consists of a 2-D gold nanostructure imprinted on top of a glass substrate, followed by a 3 ?m PDMS layer and a 30 nm gold layer. A laser pulse at the resonance wavelength of the gold nanostructure is focused onto the surface for ultrasound generation, while the gold nanostructure, together with the 30 nm thick gold layer and the PDMS layer in between, forms an etalon for ultrasound detection, which uses a CW laser at a wavelength far from resonance as the probing beam. The center frequency of a pulse-echo signal recorded in the far field of the transducer is 40 MHz with -6 dB bandwidth of 57 MHz. The signal to noise ratio (SNR) from a 70 ?m diameter transmit element combined with a 20 ?m diameter receive element probing a near perfect reflector positioned 1.5 mm from the transducer surface is more than 10 dB and has the potential to be improved by at least another 40 dB. A high-frequency ultrasound array has been emulated using multiple measurements from the transducer while mechanically scanning an imaging target. Characterization of the device’s optical and acoustical properties, as well as preliminary imaging results, strongly suggest that all-optical ultrasound transducers can be used to build high-frequency arrays for real-time high-resolution ultrasound imaging.

Hou, Yang; Kim, Jin-Sung; Huang, Sheng-Wen; Ashkenazi, Shai; Guo, L. Jay; O'Donnell, Matthew

2009-01-01

177

Determination of mechanical properties of layered materials with vector-contrast scanning acoustic microscopy by polar diagram image representation  

NASA Astrophysics Data System (ADS)

Microscopic objects including living cells on a planar substrate are investigated in bio-medical applications of scanning acoustic microscopy. Beside of the observation of lateral structures, the determination of sample properties such as density, sound velocity, and attenuation is desired, from which elastic properties can be derived. This can be achieved with the aid of the acoustic phase and magnitude contrast represented in a polar plot. For homogeneous and sufficiently planar objects the contrast in magnitude and phase is a function of the properties of the substrate and the coupling fluid, which both can easily be determined, and of the mechanical properties of the sample under observation. For observation in reflection and variable thickness of the sample the signal will depend on the actual thickness. This signature of the object can be fitted based on a conventional ray model for the sound propagating in the coupling medium and the sample. The model includes also the refraction and reflection at all interfaces between transducer, lens material, coupling fluid, object, and substrate. The method is demonstrated for a chitosan film deposited on a glass substrate. The scheme presented here is capable to reach a resolution of about and even below 1% for relevant quantities in applications involving imaging at 1.2 GHz in aqueous coupling fluids.

Ahmed Mohamed, E. T.; Kamanyi, A.; von Buttlar, M.; Wannemacher, R.; Hillman, K.; Ngwa, W.; Grill, W.

2008-05-01

178

Tuneable intramolecular intermetallic interactions as a new tool for programming linear heterometallic 4f-4f complexes.  

PubMed

Statistical mechanics predicts that the design of pure organized heteropolymetallic chains of metal ions bound to linear receptors depends on controlled deviations from the mixing rule DeltaE(MiMj) = 1/2 (DeltaE(MiMi) + DeltaE(MjMj)), whereby DeltaE(MiMj) is the intramolecular intermetallic interaction between neighboring metal i and metal j along the receptor. A thorough investigation of linear polymetallic trivalent lanthanide triple-stranded helicates shows that such deviations are amplified by an increase in the nuclearity of the final complexes and are thus easily evidenced in the tetranuclear heterobimetallic helicates [La(4-y)Lu(y)(L6)3](12+) (y = 0-4). The chemical and physical origins of this unprecedented behavior are discussed together with its practical consequences for programming pure heteropolymetallic 4f-4f complexes. PMID:17915861

Dalla-Favera, Natalia; Hamacek, Josef; Borkovec, Michal; Jeannerat, Damien; Ercolani, Gianfranco; Piguet, Claude

2007-10-04

179

Probability of Yb3+ 4f-4f transitions in gadolinium gallium garnet crystals at high hydrostatic pressures  

NASA Astrophysics Data System (ADS)

We show that the probability of f-f radiative transitions (F7/22?F5/22) of Yb3+ ions in gadolinium gallium garnet (GGG) crystals is sensitive to hydrostatic pressure application. The changes of the transition energy with pressure are very small, almost negligible. However, we observed much more pronounced variations of the transition probability, which are ascribed to a coupling between the 4f13 with the 4f125d1 electronic configurations and variations of the coupling coefficient with pressure. The theoretical model, explaining this behavior, assumes nonmonotonic changes of the odd-parity crystal-field terms associated with lattice distortions induced by pressure. The magnitude of these distortions correlates well with the magnitude of the distortion from the noncubic symmetry of the dodecahedral crystallographic sites in GGG host, monitored by the pressure dependence of the splitting of the F3/24 level of Nd3+ ions.

Kami?ska, A.; Biernacki, S.; Kobyakov, S.; Suchocki, A.; Boulon, G.; Ramirez, M. O.; Bausa, L.

2007-05-01

180

High-speed imaging of an ultrasound-driven bubble in contact with a wall: ``Narcissus'' effect and resolved acoustic streaming  

NASA Astrophysics Data System (ADS)

We report microscopic observations of the primary flow oscillation of an acoustically driven bubble in contact with a wall, captured with the ultra high-speed camera Brandaris 128 (Chin et al. 2003). The driving frequency is up to 200 kHz, and the imaging frequency is up to 25 MHz. The details of the bubble motion during an ultrasound cycle are thus resolved, showing a combination of two modes of oscillations: a radius oscillation and a translation oscillation, perpendicular to the wall. This motion is interpreted using the theory of acoustic images to account for the presence of the wall. We conclude that the bubble is subjected to a periodic succession of attractive and repulsive forces, exerted by its own image. Fast-framing recordings of a tracer particle embedded in the liquid around the particle are performed. They fully resolve the acoustic streaming flow induced by the bubble oscillations. This non-linear secondary flow appears as a tiny drift of the particle position cycle after cycle, on top of the primary back and forth oscillation. The high oscillation frequency accounts for a fast average particle velocity, with characteristic timescales in the millisecond range at the lengthscale of the bubble. The features of the bubble motion being resolved, we can apply the acoustic streaming theory near a wall, which provides predictions in agreement with the observed streaming velocity.

Marmottant, Philippe; Versluis, Michel; de Jong, Nico; Hilgenfeldt, Sascha; Lohse, Detlef

2006-08-01

181

Electronic excitation of C4F6 isomers by electron impact  

NASA Astrophysics Data System (ADS)

We have measured electronic excitation differential cross sections for C4F6 molecules isomers by electron impact. In the case of hexafluoro-1,3-butadiene we observed an optical forbidden transition at around 5 eV. The spectra of the three C4F6 isomers show the most intense band clearly shifted to lower energies when going from 2-C4F6, to c-C4F6 and to 1,3-C4F6.

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

2012-11-01

182

Classroom Acoustics  

MedlinePLUS

... Information for the Public › Hearing and Balance Classroom Acoustics A student's ability to hear and understand what ... reverberation time. Who is affected by poor classroom acoustics? All children are affected by poor classroom acoustics, ...

183

4f2/4f6p configuration interaction in LiYF4 :Pr3+s  

NASA Astrophysics Data System (ADS)

In two other papers [M. D. Faucher, O. K. Moune, D. Garcia, and P. Tanner, Phys. Rev. B 53, 9501 (1996); M. D. Faucher and O. K. Moune, J. Alloys Compounds (to be published)], it was shown that the introduction of the 5fn/5fn-17p (or 4fn/4fn-16p) configuration interaction eliminated large discrepancies in the crystal-field analysis of (i) U4+ (5f2) in Cs2UBr6 and Cs2ZrBr6, for which the least root-mean-square deviation between experimental and calculated energy levels falls down from 241 to 56 cm-1, and (ii) Nd3+ in Nd2O2S, for which the discrepancy of the 2H(2)11/2 level is eliminated by the configuration interaction with the excited 4f26p configuration. The demonstration is now extended to Pr3+ and seems to be of general application. For LiYF4:Pr3+ the mean deviation is divided by more than 2 by utilizing an interaction matrix including 4f6p in addition to the ground configuration 4f2.

Faucher, M. D.; Moune, O. K.

1997-06-01

184

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

185

Combined photoacoustic and acoustic imaging of human breast specimens in the mammographic geometry.  

PubMed

A photoacoustic volume imaging (PAVI) system was designed to study breast cancer detection and diagnosis in the mammographic geometry in combination with automated 3-D ultrasound (AUS). The goal of the work described here was to validate the design and evaluate its performance in human breast tissues for non-invasive imaging of deeply positioned structures covering such geometry. The good penetration of near-infrared light and high receiving sensitivity of a broad-bandwidth, 572-element, 2-D polyvinylidene fluoride (PVDF) array at a low center frequency of 1 MHz were used with 20 channel simultaneous acquisition. Pseudo-lesions filled with dilute blood were imaged in three human breast specimens at various depths up to 49 mm. With near-infrared light illumination and 256-sample averaging, the extrapolated maximum depth in imaging a 2.4-mm blood-rich lesion with a 3-dB contrast-to-noise ratio in a compressed breast was 54 mm. Three-dimensional photoacoustic volume image stacks of the breasts were co-registered with 3-D ultrasound image stacks, suggesting for the first time that PAVI, based on the intrinsic tissue contrast, can visualize tissue interfaces other than those with blood, including the inner skin surface and connective tissue sheets. With the designed system, PAVI revealed satisfactory imaging depth and sensitivity for coverage of the entire breast when imaged from both sides in the mammographic geometry with mild compression. PMID:23972486

Xie, Zhixing; Hooi, Fong Ming; Fowlkes, J Brian; Pinsky, Renee W; Wang, Xueding; Carson, Paul L

2013-08-22

186

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

Kopecky, David; Martis, Mihaela; Cíhalíková, Jarmila; Hribová, Eva; Vrána, Jan; Bartos, Jan; Kopecká, Jitka; Cattonaro, Federica; Stoces, Stepán; Novák, Petr; Neumann, Pavel; Macas, Jirí; Simková, Hana; Studer, Bruno; Asp, Torben; Baird, James H; Navrátil, Petr; Karafiátová, Miroslava; Kubaláková, Marie; Safár, Jan; Mayer, Klaus; Dolezel, Jaroslav

2013-10-04

187

Image-guided acoustic hemostasis for hemorrhage in the posterior liver.  

PubMed

We investigated the use of ultrasound image-guided high intensity focused ultrasound (HIFU) to stop bleeding from injuries in the posterior liver. A HIFU transducer with focal length of 3.5 cm and frequency of 3.2 MHz was integrated with an intraoperative high-resolution ultrasound-imaging probe. Wedge tissue extractions, 30-mm long, 5-mm wide and 8-mm deep, were made in the posterior liver surface of five pigs to induce bleeding. The device was positioned on the anterior surface of the liver and HIFU was applied using ultrasound image-guidance. Hemostasis was achieved in 66 +/- 18 s (mean +/- standard deviation) for 17 HIFU treatments. During 7 min of sham HIFU treatment, none of the control incisions (n = 7) became hemostatic. Ultrasound image-guided HIFU offers a promising method for hemostasis in surgical settings in which the hemorrhage site is hidden and/or not accessible. PMID:17189053

Burgess, Sean; Zderic, Vesna; Vaezy, Shahram

2007-01-01

188

Image-guided acoustic hemostasis for hemorrhage in the posterior liver  

Microsoft Academic Search

We investigated the use of ultrasound image-guided high intensity focused ultrasound (HIFU) to stop bleeding from injuries in the posterior liver. A HIFU transducer with focal length of 3.5 cm and frequency of 3.2 MHz was integrated with an intraoperative high-resolution ultrasound-imaging probe. Wedge tissue extractions, 30-mm long, 5-mm wide and 8-mm deep, were made in the posterior liver surface

Sean Burgess; Vesna Zderic; Shahram Vaezy

2007-01-01

189

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

190

Application of computed tomography to the acoustic imaging of sea mines at safe standoff distances  

NASA Astrophysics Data System (ADS)

Typical imaging sonars make use of very high frequencies and arrays with a large number of sensors to provide high angular resolution. With such arrays the spatial resolution degrades and high propagation losses occur as the sonar is moved away from the target being imaged and operational ranges are generally 5 m or less. An alternative imaging technique has been implemented using computed tomography in which the target is insonified with a broad beam from multiple aspects. The spatial resolution achievable with this method is determined only by the bandwidth of the test signal and not by the beamwidth of the sonar or the distance of the sonar from the target. Results are presented showing clear images of mines and mine-like objects in which a spatial resolution of better than 2 cm is achieved at a range of 60 m, even for low target strength mines. Features are evident in the images that are related to both the internal and external shape of the targets as well as structural waves propagating within the targets. This offers the potential to provide unambiguous classification of mines from long ranges, even in a harsh operational environment.

Wyber, Ron; Ferguson, Brian

2002-05-01

191

Review of Advanced Acoustical Imaging Techniques for Nondestructive Evaluation of Art Objects  

Microsoft Academic Search

Proper preventative diagnosis of different art objects, including wooden, bronze and marble sculptures, frescoes, and paintings (on canvas, wood, metal, and glass), is very important for conservation purposes. Various advanced ultrasonic imaging methods for analysis and assessment of art objects can bring about drastic changes in the regular evaluation and inventory carried out by museums and can bring advanced, powerful,

R. G. Maev; R. E. Green Jr; A. M. Siddiolo

2006-01-01

192

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

193

Electronic excitation to singlet states of 1,3-C4F6, c-C4F6 and 2-C4F6 by electron impact--electron energy-loss spectroscopy and ab initio calculations.  

PubMed

We report on the first measurements of the electron impact electronic excitation cross sections for C(4)F(6) isomers, hexafluoro-1,3-butadiene (1,3-C(4)F(6)), hexafluorocyclobutene (c-C(4)F(6)), and hexafluoro-2-butyne (2-C(4)F(6)), measured at 100 eV, 3° scattering angle, while sweeping the energy loss over the range 2.0-15.0 eV. Under these experimental conditions, optically allowed transitions are favored. The electronic state spectroscopy has been investigated and the assignments supported by quantum chemical calculations. The n = 3 members of the Rydberg series have been assigned converging to the lowest ionization energy limits of the C(4)F(6) isomers and classified according to the magnitude of the quantum defects (?). PMID:23074974

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

2012-10-17

194

28 CFR 55.5 - Coverage under section 4(f)(4).  

Code of Federal Regulations, 2013 CFR

...DEPARTMENT OF JUSTICE (CONTINUED) IMPLEMENTATION OF THE PROVISIONS OF THE VOTING RIGHTS ACT REGARDING LANGUAGE MINORITY GROUPS Nature of Coverage § 55.5 Coverage under section 4(f)(4). (a) Coverage formula. Section 4(f)(4)...

2013-07-01

195

Salmon enumeration in the Fraser River with the dual-frequency identification sonar (DIDSON) acoustic imaging system  

NASA Astrophysics Data System (ADS)

Reliable data on the number of salmon entering tributaries of the Fraser River to spawn (escapement) is needed for Pacific salmon management. Existing escapement techniques are costly and the number of populations requiring assessments has risen because of stock rebuilding efforts. The efficacy of a DIDSON acoustic imaging system for salmon stock assessment was investigated. Sixteen potential sites within the Fraser watershed were surveyed and based on channel morphology, bottom morphology, flow pattern, fish behavior and location relative to spawning grounds, ten sites in six rivers meet the needs of fisheries managers and the DIDSON system for escapement estimates. Fish count data from the DIDSON were compared to data from a counting fence (used as a standard) using regression techniques, resulting in relationships with slopes ranging from 0.98 to 1.02. The precison of DIDSON counts >50 (measured by CV) among three readers was 1.7%. This work supports the conclusion that the DIDSON system can deliver escapement estimates whose accuracy, precision and scientific defensibility is consistent with or better than existing escapment techniques and at a lower operating cost to assessment programs. [Work supported by the Southern Boundary Restoration and Enhancement Fund of the Pacific Salmon Commission.

Holmes, John A.; Cronkite, George; Enzenhofer, Hermann J.

2005-04-01

196

Gradient-induced acoustic and magnetic field fluctuations in a 4T whole-body MR imager  

Microsoft Academic Search

Both the acoustic and magnetic fluctuation frequency response functions for a Siemens AS25 body gradient coil inside a 4 Tesla whole-body MR system were measured and analyzed in this study. In an attempt to correlate the acoustic noise inside the gradient coil with magnetic field oscillations, triangular and trap- ezoidal gradient impulses of varying amplitudes and widths were used to

Yuhua Wu; Blaine A. Chronik; Chris Bowen; Chris K. Mechefske; Brian K. Rutt

2000-01-01

197

The E4F Protein Is Required for Mitotic Progression during Embryonic Cell Cycles  

Microsoft Academic Search

The ubiquitously expressed E4F protein was originally identified as an E1A-regulated cellular transcription factor required for adenovirus replication. The function of this protein in normal cell physiology remains largely unknown. To address this issue, we generated E4F knockout mice by gene targeting. Embryos lacking E4F die at the peri-implantation stage, while in vitro-cultured E4F\\/ blastocysts exhibit defects in mitotic progression,

Laurent Le Cam; Matthieu Lacroix; Maria A. Ciemerych; Claude Sardet; Piotr Sicinski

2004-01-01

198

Spectral Morphological Analysis of Acoustical Images of Biological Tissues and Composite Structures: I. Statistical Approach  

NASA Astrophysics Data System (ADS)

The problem of classifying images of different biological tissues and composite structures is solved using the spectral and morphological analysis based on the Bayesian method for statistical hypothesis verification. The basis functions are constructed from a learning set. The spectral approach and its particular realizations in the form of Bartlett’s and Pisarenko’s methods adapted to the problem are considered. An extension of the spectral approach to the more general spectral-morphological classification is proposed. The latter takes into account the spatial-spectrum features of the structure types to be classified, as well as their morphological features, which manifest themselves in a correlation between the expansion coefficients. The characteristic properties of the spectral and spectral-morphological approaches are discussed using numerical classification examples. The method is generalized to the classification of multiparameter images of structures, which may be represented, for example, by the distributions of the sound velocity, density, absorption, and values of the nonlinear parameter.

Burov, V. A.; Kim, E. L.; Rumyantseva, O. D.

2005-02-01

199

Sound source imaging of low-flying airborne targets with an acoustic camera array  

Microsoft Academic Search

Two-dimensional images of sound source distribution from near-ground airborne sounds are created using an array of 32 microphones and time-domain beamforming. The signal processing is described and array configurations spanning a square area with a side length of 3.45m, approximately five wavelengths for a 500Hz sound, are examined. Simulations of a 32-element under-populated log6×log6 spaced array are given for sound

T. Scott Brandes; Robert H. Benson

2007-01-01

200

Acoustic thoracic image of crackle sounds using linear and nonlinear processing techniques  

Microsoft Academic Search

In this study, a novel approach is proposed, the imaging of crackle sounds distribution on the thorax based on processing\\u000a techniques that could contend with the detection and count of crackles; hence, the normalized fractal dimension (NFD), the\\u000a univariate AR modeling combined with a supervised neural network (UAR-SNN), and the time-variant autoregressive (TVAR) model\\u000a were assessed. The proposed processing schemes

Sonia Charleston-Villalobos; Guadalupe Dorantes-Méndez; Ramón González-Camarena; Georgina Chi-Lem; José G. Carrillo; Tomás Aljama-Corrales

2011-01-01

201

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

202

Kenyon College: Acoustics Instruments  

NSDL National Science Digital Library

This web page is an extensive collection of images and descriptions of historical instruments used in the teaching acoustics. Many of the items were used for demonstrations, labs, or other teaching purposes. This is part of a large collection of image covering all classical physics topics.

Greenslade Jr., Thomas

2011-04-09

203

Acoustic Neuroma  

MedlinePLUS

An acoustic neuroma is a benign tumor that develops on the nerve that connects the ear to the brain. ... can press against the brain, becoming life-threatening. Acoustic neuroma can be difficult to diagnose, because the ...

204

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

2013-09-24

205

Accessing 4f-states in single-molecule spintronics  

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

206

Acoustic sniper localization system  

NASA Astrophysics Data System (ADS)

Technologies for sniper localization have received increased attention in recent months as American forces have been deployed to various trouble spots around the world. Among the technologies considered for this task acoustics is a natural choice for various reasons. The acoustic signatures of gunshots are loud and distinctive, making them easy to detect even in high noise background environments. Acoustics provides a passive sensing technology with excellent range and non line of sight capabilities. Last but not least, an acoustic sniper location system can be built at a low cost with off the shelf components. Despite its many advantages, the performance of acoustic sensors can degrade under adverse propagation conditions. Localization accuracy, although good, is usually not accurate enough to pinpoint a sniper's location in some scenarios (for example which widow in a building or behind which tree in a grove). For these more demanding missions, the acoustic sensor can be used in conjunction with an infra red imaging system that detects the muzzle blast of the gun. The acoustic system can be used to cue the pointing system of the IR camera in the direction of the shot's source.

Prado, Gervasio; Dhaliwal, Hardave; Martel, Philip O.

1997-02-01

207

Acoustic radiation force impulse imaging with Virtual Touch™ tissue quantification: mean shear wave velocity of malignant and benign breast masses.  

PubMed

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. PMID:24109199

Wojcinski, Sebastian; Brandhorst, Kathrin; Sadigh, Gelareh; Hillemanns, Peter; Degenhardt, Friedrich

2013-09-30

208

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

209

Feasibility of High Frequency Acoustic Imaging for Inspection of Containments: Phase II  

SciTech Connect

The nuclear power industry is concerned with corrosive thinning of portions of the metallic pressure boundary, particularly in areas that are not directly accessible for inspection. This study investigated the feasibility of detecting these thickness degradations using ultrasonic imaging. A commercial ultrasonic system was used to carry out several full-scale, controlled laboratory experiments. Measurements of 0.5 MHz shear wave levels propagated in 25-mm-thick steel plate embedded in concrete showed 1.4-1.6 dB of signal loss for each centimeter of two-way travel in the steel plate (compared to previous numerical predictions of 3-4 dB), and 1.3 dB of signal loss per centimeter of two-way travel in steel plates embedded in concrete prior to setting of the concrete (i.e., plastic). Negligible losses were measured in plates with a decoupling treatment applied between the steel and concrete to simulate the unbonded portions of the pressure boundary. Scattered signals from straight slots of different size and shape were investigated. The return from a 4-mm-deep rectangular slots exhibited levels 23 dB down relative to incidence and 4-6 dB higher than those obtained from both ''v'' shaped and rounded slots of similar depth. The system displayed an input/output dynamic range of 125 dB and measurement variability less than 1-2dB. Based on these results, a 4-mm-deep, rounded degradation embedded 30 cm in concrete has expected returns of -73dB relative to the input and should therefore be detectable. Results of this and a prior study indicate that the technique has merit and should be developed more fully and demonstrated in the field.

Rudzinsky, J.; Bondaryk, J.; Conti, M.

1999-07-01

210

Remote sensing and acoustic telemetry  

Microsoft Academic Search

There is a growing need for remote underwater sensing and imaging without the burden of cabled connectivity to the outside world, and the best method for achieving this is with acoustic communications. However, the acoustic link is only one aspect of the problem, as the sensor system needs to interface with the modem, and perhaps with intermediary subsystems to provide

D. Green; T. Nguyen

2001-01-01

211

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; Feltovich, Helen; Homyk, Andrew; Carlson, Lindsey; Hall, Timothy

2013-10-01

212

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

213

Acoustic field enhancement for a stereo headphone  

Microsoft Academic Search

In this work, acoustic field enhancement for a stereo headphone is developed based on sound image widening and deepening. In sound image widening, the correlation between left and right channels is effectively decreased by using decorrelator, adaptive-gain differential signal module and energy conservation module with consideration of psychoacoustic critical bands. In sound image deepening, acoustic echoes and shadowing in stereo

Meng-Yu Chung; Chih-Chang Chen; Meng-Lin Hsia; Oscal T.-C. Chen

2011-01-01

214

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

215

Spectroscopy and Calculations for 4f(N) ? 4f(N-1)5d Transitions of Lanthanide Ions in K(3)YF(6).  

PubMed

In the present work, we report on the combined experimental and theoretical studies of the 4f-5d spectra of Ce(3+), Pr(3+), Nd(3+), Eu(3+), Gd(3+), Tb(3+), Dy(3+), and Er(3+) ions in a newly synthesized K(3)YF(6) matrix. The low temperature experimental 4f-5d excitation spectra have been analyzed and compared with the results of the energy-level and intensity calculations. For this theoretical analysis, the extended phenomenological crystal-field model for the 4f(N-1)5d configuration (i.e., the extended f-shell programs, developed by Prof. M. F. Reid) and exchange charge model (developed by Prof. B. Z. Malkin) have been used together to estimate the crystal field parameters and implement the spectral simulations. On the basis of the results of the performed theoretical analysis, we suggest the most probable positions occupied by optically active ions. Although the spectra of only eight lanthanide ions have been studied, the Hamiltonian parameters of the 4f(N-1)5d configuration have been evaluated for the whole lanthanide series and reported here for the first time, to give a complete and unified description of the spectroscopic properties of the trivalent rare earth ions in the chosen host. In addition to the studies of the 4f-5d transitions, various possible competitive excitation channels overlapping with 4f-5d ones have also been discussed, where a theoretical scheme giving rudiments to understand 4f-6s spectra are proposed for the first time. An excellent agreement between the calculated and measured excitation spectra shapes confirms validity of the performed analysis. The obtained parameters of the crystal field Hamiltonians for different ions and various electron configurations can be used in a straightforward way to generate the energy level positions and calculate the particular transition intensities for any rare earth ion in any particular spectral region. With the aid of the obtained parameters, the positions of the lowest energy levels of the 4f(N), 4f(N-1)5d ,and 4f(N-1)6s configurations of rare earth ions and 4f(N+1)(np)(5) configuration of rare earth ions and ligands (corresponding to the ligand-impurity ion charge transfer transitions) in the band gap of K(3)YF(6) have all been estimated. The obtained Hamiltonian parameters and energy levels diagrams, which include the electronic structure of a host material, can be used as a starting point for analysis of spectroscopic properties of trivalent lanthanides in similar fluorides. PMID:22881828

Ma, Chong-Geng; Brik, Mikhail G; Ryba-Romanowski, Witold; Swart, Hendrik C; Gusowski, Marek A

2012-08-28

216

Circular dichroism in 4 f photoemission from magnetically ordered rare-earth materials  

Microsoft Academic Search

4f Photoemission (PE) spectra from magnetically ordered rare-earth materials using circularly polarized X-rays exhibit strong Magnetic Circular Dichroism (MCD), i.e., the intensities of the individual multiplet lines depend on the relative orientation of sample magnetization and photon spin. On the example of the wellresolved Tb 4f PE multiplet, it is shown that in relevant cases 4f PE lines are essentially

K. Starke; E. Navas; E. Arenholz; L. Baumgarten; G. Kaindl

1995-01-01

217

The screening of 4f moments and delocalization in the compressed light rare earths  

SciTech Connect

Spin and charge susceptibilities and the 4f{sup n}, 4f{sup n{+-}1} configuration weights are calculated for compressed Ce (n=1), Pr (n=2), and Nd (n=3) metals using dynamical mean field theory combined with the local-density approximation. At ambient and larger volumes these trivalent rare earths are pinned at sharp 4f{sup n} configurations, their 4f moments assume atomic-limiting values, are unscreened, and the 4f charge fluctuations are small indicating little f state density near the Fermi level. Under compresssion there is dramatic screening of the moments and an associated increase in both the 4f charge fluctuations and static charge susceptibility. These changes are coincident with growing weights of the 4f{sup n-1} configurations, which it is argued are better measures of delocalization than the 4f{sup n+1} weights which are compromised by an increase in the number of 4f electrons caused by rising 6s, 6p bands. This process is continuous and prolonged as a function of volume, with strikingly similarity among the three rare earths, aside from the effects moderating and shifting to smaller volumes for the heavier members. The observed {alpha}-{gamma} collapse in Ce occurs over the large-volume half of this evolution, the Pr analog at smaller volumes, and Nd has no collapse.

McMahan, A K; Scalettar, R T; Jarrell, M

2009-08-19

218

Optimization of real-time acoustical and mechanical monitoring of high intensity focused ultrasound (HIFU) treatment using harmonic motion imaging for high focused ultrasound (HMIFU).  

PubMed

Harmonic Motion Imaging (HMI) for Focused Ultrasound (HMIFU) is a recently developed high-intensity focused ultrasound (HIFU) treatment monitoring method with feasibilities demonstrated in silica, in vitro and in vivo. Its principle is based on emission of an Amplitude-modulated therapeutic ultrasound beam utilizing a therapeutic transducer to induce an oscillatory radiation force while tracking the focal tissue mechanical response during the HIFU treatment using a confocally-aligned diagnostic transducer. In order to translate towards the clinical implementation of HMIFU, a complete assessment study is required in order to investigate the optimal radiation force threshold for reliable monitoring the local tissue mechanical property changes, i.e., the estimation HMIFU displacement under thermal, acoustical, and mechanical effects within focal medium (i.e., boiling, cavitation, and nonlinearity) using biological specimen. In this study, HMIFU technique is applied on HIFU treatment monitoring on freshly excised ex vivo canine liver specimens. In order to perform the multi-characteristic assessment, the diagnostic transducer was operated as either a pulse-echo imager or Passive Cavitation Detector (PCD) to assess the acoustic and mechanical response, while a bare-wire thermocouple was used to monitor the focal temperature change. As the acoustic power of HIFU treatment was ranged from 2.3 to 11.4 W, robust HMI displacement was observed across the entire range. Moreover, an optimized range for high quality displacement monitoring was found to be between 3.6 to 5.2W, where displacement showed an increase followed by significant decrease, indicating a stiffening of focal medium due to thermal lesion formation, while the correlation coefficient was maintained above 0.95. PMID:24111176

Hou, Gary Y; Marquet, Fabrice; Wang, Shutao; Konofagou, Elisa E

2013-07-01

219

Kinetics and mechanism of gas-phase reactions of n-C4F9OCH3, i-C4F9OCH3, n-C4F9OC(O)H, and i-C4F9OC(O)H with OH radicals in an environmental reaction chamber at 253-328 K  

NASA Astrophysics Data System (ADS)

The rate constants of the reactions of n-C4F9OCH3 (k1), i-C4F9OCH3 (k2), n-C4F9OC(O)H (k3), and i-C4F9OC(O)H (k4) with OH radicals were studied in an 11.5-dm3 environmental reaction chamber. k1 and k2 were determined to be (1.44 ± 0.33) × 10-12 exp[-(1450 ± 70)/T] and (1.59 ± 0.41) × 10-12 exp[-(1470 ± 80)/T] cm3 molecule-1 s-1 at 253-328 K. At 298 K, k3 and k4 were deduced to be (1.71 ± 0.32) × 10-14 and (1.67 ± 0.19) × 10-14 cm3 molecule-1 s-1. The observed products of the reaction of n-C4F9OCH3 with OH radicals were n-C4F9OC(O)H, CF3CF2CF2C(O)F, and COF2, and those for the reaction of i-C4F9OCH3 were i-C4F9OC(O)H, (CF3)2CFC(O)F, CF3C(O)F, and COF2.

Chen, L.; Uchimaru, T.; Kutsuna, S.; Tokuhashi, K.; Sekiya, A.

2011-10-01

220

Acoustic hemostasis  

NASA Astrophysics Data System (ADS)

In cases of severe injury, physicians speak of a ``golden hour''-a brief grace period in which quickly applied, proper therapy can save the life of the patient. Much of this mortality results from exsanguination, i.e., bleeding to death-often from internal hemorrhage. The inability of a paramedic to treat breaches in the vascular system deep within the body or to stem the loss of blood from internal organs is a major reason for the high level of mortality associated with blunt trauma. We have undertaken an extensive research program to treat the problem of internal bleeding. Our approach is as follows: (a) We use scanning ultrasound to identify internal bleeding and hemorrhage, (b) we use ultrasound imaging to locate specific breaches in the vascular system, both from damaged vessels and gross damage to the capillary bed, and (c) we use High Intensity Focused Ultrasound (HIFU) to treat the damaged region and to induce hemostasis. We present a general review of this research with some emphasis on the role of nonlinear acoustics. .

Crum, Lawrence; Beach, Kirk; Carter, Stephen; Chandler, Wayne; Curra, Francesco; Kaczkowski, Peter; Keilman, George; Khokhlova, Vera; Martin, Roy; Mourad, Pierre; Vaezy, Shahram

2000-07-01

221

Comparison of Scanning Acoustic Microscopy and Histology Images in Characterizing Surface Irregularities Among Engineered Human Oral Mucosal Tissues  

Microsoft Academic Search

Acoustic microscopy was used to monitor an ex vivo produced oral mucosal equivalent (EVPOME) developed on acellular cadaveric dermis (AlloDerm®). As seeded cells adhered and grew, they filled in and smoothed out the surface irregularities, followed by the production of a keratinized protective outermost layer. If noninvasive in vitro ultrasonic monitoring of these cellular changes could be developed, then tissue cultivation could

Frank Winterroth; Kyle W. Hollman; Shiuhyang Kuo; Kenji Izumi; Stephen E. Feinberg; Scott J. Hollister; J. Brian Fowlkes

2011-01-01

222

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

223

Experimental demonstration of an acoustic magnifying hyperlens  

Microsoft Academic Search

Acoustic metamaterials can manipulate sound waves in surprising ways, which include collimation, focusing, cloaking, sonic screening and extraordinary transmission. Recent theories suggested that imaging below the diffraction limit using passive elements can be realized by acoustic superlenses or magnifying hyperlenses. These could markedly enhance the capabilities in underwater sonar sensing, medical ultrasound imaging and non-destructive materials testing. However, these proposed

Jensen Li; Lee Fok; Xiaobo Yin; Guy Bartal; Xiang Zhang

2009-01-01

224

Acoustic-emission linear-pulse holography  

SciTech Connect

This paper describes Acoustic Emission Linear Pulse Holography which combines the advantages of linear imaging and acoustic emission into a single NDE inspection system. This unique system produces a chronological linear holographic image of a flaw by utilizing the acoustic energy emitted during crack growth. Conventional linear holographic imaging uses an ultrasonic transducer to transmit energy into the volume being imaged. When the crack or defect reflects that energy, the crack acts as a new source of acoustic waves. To formulate an image of that source, a receiving transducer is scanned over the volume of interest and the phase of the received signals is measured at successive points on the scan. The innovation proposed here is the utilization of the crack generated acoustic emission as the acoustic source and generation of a line image of the crack as it grows. A thirty-two point sampling array is used to construct phase-only linear holograms of simulated acoustic emission sources on large metal plates. The phases are calculated using the pulse time-of-flight (TOF) times from the reference transducer to the array of receivers. Computer reconstruction of the image is accomplished using a one-dimensional FFT algorithm (i.e., backward wave). Experimental results are shown which graphically illustrate the unique acoustic emission images of a single point and a linear crack in a 100 mm x 1220 mm x 1220 mm aluminum plate.

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

1982-06-01

225

Pulse Compression Acoustic Microscopy Using SAW Filters  

Microsoft Academic Search

The basic principles of surface-acoustic.,wave pulse compression acoustic microscopy is described and demonstrated by re- sults obtained at 60 and 750 MHz. A theoretical analysis discusses the behavior of such a system in terms of the required signal processing and the attainable imaging resolution. advantageous. At sufficiently high intensities, the imaging of the microscope will be affected by harmonic genera-

MEHRDAD NIKOONAHAD; Guang-Qi Yue; E. A. Ash

1985-01-01

226

Determination of the decay channel of the 4d. -->. 4f resonance in Tm  

SciTech Connect

We have found that the shape of the potential for 4f electrons in Tm predicts quite well the character of the 4d..-->..4f autoionization resonance observed in the photoelectron spectra. The direct photoemission from the 4d shell is suppressed by a barrier in the potential. Tunneling through this barrier is significantly slower than the decay of the excited electron back into the 4d hole. This decay is thus the dominant channel and is observed to lead predominantly to autoionization of the 4f shell.

Egelhoff, W.F. Jr.; Tibbetts, G.G.; Hecht, M.H.; Lindau, I.

1981-04-20

227

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

228

Communication acoustics  

NASA Astrophysics Data System (ADS)

Those aspects of acoustics which concern the relations of acoustics to the information and communication technologies are now frequently called ``communication acoustics.'' After a short review of the history of this field, relevant results from recent research at the Institute of Communication Acoustics at the Ruhr-University of Bochum, Germany, will be reported. This work can be seen in light of the research areas of computational auditory scene analysjs (CASA) and auditory virtual environments (AVE)-both dealing with the parametric representation of auditory scenes. Recent application opportunities and future trends will be discussed. It will be argued that modern communication-acoustical systems-which are often only embedded components in more complex communication systems-require more and more built-in explicit knowledge. Among other things, the development of such components and systems calls for data and knowledge from the cognitive sciences. Today's programs for education in communication engineering and communication acoustics often do not take sufficient account of this trend.

Blauert, Jens

2001-05-01

229

Kinetics and mechanism of gas-phase reactions of nC4F9OCH3, iC4F9OCH3, nC4F9OC(O)H, and iC4F9OC(O)H with OH radicals in an environmental reaction chamber at 253-328 K  

Microsoft Academic Search

The rate constants of the reactions of n-C4F9OCH3 (k1), i-C4F9OCH3 (k2), n-C4F9OC(O)H (k3), and i-C4F9OC(O)H (k4) with OH radicals were studied in an 11.5-dm3 environmental reaction chamber. k1 and k2 were determined to be (1.44 ± 0.33) × 10-12 exp[-(1450 ± 70)\\/T] and (1.59 ± 0.41) × 10-12 exp[-(1470 ± 80)\\/T] cm3 molecule-1 s-1 at 253-328 K. At 298 K,

L. Chen; T. Uchimaru; S. Kutsuna; K. Tokuhashi; A. Sekiya

2011-01-01

230

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

Code of Federal Regulations, 2013 CFR

...DEPARTMENT OF JUSTICE (CONTINUED) IMPLEMENTATION OF THE PROVISIONS OF THE VOTING RIGHTS ACT REGARDING LANGUAGE MINORITY GROUPS Nature of Coverage § 55.8 Relationship between section 4(f)(4) and section 203(c). (a) The statutory...

2013-07-01

231

Acoustic emission linear pulse holography  

SciTech Connect

Defects in a structure are imaged as they propagate, using their emitted acoustic energy as a monitored source. Short bursts of acoustic energy propagate through the structure to a discrete element receiver array. A reference timing transducer located between the array and the inspection zone initiates a series of time-of-flight measurements. A resulting series of time-of-flight measurements are then treated as aperture data and are transferred to a computer for reconstruction of a synthetic linear holographic image. The images can be displayed and stored as a record of defect growth.

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

1985-07-30

232

Acoustic emission linear pulse holography  

Microsoft Academic Search

Defects in a structure are imaged as they propagate, using their emitted acoustic energy as a monitored source. Short bursts of acoustic energy propagate through the structure to a discrete element receiver array. A reference timing transducer located between the array and the inspection zone initiates a series of time-of-flight measurements. A resulting series of time-of-flight measurements are then treated

H. Dale Collins; Lawrence J. Busse; Douglas K. Lemon

1985-01-01

233

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

234

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

235

Long-term tropospheric trend of octafluorocyclobutane (cC4F8 or PFC318)  

Microsoft Academic Search

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 (-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

D. E. Oram; F. S. Mani; J. C. Laube; M. J. Newland; C. E. Reeves; W. T. Sturges; S. A. Penkett; C. A. M. Brenninkmeijer; T. Röckmann; P. J. Fraser

2011-01-01

236

Acoustic characterization in whole blood and plasma of site-targeted nanoparticle ultrasound contrast agent for molecular imaging  

NASA Astrophysics Data System (ADS)

The ability to enhance specific molecular markers of pathology with ultrasound has been previously demonstrated by our group employing a nanoparticle contrast agent [Lanza et al., Invest. Radiol. 35, 227-234 (2000); Ultrasound Med. Biol. 23, 863-870 (1997)]. One of the advantages of this agent is very low echogenicity in the blood pool that allows increased contrast between the blood pool and the bound, site-targeted agent. We measured acoustic backscatter and attenuation coefficient as a function of the contrast agent concentration, ambient pressure, peak acoustic pressure, and as an effect of duty cycle and wave form shape. Measurements were performed while the nanoparticles were suspended in either whole porcine blood or plasma. The nanoparticles were only detectable when insonified within plasma devoid of red blood cells and were shown to exhibit backscatter levels more than 30 dB below the backscatter from whole blood. Attenuation of nanoparticles in whole porcine blood was not measurably different from that of whole blood alone over a range of concentrations up to eight times the maximum in vivo dose. The resulting data provide upper bounds on blood pool attenuation coefficient and backscatter and will be needed to more precisely define levels of molecular contrast enhancement that may be obtained in vivo. .

Hughes, Michael S.; Marsh, Jon N.; Hall, Christopher S.; Fuhrhop, Ralph W.; Lacy, Elizabeth K.; Lanza, Gregory M.; Wickline, Samuel A.

2005-02-01

237

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

238

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

SciTech Connect

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

239

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

240

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

241

The sounds of nanoscience: acoustic STM analogues  

NASA Astrophysics Data System (ADS)

A hands-on model of scanning tunnelling microscopy (STM) is presented. It uses near-field imaging with sound and computer assisted visualization to create acoustic mappings of resonator arrangements. Due to the (partial) analogy of matter and sound waves the images closely resemble STM scans of atoms. Moreover, the method can be extended to build an acoustic analogue of a quantum corral. The acoustic models foster reflections about the nature of STM images and elucidate the productive tension of imaging and imagining matter at the nanoscale.

Euler, Manfred

2013-09-01

242

Effects of Ar and O2 additives on SiO2 etching in C4F8-based plasmas  

Microsoft Academic Search

Gas mixtures based on C4F8 are promising for the development of high-performance SiO2 plasma etching processes. Measurements of important gas phase species, thin film etching rates and surface chemistry changes were performed for inductively coupled plasmas fed with C4F8\\/Ar and C4F8\\/O2 gas mixtures. The addition of Ar to C4F8 causes a strong increase of the plasma density relative to that

Xi Li; Li Ling; Xuefeng Hua; Masanaga Fukasawa; Gottlieb S. Oehrlein; Marcos Barela; Harold M. Anderson

2003-01-01

243

External Flow of an Acoustically Levitated Droplet  

Microsoft Academic Search

One of the major recent advances for experiments in containerless processing is acoustic levitation. Although there are a\\u000a lot of previous studies for acoustic levitation, characteristic of external flow of an acoustically levitated droplet is not\\u000a experimentally examined enough. In this study, external flow field has been observed by using high speed camera and Particle\\u000a Image Velocimetry. In the case

Koji Hasegawa; Yutaka Abe; Akiko Fujiwara; Yuji Yamamoto; Kazuyoshi Aoki

2008-01-01

244

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

2011-05-31

245

Electron affinity of trans-2-C4F8 from electron attachment-detachment kinetics.  

PubMed

Electron attachment and detachment kinetics of 2-C(4)F(8) were studied over the temperature range 298-487 K with a flowing-afterglow Langmuir-probe apparatus. Only parent anions were formed in the attachment process throughout this temperature range. At the highest temperatures, thermal electron detachment of the parent anions is important. Analysis of the 2-C(4)F(8) gas showed an 82/18 mixture of trans/cis isomers. The kinetic data at the higher temperatures were used to determine the electron affinity EA(trans-2-C(4)F(8)) = 0.79 +/- 0.06 eV after making some reasonable assumptions. The same quantity was calculated using the G3(MP2) compound method, yielding 0.74 eV. The kinetic data were not sufficient to establish a reliable value for EA(cis-2-C(4)F(8)), but G3(MP2) calculations give a value 0.017 eV greater than that for trans-2-C(4)F(8). MP2 and density functional theory were used to study the structural properties of the neutral and anion isomers. PMID:20020708

Van Doren, Jane M; Condon, Laura R; DeSouza-Goding, Antonet; Miller, Thomas M; Bopp, Joseph C; Viggiano, A A

2010-01-28

246

Ocean Acoustics.  

National Technical Information Service (NTIS)

The main element of this final report is a discussion of the development of the trace method for determining the acoustic properties of the ocean bottom sediments and basement. In addition a method is reported for the uniform determination of the continuo...

D. Stickler

1984-01-01

247

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

248

Preservation of biological function despite oxidative modification of the apolipoprotein A-I mimetic peptide 4F  

PubMed Central

Myeloperoxidase (MPO)-derived hypochlorous acid induces changes in HDL function via redox modifications at the level of apolipoprotein A-I (apoA-I). As 4F and apoA-I share structural and functional properties, we tested the hypothesis that 4F acts as a reactive substrate for hypochlorous acid (HOCl). 4F reduced the HOCl-mediated oxidation of the fluorescent substrate APF in a concentration-dependent manner (ED50 ? 56 ± 3 ?M). This reaction induced changes in the physical properties of 4F. Addition of HOCl to 4F at molar ratios ranging from 1:1 to 3:1 reduced 4F band intensity on SDS-PAGE gels and was accompanied by the formation of a higher molecular weight species. Chromatographic studies showed a reduction in 4F peak area with increasing HOCl and the formation of new products. Mass spectral analyses of collected fractions revealed oxidation of the sole tryptophan (Trp) residue in 4F. 4F was equally susceptible to oxidation in the lipid-free and lipid-bound states. To determine whether Trp oxidation influenced its apoA-I mimetic properties, we monitored effects of HOCl on 4F-mediated lipid binding and ABCA1-dependent cholesterol efflux. Neither property was altered by HOCl. These results suggest that 4F serves as a reactive substrate for HOCl, an antioxidant response that does not influence the lipid binding and cholesterol effluxing capacities of the peptide.

White, C. Roger; Datta, Geeta; Buck, Amanda K. W.; Chaddha, Manjula; Reddy, Gautam; Wilson, Landon; Palgunachari, Mayakonda N.; Abbasi, Mohammad; Anantharamaiah, G. M.

2012-01-01

249

Performance limitations in underwater acoustic telemetry  

Microsoft Academic Search

Performance limitations in digital acoustic telemetry are addressed. Increases in computational capabilities have led to a number of complex but practical solutions aimed at increasing the reliability of acoustic data links. These solutions range from ocean-basin scale data telemetry to video-image transmission at a few hundred yards' distance. The opportunity to implement highly complex tasks in real time on modest

J. A. Catipovic

1990-01-01

250

Synthetic Aperture Image Holography.  

National Technical Information Service (NTIS)

The paper describes the underwater imaging method of 'Synthetic Aperture Image Holography' which has real-time imaging capability. The method utilizes image holography and computer synthetic aperture techniques. The imaging system consists of the acoustic...

T. Sato J. S. Jaffe

1985-01-01

251

Valency and 4f covalency of Cs2RbTbF7  

NASA Astrophysics Data System (ADS)

Valency and 4f covalency of Cs2RbTbF7 were studied by x-ray-absorption near-edge-structure (XANES) spectroscopy at the Tb-LI-III, Tb-MIV,V, and F-K absorption thresholds as well as by 3d core-level photoemission (3d-PE). The availability of a chemically pure and stable sample allowed the observation of solely intrinsic spectral features in the core-level spectra, which characterize Cs2RbTbF7 as the tetravalent lanthanide compound with the weakest 4f-ligand hybridization known. Both the Tb final-state spectra, analyzed on the basis of a simplified Anderson single-impurity model, and the F-K XANES spectrum provide insight into 4f-ligand-p mixing in this compound.

Hu, Z.; Cho, En-Jin; Kaindl, G.; Müller, B. G.

1995-03-01

252

Value of Acoustic Radiation Force Impulse Imaging Elastography for Non-invasive Evaluation of Patients with Nonalcoholic Fatty Liver Disease.  

PubMed

The goals of the work described here were to evaluate the clinical utility of acoustic radiation force impulse (ARFI) elastography in differentiating non-alcoholic fatty liver disease (NAFLD) histologic subtypes and to determine if ARFI elastography measurements correlate with the severity of liver fibrosis. We compared ARFI elastography measurements with clinical, biologic and histologic features (simple steatosis or steatohepatitis) in 64 patients with histologically proven NAFLD. ARFI elastography is suitable for distinguishing patients with non-alcoholic steatohepatitis from those with simple steatosis, with an area under the receiver operating characteristic curve (AUROC) of 0.867 (95% confidence interval = 0.782-0.953). There was a highly significant correlation (r = 0.843) between ARFI elastography measurements and fibrosis (p < 0.001). In patients with non-alcoholic steatohepatitis, the diagnostic performance of ARFI elastography in predicting significant fibrosis (F ? 2) had an AUROC of 0.944. ARFI elastography better predicted F = 4 fibrosis (AUROC = 0.984). In conclusion, ARFI elastography is a promising method for differentiating patients with non-alcoholic steatohepatitis from patients with simple steatosis and can also predict significant fibrosis in these patients. PMID:23932277

Fierbinteanu Braticevici, Carmen; Sporea, Ioan; Panaitescu, Eugenia; Tribus, Laura

2013-08-09

253

Kondo Physics in a Rare Earth Ion with Well Localized 4f Electrons  

NASA Astrophysics Data System (ADS)

Dilute Nd in simple cubic LaB6 shows electrical resistance and specific heat features at low temperature consistent with a Kondo scale of TK?0.3K. Nd has a well-localized 4f3 J=9/2 Hund’s rule configuration which is not anticipated to be Kondo coupled to the conduction electrons in LaB6. We conjecture that the unexpected Kondo effect arises via participation of 4f quadrupolar degrees of freedom of the Nd crystal-field, ground-state quartet.

Stankiewicz, Jolanta; Evangelisti, Marco; Fisk, Zachary; Schlottmann, Pedro; Gor'kov, Lev P.

2012-06-01

254

Kondo-like 4f delocalization in Gd at high pressure  

SciTech Connect

We present resonant inelastic x-ray scattering (RIXS) and x-ray emission spectroscopy (XES) results which suggest Kondo-like aspects in the delocalization of 4f electrons in Gd metal to 113 GPa. Analysis of the RIXS data reveal a prolonged and continuous process throughout the entire pressure range, so that the volume collapse transition at 59 GPa is only part of the delocalization phenomenon. Moreover, the L{sub {gamma}1} XES spectra indicate no apparent change in the bare 4f moment across the collapse, suggesting that Kondo screening is responsible for the expected Pauli-like behavior in magnetic susceptibility.

Maddox, B R; Lazicki, A; Yoo, C S; Iota, V; Chen, M; McMahan, A K; Hu, M Y; Chow, P; Scalettar, R T; Pickett, W E

2005-11-28

255

Regulation of POU4F3 gene expression in hair cells by 5' DNA in mice.  

PubMed

The POU-domain transcription POU4F3 is expressed in the sensory cells of the inner ear. Expression begins shortly after commitment to the hair cell (HC) fate, and continues throughout life. It is required for terminal HC differentiation and survival. To explore regulation of the murine Pou4f3 gene, we linked enhanced green fluorescent protein (eGFP) to 8.5 kb of genomic sequence 5' to the start codon in transgenic mice. eGFP was uniformly present in all embryonic and neonatal HCs. Expression of eGFP was also observed in developing Merkel cells and olfactory neurons as well as adult inner and vestibular HCs, mimicking the normal expression pattern of POU4F3 protein, with the exception of adult outer HCs. Apparently ectopic expression was observed in developing inner ear neurons. On a Pou4f3 null background, the transgene produced expression in embryonic HCs which faded soon after birth both in vivo and in vitro. Pou4f3 null HCs treated with caspase 3 and 9 inhibitors survived longer than untreated HCs, but still showed reduced expression of eGFP. The results suggest the existence of separate enhancers for different HC types, as well as strong autoregulation of the Pou4f3 gene. Bioinformatic analysis of four divergent mammalian species revealed three highly conserved regions within the transgene: 400 bp immediately 5' to the Pou4f3 ATG, a short sequence at -1.3 kb, and a longer region at -8.2 to -8.5 kb. The latter contained E-box motifs that bind basic helix-loop-helix (bHLH) transcription factors, including motifs activated by ATOH1. Cotransfection of HEK293 or VOT-E36 cells with ATOH1 and the transgene as a reporter enhanced eGFP expression when compared with the transgene alone. Chromatin immunoprecipitation of the three highly conserved regions revealed binding of ATOH1 to the distal-most conserved region. The results are consistent with regulation of Pou4f3 in HCs by ATOH1 at a distal enhancer. PMID:21958861

Masuda, M; Dulon, D; Pak, K; Mullen, L M; Li, Y; Erkman, L; Ryan, A F

2011-09-19

256

Long-term tropospheric trend of octafluorocyclobutane (cC4F8 or PFC318)  

Microsoft Academic Search

Air samples collected at Cape Grim, Tasmania\\u000abetween 1978 and 2008 and during a series of more recent\\u000aaircraft sampling programmes have been analysed to determine\\u000athe atmospheric abundance and trend of octafluorocyclobutane\\u000a(c-C4F8 or PFC-318). c-C4F8 has an atmospheric\\u000alifetime in excess of 3000 yr and a global warming potential\\u000a(GWP) of 10 300 (100 yr time horizon), making

D. E. Oram; F. S. Mani; J. C. Laube; M. J. Newland; C. E. Reeves; W. T. Sturges; S. A. Penkett; C. A. M. Brenninkmeijer; T. Röckmann; P. J. Fraser

2012-01-01

257

High-resolution imaging of gigahertz polarization response arising from the interference of reflected surface acoustic waves.  

PubMed

The surface polarization caused by traveling SAWs at 1.585 GHz has been imaged using a dynamic homodyne electrostatic force microscope technique. Instead of measuring topographic changes caused by the SAW, the reported technique measures polarization in the piezoelectric substrate arising from mechanical stress caused by the SAW. The polarization associated with this stress field modulates the scanning probe cantilever deflection amplitude, which is extracted using a lock-in-based technique. High-resolution imaging is presented with images of the interference arising from a metal reflector on a SAW device. A mathematical model combining SAW generation and force interactions between the probe and the substrate was used to verify the experimental data. In addition to overcoming the challenge associated with detecting and imaging polarization effects at gigahertz frequencies, this imaging technique will greatly assist the development of SAW-based devices that exploit the reflection and interference of SAWs in areas as diverse as microfluidic mixing, cell sorting, and quantum entanglement. PMID:22718871

Yahyaie, I; Buchanan, D A; Bridges, G E; Thomson, D J; Oliver, D R

2012-06-01

258

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

259

Acoustic Doppler velocimeter-induced acoustic streaming and its implications for measurement  

NASA Astrophysics Data System (ADS)

The acoustic Doppler velocimeter (ADV) is widely used for the characterization of fluid flow. Secondary flows (“acoustic streaming”) generated by the ADV’s acoustic pulses may affect the accuracy of measurements in experiments with small velocities. We assessed the impact of acoustic streaming on flow measurement using particle image velocimetry. The probes of two different ADVs were successively mounted in a tank of quiescent water. The probes’ ultrasound emitters were aligned with a laser light sheet. Observed flow was primarily in the axial direction, accelerating from the ultrasound emitter and peaking within centimeters of the velocimeter sampling volume before dropping off. We measured the dependence of acoustic streaming velocity on ADV configuration, finding that different settings induce streaming ranging from negligible to more than 2.0 cm s-1. From these results, we describe cases where acoustic streaming affects velocity measurements and also cases where ADVs accurately measure their own acoustic streaming.

Poindexter, C. M.; Rusello, P. J.; Variano, E. A.

2010-11-01

260

Acoustic Doppler velocimeter-induced acoustic streaming and its implications for measurement  

NASA Astrophysics Data System (ADS)

The acoustic Doppler velocimeter (ADV) is widely used for the characterization of fluid flow. Secondary flows ("acoustic streaming") generated by the ADV's acoustic pulses may affect the accuracy of measurements in experiments with small velocities. We assessed the impact of acoustic streaming on flow measurement using particle image velocimetry. The probes of two different ADVs were successively mounted in a tank of quiescent water. The probes' ultrasound emitters were aligned with a laser light sheet. Observed flow was primarily in the axial direction, accelerating from the ultrasound emitter and peaking within centimeters of the velocimeter sampling volume before dropping off. We measured the dependence of acoustic streaming velocity on ADV configuration, finding that different settings induce streaming ranging from negligible to more than 2.0 cm s-1. From these results, we describe cases where acoustic streaming affects velocity measurements and also cases where ADVs accurately measure their own acoustic streaming.

Poindexter, C. M.; Rusello, P. J.; Variano, E. A.

2011-05-01

261

Multi-frequency Hydro-acoustic Imaging of Cold Seeps on the Hikurangi Margin Offshore New Zealand  

NASA Astrophysics Data System (ADS)

The subduction of the Pacific plate underneath the Australian plate along the Hikurangi margin leads to intense fluid venting along the southeastern margin of New Zealand's North Island. In the framework of the NewVents project several areas, where active fluid venting was known or expected, have been mapped using shipborne multibeam bathymetry as well as deep-towed sidescan sonar. Among the areas investigated the area known as Wairarapa, located just north of the southern end of Cook Strait, is one of the most interesting because several sites showing different degrees of fluid venting have been identified on 75 kHz sidescan sonar data. The Wairarapa area is located in roughly 1000-m water depth on a southwest-northeast trending ridge that has a distinct cone-shaped elevation at its northern end. Relief on the ridge is rather small and erosive sediment pathways separate the area from direct input of coarse sediment. Sedimentation in the Wairarapa area is dominated by hemipelagic sedimentation together with probably only very fine-grained turbidite spill-over deposition. Distinct high backscatter features showing a rough surface on the ridge are consequently most likely the result of carbonate cementation and precipitation of authigenic carbonates, as ground-truthing by video observation and coring show. A minimum of seven such high backscatter patches with maximum diameters of several hundreds of meters can be distinguished. Active fluid venting in these areas is demonstrated by very distinct acoustic flares in the water column. Due to narrow spacing of mapping profiles and an increased swath width of the deep-tow sidescan sonar system several high backscatter patches have been surveyed several times within the space of a few hours. Interestingly the outline of the flares change over time as viewed in different profiles indicating the activity of the seeps.

Weinrebe, W.; Klaucke, I.; Greinert, J.; Linke, P.; Bialas, J.

2007-12-01

262

Contribution of the 4f-core-excited states in determination of atomic properties in the promethium isoelectronic sequence  

NASA Astrophysics Data System (ADS)

The atomic properties of Pm-like ions were comprehensively studied using relativistic atomic codes. Excitation energies of the 4f14nl (with nl=5s, 6s, 5p, 6p, 5d, 6d, and 5f) states in Pm-like ions with nuclear charge Z ranging from 74 to 100 are evaluated within the framework of relativistic many-body theory (RMBPT). First- and second-order Coulomb energies and first- and second-order Breit corrections to the energies are calculated. Two alternative treatments of the Breit interaction are investigated. In the first approach we omit Breit contributions to the Dirac-Fock potential and evaluate Coulomb and Breit-Coulomb corrections through second order perturbatively. In the second approach were included both Coulomb and Breit contributions on the same footing via the Breit-Dirac-Fock potential and then treat the residual Breit and Coulomb interactions perturbatively. The results obtained from the two approaches are compared and discussed. The important question of what is the ground state in Pm-like ions was answered. Properties of the 4f-core-excited states are evaluated using the multiconfiguration relativistic Hebrew University Lawrence Livermore atomic code (hullac code) and the Hartree-Fock-relativistic method (cowan code). We evaluate excitation energies and transition rates in Pm-like ions with nuclear charge Z ranging from 74 to 92. Our large scale calculations include the following set of configurations: 4f145s, 4f145p, 4f135s2, 4f135p2, 4f135s5p, 4f125s25p, 4f125s5p2, and 4f125p3. Trends of excitation energies as function of Z are shown graphically for selected states. Excitation energies, transition rates, and lifetimes in Pm-like tungsten are evaluated with additional inclusion of the 4f115s25p2, 4f115s5p3, 4f105s25p3, and 4f105s5p4 configurations. This represents an unusual example of an atomic system where the even-parity complex [4f145s+4f135s5p+4f125s5p2+4f115s5p3+4f105s5p4] and the odd-parity complex [4f145p+4f135s2+4f125s25p+4f115s25p2+4f105s25p3] include so different configurations. Wavelengths of the 4f145s2S1/2-4f145p2PJ transition obtained by the cowan, hullac, and RMBPT codes are compared with other theoretical results and available measurements.

Safronova, U. I.; Safronova, A. S.; Beiersdorfer, P.

2013-09-01

263

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

264

Underwater acoustics  

Microsoft Academic Search

\\u000a While the scope of this chapter is not limited to bubble acoustics, this statement by Minnaert, published at the height of\\u000a the quantum revolution, as part of his classic article “On musical air-bubbles and the sounds of running water” (Minnaert,\\u000a 1933), is a stark reminder that we do not understand fully even the mundane. Nevertheless, important advances have been made

Michael A. Ainslie

265

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

2012-01-28

266

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

267

Absorption intensity analysis of the Er3+(4f11) transitions in calcium fluorophosphate  

NASA Astrophysics Data System (ADS)

A spectroscopic analysis is performed on Er3+(4f11) ions doped in calcium fluorophosphate (FAP) in order to assess this material for its potential as a near infrared laser material. The Judd-Ofelt model is applied to the polarization-dependant room temperature absorbtion intensities of Er3+(4f11) in FAP in order to obtain the three phenomenological intensity parameters. The intensity parameters are used to determine the radiative decay rates (emission probabilities), radiative lifetimes, and branching ratios of the Er3+ transitions from the upper multiplet manifolds to the corresponding lower-lying multiplet manifolds 2S+lLJ of Er3+(4f11) in FAP. Using the radiative decay rates of the Er3+(4f11) transitions between the corresponding excited states and the lower-lying states, the radiative lifetimes of eight excited states are determined in this host. Using room temperature fluorescence lifetime and the radiative lifetime of the Er3+ 4I13/2 Dot; 4I15/2 (1.52 ?m)transition, the quantum efficiency is also determined.

Coeckelenbergh, Cody H.; Yow, Raylon M.; Russell, Charles C., III; Sardar, Dhiraj K.

2004-10-01

268

Thyroid hormone transport by 4F2hc-IU12 heterodimers expressed in Xenopus oocytes.  

PubMed

Thyroid hormone (TH) action and metabolism require hormone transport across cell membranes. We have investigated the possibility that TH are substrates of amino acid transport (System L) mediated by heterodimers of 4F2 heavy-chain (hc) and the light-chain (lc) permease IU12. Co-expression of 4F2hc and IU12 cDNAs injected into Xenopus oocytes induces saturable, Na(+) -independent transport of tri-iodothyronine (T(3)), thyroxine (T(4)) (K(m) of 1.8 and 6.3 microM respectively), tryptophan and phenylalanine. Induced TH and tryptophan uptakes are inhibited by excess BCH (synthetic System L substrate). Induced TH uptake is also inhibited by excess reverse tri-iodothyronine (rT(3)), but not by triodothyroacetic acid (TRIAC) (TH analogue lacking anamino acid moiety). T(3) and tryptophan exhibit reciprocal inhibition of their 4F2hc-IU12 induced uptake. Transport pathways produced by 4F2hc-lc permease complexes may therefore be important routes for movement and exchange of TH (as well as amino acids) across vertebrate cell membranes, with a potential role in modulating TH action. PMID:10556789

Ritchie, J W; Peter, G J; Shi, Y B; Taylor, P M

1999-11-01

269

Chemical Treatment Effect of Si(111) Surfaces in NH4F Solution Studied by Spectroscopic Ellipsometry  

Microsoft Academic Search

Chemically treated Si(111) surfaces in NH4F (40%) solution at 20° C have been studied using spectroscopic ellipsometry (SE) and exsitu atomic force microscopy (AFM). The SE data clearly indicate that the solution causesthe removal of the native oxide with an etch rate of ˜ 15 Å\\/min. Just after the native oxide is etched away completely (t˜ 70 s), the SE

Takahiro Suzuki; Sadao Adachi

1994-01-01

270

Acoustic Holography. A Bibliography With Abstracts.  

National Technical Information Service (NTIS)

The bibliography contains 64 selected abstracts of research reports retrieved using the NTIS on-line search system--NTISearch. The topics covered include techniques of acoustic holography including microwave, seismic wave, and ultrasonic imaging and their...

D. M. Craig

1974-01-01

271

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

272

The use of broadband acoustic transducers and pulse-compression techniques for air-coupled ultrasonic imaging  

Microsoft Academic Search

A pulse-compression technique has been applied to air-coupled testing of solid materials. Capacitance transducers were used to generate wide bandwidth swept-frequency (chirp) signals in air, which were then used to measure and image solid samples in through transmission. The results demonstrate that such signal processing techniques lead to an improvement in the signal to noise ratio and timing accuracy for

T. H. Gan; D. A. Hutchins; D. R. Billson; D. W. Schindel

2001-01-01

273

Acoustic Suspension System.  

National Technical Information Service (NTIS)

A device for acoustically supporting small objects under 1 mm diameter, such as hollow glass spheres during processing into nuclear fusion target pellets is described. The acoustic levitation system utilizes single acoustic source and a small reflector to...

M. C. Lee

1981-01-01

274

Modification of Kirchhoff migration with variable sound speed and attenuation for acoustic imaging of media and application to tomographic imaging of the breast  

PubMed Central

Purpose: To explore the feasibility of improving cross-sectional reflection imaging of the breast using refractive and attenuation corrections derived from ultrasound tomography data. Methods: The authors have adapted the planar Kirchhoff migration method, commonly used in geophysics to reconstruct reflection images, for use in ultrasound tomography imaging of the breast. Furthermore, the authors extended this method to allow for refractive and attenuative corrections. Using clinical data obtained with a breast imaging prototype, the authors applied this method to generate cross-sectional reflection images of the breast that were corrected using known distributions of sound speed and attenuation obtained from the same data. Results: A comparison of images reconstructed with and without the corrections showed varying degrees of improvement. The sound speed correction resulted in sharpening of detail, while the attenuation correction reduced the central darkening caused by path length dependent losses. The improvements appeared to be greatest when dense tissue was involved and the least for fatty tissue. These results are consistent with the expectation that denser tissues lead to both greater refractive effects and greater attenuation. Conclusions: Although conventional ultrasound techniques use time-gain control to correct for attenuation gradients, these corrections lead to artifacts because the true attenuation distribution is not known. The use of constant sound speed leads to additional artifacts that arise from not knowing the sound speed distribution. The authors show that in the context of ultrasound tomography, it is possible to construct reflection images of the breast that correct for inhomogeneous distributions of both sound speed and attenuation.

Schmidt, Steven; Duric, Nebojsa; Li, Cuiping; Roy, Olivier; Huang, Zhi-Feng

2011-01-01

275

Relation of LAT1/4F2hc expression with pathological grade, proliferation and angiogenesis in human gliomas  

PubMed Central

Background LAT1/4F2hc heterodimeric complex is a major route for the transport of large neutral essential amino acids through the plasma membrane. Although it has been shown that LAT1/4F2hc is highly expressed in a variety of human tumors including gliomas, and LAT1 over-expression is associated with glioma grade and poor prognosis of glioma patients, the precise tissue location of LAT1/4F2hc in gliomas and the precise role of LAT1/4F2hc in glioma biological features remain unclear. Methods In the current study, the expressions of LAT1, 4F2hc, CD34 and Ki-67 were investigated by immunohistochemistry in 62 cases of human brain glioma; LAT1/4F2hc expression level, Ki-67 labeling index (Ki-67 LI) and microvessel density (MVD) were measured semi-quantitatively; and the correlation of LAT1/4F2hc expression with histopathological features, Ki-67 LI and MVD in gliomas was further analyzed. Results The results showed that both LAT1 and 4F2hc were expressed in all examined specimens. LAT1 but 4F2hc expression levels significantly correlated with the pathological grade and both expression levels significantly correlated with Ki-67 LI of gliomas. We also demonstrated that both LAT1 and 4F2hc immunoreactivity were observed in tumor cells as well as vascular endothelia; furthermore, the LAT1 expression level was markedly associated with glioma MVD as well. Conclusion LAT1/4F2hc over-expression is closely correlates with the malignant phenotype and proliferation of gliomas, and LAT1 was associates with glioma angiogenesis. LAT1/4F2hc, especially LAT1, may become a novel potential molecular target for glioma biological therapy.

2012-01-01

276

Different HLA antigen associations for the functionally active and inactive products of the complement C4F1 allele.  

PubMed

The genetic polymorphism of the fourth component of human complement, C4, was studied in 945 unrelated Caucasian individuals. A third allele of the C4F (Rodgers) locus, termed C4F1 was demonstrated. This allele is characterized using immunofixation electrophoresis, by the presence of an additional fast-moving anodal band of C4 which distinguishes it clearly from the common C4F variant. The allelic frequencies fit the Hardy-Weinberg equilibrium assuming three alleles at the C4F locus: C4F, C4Fo, and C4F1. The functional activity of the C4F variants was investigated using a specific hemolytic overlay technique for C4. It was found that in almost all individuals (75 out of 78), the C4F1 allele codes for a functionally inactive C4 product only when it occurs on an HLA-B17 positive haplotype but that the same allele codes for a functionally active fast variant of C4 when it occurs on an HLS-B37 positive haplotype (18 out of 18). Very strong genetic linkage disequilibrium was observed for the C4F1 allele with HLA-B17 and B37. The active and inactive C4F1 variant also has marked nonrandom gametic association to different alleles of the Bf locus and to HLA-C locus determinants. No further variants of the C4S (Chido) locus have been identified so far. Rodgers (Rg) typing by the plasma inhibition test of anti-Rg antiserum has shown that plasma from individuals homozygous for the C4F1 allele is only able to partially inhibit anti-Rg whereas all C4F positive individuals totally inhibited the reaction. PMID:7263310

O'Neill, G J; Miniter, P; Pollack, M S; Dupont, B

1980-07-01

277

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

278

Human Enteric Microsomal CYP4F Enzymes O-Demethylate the Antiparasitic Prodrug Pafuramidine  

PubMed Central

CYP4F enzymes, including CYP4F2 and CYP4F3B, were recently shown to be the major enzymes catalyzing the initial oxidative O-demethylation of the antiparasitic prodrug pafuramidine (DB289) by human liver microsomes. As suggested by a low oral bioavailability, DB289 could undergo first-pass biotransformation in the intestine, as well as in the liver. Using human intestinal microsomes (HIM), we characterized the enteric enzymes that catalyze the initial O-demethylation of DB289 to the intermediate metabolite, M1. M1 formation in HIM was catalyzed by cytochrome P450 (P450) enzymes, as evidenced by potent inhibition by 1-aminoben-zotriazole and the requirement for NADPH. Apparent Km and Vmax values ranged from 0.6 to 2.4 ?M and from 0.02 to 0.89 nmol/min/mg protein, respectively (n = 9). Of the P450 chemical inhibitors evaluated, ketoconazole was the most potent, inhibiting M1 formation by 66%. Two inhibitors of P450-mediated arachidonic acid metabolism, HET0016 (N-hydroxy-N?-(4-n-butyl-2-methylphenyl)formamidine) and 17-octadecynoic acid, inhibited M1 formation in a concentration-dependent manner (up to 95%). Immunoinhibition with an antibody raised against CYP4F2 showed concentration-dependent inhibition of M1 formation (up to 92%), whereas antibodies against CYP3A4/5 and CYP2J2 had negligible to modest effects. M1 formation rates correlated strongly with arachidonic acid ?-hydroxylation rates (r2 = 0.94, P < 0.0001, n = 12) in a panel of HIM that lacked detectable CYP4A11 protein expression. Quantitative Western blot analysis revealed appreciable CYP4F expression in these HIM, with a mean (range) of 7 (3–18) pmol/mg protein. We conclude that enteric CYP4F enzymes could play a role in the first-pass biotransformation of DB289 and other xenobiotics.

Wang, Michael Zhuo; Wu, Judy Qiju; Bridges, Arlene S.; Zeldin, Darryl C.; Kornbluth, Sally; Tidwell, Richard R.; Hall, James Edwin; Paine, Mary F.

2008-01-01

279

Classroom acoustics: the national acoustic standard  

Microsoft Academic Search

This paper discusses the variables affecting classroom acoustics and a case study examination of some local classrooms. Classrooms were measured against proposed American National Standards Institute (ANSI) standards and treatment options for improving acoustics are suggested.

Stacy Allen

2004-01-01

280

Live cell imaging in a micro-array of acoustic traps facilitates quantification of natural killer cell heterogeneity.  

PubMed

Natural killer (NK) cells kill virus-infected or cancer cells through the release of cytotoxic granules into a tight intercellular contact. NK cell populations comprise individual cells with varying sensitivity to distinct input signals, leading to disparate responses. To resolve this NK cell heterogeneity, we have designed a novel assay based on ultrasound-assisted cell-cell aggregation in a multiwell chip allowing high-resolution time-lapse imaging of one hundred NK-target cell interactions in parallel. Studying human NK cells' ability to kill MHC class I deficient tumor cells, we show that approximately two thirds of the NK cells display cytotoxicity, with some NK cells being particularly active, killing up to six target cells during the assay. We also report that simultaneous interaction with several susceptible target cells increases the cytotoxic responsiveness of NK cells, which could be coupled to a previously unknown regulatory mechanism with implications for NK-mediated tumor elimination. PMID:23435966

Christakou, Athanasia E; Ohlin, Mathias; Vanherberghen, Bruno; Khorshidi, Mohammad Ali; Kadri, Nadir; Frisk, Thomas; Wiklund, Martin; Önfelt, Björn

2013-04-01

281

Kondo Physics in a Rare Earth Ion with well localized 4f electrons  

NASA Astrophysics Data System (ADS)

We observe a rise in the low temperature resistivity of dilute La1-xNdxB6 single crystals. The specific heat data for the same samples show that there is an entropy of Rln4 per mole Nd involved in the excess specific heat above that of LaB6. All these features are consistent with a Kondo scale of TK = 1 K. However, Nd has a well localized 4f ^ 3 J = 9/2 Hund's Rule configuration which is not expected to be Kondo coupled to the conduction electrons in LaB6. We conjecture that the unexpected Kondo effect arises via participation of 4f quadrupolar degrees of freedom of the Nd crystal field ground state quartet. Raman experiments as well as detailed theoretical studies do indicate that one expects strong quadrupolar influence in the properties of NdB6.

Stankiewicz, Jolanta; Fisk, Zachary; Evangelisti, Marco; Schlottman, Pedro

2012-02-01

282

Acoustic transducer  

DOEpatents

An acoustic transducer comprising a one-piece hollow mandrel into the outer surface of which is formed a recess with sides perpendicular to the central axis of the mandrel and separated by a first distance and with a bottom parallel to the central axis and within which recess are a plurality of washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material with the discs being captured between the sides of the recess in a pre-stressed interference fit, typically at 2000 psi of compressive stress. The transducer also includes a power supply and means to connect to a measurement device. The transducer is intended to be used for telemetry between a measurement device located downhole in an oil or gas well and the surface. The transducer is of an construction that is stronger with fewer joints that could leak fluids into the recess holding the piezoelectric elements than is found in previous acoustic transducers.

Drumheller, Douglas S. (Cedar Crest, NM)

1997-01-01

283

Acoustic transducer  

DOEpatents

An acoustic transducer is described comprising a one-piece hollow mandrel into the outer surface of which is formed a recess with sides perpendicular to the central axis of the mandrel and separated by a first distance and with a bottom parallel to the central axis and within which recess are a plurality of washer-shaped discs of a piezoelectric material and at least one disc of a temperature-compensating material with the discs being captured between the sides of the recess in a pre-stressed interference fit, typically at 2,000 psi of compressive stress. The transducer also includes a power supply and means to connect to a measurement device. The transducer is intended to be used for telemetry between a measurement device located downhole in an oil or gas well and the surface. The transducer is of an construction that is stronger with fewer joints that could leak fluids into the recess holding the piezoelectric elements than is found in previous acoustic transducers. 4 figs.

Drumheller, D.S.

1997-12-30

284

The surface effect on Au 4f X-ray photoelectron spectra  

Microsoft Academic Search

An investigation of the surface effect on Au 4f X-ray photoelectron spectra was made for different emission angles. It was found that surface plasmon excitations made significant contributions to the spectra in single and plural energy-loss peaks and in the multiple loss background. Our approach involved Monte Carlo simulations of photoelectrons in the interior region of the solid and Poisson

C. J. Tung; J. P. Wang; Y. F. Chen; C. M. Kwei

1996-01-01

285

Contribution of Eu 4f states to the magnetic anisotropy of EuO  

SciTech Connect

Anisotropic x-ray magnetic linear dichroism (AXMLD) provides a novel element-, site-, shell-, and symmetry-selective techniques to study the magnetic anisotropy induced by a crystalline electric field. The weak Eu2+ M4,5 AXMLD observed in EuO(001) indicates that the Eu 4f states are not rotationally invariant and hence contribute weakly to the magnetic anisotropy of EuO. The results are contrasted with those obtained for 3d transition metal oxides.

Arenholz, E.; Schmehl, A.; Schlom, D.G.; van der Laan, G.

2008-09-11

286

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

287

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

288

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 (-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). The origin of c-C4F8 is unclear. 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.

2011-07-01

289

4f/5d hybridization in the heavy rare earth elements Er and Tm  

NASA Astrophysics Data System (ADS)

We present experimental data and first-principles calculations of the x-ray resonant magnetic scattering (XRMS) line shapes of Er and Tm metals. Band structure calculations are presented that illustrate the existence of 4f/5d hybridization of unoccupied electron levels. This leads to spin and orbital features in the XRMS spectra that are not representative of the 5d occupied moments. General trends through the heavy rare earth series are discussed with reference to previous work.

Brown, S. D.; Strange, P.; Bouchenoire, L.; Thompson, P. B. J.

2013-04-01

290

Imaging Transverse Isotropic Properties of Muscle by Monitoring Acoustic Radiation Force Induced Shear Waves using a 2D Matrix Ultrasound Array  

PubMed Central

A 2D matrix ultrasound array is used to monitor acoustic radiation force impulse (ARFI) induced shear wave propagation in 3D 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 3D. The true fiber orientation found using the 3D 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.

Wang, Michael; Byram, Brett; Palmeri, Mark; Rouze, Ned; Nightingale, Kathryn

2013-01-01

291

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

2013-05-14

292

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

293

Pb 4f photoelectron spectroscopy on mass-selected anionic lead clusters at FLASH  

NASA Astrophysics Data System (ADS)

4f core level photoelectron spectroscopy has been performed on negatively charged lead clusters, in the size range of 10-90 atoms. We deploy 4.7 nm radiation from the free-electron laser FLASH, yielding sufficiently high photon flux to investigate mass-selected systems in a beam. A new photoelectron detection system based on a hemispherical spectrometer and a time-resolving delayline detector makes it possible to assign electron signals to each micro-pulse of FLASH. The resulting 4f binding energies show good agreement with the metallic sphere model, giving evidence for a fast screening of the 4f core holes. By comparing the present work with previous 5d and valence region data, the paper presents a comprehensive overview of the energetics of lead clusters, from atoms to bulk. Special care is taken to discuss the differences of the valence- and core-level anion cluster photoionizations. Whereas in the valence case the escaping photoelectron interacts with a neutral system near its ground state, core-level ionization leads to transiently highly excited neutral clusters. Thus, the photoelectron signal might carry information on the relaxation dynamics.

Bahn, J.; Oelßner, P.; Köther, M.; Braun, C.; Senz, V.; Palutke, S.; Martins, M.; Rühl, E.; Ganteför, G.; Möller, T.; von Issendorff, B.; Bauer, D.; Tiggesbäumker, J.; Meiwes-Broer, K.-H.

2012-07-01

294

Ligand field effects on the multiplet structure of the U4f XPS of UO2  

SciTech Connect

Ab initio, fully relativistic four component theory was used to determine atomic and interatomic many-body effects for the 4f X-ray photoelectron spectrum of an embedded UO8-12 cluster representing UO2. Many-body effects were included through the use of configuration interaction wavefunctions that allow the mixing of XPS allowed and XPS forbidden configurations. Charge transfer configurations were not included. This work extends our earlier studies on simulations of the U 4f XPS for the free U4+ cation. While the main XPS features are similar in both cases, ligand field effects changed the multiplet structure in important ways that better simulated experimental data for UO2. Neither initial nor final state covalency significantly reduced the 4f-5f exchange integrals, and the differences between the atom and cluster model was due to ligand field splitting of the 5f band and increased distributions of intensity from XPS allowed to XPS forbidden peaks. The prominent 7 eV satellites associated with UO2 were absent in the simulations, and provides further evidence that these satellites are due to charge transfer and not other interatomic effects.

Ilton, Eugene S.; Bagus, Paul S.

2008-03-01

295

End-on azido-bridged 3d-4f complexes showing single-molecule-magnet property.  

PubMed

Four tetranuclear 3d-4f complexes with the 4f centers bridged solely by end-on azide bridges were reported. The [CuTb]2 compound displays single-molecule-magnet behavior with hysteresis loops observed at up to 2.4 K. PMID:23746362

Huang, Xing-Cai; Zhou, Chun; Wei, Hai-Yan; Wang, Xin-Yi

2013-06-07

296

TOPICAL REVIEW: Acoustic cloaking and transformation acoustics  

NASA Astrophysics Data System (ADS)

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 that make an object invisible to acoustic waves, and the cloak can either encompass or lie outside the object to be concealed. Transformation acoustics, as an analog of transformation optics, can go beyond invisibility cloaking. As an illustration for manipulating linear liquid surface waves, we show that a liquid wave rotator can be designed and fabricated to rotate the wave front. The acoustic transformation media require acoustic materials which are anisotropic and inhomogeneous. Such materials are difficult to find in nature. However, composite materials with embedded sub-wavelength resonators can in principle be made and such 'acoustic metamaterials' can exhibit nearly arbitrary values of effective density and modulus tensors to satisfy the demanding material requirements in transformation acoustics. We introduce resonant sonic materials and Helmholtz resonators as examples of acoustic metamaterials that exhibit resonant behaviour in effective density and effective modulus.

Chen, Huanyang; Chan, C. T.

2010-03-01

297

Acoustic cryocooler  

SciTech Connect

This patent describes an acoustic cryocooler with no moving parts is formed from a thermoacoustic driver (TAD) driving a pulse tube refrigerator (PTR) through a standing wave tube. Thermoacoustic elements in the TAD are spaced apart a distance effect to accommodate the increased thermal penetration length arising from the relatively low TAD operating frequency in the range of 15--60 Hz. At these low operating frequencies, a long tube is required to support the standing wave. The tube may be coiled to reduce the overall length of the cryocooler. One or two PTR's are located on the standing wave tube adjacent antinodes in the standing wave to be driven by the standing wave pressure oscillations. It is predicted that a heat input of 1000 W at 1000 K will maintain a cooling load of 5 W at 80 K.

Swift, G.W.; Martin, R.A.; Radebaugh, R.

1990-09-04

298

Acoustic cryocooler  

SciTech Connect

An acoustic cryocooler with no moving parts is formed from a thermoacoustic driver (TAD) driving a pulse tube refrigerator (PTR) through a standing wave tube. Thermoacoustic elements in the TAD are spaced apart a distance effective to accommodate the increased thermal penetration length arising from the relatively low TAD operating frequency in the range of 15-60 Hz. At these low operating frequencies, a long tube is required to support the standing wave. The tube may be coiled to reduce the overall length of the cryocooler. One or two PTR's are located on the standing wave tube adjacent antinodes in the standing wave to be driven by the standing wave pressure oscillations. It is predicted that a heat input of 1000 W at 1000 K will maintain a cooling load of 5 W at 80 K. 3 figs.

Swift, G.W.; Martin, R.A.; Radebaugh, R.

1989-09-26

299

Acoustic cryocooler  

SciTech Connect

An acoustic cryocooler with no moving parts is formed from a thermoacoustic driver (TAD) driving a pulse tube refrigerator (PTR) through a standing wave tube. Thermoacoustic elements in the TAD are spaced apart a distance effective to accommodate the increased thermal penetration length arising from the relatively low TAD operating frequency in the range of 15-60 Hz. At these low operating frequencies, a long tube is required to support the standing wave. The tube may be coiled to reduce the overall length of the cryocooler. One or two PTR's are located on the standing wave tube adjacent antinodes in the standing wave to be driven by the standing wave pressure oscillations. It is predicted that a heat input of 1000 W at 1000 K will maintian a cooling load of 5 W at 80 K.

Swift, Gregory W. (Santa Fe, NM); Martin, Richard A. (Los Alamos, NM); Radenbaugh, Ray (Louisville, CO)

1990-01-01

300

Acoustic transducer  

DOEpatents

An active acoustic transducer tool for use down-hole applications. The tool includes a single cylindrical mandrel including a shoulder defining the boundary of a narrowed portion over which is placed a sandwich-style piezoelectric tranducer assembly. The piezoelectric transducer assembly is prestressed by being placed in a thermal interference fit between the shoulder of the mandrel and the base of an anvil which is likewise positioned over the narrower portion of the mandrel. In the preferred embodiment, assembly of the tool is accomplished using a hydraulic jack to stretch the mandrel prior to emplacement of the cylindrical sandwich-style piezoelectric transducer assembly and anvil. After those elements are positioned and secured, the stretched mandrel is allowed to return substantially to its original (pre-stretch) dimensions with the result that the piezoelectric transducer elements are compressed between the anvil and the shoulder of the mandrel.

Drumheller, Douglas S. (Cedar Crest, NM)

2000-01-01

301

Acoustic cryocooler  

DOEpatents

An acoustic cryocooler with no moving parts is formed from a thermoacoustic driver (TAD) driving a pulse tube refrigerator (PTR) through a standing wave tube. Thermoacoustic elements in the TAD are spaced apart a distance effective to accommodate the increased thermal penetration length arising from the relatively low TAD operating frequency in the range of 15-60 Hz. At these low operating frequencies, a long tube is required to support the standing wave. The tube may be coiled to reduce the overall length of the cryocooler. One or two PTR's are located on the standing wave tube adjacent antinodes in the standing wave to be driven by the standing wave pressure oscillations. It is predicted that a heat input of 1000 W at 1000 K will maintain a cooling load of 5 W at 80 K. 3 figs.

Swift, G.W.; Martin, R.A.; Radebaugh, R.

1989-09-26

302

Acoustic cryocooler  

DOEpatents

An acoustic cryocooler with no moving parts is formed from a thermoacoustic driver (TAD) driving a pulse tube refrigerator (PTR) through a standing wave tube. Thermoacoustic elements in the TAD are spaced apart a distance effective to accommodate the increased thermal penetration length arising from the relatively low TAD operating frequency in the range of 15-60 Hz. At these low operating frequencies, a long tube is required to support the standing wave. The tube may be coiled to reduce the overall length of the cryocooler. One or two PTR's are located on the standing wave tube adjacent antinodes in the standing wave to be driven by the standing wave pressure oscillations. It is predicted that a heat input of 1000 W at 1000 K will maintian a cooling load of 5 W at 80 K.

Swift, Gregory W. (Santa Fe, NM); Martin, Richard A. (Los Alamos, NM); Radenbaugh, Ray (Louisville, CO)

1990-01-01

303

Acoustic fluidization  

NASA Astrophysics Data System (ADS)

Evidence for the fluid-like flow of rock debris is discussed, together with a conceptual model for the underlying processes. The phenomenon occurs with both crater walls and long-runout landslides. It is suggested that individual rocks in a debris mass may possess a degree of random motion and act like a dense gas, thereby being capable of flowing like a fluid. A sound wave propagating through a pile of rocks in contact and supporting an overburden of debris can be separated by half the sound wavelength and relieve the immobilizing overburden pressure. Exceeding the pressure permits the rocks to flow. The debris can be located on a gentle slope because of the efficiency of the conversion of gravitational potential energy to acoustic energy. The distance the mass will slide forward is proportional to its thickness. Applications of the principle for moving grain, sugar, and coal in storage bins are suggested.

Melosh, H. J.

1983-04-01

304

Acoustic telemetry.  

SciTech Connect

Broadcasting messages through the earth is a daunting task. Indeed, broadcasting a normal telephone conversion through the earth by wireless means is impossible with todays technology. Most of us don't care, but some do. Industries that drill into the earth need wireless communication to broadcast navigation parameters. This allows them to steer their drill bits. They also need information about the natural formation that they are drilling. Measurements of parameters such as pressure, temperature, and gamma radiation levels can tell them if they have found a valuable resource such as a geothermal reservoir or a stratum bearing natural gas. Wireless communication methods are available to the drilling industry. Information is broadcast via either pressure waves in the drilling fluid or electromagnetic waves in the earth and well tubing. Data transmission can only travel one way at rates around a few baud. Given that normal Internet telephone modems operate near 20,000 baud, these data rates are truly very slow. Moreover, communication is often interrupted or permanently blocked by drilling conditions or natural formation properties. Here we describe a tool that communicates with stress waves traveling through the steel drill pipe and production tubing in the well. It's based on an old idea called Acoustic Telemetry. But what we present here is more than an idea. This tool exists, it's drilled several wells, and it works. Currently, it's the first and only acoustic telemetry tool that can withstand the drilling environment. It broadcasts one way over a limited range at much faster rates than existing methods, but we also know how build a system that can communicate both up and down wells of indefinite length.

Drumheller, Douglas Schaeffer; Kuszmaul, Scott S.

2003-08-01

305

Acoustic optic hybrid (AOH) sensor  

PubMed

The ability of laser vibrometers to receive and process acoustic echoes from the water surface above a submerged target is established and evaluated. Sonar echoes from a submerged target are collected from the water surface by a laser vibrometer. Feasibility of this approach to sensing underwater sound is demonstrated. If the acoustic excitation at an otherwise undisturbed water surface is 195 to 168 dB re: 1 microPa, signal-to-noise ratio (SNR), at the vibrometer output, is shown to range from about 46 to 6 dB. Capillary waves and gravity waves at the water surface are expected and shown to have some destructive effect on the process of echo retrieval. A series of experiments to quantify the surface wave effects is described. The wave experiment results are reported. A successful attempt to acquire echoes from a submerged target over a grid of points for further processing into a three-dimensional image is made and described. The data acquisition and beamforming techniques constitute a three-dimensional, acoustic optic, synthetic aperture sonar (SAS). Beamformed images are included. For an aircraft towing acoustic sensors through the water with a mechanical link, this technique holds the promise of increased safety and improved fuel efficiency. PMID:11008811

Matthews; Arrieta

2000-09-01

306

Broadband acoustic quantification of stratified turbulence.  

PubMed

High-frequency broadband acoustic scattering techniques have enabled the remote, high-resolution imaging and quantification of highly salt-stratified turbulence in an estuary. Turbulent salinity spectra in the stratified shear layer have been measured acoustically and by in situ turbulence sensors. The acoustic frequencies used span 120-600 kHz, which, for the highly stratified and dynamic estuarine environment, correspond to wavenumbers in the viscous-convective subrange (500-2500 m(-1)). The acoustically measured spectral levels are in close agreement with spectral levels measured with closely co-located micro-conductivity probes. The acoustically measured spectral shapes allow discrimination between scattering dominated by turbulent salinity microstructure and suspended sediments or swim-bladdered fish, the two primary sources of scattering observed in the estuary in addition to turbulent salinity microstructure. The direct comparison of salinity spectra inferred acoustically and by the in situ turbulence sensors provides a test of both the acoustic scattering model and the quantitative skill of acoustical remote sensing of turbulence dissipation in a strongly sheared and salt-stratified estuary. PMID:23862783

Lavery, Andone C; Geyer, W Rockwell; Scully, Malcolm E

2013-07-01

307

Experimental demonstration of an acoustic magnifying hyperlens  

NASA Astrophysics Data System (ADS)

Acoustic metamaterials can manipulate sound waves in surprising ways, which include collimation, focusing, cloaking, sonic screening and extraordinary transmission. Recent theories suggested that imaging below the diffraction limit using passive elements can be realized by acoustic superlenses or magnifying hyperlenses. These could markedly enhance the capabilities in underwater sonar sensing, medical ultrasound imaging and non-destructive materials testing. However, these proposed approaches suffer narrow working frequency bands and significant resonance-induced loss, which hinders them from successful experimental realization. Here, we report the experimental demonstration of an acoustic hyperlens that magnifies subwavelength objects by gradually converting evanescent components into propagating waves. The fabricated acoustic hyperlens relies on straightforward cutoff-free propagation and achieves deep-subwavelength resolution with low loss over a broad frequency bandwidth.

Li, Jensen; Fok, Lee; Yin, Xiaobo; Bartal, Guy; Zhang, Xiang

2009-12-01

308

Experimental demonstration of an acoustic magnifying hyperlens.  

PubMed

Acoustic metamaterials can manipulate sound waves in surprising ways, which include collimation, focusing, cloaking, sonic screening and extraordinary transmission. Recent theories suggested that imaging below the diffraction limit using passive elements can be realized by acoustic superlenses or magnifying hyperlenses. These could markedly enhance the capabilities in underwater sonar sensing, medical ultrasound imaging and non-destructive materials testing. However, these proposed approaches suffer narrow working frequency bands and significant resonance-induced loss, which hinders them from successful experimental realization. Here, we report the experimental demonstration of an acoustic hyperlens that magnifies subwavelength objects by gradually converting evanescent components into propagating waves. The fabricated acoustic hyperlens relies on straightforward cutoff-free propagation and achieves deep-subwavelength resolution with low loss over a broad frequency bandwidth. PMID:19855382

Li, Jensen; Fok, Lee; Yin, Xiaobo; Bartal, Guy; Zhang, Xiang

2009-10-25

309

Acoustic microscopy in the food industry  

NASA Astrophysics Data System (ADS)

Acoustic microscopy has been used for many years to image and measure the elastic properties of materials across a wide range of scientific disciplines. However the application of this technique in the food industry is scarce. In this paper we outline the operation of a reflection-mode acoustic microscope and discuss some of the issues relevant to its operation in the food sector. We then present two relevant case studies in which we employ acoustic microscopy to analyse potato cells and the fat structure in Iberian ham and chorizo.

Watson, N.; Povey, M.; Corona, E.; Benedito, J.; Parker, N.

2012-12-01

310

Frequency steerable acoustic transducers  

NASA Astrophysics Data System (ADS)

Structural health monitoring (SHM) is an active research area devoted to the assessment of the structural integrity of critical components of aerospace, civil and mechanical systems. Guided wave methods have been proposed for SHM of plate-like structures using permanently attached piezoelectric transducers, which generate and sense waves to evaluate the presence of damage. Effective interrogation of structural health is often facilitated by sensors and actuators with the ability to perform electronic, i.e. phased array, scanning. The objective of this research is to design an innovative directional piezoelectric transducer to be employed for the localization of broadband acoustic events, or for the generation of Lamb waves for active interrogation of structural health. The proposed Frequency Steerable Acoustic Transducers (FSATs) are characterized by a spatial arrangement of active material which leads to directional characteristics varying with frequency. Thus FSATs can be employed both for directional sensing and generation of guided waves without relying on phasing and control of a large number of channels. The analytical expression of the shape of the FSATs is obtained through a theoretical formulation for continuously distributed active material as part of a shaped piezoelectric device. The FSAT configurations analyzed in this work are a quadrilateral array and a geometry which corresponds to a spiral in the wavenumber domain. The quadrilateral array is experimentally validated, confirming the concept of frequency-dependent directionality. Its limited directivity is improved by the Wavenumber Spiral FSAT (WS-FSAT), which, instead, is characterized by a continuous frequency dependent directionality. Preliminary validations of the WS-FSAT, using a laser doppler vibrometer, are followed by the implementation of the WS-FSAT as a properly shaped piezo transducer. The prototype is first used for localization of acoustic broadband sources. Signal processing algorithms and related imaging techniques for damage location are also presented. Finally, the WS-FSAT has also been experimentally validated in generation.

Senesi, Matteo

311

LETTER TO THE EDITOR: Energy levels of 4f3 in the Nd3+ free ion from emission spectra  

NASA Astrophysics Data System (ADS)

The emission spectrum of neodymium produced by vacuum spark sources was observed in the vacuum ultraviolet on two normal-incidence spectrographs. In an initial result, more than 550 lines have been identified as transitions from 85 4f25d levels to 37 levels of the 4f3 ground configuration in the free ion Nd3+. The levels 4f34F3/2 and 4I11/2, responsible for the well-known 1064 nm laser line, have respective positions of 11 698.57 ±0.1 cm-1 and 1897.07 ±0.1 cm-1 above the ground level 4I9/2. The newly found levels of 4f3 constitute the first isolated 4fN configuration (N > 2) and therefore enable checks of effective parameters that represent far configuration interaction. Slater parameters Fk(4f, 4f) derived from Nd3+:LaCl3 are 3% to 5% smaller than in the free ion.

Wyart, Jean-François; Meftah, Ali; Bachelier, Annik; Sinzelle, Jocelyne; Tchang-Brillet, Wan-Ü. Lydia; Champion, Norbert; Spector, Nissan; Sugar, Jack

2006-03-01

312

The bonding in thiolate protected gold nanoparticles from Au4f photoemission core level shifts  

NASA Astrophysics Data System (ADS)

Density functional theory calculations are used to evaluate Au4f core level shifts of methyl thiolate protected Au25, Au102 and Au144 nanoparticles. The shifts are found to provide sensitive fingerprints of the chemical environment. In particular, Au atoms in protective gold-thiolate complexes have higher binding energies than Au atoms with solely metal neighbors. The core level shifts for the nanoparticles are compared to the corresponding results for methyl thiolates adsorbed on Au(111) and implications for the understanding of the gold-sulfur bond is discussed.

Grönbeck, Henrik

2012-06-01

313

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

314

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

315

De novo facioscapulohumeral muscular dystrophy defined by DNA probe p13E-11 (D4F104S1).  

PubMed Central

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant condition with variable age of onset and severity. Identification of a de novo DNA fragment by probe p13E-11 (D4F104S1) established the diagnosis of new mutation FSHD in 27 of 31 sporadic cases. The clinical data for these certain new mutation cases were as follows: 13 boys, 14 girls; mean age of onset 6.8 years; significant leg weakness in 19/27 (70%) (8/27 (30%) used wheelchairs at a mean age of 17.7 years); high tone sensorineural deafness in 10/27; visual acuity and direct ophthalmoscopy were normal. Congenital facial diplegia and sensorineural deafness in three children suggest that infantile FSHD is not a genetically separate disorder from FSHD. Ascertainment bias may explain the difference in severity between this group and typical familial cases. Molecular analysis for FSHD should be considered in children with either congenital or early onset facial weakness or diplegia. Images

Jardine, P E; Koch, M C; Lunt, P W; Maynard, J; Bathke, K D; Harper, P S; Upadhyaya, M

1994-01-01

316

Acoustic shear wave displacement measurement using ultrasound  

Microsoft Academic Search

Echo ultrasound can be used to detect and measure acoustic shear waves. Earlier it has been shown that a phase contrast based magnetic resonance imaging technique can be used for cyclic shear wave displacement measurement. Echo ultrasound presents an alternate method for imaging of such shear waves. The ultrasound based method uses the phase of quadrature echo signals to estimate

Vinayak Dutt; Randall R. Kinnick; James F. Greenleaf

1996-01-01

317

Scanning acoustic force microscopy characterization of thermal expansion effects on the electromechanical properties of film bulk acoustic resonators  

NASA Astrophysics Data System (ADS)

This letter demonstrates the application of scanning acoustic force microscopy for the characterization of film bulk acoustic resonators beyond detection of the gigahertz vibration amplitude and acoustic wave field imaging. We present a method to measure thermal expansion effects on these resonators by modulating the driving signal amplitude and then varying the modulation frequency from a few hertz to several tens of kilohertz. For the particular device considered here, we show the influence of thermal expansion effects on its electromechanical response and the acoustic wave field images. The thermal relaxation time constant of the resonator is measured and compared with a theoretical estimation based on the heat transfer analysis of the system.

San Paulo, A.; Liu, X.; Bokor, J.

2005-02-01

318

Acoustic-photorefractive recording of acoustical oscillations  

SciTech Connect

The process whereby acoustic waves are recorded in photorefractive piezoelectric crystals by means of the acoustophotorefractive effect is studied. Expression are obtained for the electric fields and elastic displacements of the recorded holographic lattice. The kinetics of the recording of monochromatic waves and complex acoustic signals under the action of pulsed uniform illumination is studied. It is shown that in the case when a complex acoustic signal is recorded the signal recorded with short recording times is the derivative of the input signal.

Zelenskaya, T.E.; Shandarov, S.M.

1988-01-01

319

Opto-acoustic thrombolysis  

DOEpatents

This invention is a catheter-based device for generating an ultrasound excitation in biological tissue. Pulsed laser light is guided through an optical fiber to provide the energy for producing the acoustic vibrations. The optical energy is deposited in a water-based absorbing fluid, e.g. saline, thrombolytic agent, blood or thrombus, and generates an acoustic impulse in the fluid through thermoelastic and/or thermodynamic mechanisms. By pulsing the laser at a repetition rate (which may vary from 10 Hz to 100 kHz) an ultrasonic radiation field can be established locally in the medium. This method of producing ultrasonic vibrations can be used in vivo for the treatment of stroke-related conditions in humans, particularly for dissolving thrombus or treating vasospasm. The catheter can also incorporate thrombolytic drug treatments as an adjunct therapy and it can be operated in conjunction with ultrasonic detection equipment for imaging and feedback control and with optical sensors for characterization of thrombus type and consistency.

Celliers, Peter (Berkeley, CA); Da Silva, Luiz (Danville, CA); Glinsky, Michael (Livermore, CA); London, Richard (Orinda, CA); Maitland, Duncan (Livermore, CA); Matthews, Dennis (Moss Beach, CA); Fitch, Pat (Livermore, CA)

2000-01-01

320

Jahn Teller effect on the [TiF4F4Fint]6-(C4v) and [NiF4F4Fint]7-(C4v) clusters embedded into SrF2 crystals  

NASA Astrophysics Data System (ADS)

By means of EPR method the associative [TiF4F4Fint]6-(C4v) and [NiF4F4Fint]7-(C4v) centers were revealed in the fluorite type SrF2:Ti and SrF2:Ni crystals grown by Bridgman method in helium atmosphere containing some amount of a fluorine gas. It was found that at low temperatures the local structures of these associative centers were exposed to a static rhombic distortion. The reasons of such distortions were accounted for by the assumption that the E ? (b1 + b2) vibronic interaction became effective due to that the ground orbital states of the [TiF4F4Fint]6-(C4v) and [NiF4F4Fint]7-(C4v) centers occurred to be doubly degenerated.

Ulanov, V. A.; Zhiteitcev, E. R.; Varlamov, A. G.

2007-07-01

321

A multilayered acoustic hyperlens with acoustic metamaterials  

NASA Astrophysics Data System (ADS)

The acoustic hyperlens can be realized by an alternating layered structure of water and fluid with negative mass density. Based on this alternating layered principle, we propose that an acoustic metamaterial consisting of three layers in water background can be designed to replace the fluid with negative mass density. The effective mass density and bulk modulus of the system which is composed of acoustic metamaterial and water are functions of the frequency. The effective mass density of such a system is close to the negative mass density of the fluid at a specific frequency; thus an acoustic metamaterial hyperlens can be achieved.

Chiang, Tzeh-Yi; Wu, Liang-Yu; Tsai, Chia-Nien; Chen, Lien-Wen

2011-05-01

322

Real-time sonar system using acoustic lens and numerical analysis based on 2D\\/3D parabolic equation method  

Microsoft Academic Search

The autonomous underwater vehicle mounted on the forward obstacle avoidance sonar is developed to investigate ocean environments. In order to obtain real time, high efficiency and clear acoustic images, the real-time sonar system using an acoustic lens has been studied. The propagation of sound through acoustic lenses can be modeled using either the ray-tracing, wave acoustics or a combination of

Y. Takasea; T. Anadaa; T. Tsuchiyaa; N. Endoha; N. Nakamura; T. Tukioka

2005-01-01

323

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

324

Atomic Force Acoustic Microscopy  

NASA Astrophysics Data System (ADS)

This chapter shortly reviews the scientific background of Atomic Force Acoustic Microscopy (AFAM), the basic theoretical models, the experimental techniques to obtain quantitative values of local elastic constants, and non-linear AFAM. Analytical and finite element models describing transverse flexural vibrations of AFM cantilevers with and without tip-surface contact are recapitulated. The models are suitable for micro fabricated silicon cantilevers of approximately rectangular cross section which are typically used in AFAM. Experimental methods to obtain single-point as well as array measurements and full spectroscopy images are discussed in combination with the respective reference methods for calibration. In a non-linear AFAM experiment, the vibration amplitudes of the sample surface and the cantilever are measured quantitatively with an interferometer at different excitation amplitudes, and the full tip-sample interaction force curve is reconstructed using a frequency dependent transfer function.

Rabe, U.; Kopycinska-Müller, M.; Hirsekorn, S.

325

Opto-Acoustic Hydrophone.  

National Technical Information Service (NTIS)

The patent describes an opto-acoustic hydrophone for converting acoustic signals to corresponding modulated optical signals and transmitting the converted signals via a fiber optics cable to a sonobuoy. Light reflected from a mirror or equivalent oscillat...

M. Stimler

1975-01-01

326

Acoustic Neuroma Association  

MedlinePLUS

... Click here for survey information UCSF Tinnitus Survey Acoustic Neuroma Patients Study Dr. Steven W. Cheung, a ... recommends treatment from a medical team with substantial acoustic neuroma experience." This statement was adopted by the ...

327

Calculation of electron-photon coincidence parameters for singlet-triplet mixed 4F states of helium  

NASA Astrophysics Data System (ADS)

We present the theoretical formalism required to interpret the electron-photon coincidence measurements of the helium 4F state by Cvejanovi? and Crowe [Phys. Rev. Lett. 80, 3033 (1998)]. The results of the convergent close-coupling theory are compared with experiment and found to be in good qualitative agreement. We demonstrate that the singlet-triplet mixing in the 4F states does not affect the calculated results significantly.

Fursa, Dmitry V.; Bray, Igor

1999-02-01

328

A small-size multichannel scanning acoustic microscope  

Microsoft Academic Search

A multichannel scanning acoustic microscope, the ultrasonic element of which consists of several focused transducers, is proposed.\\u000a In this device, images are generated by the electronic switching of the transducers with simultaneous mechanical translation\\u000a of the acoustic element, thus reducing the data acquisition time. The design of the microscope, the acoustic element of which\\u000a contains eight transducers with a 100-MHz

S. A. Titov; R. G. Maev; A. N. Bogachenkov

2009-01-01

329

Spacecraft and acoustics  

NASA Astrophysics Data System (ADS)

The current understanding of the acoustic environment for launch vehicle liftoff and its effects on spacecraft is reviewed, giving attention to the accurate simulation of the flight environment in ground acoustic test facilities as a means to reaching spacecraft reliability goals. A detailed account is given of the generation of acoustic test specifications for spacecraft and their subsystems, as well as to measures of acoustic facility effectiveness in the reproduction of flight dynamic responses.

Reddy, C. V. R.; Prabhu, M. S. S.

1993-01-01

330

Surface and bulk 4f-photoemission spectra of CeIn{sub 3} and CeSn{sub 3}  

SciTech Connect

Resonant photoemission spectroscopy was performed on CeIn{sub 3} and CeSn{sub 3} at the 4d-4f and 3d-4f core thresholds. Using the different surface sensitivity between the two photon energies, surface and bulk 4f-photoemission spectra were derived for both compounds. With the noncrossing approximation of the Anderson impurity model, the 4d-4f resonant spectra together with the surface and bulk spectra were self-consistently analyzed to obtain the microscopic parameters such as the 4f-electron energy and the hybridization strength with conduction electrons. The result shows a substantial difference in these parameters between the surface and the bulk, indicating that it is important to take into account the surface effect in analyzing photoemission spectra of Ce compounds. It is also found that the 4f surface core-level shift is different between CeIn{sub 3} and CeSn{sub 3}. {copyright} {ital 1997} {ital The American Physical Society}

Kim, H. [Department of Physics, Tohoku University, Sendai 980-77 (Japan); Tjernberg, O. [Material Physics, Royal Institute of Technology, S-10044, Stockholm (Sweden); Chiaia, G. [INFM-Dip. Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133, Milano (Italy); Kumigashira, H.; Takahashi, T. [Department of Physics, Tohoku University, Sendai 980-77 (Japan); Duo, L. [INFM-Dip. Fisica, Politecnico di Milano, Piazza Leonardo da Vinci 32, I-20133, Milano (Italy); Sakai, O.; Kasaya, M. [Department of Physics, Tohoku University, Sendai 980-77 (Japan); Lindau, I. [Department of Synchrotron Radiation Research, Institute of Physics, Lund University, Soelvegatan 14 S-223 62 Lund (Sweden)

1997-07-01

331

Human cytochrome P450 4F11: Heterologous expression in bacteria, purification, and characterization of catalytic function  

PubMed Central

Human cytochrome P450 (P450) 4F11 is still considered an “orphan” because its function is not well characterized. A bacterial expression system was developed for human P450 4F11, producing ~230 nmol P450 from a 3-liter culture of Escherichia coli. P450 4F11 was purified and utilized for untargeted substrate searches in human liver extract using a liquid chromatography/mass spectrometry-based metabolomic and isotopic labeling approach (Z. Tang et al., Anal. Chem. 81, 3071–3078, 2009). Four fatty acids—palmitic, oleic, arachidonic, and docosahexaenoic—were identified in human liver and verified as substrates of P450 4F11. The products were characterized as ?-hydroxylated fatty acids by gas chromatography-mass spectrometry analysis of their trimethylsilyl derivatives. Kinetic analysis of the oxidation products confirmed that the fatty acids are substrates oxidized by P450 4F11. P450 4F11 also exhibited low activity for some drug N-demethylation reactions but none for activation of several procarcinogens.

Tang, Zhongmei; Salamanca-Pinzon, Sandra Giovanna; Wu, Zhong-Liu; Xiao, Yi; Guengerich, F. Peter

2009-01-01

332

STOVL acoustic fatigue technologies  

Microsoft Academic Search

This paper assesses the state of the art in acoustic fatigue technologies as applied to an advanced supersonic short takeoff and vertical landing (STOVL) aircraft. The topics covered include advanced materials, fatigue, acoustic loads prediction, and stress response prediction. Advanced materials are compared from the standpoints of fatigue resistance and fatigue data availability. State of the art acoustic load prediction

David S. Groen

1988-01-01

333

Negative acoustic index metamaterial  

Microsoft Academic Search

Acoustic metamaterials utilizing periodic deep subwavelength resonators can attain negative acoustic properties unavailable in nature. We have developed a negative acoustic index metamaterial for water that combines Helmholtz and rod-spring resonators to control effective bulk modulus and mass density, respectively. Effective properties extracted from full-wave simulations of our metamaterial show that negative real components of bulk modulus and density occur

L. Fok; X. Zhang

2011-01-01

334

Acoustic Control System  

Microsoft Academic Search

This paper describes some features of an acoustic control system. It is designed primarily for acoustic control of blow out preventers and subsea production units. The system is combined with a super short baseline acoustic navigation system. The communication between the central unit and the subsea unit to be controlled is 2-way. The communication from the subsea unit is used

H. Jacobsen; K. Vestgard; F. Knudsen

1982-01-01

335

Acoustic sniper localization system  

Microsoft Academic Search

Technologies for sniper localization have received increased attention in recent months as American forces have been deployed to various trouble spots around the world. Among the technologies considered for this task acoustics is a natural choice for various reasons. The acoustic signatures of gunshots are loud and distinctive, making them easy to detect even in high noise background environments. Acoustics

Gervasio Prado; Hardave Dhaliwal; Philip O. Martel

1997-01-01

336

Acoustic tomography. Laboratory technique Implementation.  

NASA Astrophysics Data System (ADS)

From geomechanical tests carried out on rocks it is possible to determine its physico-mechanical properties, which relate the strain and applied stress; even so, conventional tests do not allow to identify how stress is distributed and how it has affected porous media. Today, techniques like acoustic tomography widely used in medicine, geophysics and others sciences, generates images by sections of the interior of a body. Acoustic tomography allows inferring the stress state within porous media; since wave velocities are closely related to media density, if a stress is applied to a rock, it will generate grains compaction and this will be showed by an increase of wave velocity. Implementation was conducted on rock plugs under diverse stress fields, simultaneously recording P-wave velocities (Compressional) on perpendicular planes to sample vertical axis. Transmission and reception of acoustic waves through porous media were done by piezoelectric crystals (PZT) used as sensors. A transmitting crystal excited by a voltage pulse causes a mechanical vibration, which travels across media; this is known as inverse piezoelectric effect. This vibration is recorded by a receiving crystal in which the direct piezoelectric effect appears; which dictates that if a piezoelectric is disturbed mechanically, an electrical signal between its terminals will appear. This electrical signal is used to obtain the wave velocity. Nevertheless, acoustic tomography corresponds to one of those called inverse Problems that arise when from observed data the model parameters must be obtained; in this way, tomography involves iterative reconstruction techniques (ART or SIRT) which are projections of observed data and its later inversion. Obtained results are cross-sectional images of velocity within the rock. In these images it is possible to identify where stress has a greater concentration observing the color map generated; thus, a greater velocity density area corresponding to a greater stress will be colored with a higher tonality within the palette used.

Galvis, Jorge; Carvajal, Jenny

2010-05-01

337

Acoustic Imaging Evaluation of Juvenile Salmonid Behavior in the Immediate Forebay of the Water Temperature Control Tower at Cougar Dam, 2010  

SciTech Connect

This report presents the results of an evaluation of juvenile Chinook salmonid (Oncorhynchus tshawytscha) behavior in the immediate forebay of the Water Temperature Control (WTC) tower at Cougar Dam in 2010. The study was conducted by the Pacific Northwest National Laboratory for the U.S. Army Corps of Engineers. The overall goal of the study was to characterize juvenile salmonid behavior and movement patterns in the immediate forebay of the WTC tower for fisheries resource managers to use to make decisions on bioengineering designs for long-term structures and/or operations to facilitate safe downstream passage for juvenile salmonids. We collected acoustic imaging (Dual-Frequency Identification Sonar; DIDSON) data from February 1, 2010 through January 31, 2011 to evaluate juvenile salmonid behavior year-round in the immediate forebay surface layer of the WTC tower (within 20 m, depth 0-5 m). From October 28, 2010 through January 31, 2011 a BlueView acoustic camera was also deployed in an attempt to determine its usefulness for future studies as well as augment the DIDSON data. For the DIDSON data, we processed a total of 35 separate 24-h periods systematically covering every other week in the 12-month study. Two different 24-hour periods were processed for the BlueView data for the feasibility study. Juvenile salmonids were present in the immediate forebay of the WTC tower throughout 2010. The juvenile salmonid abundance index was low in the spring (<200 fish per sample-day), began increasing in late April and peaked in mid-May. Fish abundance index began decreasing in early June and remained low in the summer months. Fish abundance increased again in the fall, starting in October, and peaked on November 8-9. A second peak occurred on December 22. Afterwards, abundance was low for the rest of the study (through January 2011). Average fish length for juvenile salmonids during early spring 2010 was 214 {+-} 86 mm (standard deviation). From May through early November, average fish length remained relatively consistent (132 {+-} 39 mm), after which average lengths increased to 294 {+-} 145 mm for mid-November though early December. Fish behavior analysis indicates milling in front of the intake tower was the most common behavior observed throughout the study period (>50% of total fish events). The next most common movement patterns were fish traversing along the front of the tower, east-to-west and west-to-east. The proportion of fish events seen moving into (forebay to tower) or out of (tower to forebay) the tower was generally low throughout the spring, summer, and early fall for both directions combined. From mid-December 2010 through the end of the study, the combined proportions of fish moving into and out of the tower were higher than previous months of this study. Schooling behavior was most distinct in the spring from late April through mid-June. Schooling events were present in 30 - 96% of the fish events during that period, with a peak in mid-May. Schooling events were also present in the summer, but at lower numbers. Diel distributions for schooling fish during spring, fall, and winter months indicate schooling was concentrated during daylight hours. No schooling was observed at night. Predator activity was observed during late spring, when fish abundance and schooling were highest for the year, and again in the fall months when fish events increased from a summer low. No predator activity was observed in the summer, and little activity occurred during the winter months. For the two days of BlueView data analyzed for vertical distribution in the forebay, a majority of fish (>50%) were present in the middle of the water column (10 - 20 m deep). Between 20 and 41 % of total fish abundance were found in the bottom of the water column (20 - 30 m deep). Few fish were observed in the top 10 m of the water column.

Khan, Fenton; Johnson, Gary E.; Royer, Ida M.; Phillips, Nathan RJ; Hughes, James S.; Fischer, Eric S.; Ploskey, Gene R.

2011-10-01

338

Conduction band states and the 5d-4f laser transition of rare earth ion dopants  

SciTech Connect

We discuss how the interactions of the 5d orbital with the conduction band of the host medium play a crucial role in determining whether rare earth containing materials can serve as useful laser materials, based on their 5d-4f transition. To explore this issue, we examine the pump-probe spectra of Sm[sup 2+], Eu[sup 2+], and Ce[sup 3+] dopants in various fluoride and chloride crystals. In addition we suggest that the luminescence properties are also profoundly impacted by this interaction. The outstanding UV laser performance achieved by the Ce:LiSrAlF[sub 6] crystal is rationalized in terms of the reduced overlap of conduction band states with the cerium ions.

Payne, S.A.; Marshall, C.D.; Bayramian, A.; Lawson, J.K.

1996-12-31

339

Magnetism and superconductivity driven by identical 4f states in a heavy-fermion metal  

PubMed Central

The apparently inimical relationship between magnetism and superconductivity has come under increasing scrutiny in a wide range of material classes, where the free energy landscape conspires to bring them in close proximity to each other. Particularly enigmatic is the case when these phases microscopically interpenetrate, though the manner in which this can be accomplished remains to be fully comprehended. Here, we present combined measurements of elastic neutron scattering, magnetotransport, and heat capacity on a prototypical heavy fermion system, in which antiferromagnetism and superconductivity are observed. Monitoring the response of these states to the presence of the other, as well as to external thermal and magnetic perturbations, points to the possibility that they emerge from different parts of the Fermi surface. Therefore, a single 4f state could be both localized and itinerant, thus accounting for the coexistence of magnetism and superconductivity.

Nair, Sunil; Stockert, O.; Witte, U.; Nicklas, M.; Schedler, R.; Kiefer, K.; Thompson, J. D.; Bianchi, A. D.; Fisk, Z.; Wirth, S.; Steglich, F.

2010-01-01

340

Comparison of the performance of 2-f versus 4-f correlators with limited coding domain SLM  

NASA Astrophysics Data System (ADS)

A new interesting hybrid digital/optical correlator, which performs the first Fourier transform electronically, hereafter referred to as a 2-f correlator, has been presented by Young. One of the advantages of this architecture compared to the classical 4-f correlator, an example of this architecture is presented by Chao, is that the optical system becomes less complex and does not require the same strict optical tolerances. The signal processing performance of these two architectures is expected to be the same if ideal Spatial Light Modulators (SLMs) with fully complex-valued coding domains are available. This study investigates the influence of a limited coding domain on the signal processing performance provided by current available SLMs. Optimal trade-off filters3 have been used for this investigation since they can be tuned, as the name suggests, to an optimal trade-off between being discriminant against distortions and being robust against noise. This has been used to evaluate the influence of different coding domains on the two optical correlator architectures. The coding domains of some commercially available SLMs have been implemented and their effect on the different correlator architectures have been analysed. These SLMs are: binary phase/amplitude SLM from Displaytech, Colorado, USA; micromirror SLM from Fraunhofer Institute, Dresden, Germany and the bipolar grey-scale FLC SLM from Boulder Nonlinear Systems, Colorado, USA. The coding domain has a strong influence on the signal processing capabilities. Generally, the 2-f architecture shows to be more discriminant and the 4-f architecture more robust to noise. The final choice between the two correlator systems depends however on available SLMs and the required trade-off between robustness and discriminance that is needed for the application.

Selberg, Daniel; Noharet, Bertrand; Brunnstroem, Kjell E.

2002-03-01

341

Opto-Acoustic Characterization of Melanosome  

NASA Astrophysics Data System (ADS)

A wide-band LiNbO3 piezoelectric transducer was used to investigate the properties of bovine melanosome. The second harmonic laser pulses at 523 nm wavelength and 10 ns duration were delivered to the sample from a Quanta-Ray pulsed, Q-switched Nd:YAG laser. The opto-acoustic signal was detected and recorded using a computerized ocilloscpe/data acquisition system. The results of the opto-acoustic experiment suggest that this technique has a great potential for materials imaging, medical laser dosimetry as well as diagnostic imaging.

Mayo, Michael L.; Sardar, Dhiraj K.

1999-10-01

342

Plasma-surface interactions of nanoporous silica during plasma-based pattern transfer using C{sub 4}F{sub 8} and C{sub 4}F{sub 8}/Ar gas mixtures  

SciTech Connect

We have investigated plasma surface interactions of nanoporous silica (NPS) films with porosities up to 50%, and SiO{sub 2} with C{sub 4}F{sub 8}/Ar discharges used for plasma etching. The pore size was about 2-3 nm for all films. In highly polymerizing plasmas (e.g., pure C{sub 4}F{sub 8} discharges), the porous structure of NPS material favors surface polymerization over etching and porosity-corrected etching rates (CER) were suppressed and lower than SiO{sub 2} etching rate for the same conditions. The etching rates of NPS were dramatically enhanced in ion rich discharges (e.g., C{sub 4}F{sub 8}/90%Ar) and the CER in this case is greater than the SiO{sub 2} etching rate. Both x-ray photoelectron spectroscopy (XPS) and static secondary ion mass spectroscopy (static SIMS) show that fairly thick ({approx}2-3 nm) fluorocarbon layers exist on the NPS surface during C{sub 4}F{sub 8} etching. This layer blocks the direct interaction of ions with the NPS surface and results in a low etching rate. For C{sub 4}F{sub 8}/90%Ar discharges, little fluorocarbon coverage is observed for NPS surfaces and the direct ion surface interaction is significantly enhanced, explaining the enhancement of CER. We can deduce from analysis of angular resolved XPS data that the surface of NPS materials and SiO{sub 2} remain smooth during C{sub 4}F{sub 8} etching. For C{sub 4}F{sub 8}/90%Ar etching, the NPS surfaces became rough. The surface roughening is due to angle-dependent ion etching effects. These surface models were directly verified by the transmission electron microscopy. Depth profiling study of NPS partially etched using C{sub 4}F{sub 8} or C{sub 4}F{sub 8}/90%Ar discharges using dynamic SIMS indicates that the plasma induced modification of NPS was enhanced significantly compared with SiO{sub 2} due to the porous structure, which allows the plasma attack of the subsurface region. The modified layer thickness is related to the overall porosity and dramatically increases for NPS with an overall porosity of 50%. The distinct etching behavior of high porosity NPS ({approx}50%) in fluorocarbon-based discharges relative to NPS material with lower overall porosity is possibly due to interconnected pores, which allow plasma species to more easily penetrate into the subsurface region.

Hua Xuefeng; Stolz, Christian; Oehrlein, G.S.; Lazzeri, P.; Coghe, N.; Anderle, M.; Inoki, C.K.; Kuan, T.S.; Jiang, P. [Department of Physics and Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States); Department of Materials Science and Engineering and Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742 (United States); ITC-irst, Center for Scientific and Technological Research, 38050 Povo, Trento (Italy); Department of Physics, University at Albany, SUNY, Albany, New York 12222 (United States); Texas Instruments, Inc., Dallas, Texas 75243 (United States)

2005-01-01

343

Acoustic tomography for decay detection in black cherry trees  

Treesearch

Twelve black cherry (Prunus serotina) trees that had a wide range of ... The trees were felled after the field test and a disc from each sampling height ... nondestructive testing, tomography, acoustic imaging, deterioration, testing, evaluation, acoustic properties, quality, wood defects. View and Print this Publication (1.6 MB).

344

Acoustic holography. Citations from the Engineering Index data base  

Microsoft Academic Search

Worldwide research on acoustic holography is covered. Theory, uses, equipment design, and imaging techniques are presented. Most of the studies are general and not applied to a specific use of acoustic holography. However, there are citations which do discuss its use in medicine, nuclear reactors, and nondestructive testing. This updated bibliography contains 328 citations, 34 of which are new entries

W. E. Reed

1980-01-01

345

Acoustic holography. Citations from the engineering index data base  

Microsoft Academic Search

Worldwide research on acoustic holography is covered. Theory, uses, equipment design, and imaging techniques are presented. Most of the studies are general and not applied to a specific use of acoustic holography. However, there are citations which do discuss its use in medicine, nuclear reactors, and nondestructive testing. (This updated bibliography contains 242 abstracts, 32 of which are new entries

W. E. Reed

1978-01-01

346

Acoustic holography. Citations from the Engineering Index data base  

Microsoft Academic Search

Worldwide research on acoustic holography is covered. Theory uses, equipment design, and imaging techniques are presented. Most of the studies are general and not applied to a specific use of acoustic holography. However, there are citations which do discuss its use in medicine, nuclear reactors, and nondestructive testing. This updated bibliography contains 294 abstracts, 51 of which are new entries

W. E. Reed

1979-01-01

347

Use of the 4F Roesch Inferior Mesenteric Catheter in Embolization Procedures in the Pelvis: A Review of 300 Cases  

SciTech Connect

The aim of this study is to evaluate the use of a 4F Roesch inferior mesenteric (RIM) catheter for pelvic embolization procedures. Between October 2000 and January 2006, 364 patients (357 female, 7 male; age: 23-67 years) underwent embolization of various pathologies [uterine fibroids (n = 324), pure adenomyosis of the uterus (n = 19), postpartum hemorrhage (n =1), traumatic or postoperative hemorrhage (n = 9), bleeding related to cervical cancer (n =7), AV malformation of the uterus (n = 2) and high-flow priapism (n = 2)] at a single institution. In all cases, bilateral catheterization was primarily attempted with the use of a 4F hook-shaped braided endhole catheter (Roesch-Inferior-Mesenteric, RIM-Catheter, Cordis, Miami, FL). Frequency of initial failure to catheterize the vascular territory of interest and carry out the embolization were recorded and the types of difficulty encountered were noted. Catherization of the main stem of the vessel territory of interest with the use of a unilateral femoral approach and the 4F RIM catherer was successful in 334/364 (91.8%) the embolization cases. Bilateral catheterization of the internal iliac arteries using a single common femoral artery access and the 4F RIM catheter was achieved in 322/364 (88.5%) patients. In 12/364 (3.3%) patients, a contralateral puncture was performed and the same 4F catheter was used. In 28/364 (7.7%) cases the 4F RIM catheter was exchanged for a catheter with a cobra-shaped or sidewinder configuration. The 4F RIM catheter is a simple and valuable alternative to catheters and techniques commonly employed for pelvic artery embolization.

Kroencke, Thomas J., E-mail: thomas.kroencke@charite.de; Kluner, Claudia; Hamm, Bernd [Charite Universitaetsmedizin Berlin, Department of Radiology (Germany); Gauruder-Burmester, Annett [St. Hedwig Hospital, German Pelvic Floor Centre, Department of Urogynecology (Germany)

2007-04-15

348

Challenges with acoustic backing of CMUT arrays on silicon with integrated electronics  

Microsoft Academic Search

Capacitive micromachined ultrasonic transducers (CMUTs) have in the last decade shown promising qualities for medical imaging. But there are some acoustical challenges that have to be overcome before the performance of a CMUT array with integrated electronics is satisfactory. Acoustic backing is necessary to avoid surface acoustic waves (SAW) excited in the surface of the silicon substrate to affect the

Sigrid Berg; A. Ronnekleiv

2009-01-01

349

Characterizing Acoustic Attenuation of Homogeneous Media Using Focused Impulsive Acoustic Radiation Force  

PubMed Central

A new method to characterize a material’s attenuation using acoustic radiation force is proposed. Comparison of displacement magnitudes generated in a homogeneous material by acoustic radiation force excitations can be used to estimate the material’s attenuation when the excitations are applied over a range of focal depths while maintaining a constant lateral focal configuration. Acoustic attenuations are related to the inverse of the excitation focal depth that yields the greatest focal zone displacement for this protocol. Experimental studies in calibrated tissue-mimicking phantoms are presented to demonstrate the feasibility of this method. Attenuations ranging from 0.3 – 1.5 dB/cm/MHz were characterized over excitation focal depths ranging from 5 – 30 mm, with an accuracy of 0.1 ± 0.15 dB/cm/MHz. As currently implemented, this method is limited to characterizing materials that have homogeneous material properties and acoustic attenuations. This method for characterizing acoustic attenuation can be performed using conventional diagnostic scanners without any additional hardware and could also be performed concurrently with acoustic radiation force-based imaging modalities to generate images of mechanical properties and attenuation that are spatially co-registered with B-mode images.

Palmeri, Mark L.; Frinkley, Kristin D.; Oldenburg, Katherine G.; Nightingale, Kathryn R.

2007-01-01

350

Acoustic Imaging Evaluation of Juvenile Salmonid Behavior in the Immediate Forebay of the Water Temperature Control Tower at Cougar Dam, 2010  

SciTech Connect

This report presents the results of an evaluation of juvenile Chinook salmon (Oncorhynchus tshawytscha) behavior at Cougar Dam on the south fork of the McKenzie River in Oregon in 2010. The study was conducted by the Pacific Northwest National Laboratory for the U.S. Army Corps of Engineers (USACE). The overall goal of the study was to characterize juvenile salmonid behavior and movement patterns in the immediate forebay of the Water Temperature Control (WTC) tower of the dam for USACE and fisheries resource managers use in making decisions about bioengineering designs for long-term structures and/or operations to facilitate safe downstream passage for juvenile salmonids. We collected acoustic imaging (Dual-Frequency Identification Sonar; DIDSON) data from March 1, 2010, through January 31, 2011. Juvenile salmonids (hereafter, called 'fish') were present in the immediate forebay of the WTC tower throughout the study. Fish abundance index was low in early spring (<200 fish per sample-day), increased in late April, and peaked on May 19 (6,039 fish). A second peak was observed on June 6 (2904 fish). Fish abundance index decreased in early June and remained low in the summer months (<100 fish per sample-day). During the fall and winter, fish numbers varied with a peak on November 10 (1881 fish) and a minimum on December 7 (12 fish). A second, smaller, peak occurred on December 22 (607 fish). A univariate statistical analysis indicated fish abundance index (log10-transformed) was significantly (P<0.05) positively correlated with forebay elevation, velocity over the WTC tower intake gate weirs, and river flows into the reservoir. A subsequent multiple regression analysis resulted in a model (R2=0.70) predicting fish abundance (log-transformed index values) using two independent variables of mean forebay elevation and the log10 of the forebay elevation range. From the approximate fish length measurements made using the DIDSON imaging software, the average fish length during early spring 2010 was 214 {+-} 86 mm (standard deviation). From May through early November, the average fish length remained relatively consistent (132 {+-} 54 mm), after which average lengths increased to 295 {+-} 148 mm for mid-November though early December. From mid-December through January the average fish length decreased to 151 {+-} 76 mm. Milling in front of the WTC tower was the most common fish behavior observed throughout the study period. Traversing along the front of the tower, east-to-west and west-to-east, was the next common behavior. The percentage of fish events showing movement from the forebay to the tower or from the tower to the forebay was generally low throughout the spring, summer, and early fall (0 to 30% for both directions combined, March through early November). From mid-November 2010 through the end of the study (January 31, 2011), the combined percentages of fish moving into and out of the tower were higher (25 to 70%) than during previous months of the study. Schooling behavior was most distinct in the spring. Schooling events were present in 30 to 96% of the fish events during that period, with a peak on May 19. Schooling events were also present in the summer, but at lower numbers. With the exception of some schooling in mid-December, few to no schooling events were observed in the fall and winter months. Diel distributions for schooling fish during spring and fall months indicate schooling was concentrated during daylight hours and no schooling was observed at night. However, in December, schooling occurred at night, after midnight, and during daylight hours. Predator activity, most likely bull trout or rainbow trout according to a USACE biologist, was observed during late spring, when fish abundance index and schooling were highest for the year, and again in the fall months when fish events increased from a summer low. No predator activity was observed in the summer, and little activity occurred during the winter months.

Khan, Fenton; Johnson, Gary E.; Royer, Ida M.; Phillips, Nathan RJ; Hughes, James S.; Fischer, Eric S.; Ham, Kenneth D.; Ploskey, Gene R.

2012-04-01

351

Electronic structure of CeNiGe2-xSi studied by Ce 4d 4f resonant photoemission  

NASA Astrophysics Data System (ADS)

We have performed Ce 4d 4f resonant photoemission (RPE) spectroscopy on the isostructural heavy fermion system CeNiGe2-xSi(0?x?1). With increasing x, the unit volume decreases by about 5% and the ground state originating in Ce 4f character varies from an antiferromagnetic regime (AFM, 0?x?0.8) to a quantum critical point (QCP, x=1). RPE data reveals that the cf-hybridization intensity becomes stronger as the ground state of Ce 4f electron changes from AFM to QCP, which is exclusively caused by the increase of chemical pressure due to the reduction of lattice constant in CeNiGe2-xSi system.

Im, H. J.; Ito, Takahiro; Kimura, Shin-Ichi; Kim, Hyeong-Do; Hong, J. B.; Kwon, Y. S.

2007-03-01

352

Ultrasonic Stimulated Acoustic Emission for Detection of Breast Microcalcifications.  

National Technical Information Service (NTIS)

The purpose of this research is to build an experimental system based on Ultrasound Stimulated Acoustic Emission for in vitro imaging of breast tissue specimens, with the goal of detecting microcalcifications with sufficient accuracy. The scope of this re...

M. Fatemi

2000-01-01

353

An acoustic switch.  

PubMed

The benefits derived from the development of acoustic transistors which act as switches or amplifiers have been reported in the literature. Here we propose a model of acoustic switch. We theoretically demonstrate that the device works: the input signal is totally restored at the output when the switch is on whereas the output signal nulls when the switch is off. The switch, on or off, depends on a secondary acoustic field capable to manipulate the main acoustic field. The model relies on the attenuation effect of many oscillating bubbles on the main travelling wave in the liquid, as well as on the capacity of the secondary acoustic wave to move the bubbles. This model evidences the concept of acoustic switch (transistor) with 100% efficiency. PMID:23816529

Vanhille, Christian; Campos-Pozuelo, Cleofé

2013-06-15

354

The extreme ultraviolet emissions of W23+(4f5)  

NASA Astrophysics Data System (ADS)

In order to comply with the special challenges (open 4f-shell, configuration mixing) of simulating the spectrum of W23+ an extensive atomic model was implemented using the flexible atomic code (FAC). In detail, the basis functions from 11 configurations were used to model about 12000 levels, which give rise to roughly 60 million transitions including nearly 6 million electric and magnetic dipole transitions. A collisional radiative model has been put together which could handle the size of the input data. The modelled spectra (4-40 nm) show low sensitivity on the electron density, which validates the comparison of EBIT and tokamak spectra. The emissions between 4 and 7 nm are discussed in the context of the observations at fusion plasmas. In this range, the influence of W23+ is limited due to the small contribution to the measurement - however, elements of the presented modelling might explain the second, not understood spectral feature at 6 nm. Further details of the spectra are only briefly discussed as a close comparison to experimental data requires also models for the neighbouring ionisation stages. Additionally, the importance of configuration mixing becomes apparent motivating further investigations on neighbouring ionisation stages with similarly complex models.

Pütterich, T.; Jonauskas, V.; Neu, R.; Dux, R.; ASDEX Upgrade Team

2013-07-01

355

A Study of EUV Line Emission from the O4f Star Zeta Puppis  

NASA Astrophysics Data System (ADS)

We propose a 140 ks EUVE SW Spectrometer observation of the O4f star, Zeta Puppis. Due to its low ISM column density and highly ionized stellar wind, a unique EUV window is accessible for viewing between 128-140 A, SUGGESTING THAT THIS STAR MAY BE THE ONLY O STAR OBSERVABLE WITH THE EUVE. The major objective of this proposal is straightforward; a positive detection will provide a yes or no answer. A long withstanding problem in OB stars concerns the spatial location of the X-ray source. Our modelling efforts suggest that the strength of observable EUV radiation will provide very strong constraints on the location of the X-ray source; the stronger the EUV flux, the more deeply embedded is the X-ray source. Whereas, a detection would rule out the possibility that the X-ray emission is deeply embedded in the stellar wind. For the deeply embedded X-ray source model, we present a simulated EUVE SW spectrum which shows that a significant S/N is predicted. Our simulation predicts that three emission lines should be detected (OV 135.8A; FeVIII 131A; MgV 132.5A). If the weaker Fe and Mg lines are detected, we will also be able to test a recent ASCA SIS prediction; Fe and Mg abundances appear to be significantly non-solar.

Waldron, Wayne Lee

356

CLEC4F is an inducible C-type lectin in F4/80-positive cells and is involved in alpha-galactosylceramide presentation in liver.  

PubMed

CLEC4F, a member of C-type lectin, was first purified from rat liver extract with high binding affinity to fucose, galactose (Gal), N-acetylgalactosamine (GalNAc), and un-sialylated glucosphingolipids with GalNAc or Gal terminus. However, the biological functions of CLEC4F have not been elucidated. To address this question, we examined the expression and distribution of murine CLEC4F, determined its binding specificity by glycan array, and investigated its function using CLEC4F knockout (Clec4f-/-) mice. We found that CLEC4F is a heavily glycosylated membrane protein co-expressed with F4/80 on Kupffer cells. In contrast to F4/80, CLEC4F is detectable in fetal livers at embryonic day 11.5 (E11.5) but not in yolk sac, suggesting the expression of CLEC4F is induced as cells migrate from yolk cells to the liver. Even though CLEC4F is not detectable in tissues outside liver, both residential Kupffer cells and infiltrating mononuclear cells surrounding liver abscesses are CLEC4F-positive upon Listeria monocytogenes (L. monocytogenes) infection. While CLEC4F has strong binding to Gal and GalNAc, terminal fucosylation inhibits CLEC4F recognition to several glycans such as Fucosyl GM1, Globo H, Bb3?4 and other fucosyl-glycans. Moreover, CLEC4F interacts with alpha-galactosylceramide (?-GalCer) in a calcium-dependent manner and participates in the presentation of ?-GalCer to natural killer T (NKT) cells. This suggests that CLEC4F is a C-type lectin with diverse binding specificity expressed on residential Kupffer cells and infiltrating monocytes in the liver, and may play an important role to modulate glycolipids presentation on Kupffer cells. PMID:23762286

Yang, Chih-Ya; Chen, Jiun-Bo; Tsai, Ting-Fen; Tsai, Yi-Chen; Tsai, Ching-Yen; Liang, Pi-Hui; Hsu, Tsui-Ling; Wu, Chung-Yi; Netea, Mihai G; Wong, Chi-Huey; Hsieh, Shie-Liang

2013-06-06

357

Modification of magnetic anisotropy through 3d-4f coupling in La0.75Pr0.25Co2P2  

NASA Astrophysics Data System (ADS)

Magnetic behavior of La0.75Pr0.25Co2P2 was investigated by a combination of magnetic measurements, magneto-optical imaging, neutron diffraction, and x-ray absorption spectroscopy, including x-ray magnetic circular dichroism. The material crystallizes in the ThCr2Si2 structure type and exhibits three consecutive magnetic phase transitions. At 167 K, the Co magnetic moments order ferromagnetically in the ab plane of the tetragonal crystal structure. At 66 K, a ferromagnetic ordering of Pr(4f) moments parallel to the c axis causes a rotation of the Co(3d) moments towards the c axis in the direction opposite to the Pr moments, thus forming a noncollinear ferrimagnetically ordered structure and switching the direction of the total magnetization from the ab plane to the c axis. The third magnetic transition observed at 35 K is likely associated with the establishment of the collinear ferrimagnetic order along the c axis.

Kovnir, Kirill; Thompson, Corey M.; Garlea, V. Ovidiu; Haskel, Daniel; Polyanskii, Anatolii A.; Zhou, Haidong; Shatruk, Michael

2013-09-01

358

Asymmetric acoustic gratings  

NASA Astrophysics Data System (ADS)

The unidirectional transmission of acoustic waves is realized by a simple geometrically asymmetric steel grating structure. This exotic phenomenon stems from the one-way diffraction effect induced by the different periods of the slits on the both surfaces of the sample. And the frequency range of unidirectional transmission is simply determined by the structure periods. The experimental results agree well with the theoretical simulation. This remarkable effect is expected potential applications in ultrasonic devices, such as acoustic rectifiers and acoustic diodes.

He, Zhaojian; Peng, Shasha; Ye, Yangtao; Dai, Zhongwei; Qiu, Chunyin; Ke, Manzhu; Liu, Zhengyou

2011-02-01

359

Laser flash photolysis and pulse radiolysis of aqueous solutions of the fluoroxysulfate ion, SO sub 4 F sup minus  

SciTech Connect

The fluoroxysulfate ion, SO{sub 4}F{sup {minus}}, is the only known ionic hypofluorite. It is a very strong oxidant capable of oxidizing water, but the rate of its reaction with water is sufficiently low to allow studies of its chemistry in aqueous solution. Aqueous fluoroxysulfate appears to react primarily as a 1-electron oxidant, and an F atom transfer mechanism has been proposed to account for many of its reactions. The present work is a study of the laser flash photolysis and pulse radiolysis of aqueous solutions of SO{sub 4}F{sup {minus}}.

Klaening, U.K. (Aarhus Univ. (Denmark)); Sehested, K. (Risoe National Lab., Roskilde (Denmark)); Appelman, E.H. (Argonne National Lab., IL (United States))

1991-09-04

360

Assignment of 4f->5d excitation spectra of Nd{sup 3+} in crystals using the simple model  

SciTech Connect

The measured low-temperature (4f){sup 3}->(4f){sup 2}5d excitation spectra of Nd{sup 3+} doped in crystals YPO{sub 4}, CaF{sub 4} and LiYF{sub 4} [van Pieterson et al., Phys. Rev. B 65 (2002) 045113] are assigned and analyzed using the simple model proposed by Duan et al. [Phys. Rev. B 66 (2002) 155108] and Ning et al. [J. Alloy. Compd. 366 (2004) 34]. The agreement between theoretical and observed energies and intensities are acceptable, and at the same time the spectra are assigned in more detail.

Xia Shangda [Institute of Modern Physics, Chongqing University of Post and Telecommunications, Chongqing 400065 (China); Department of Physics, University of Science and Technology of China, Hefei 230036 (China); Duan Changkui [Institute of Modern Physics, Chongqing University of Post and Telecommunications, Chongqing 400065 (China)]. E-mail: duanck@cqupt.edu.cn; Deng Quan [Institute of Modern Physics, Chongqing University of Post and Telecommunications, Chongqing 400065 (China); Ruan Gang [Institute of Modern Physics, Chongqing University of Post and Telecommunications, Chongqing 400065 (China)

2005-09-15

361

STOVL acoustic fatigue technologies  

NASA Astrophysics Data System (ADS)

This paper assesses the state of the art in acoustic fatigue technologies as applied to an advanced supersonic short takeoff and vertical landing (STOVL) aircraft. The topics covered include advanced materials, fatigue, acoustic loads prediction, and stress response prediction. Advanced materials are compared from the standpoints of fatigue resistance and fatigue data availability. State of the art acoustic load prediction techniques are evaluated. Subsonic and supersonic jet noise generation mechanisms, axisymmetric and two-dimensional nozzles, and noise suppression methods are covered. Stress response prediction methods for acoustic, thermal, and maneuvering loads are addressed and the necessity of structural analysis with all three loading types applied simultaneously is assessed.

Groen, David S.

362

Micromachined acoustic matching layers  

NASA Astrophysics Data System (ADS)

Efficient coupling of acoustic energy between different media requires fabrication of materials with precisely controlled acoustic properties. Current materials are formed by suspending particles in an epoxy matrix. Last year, we proposed a technique for making such materials using silicon micromachining. This paper describes the fabrication procedure and acoustic measurements of these materials and their applications. The acoustic properties of the composite materials described in this paper depend on the volume fraction of silicon, and the material used for the other phase of the composite. We investigated two different fillers, epoxy resin and RTV. Silicon structures with graded volume fractions were fabricated to provide broader bandwidth matching.

Haller, Matthew I.; Khuri-Yakub, Butrus T.

1992-11-01

363

Low frequency acoustic microscope  

DOEpatents

A scanning acoustic microscope is disclosed for the detection and location of near surface flaws, inclusions or voids in a solid sample material. A focused beam of acoustic energy is directed at the sample with its focal plane at the subsurface flaw, inclusion or void location. The sample is scanned with the beam. Detected acoustic energy specularly reflected and mode converted at the surface of the sample and acoustic energy reflected by subsurface flaws, inclusions or voids at the focal plane are used for generating an interference signal which is processed and forms a signal indicative of the subsurface flaws, inclusions or voids.

Khuri-Yakub, Butrus T. (Palo Alto, CA)

1986-11-04

364

Non-Linear Acoustic Concealed Weapons Detector.  

National Technical Information Service (NTIS)

The major findings of this effort clearly demonstrate that Non- linear Acoustics is a low cost alternative to conventional imaging methods for concealed weapons detection. Our approach is to use ultrasonics to create a localized zone where non-linear inte...

A. Achanta

2006-01-01

365

Acoustic Detection of Blowout in Premixed Flames  

Microsoft Academic Search

Work to develop a practical, fast diagnostic technique to monitor the proximity of a combustor to blowout using measurements of the flame's acoustic signature is described. The feasibility of this approach was demonstrated on three combustors with different flame holding mechanisms that are used in most practical combustion devices: pilot, swirl, and bluff-body stabilized flames. Extensive high-speed flame images were

Suraj Nair; Tim Lieuwen

2005-01-01

366

Ion Acoustic Waves in Ultracold Neutral Plasmas  

SciTech Connect

We photoionize laser-cooled atoms with a laser beam possessing spatially periodic intensity modulations to create ultracold neutral plasmas with controlled density perturbations. Laser-induced fluorescence imaging reveals that the density perturbations oscillate in space and time, and the dispersion relation of the oscillations matches that of ion acoustic waves, which are long-wavelength, electrostatic, density waves.

Castro, J.; McQuillen, P.; Killian, T. C. [Department of Physics and Astronomy and Rice Quantum Institute, Rice University, Houston, Texas 77005 (United States)

2010-08-06

367

Comment on paper entitled, "An inversion of Freedman's 'image pulse' model in air". Acoust. Soc. Am. 119(2), 965-975 (2006).  

PubMed

Echolocation (i.e., perceiving objects using acoustic echoes) is well-known in underwater detection and to a lesser extent in robot guidance and machine perception. The paper by Tsakiris and McKerrow is concerned with machine perception in air using Freedman's asymptotic model, which was originally developed to predict the backscattering multiple-echo effect observed in sonar detection. This effect was subsequently shown to be due to the elastic response of underwater targets. Freedman's model can be used in air because the acoustic target is assumed to be rigid. Also, the model's prediction of multiple echoes can be used to obtain information about the shape of the target. This is the so-called inversion of the Freedman model by Tsakiris and McKerrow. In their paper, various simple bodies are tested in air using ultrasound and it is shown that the model provides relatively poor information about body shape. Several explanations are given. However, one explanation is not considered, namely that the model itself is not satisfactory. First, there is poor agreement with exact backscattering theory. Second, deriving information about target shape from the multiple echoes predicted by the model is a highly questionable procedure. Both these aspects are examined here. PMID:16938943

Hickling, Robert; Gaunaurd, Guillermo C

2006-08-01

368

Syntheses and characterizations of compounds Ba4F4XGa2S6 (X = Cr, Mn, Fe) and Ba4F4MnIn2S6 with 2D layered structures.  

PubMed

Four new 2D layered quinary sulfides, Ba4F4CrGa2S6 (1), Ba4F4MnGa2S6 (2), Ba4F4FeGa2S6 (3) and Ba4F4MnIn2S6 (4), have been synthesized by the traditional solid state reaction method. Single crystal X-ray diffraction analyses show that the isostructural complexes 1, 3 and 4 belong to the Ba2F2Fe1.5S3 structure type and crystallize in the space group Pnma of the orthorhombic system, whereas the complex 2 crystallizes in the space group Cmca. The crystal structures of the four compounds can be viewed as the alternated stacking of the fluorite type [Ba2F2](2+) blocks and the newly discovered [X0.5GaS3](2-) or [X0.5InS3](2-) blocks. First-principles electronic structure calculations performed with DFT indicate that the title compounds are semiconductors with the band gaps of 1.83, 3.21, 1.16 and 2.93 eV for 1, 2, 3 and 4, respectively. PMID:23698170

Luo, Zhong-Zhen; Lin, Chen-Sheng; Cheng, Wen-Dan; Li, Yuan-Bing; Zhang, Hao; Zhang, Wei-Long; He, Zhang-Zhen

2013-05-22

369

Engineering Magnetic Anisotropy in Nanostructured 3d and 4f Ferromagnets  

NASA Astrophysics Data System (ADS)

Due to the increased demand for clean energy in recent years, there is a need for the scientific community to develop technology to harvest thermal energy which is ubiquitous but mostly wasted in our environment. However, there is still no efficient approach to harvest thermal energy to date. In this study, the theory of thermomagnetic energy harvesting is reviewed and unique applications of multiferroics (ferromagnetic plus ferroelectric) are introduced. Based on an efficiency analysis using experimentally measured magneto-thermal properties of 3d transitional and 4f rare earth ferromagnetic elements, the idea of using single domain ferromagnetic elements to obtain higher thermomagnetic conversion efficiencies is proposed. In order to fabricate a ferromagnetic single domain, the magnetic anisotropy of gadolinium (Gd) and nickel (Ni) is engineered at the nanoscale. Both thin films and nanostructures are fabricated and characterized with a focus on the change of magnetic anisotropy governed by shape, crystal structure, and strain. The fabrication processes include sputtering, e-beam lithography (writing and evaporation), and focused ion beam milling. Characterization techniques involving atomic/magnetic force microscopy, energy dispersive X-ray spectroscopy, magneto-optical Kerr effect magnetometry, superconducting quantum interference device magnetometry, scanning/transmission electron microscopy, and X-ray diffraction will also be discussed. Experimental results show that the magnetic domain structure of nanostructured Ni can be stably controlled with geometric constraints or by strain induced via electric field. The magnetic properties of nanostructured Gd, on the other hand, is sensitive to crystal structure. These results provide critical information toward the use of ferromagnetic nanostructures in thermomagnetic energy harvesting and multiferroic applications.

Hsu, Chin-Jui

370

Correlation between single nucleotide polymorphisms in CYP4F2 and warfarin dosing in chinese valve replacement patients  

PubMed Central

Background Individuals with implanted mechanical valve prostheses require lifelong anticoagulation therapy with warfarin. The narrow therapeutic index of warfarin makes it difficult to dose and maintain proper anticoagulation. A number of single nucleotide polymorphisms (SNPs) affecting vitamin K or warfarin metabolism have been shown to affect warfarin dosing. Our aim was to study the effect of the CYP4F2 rs2108622-1347 (C?>?T) variant on warfarin dosing in Chinese patients. Methods We studied 352 patients after heart valve replacement surgery. Warfarin dosing for patients was adjusted to achieve 1.8 ? INR???2.5. We determined the presence of SNPs in CYP4F2 in these patients and investigated their association with warfarin dosing. Results We found the frequency of the CYP4F2 rs2108622 C allele was 79.5% and T-allele frequency was 20.5%. The warfarin dose requirement for CC individuals was significantly lower than that for CT or TT individuals (P?4F2 rs2108622 significantly affects the warfarin dose requirement to achieve adequate anticoagulant activity in Chinese individuals. Genotyping of this SNP may allow clinicians to determine the initiation dose for patients following valve-replacement surgery in China.

2012-01-01

371

Strong dichroism in the Dy 3d-->4f x-ray absorption at Dy/Si(111) interfaces  

NASA Astrophysics Data System (ADS)

We report experimental evidence for strong 3d-->4f x-ray-absorption dichroism in rare-earth ions on a nonmagnetic substrate: Dy on Si(111)7×7. The results are discussed by evaluating the role of the crystal-field splitting of the ground state as an alternative to the Zeeman splitting underlying the magnetic x-ray dichroism theory.

Sacchi, Maurizio; Sakho, Oumar; Rossi, Giorgio

1991-01-01

372

Attacking a Nexus of the Oncogenic Circuitry by Reversing Aberrant eIF4F-Mediated Translation  

PubMed Central

Notwithstanding their genetic complexity, different cancers share a core group of perturbed pathways converging upon a few regulatory nodes that link the intracellular signaling network with the basic metabolic machinery. The clear implication of this view for cancer therapy is that instead of targeting individual genetic alterations one-by-one, the next generation of cancer therapeutics will target critical hubs in the cancer network. One such hub is the translation initiation complex eIF4F, which integrates several cancer-related pathways into a self-amplifying signaling system. When hyperactivated by apical oncogenic signals, the eIF4F-driven translational apparatus selectively switches the translational repertoire of a cell towards malignancy. This central integrative role of pathologically activated eIF4F has motivated the development of small molecule inhibitors to correct its function. A genome-wide, systems-level means to objectively evaluate the pharmacological response to therapeutics targeting eIF4F remains an unmet challenge.

Bitterman, Peter B.; Polunovsky, Vitaly A.

2012-01-01

373

Preparation and electrochemical investigation of Li2CoPO4F cathode material for lithium-ion batteries  

SciTech Connect

We report the electrochemical characteristics of a novel cathode material Li2CoPO4F/C, which was prepared via a ceramic process. In cyclic voltammetry (CV) measurements, two reactions taking place at 4.81V and 5.12 V in the first anodic scan evolve to one broad oxidative peak in the subsequent cycles. This shape change of CV curves demonstrates that the charge/discharge mechanism is varied after the first charge. Correspondingly the XRD pattern of Li2CoPO4F shows a minor difference after discharge from 5.5 V. Further experimental results prove that this change is associated with the second reaction peaked at 5.12 V. In the constant current cycling measurement, the prepared Li2CoPO4F exhibits a reversible capacity of 109 mAh/g between 2.0 and 5.5 V. The discharge capacity keeps stable in the first 12 cycles accompanied by the serious electrolyte decomposition between the interface of electrolyte and Li2CoPO4F.

Wang, Deyu; Xiao, Jie; Xu, Wu; Nie, Zimin; Wang, Chong M.; Graff, Gordon L.; Zhang, Jiguang

2011-02-15

374

Investigation of acoustic fields generated by eddy currents using an atomic force microscope  

NASA Astrophysics Data System (ADS)

This paper reports the experimental measurement and imaging of the acoustic fields generated by low-frequency eddy currents in metals in the absence of an external static magnetic field using a modified atomic force microscope. Acoustic displacements in a typical metal placed in eddy current field without static magnetic field were theoretically computed and found to be in the range of few hundred picometers. A modified atomic force microscope was used to detect and measure the acoustic displacements in a single crystal copper. The setup was also used to image acoustic fields in a titanium alloy sample. Details of the modified AFM to measure and image acoustic displacements are presented. The role of electrical and elastic properties on the contrast in acoustic images of Ti-6Al-4V sample is discussed.

Nalladega, V.; Sathish, S.; Blodgett, M.

2013-01-01

375

Host effects on the optically active 4f and 5d levels of Ce(3+) in garnets.  

PubMed

When Ce(3+) is doped in a garnet, it substitutes for some cations. The effect of the substitution on the optically active 4f and 5d levels of Ce(3+) can be analyzed in terms of an undistorted substitution followed by a structural relaxation, but, whereas the contribution of the undistorted substitution can be predicted/calculated using the crystallographic structure of the pure garnet, which is at hand, that of the structural relaxation demands the detailed local structure around the Ce(3+) impurity, which is hard to know. Hence the importance of knowing the role of the undistorted substitution. What we study in this paper is the role of the unrelaxed host effects on the 4f and 5d levels of Ce(3+)-doped garnets (i.e. the interactions between Ce and the second and more distant neighbors). When they are added to the (previously studied) unrelaxed first-neighbor effects, they give the contributions of the undistorted substitutions. We performed spin-orbit coupling, relativistic, embedded cluster, wave function based ab initio calculations on the (CeO8)(13-) cluster under the effects of the embedding potentials of 21 selected garnets of Si, Al, and Ga, which have been obtained in this work, using experimental unrelaxed structures of the pure garnets. The calculations reveal that the unrelaxed host effect: (1) produces a red shift of the first 4f ? 5d transition and (2) is an important contribution to this transition which plays a very important role in differentiating the values it has in different garnet families. The unrelaxed host effect is found to be responsible for the low value of the first 4f ? 5d transition in Ce(3+)-doped Lu2CaMg2Si3O12. It is analyzed in terms of 5d and 4f centroid energy contributions and crystal field splitting contributions in the 21 doped garnets. The effect on the splittings of the 4f and 5d levels is also discussed. The undistorted host approximation is found to give reasonable comparison with experiments, so that it represents a relatively fast way to provide reliable ab initio information on the 4f and 5d levels of Ce(3+) in garnets. PMID:24107971

Seijo, Luis; Barandiarán, Zoila

2013-10-23

376

Acoustic sensor technology  

Microsoft Academic Search

The recent development in monolithic devices has enabled a breakthrough in the applications of acoustic sensors in navigation and communications signal processing. A piezoelectric thin film material, such as ZnO, AlN or PZT, permits both acoustoelectric SAW and semiconductor electronic device components to be fabricated on the same monolithic substrate. Here, we discuss acoustic sensor applications such as pressure, gas

M. E. Motamedi

1994-01-01

377

The Acoustical Environment.  

ERIC Educational Resources Information Center

|Asserting that without an adequate acoustical environment, learning activities can be hindered, this paper reviews the literature on classroom acoustics, particularly noise, reverberation, signal-to-noise ratio, task performance, and recommendations for improvement. Through this review, the paper seeks to determine whether portable classrooms…

Smith, Melissa

378

Acoustics of friction  

Microsoft Academic Search

This article presents an overview of the acoustics of friction by covering friction sounds, friction-induced vibrations and waves in solids, and descriptions of other frictional phenomena related to acoustics. Friction, resulting from the sliding contact of solids, often gives rise to diverse forms of waves and oscillations within solids which frequently lead to radiation of sound to the surrounding media.

Adnan Akay

2002-01-01

379

Acoustic Wave Filters  

Microsoft Academic Search

Acoustic Wave Filters Composed of a Series of Like Sections.-(1) Theory. Taking the impedance of any part of an acoustic circuit to be equal to the complex ratio of the applied pressure difference to the rate of change of volume displacement, it is shown that, neglecting dissipative forces, it is possible to construct a filter having limiting frequency values of

G. W. Stewart

1922-01-01

380

An acoustic scattering code  

Microsoft Academic Search

Acoustical scattering from atmospheric turbulence is of interest to the Army because it has been identified as a candidate cause of higher than expected sound levels in shadow zones. Shadow zones are those regions where ray theory indicates no sound penetrates. Scattering into these zones may give non-line-of-sight detection through acoustic detection. This report documents the creation of a computer

Jose Lopez; G. H. Goedecke; Harry J. Auvermann

1993-01-01

381

Acoustic coupling in capacitive microfabricated ultrasonic transducers: modeling and experiments.  

PubMed

In the design of low-frequency transducer arrays for active sonar systems, the acoustic interactions that occur between the transducer elements have received much attention. Because of these interactions, the acoustic loading on each transducer depends on its position in the array, and the radiated acoustic power may vary considerably from one element to another. Capacitive microfabricated ultrasonic transducers (CMUT) are made of a two-dimensional array of metallized micromembranes, all electrically connected in parallel, and driven into flexural motion by the electrostatic force produced by an applied voltage. The mechanical impedance of these membranes is typically much lower than the acoustic impedance of water. In our investigations of acoustic coupling in CMUTs, interaction effects between the membranes in immersion were observed, similar to those reported in sonar arrays. Because CMUTs have many promising applications in the field of medical ultrasound imaging, understanding of cross-coupling mechanisms and acoustic interaction effects is especially important for reducing cross-talk between array elements, which can produce artifacts and degrade image quality. In this paper, we report a finite-element study of acoustic interactions in CMUTs and experimental results obtained by laser interferometry measurements. The good agreement found between finite element modeling (FEM) results and optical displacement measurements demonstrates that acoustic interactions through the liquid represent a major source of cross coupling in CMUTs. PMID:16463488

Caronti, Alessandro; Savoia, Alessandro; Caliano, Giosuè; Pappalardo, Massimo

2005-12-01

382

Practical acoustic thermometry with acoustic waveguides  

NASA Astrophysics Data System (ADS)

Acoustic thermometry is the most accurate technique of primary thermometry ever devised. However, resonator based techniques are not practical and are rarely used in practice. Previously we have demonstrated the basic functionality of an acoustic thermometer operating at up to 1000 °C based on the time-of-flight measurements of short pulses in an acoustic waveguide. Here we report progress in assessing the practical and theoretical performance limitations of such a device. In this paper we report improvements in timing techniques which significantly improve the signal-to-noise ratio, a feature likely to be important in many industrial settings. We discuss the inference of the free field speed of sound from timing measurements and report results from a simple twin tube thermometer operating up to 500 °C. Finally we consider the shortcomings of current designs and prospects for future improvements including frequency domain analysis of the system.

Sutton, G.; de Podesta, M.; Veltcheva, R. I.; Gélat, P.; Minh, H. D.; Edwards, G.

2013-09-01

383

Negative acoustic index metamaterial  

NASA Astrophysics Data System (ADS)

Acoustic metamaterials utilizing periodic deep subwavelength resonators can attain negative acoustic properties unavailable in nature. We have developed a negative acoustic index metamaterial for water that combines Helmholtz and rod-spring resonators to control effective bulk modulus and mass density, respectively. Effective properties extracted from full-wave simulations of our metamaterial show that negative real components of bulk modulus and density occur simultaneously, resulting in a negative real component of the acoustic index. Experimental measurements on a sample of this metamaterial confirm that the real components of the acoustic index and bulk modulus attain negative values, but the density does not become negative. The primary causes of this are identified and potential solutions are presented.

Fok, L.; Zhang, X.

2011-06-01

384

Ultrasound-modulated optical tomography with intense acoustic bursts  

NASA Astrophysics Data System (ADS)

Ultrasound-modulated optical tomography (UOT) detects ultrasonically modulated light to spatially localize multiply scattered photons in turbid media with the ultimate goal of imaging the optical properties in living subjects. A principal challenge of the technique is weak modulated signal strength. We discuss ways to push the limits of signal enhancement with intense acoustic bursts while conforming to optical and ultrasonic safety standards. A CCD-based speckle-contrast detection scheme is used to detect acoustically modulated light by measuring changes in speckle statistics between ultrasound-on and ultrasound-off states. The CCD image capture is synchronized with the ultrasound burst pulse sequence. Transient acoustic radiation force, a consequence of bursts, is seen to produce slight signal enhancement over pure ultrasonic-modulation mechanisms for bursts and CCD exposure times of the order of milliseconds. However, acoustic radiation-force-induced shear waves are launched away from the acoustic sample volume, which degrade UOT spatial resolution. By time gating the CCD camera to capture modulated light before radiation force has an opportunity to accumulate significant tissue displacement, we reduce the effects of shear-wave image degradation, while enabling very high signal-to-noise ratios. Additionally, we maintain high-resolution images representative of optical and not mechanical contrast. Signal-to-noise levels are sufficiently high so as to enable acquisition of 2D images of phantoms with one acoustic burst per pixel.

Zemp, Roger J.; Kim, Chulhong; Wang, Lihong V.

2007-04-01

385

Ocean seismo-acoustics. Low-frequency underwater acoustics  

SciTech Connect

This book presents information on seismo-acoustic propagation in seawater and sea beds that includes theoretical developments, modelling and experiments, and fluctuations. Boundary scatteiring, seismo-acoustic waves and seismo-acoustic noise are discussed. Technology and new approaches in seismo-acoustic measurements are presented.

Akal, T.; berkson, J.M.

1986-01-01

386

Turbulence induced by an acoustic field - Application to acoustic agglomeration  

Microsoft Academic Search

The efficiency of sonic coagulation and precipitation of particles in an acoustic field is strongly reinforced, above the acoustic intensity corresponding to the enhancement of acoustic turbulence. The aim of this work is to evaluate the turbulence properties of the experimental system in order to calculate the acoustic agglomeration kernels and precipitation rates. The knowledge of the aerodynamic behavior of

Claire Malherbe; Denis Boulaud; Alain Boutier; Jean Lefevre

1988-01-01

387

The crystal structure of bøgvadite (Na2SrBa2Al4F20)  

NASA Astrophysics Data System (ADS)

The crystal structure of bøgvadite, Na2SrBa2Al4F20, has been solved and refined to a R1 factor of 4.4 % from single-crystal data (MoK? X-ray diffraction, CCD area detector) on a sample from the cryolite deposit at Ivittuut, SW Greenland. Bøgvadite is monoclinic, P21/n space group, with unit cell parameters a = 7.134(1), b = 19.996(3) and c = 5.3440(8) Å, ? = 90.02(1)o. A close proximity of the crystal structure to an orthorhombic symmetry and the presence of the two twin components in a nearly 1:1 ratio suggest that the investigated bøgvadite crystal has originally formed as a high-temperature orthorhombic polymorph which on cooling transformed to the stable low temperature monoclinic structure. The bøgvadite crystal structure has groupings of cation-fluoride coordination polyhedra similar to those found in the crystal structures of the genetically closely associated minerals jarlite and jørgensenite. However, its structure type is different from the latter two. The fluoridoaluminate framework of bøgvadite consists of infinite zig-zag chains of cis-connected AlF6 coordination octahedra. The 1 ?[AlF5] chains are interconnected by infinite chains of Na-F coordination polyhedra which extend in the same direction. Na is coordinated by nine F atoms if its full surrounding is taken in consideration, but makes significant chemical bonds only to closest five. The chains of AlF6 and NaF9 coordination polyhedra form double layers. In the centre of layers, relatively large voids in the form of pentagonal antiprisms are occupied by Sr atoms which make chemical bonds with the closest six F atoms. Between the SrF10 coordinations in the centre of layers run empty channels. The double layers are interconnected by Ba atoms which are coordinated by eight F atoms and fill the spaces between the layers. Bøgvadite belongs to the group of fluoridoaluminates with infinite chains of cis-connected AlF6 coordination octahedra, alike those found in the crystal structures of Ba-fluoridoaluminates.

Bali?-Žuni?, Ton?i

2013-09-01

388

Design for Underwater Aplanatic Acoustic Mirror  

NASA Astrophysics Data System (ADS)

Underwater acoustic lenses are useful devices for underwater imaging because of their small dimension and low power consumption but have a problem under the condition of changing water temperature because the refractive index depends on the water temperature. To solve this problem, we propose aplanatic acoustic mirrors, which consist of two aspherical mirrors and can remove spherical and coma aberrations. These mirrors are designed by a method used in the Ritchey Chrétien astronomical telescopes. The aplanatic mirror shows a larger focal sound pressure and better temperature characteristic than an aplanatic acoustic lens but has a narrow field of angle. Then, an off-axis aplanatic mirror, which consists of two aspherical off-axis mirrors, is designed by extraction of parts from a normal aplanatic mirror to obtain a wider field of angle.

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

2010-07-01

389

Acoustical properties of double porosity granular materials.  

PubMed

Granular materials have been conventionally used for acoustic treatment due to their sound absorptive and sound insulating properties. An emerging field is the study of the acoustical properties of multiscale porous materials. An example of these is a granular material in which the particles are porous. In this paper, analytical and hybrid analytical-numerical models describing the acoustical properties of these materials are introduced. Image processing techniques have been employed to estimate characteristic dimensions of the materials. The model predictions are compared with measurements on expanded perlite and activated carbon showing satisfactory agreement. It is concluded that a double porosity granular material exhibits greater low-frequency sound absorption at reduced weight compared to a solid-grain granular material with similar mesoscopic characteristics. PMID:22087905

Venegas, Rodolfo; Umnova, Olga

2011-11-01

390

Acoustic microstreaming applied to batch micromixing  

NASA Astrophysics Data System (ADS)

Experiments are presented in which acoustic microstreaming is investigated and applied to a batch micromixing case appropriate to a point-of-care pathology screening test. The flows presented can be created without complex engineering of contacts or surfaces in the microdevice, which could thus be made disposable. Fundamental flow patterns are measured with a micro-Particle-Image Velocimetry (micro-PIV) system, enabling a quantification of the fluiddynamical processes causing the flows. The design of micromixers based on this principle requires a quantification of the mixing. A simple technique based on digital image processing is presented that enables an assessment of the improvement in mixing due to acoustic microstreaming. The digital image processing technique developed was shown to be non-intrusive, convenient and able to generate useful quantitative data. Preliminary indications are that microstreaming can at least halve the time required to mix quantities of liquid typical of a point-of-care test, and significantly greater improvements seem feasible.

Manasseh, Richard; Petkovic-Duran, Karolina; Tho, Paul; Zhu, Yonggang; Ooi, Andrew

2006-01-01

391

Fast marching and acoustic descriptors based method for fish proportion interpolation  

Microsoft Academic Search

We propose a new method for the estimation of fish abundance from both acoustic data and some trawl hauls catches. In this work, we operate at a global level and we aim at estimating fish abundance from these images and not to identify the species of each school. We associate each trawl catch to the nearest acoustic image and we

Imen Karoui; Ronan Fablet; Jean-Marc Boucher

2008-01-01

392

4 f 135 s 25 p 6-4 f 135 s 25 p 56 s transitions in the W VIII spectrum and spectra of isoelectronic hafnium, tantalum, and rhenium ions  

NASA Astrophysics Data System (ADS)

Spectra of hafnium, tantalum, tungsten, and rhenium in the range of 145-350Å, excited in a low-inductive vacuum spark, have been recorded on a grazing-incidence vacuum spectrograph using a grating with 3600 lines/mm and a radius of 3 m. The wavelengths and intensities of more than 3800 lines in the tungsten spectrum have been measured. Comparison with the Hartree-Fock calculations showed that most spectral lines should be due to transitions in the W VIII spectrum. Short-wavelength lines due to the 4 f 135 s 25 p 6-4 f 135 s 25 p 56 s transitions have been identified in the W VIII spectrum and the Re IX, Ta VII, and Hf VI isoelectronic spectra.

Ryabtsev, A. N.; Kononov, E. Ya.; Kildiyarova, R. R.; Tchang-Brillet, W.-Ü. L.; Wyart, J.-F.

2012-08-01

393

Evaporation of acoustically levitated droplets  

Microsoft Academic Search

The rate of heat and mass transfer at the surface of acoustically levitated pure liquid droplets is predicted theoretically for the case where an acoustic boundary layer appears near the droplet surface resulting in an acoustic streaming. The theory is based on the computation of the acoustic field and squeezed droplet shape by means of the boundary element method developed

A. L. Yarin; G. Brenn; O. Kastner; D. Rensink; C. Tropea

1999-01-01

394

AFT FAN DUCT ACOUSTIC RADIATION  

Microsoft Academic Search

A finite element code has been developed for the prediction of the radiated acoustic field from the aft fan duct of a turbofan engine. The acoustic field is modelled based on the assumption that the steady flow in and around the nacelle is irrotational as is the acoustic perturbation. The geometry of the nacelle is axisymmetric and the acoustic source

W. Eversman; D. Okunbor

1998-01-01

395

Acoustic cooling engine  

DOEpatents

An acoustic cooling engine with improved thermal performance and reduced internal losses comprises a compressible fluid contained in a resonant pressure vessel. The fluid has a substantial thermal expansion coefficient and is capable of supporting an acoustic standing wave. A thermodynamic element has first and second ends and is located in the resonant pressure vessel in thermal communication with the fluid. The thermal response of the thermodynamic element to the acoustic standing wave pumps heat from the second end to the first end. The thermodynamic element permits substantial flow of the fluid through the thermodynamic element. An acoustic driver cyclically drives the fluid with an acoustic standing wave. The driver is at a location of maximum acoustic impedance in the resonant pressure vessel and proximate the first end of the thermodynamic element. A hot heat exchanger is adjacent to and in thermal communication with the first end of the thermodynamic element. The hot heat exchanger conducts heat from the first end to portions of the resonant pressure vessel proximate the hot heat exchanger. The hot heat exchanger permits substantial flow of the fluid through the hot heat exchanger. The resonant pressure vessel can include a housing less than one quarter wavelength in length coupled to a reservoir. The housing can include a reduced diameter portion communicating with the reservoir. The frequency of the acoustic driver can be continuously controlled so as to maintain resonance.

Hofler, Thomas J. (Los Alamos, NM); Wheatley, John C. (Los Alamos, NM); Swift, Gregory W. (Santa Fe, NM); Migliori, Albert (Santa Fe, NM)

1988-01-01

396

Microwave-field-driven acoustic modes in DNA.  

PubMed Central

The direct coupling of a microwave field to selected DNA molecules is demonstrated using standard dielectrometry. The absorption is resonant with a typical lifetime of 300 ps. Such a long lifetime is unexpected for DNA in aqueous solution at room temperature. Resonant absorption at fundamental and harmonic frequencies for both supercoiled circular and linear DNA agrees with an acoustic mode model. Our associated acoustic velocities for linear DNA are very close to the acoustic velocity of the longitudinal acoustic mode independently observed on DNA fibers using Brillouin spectroscopy. The difference in acoustic velocities for supercoiled circular and linear DNA is discussed in terms of solvent shielding of the nonbonded potentials in DNA. Images FIGURE 5 FIGURE 6 FIGURE 7

Edwards, G S; Davis, C C; Saffer, J D; Swicord, M L

1985-01-01

397

Thirty years of underwater acoustic signal processing in China  

NASA Astrophysics Data System (ADS)

Advances in technology and theory in 30 years of underwater acoustic signal processing and its applications in China are presented in this paper. The topics include research work in the field of underwater acoustic signal modeling, acoustic field matching, ocean waveguide and internal wave, the extraction and processing technique for acoustic vector signal information, the space/time correlation characteristics of low frequency acoustic channels, the invariant features of underwater target radiated noise, the transmission technology of underwater voice/image data and its anti-interference technique. Some frontier technologies in sonar design are also discussed, including large aperture towed line array sonar, high resolution synthetic aperture sonar, deep sea siren and deep sea manned subsea vehicle, diver detection sonar and demonstration projector of national ocean monitoring system in China, etc.

Li, Qihu

2012-11-01

398

Studies on the complexation of Pr(III) and Nd(III) with glycyl-glycine (gly-gly) using spectral analysis of 4f-4f transitions and potentiometric titrations  

NASA Astrophysics Data System (ADS)

The interaction of gly-gly with Pr(III) and Nd(III) have been studied in different aquated organic solvents like CH3OH, CH3CN, dioxane and DMF by using 4f-4f transitions spectra. Various energy interaction parameters like Slater Condon (Fk), Racah (Ek), Lande (?4f), nephelauxetic effect (?), bonding (b1/2) and percent covalency (?) parameters have been calculated to explain the nature of complexation. The intensity parameters like oscillator strength (P) and Judd-Ofelt parameters (T?, ? = 2, 4, 6) also support the mode of binding of gly-gly to metal ions. The results show that Pr(III) and Nd(III) with gly-gly form complexes by ionic linkages with carboxylate anion with weak covalency. The protonation constants and metal-ligand stability constants have also been determined by potentiometric measurements in aqueous medium at different temperatures (290, 300 and 310 K) at constant ionic strength, 0.1 mol dm-1. The results show the formation of metal-ligand complexes in the stoichiometric ratio 1:1. The stability of complexes is more in Nd(III) complexes as compared to Pr(III) complexes. Thermodynamic parameters (?G, ?H and ?S) of complexes were also calculated and the negative values of ?G and ?H show that the complex reactions are spontaneous and exothermic. The positive values of ?S indicate high stability of complex reactions which are enthalpy-driven.

Ranjana Devi, N.; Huidrom, Bimola; Rajmuhon Singh, N.

2012-10-01

399

Comparison of energy interaction parameters for the complexation of Pr(III) with glutathione reduced (GSH) in absence and presence of Zn(II) in aqueous and aquated organic solvents using 4f-4f transition spectra as PROBE.  

PubMed

The coordination chemistry of glutathione reduced (GSH) is of great importance as it acts as excellent model system for the binding of metal ions. The GSH complexation with metal ions is involved in the toxicology of different metal ions. Its coordination behaviour for soft metal ions and hard metal ions is found different because of the structure of GSH and its different potential binding sites. In our work we have studied two chemically dissimilar metal ions viz. Pr(III), which prefer hard donor site like carboxylic groups and Zn(II) the soft metal ion which prefer peptide-NH and sulphydryl groups. The absorption difference and comparative absorption spectroscopy involving 4f-4f transitions of the heterobimetallic Complexation of GSH with Pr(III) and Zn(II) has been explored in aqueous and aquated organic solvents. The variation in the energy parameters like Slater-Condon (F(K)), Racah (E(K)) and Lande (xi(4f)), Nephelauxetic parameter (beta) and bonding parameter (b(1/2)) are computed to explain the nature of complexation. PMID:15741124

Singh, Th David; Sumitra, Ch; Yaiphaba, N; Devi, H Debecca; Devi, M Indira; Singh, N Rajmuhon

2005-04-01

400

Acoustical heat pumping engine  

DOEpatents

The disclosure is directed to an acoustical heat pumping engine without moving seals. A tubular housing holds a compressible fluid capable of supporting an acoustical standing wave. An acoustical driver is disposed at one end of the housing and the other end is capped. A second thermodynamic medium is disposed in the housing near to but spaced from the capped end. Heat is pumped along the second thermodynamic medium toward the capped end as a consequence both of the pressure oscillation due to the driver and imperfect thermal contact between the fluid and the second thermodynamic medium. 2 figs.

Wheatley, J.C.; Swift, G.W.; Migliori, A.

1983-08-16

401

Acoustic wave viscosity sensor  

NASA Astrophysics Data System (ADS)

An acoustic wave device utilizing plate modes having components of displacement parallel to a crystal surface has been demonstrated to be an effective sensor of liquid shear viscosity (eta) over a wide viscosity range. When a liquid is present on the sensor surface, the propagation loss of the acoustic wave depends upon eta in a calculable fashion. Because the device functioons at 159 MHz, liquid relaxation effects occur with high-viscosity liquids, causing the proapgation loss to saturate. Viscosity is sampled in the 50-mm-thick liquid layer which couples to the acoustic wave, so that only a single drop of liquid is required for measurement.

Ricco, A. J.; Martin, S. J.

1987-05-01

402

Acoustic well cleaner  

DOEpatents

A method and apparatus are disclosed for cleaning the wellbore and the near wellbore region. A sonde is provided which is adapted to be lowered into a borehole and which includes a plurality of acoustic transducers arranged around the sonde. Electrical power provided by a cable is converted to acoustic energy. The high intensity acoustic energy directed to the borehole wall and into the near wellbore region, redissolves or resuspends the material which is reducing the permeability of the formation and/or restricting flow in the wellbore.

Maki, Jr., Voldi E. (11904 Bell Ave., Austin, TX 78759-2415); Sharma, Mukul M. (Dept. of Petroleum Engr. Univ. of Texas, Austin, TX 78712)

1997-01-21

403

Effects of Ar and O2 additives on SiO2 etching in C4F8-based plasmas  

NASA Astrophysics Data System (ADS)

Gas mixtures based on C4F8 are promising for the development of high-performance SiO2 plasma etching processes. Measurements of important gas phase species, thin film etching rates and surface chemistry changes were performed for inductively coupled plasmas fed with C4F8/Ar and C4F8/O2 gas mixtures. The addition of Ar to C4F8 causes a strong increase of the plasma density relative to that of pure C4F8 (by up to a factor of 4× at 90% Ar). For O2 addition the changes in plasma density are small up to 90% O2 relative to pure C4F8. Infrared laser absorption spectroscopy was used to determine the absolute densities of neutral CF, CF2 and COF2 radical species as a function of the gas composition. The densities of CF and CF2 were enhanced for certain operating conditions when Ar was added to C4F8 as long as the amount of Ar remained below 20%. For instance, the partial pressure of CF was 0.1 mTorr for a 20 mTorr 1400 W source power discharge for pure C4F8, and increased to 0.13 mTorr at 20% Ar. Above 20% Ar it decreased, roughly following the gas dilution. The CF2 partial pressure was about 5 mTorr for the same conditions, and increased by about 10% at 20% Ar. Above 20% Ar the CF2 partial pressure decreased roughly linearly with the amount of Ar added, to about 2 mTorr at 50% Ar. Of particular interest was the analysis of the difference in behavior of CF, CF2 and COF2 partial pressures over SiO2 and Si surfaces, with and without rf bias power (in the latter case a self-bias voltage of -100 V was used). For pure C4F8 discharges at 20 mTorr and 1400 W inductive power without rf bias the partial pressures of CF, CF2 and COF2 radicals are comparable over SiO2 and Si surfaces. Upon applying a rf bias, the CF2 partial pressure over a SiO2 surface is reduced much more strongly than for a Si surface. The overall reduction appears to be consistent with the relative SiO2/Si etch rate ratios observed for these conditions. These results indicate that CF2 is consumed during the etching of SiO2 and Si. We also measured fluorocarbon deposition rates without rf bias and etching rates of blanket SiO2, silicon, resist and deposited fluorocarbon films as a function of the rf bias and feed gas composition. Important differences in the response of the etching rates of those materials upon the addition of O2 and Ar to C4F8 were observed. In particular, we show that the SiO2/Si and SiO2/resist etching selectivities can be doubled by adding up to 90% Ar to C4F8, without inducing an unacceptably large reduction of the SiO2 etching rate. The change in etch rate ratios is at least in part due to strong surface chemical changes seen for Ar-rich fluorocarbon gas mixtures. The surface chemical changes of Si and SiO2 surfaces were investigated by real-time ellipsometry and x-ray photoelectron spectroscopy. A strong reduction of the fluorine content of the fluorocarbon steady-state layer and an increase in thickness is seen when up to 90% Ar was added to C4F8, and this coincides with an increase of the SiO2/Si etching selectivity. The change in fluorocarbon surface chemistry can be explained by the strongly increased ion/neutral flux ratio that is characteristic of Ar-rich C4F8/Ar gas mixtures.

Li, Xi; Ling, Li; Hua, Xuefeng; Fukasawa, Masanaga; Oehrlein, Gottlieb S.; Barela, Marcos; Anderson, Harold M.

2003-01-01

404

Modeling and prediction of density distribution and microstructure in particleboards from acoustic properties by correlation of non-contact high-resolution pulsed air-coupled ultrasound and X-ray images.  

PubMed

Non-destructive density and microstructure quality control testing in particleboards (PBs) is necessary in production lines. A pulsed air-coupled ultrasound (ACU) high-resolution normal transmission system, together with a first wave tracking algorithm, were developed to image amplitude transmission G(p) and velocity c(p) distributions at 120kHz for PBs of specific nominal densities and five particle geometries, which were then correlated to X-ray in-plane density images ?(s). Test PBs with a homogeneous vertical density profile were manufactured in a laboratory environment and conditioned in a standard climate (T=20°C, RH=65%) before the measurements. Continuous trends (R(2)>0.97) were obtained by matching the lateral resolution of X-ray images with the ACU sound field radius (?(w)(o)=21mm) and by clustering the scatter plots. ?(s)?c(p) was described with a three-parameter non-linear model for each particle geometry, allowing for ACU density prediction with 3% uncertainty and PB testing according to EN312. ?(s)?G(p) was modeled by calculating ACU coupling gain and by fitting inverse power laws with offset of ?(s) and c(p) to material attenuation, which scaled with particle volume. G(p) and c(p) variations with the frequency were examined, showing thickness resonances and scattering attenuation. The combination of ACU and X-ray data enabled successful particle geometry classification. The observed trends were interpreted in terms of multi-scale porosity and grain scattering with finite-difference time-domain simulations, which modeled arbitrarily complex stiffness and density distributions. The proposed method allows for non-contact determination of relations between acoustic properties and in-plane density distribution in plate materials. In future work, commercial PBs with non-uniform vertical density profiles should be investigated. PMID:22677469

Sanabria, Sergio J; Hilbers, Ulrich; Neuenschwander, Jürg; Niemz, Peter; Sennhauser, Urs; Thömen, Heiko; Wenker, Jan L

2012-05-19

405

Theoretical study of ground-state configurations 4fN in Nd IV, Pr IV and Nd V  

NASA Astrophysics Data System (ADS)

Although the trivalent lanthanide ions embedded in compounds have a wealth of applications in laser physics and the lighting industry, the theoretical interpretation of their ground-state configurations 4fN in the free ion spectra was restricted by the lack of experimental data. In the first part of this paper, the present status of their group-theoretical description and prospects for improvement are given. In the second part, this description is applied for the first time to a truly isolated configuration 4f3 in Nd IV by performing a parametric fit of level energies, taking into account Coulomb and spin-dependent interactions beyond the first order of perturbation. A root mean square (rms) deviation 5.39 cm-1 (i.e. 1/13 000 of the energy spread of the configuration) is obtained with 23 free parameters and 41 newly determined levels. The contributions of all parameters to the level energies are detailed for the first time. It is shown that energy shifts caused by the effective electrostatic parameters related to the third order of perturbation amount to about 10-3 of the total energy spread of the configuration 4f3. As concerns spin-dependent operators, the relative contributions of the spin-orbit interaction (SO), of the combined effects of spin-other-orbit and configuration interaction (SOO + CI) and of the spin-spin interaction (SS) are in the ratios 571:12:1. The Marvin integrals derived from the experimental energies are in a very good agreement with Hartree-Fock estimates. The ground-state configurations 4f2 of Pr IV and of the newly analysed spectrum Nd V are studied with the same methods.

Wyart, Jean-François; Meftah, Ali; Sinzelle, Jocelyne; Tchang-Brillet, Wan-Ü. Lydia; Spector, Nissan; Judd, Brian R.

2008-04-01

406

Oxide Etch Behavior in an Inductively Coupled C4F8 Discharge Characterized by Diode Laser Spectroscopy.  

NASA Astrophysics Data System (ADS)

This study reports on oxide and photoresist etch characteristics in an inductively coupled GEC Reference Cell as a function of reactor source power, bias power and pressure using C4F8. Diode laser absorption spectroscopy (DLAS) has shown that C4F8 is largely dissociated to form C2F4, CF2 and CF in the discharge. Over an oxide surface, CF2 and CF are consumed in the oxide etch process, but only when the bias power is sufficient to keep the oxide surface clean through energetic ion bombardment. For C4F8, this transition occurs at 60 eV (75 W bias power) in the GEC Cell. At higher bias powers (125 W) where oxide etching is fast ( 600 nm/min.), CF2 appears to be the key radical for the etch process since 50 percent (2.7-3.0 mTorr in a 15 mTorr C4F8 discharge) is consumed. These values were obtained by comparing the CF2 concentrations over non-reactive wafer surfaces versus blanket oxide wafer surfaces undergoing etching. CF is shown to display a similar trend, but its concentration is an order of magnitude less than CF2, and consequently cannot account on a mass basis for the amount of reactants necessary to balance the amount of etch products. Over a PR surface, neither CF2 nor CF concentrations vary as a function of PR etch rate. Consequently, they do not appear to be involved in the PR etch mechanism. However, PR etching is also critically dependent on bias power. PR films etch presumably due to energetic ion bombardment that degrades the PR film, making it liable to attack by fluorine.

Anderson, Harold; Barela, Marcus; Courtin, Geoff; Waters, Karla

2001-10-01

407

Thick self-organized porous zirconium oxide formed in H 2SO 4\\/NH 4F electrolytes  

Microsoft Academic Search

We report the formation of self-organized porous layer of ZrO 2 by anodization of zirconium in H 2SO 4 electrolytes containing low concentrations of NH 4F. Under optimized electrolyte conditions and polarization in range of several 10 V, ordered sponge-like porous ZrO 2 is obtained. The pores typically have a diameter ranged from 10 to 100 nm. Most remarkably the

Hiroaki Tsuchiya; Patrik Schmuki

2004-01-01

408

Lowest 4f-->5d Transition of Trivalent Rare-Earth Ions in CaF2 Crystals  

Microsoft Academic Search

The lowest 4f-->5d ultraviolet absorption band of eleven (Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb) of the fourteen trivalent rare-earth (RE) ions in host CaF2 crystals has been measured. The room temperature absorption cross section [cm2] and half-width [cm-1] of these bands for the first-half series of RE3+ are larger than that of the second-half

Eugene Loh

1966-01-01

409

Noncytotoxic Inhibition of Viral Infection through eIF4F-Independent Suppression of Translation by 4EGi-1?  

PubMed Central

The eukaryotic initiation factor eIF4F recruits ribosomes to capped mRNAs while eIF2 mediates start codon recognition to initiate protein synthesis. Increasing interest in targeting translation to suppress tumor growth has led to the development of new classes of inhibitors, including 4EGi-1, which disrupts eIF4F complexes. However, the full effects of this inhibitor and its potential uses in the treatment of other disease states remain unclear. Here, we show that overall rates of protein synthesis in primary human cells were affected only modestly by eIF4F disruption using the mTOR inhibitor Torin1, yet were highly sensitive to 4EGi-1. Translational suppression occurred even at concentrations of 4EGi-1 that were below those required to significantly alter eIF4F levels but were instead found to increase the association of ribosomal complexes containing inactive eIF2?. Although highly stable in culture, the effects of 4EGi-1 on both cellular protein synthesis and ribosome association were readily reversible upon inhibitor removal. In addition, despite potently inhibiting translation, prolonged exposure to 4EGi-1 had only modest effects on cell morphology and protein abundance without affecting viability or stress tolerance to any significant degree, although differential effects on heat shock protein (hsp) expression highlighted distinct 4EGi-1-sensitive modes of hsp induction. In contrast, 4EGi-1 potently suppressed poxvirus replication as well as both reactivation and lytic phases of herpesvirus infection. T