bluuebunny/crossref_metadata_2025 huggingface dataset:
Fetuin‐A and interleukin‐18 levels in ankylosing spondylitis
Authors: SARI Ismail , KEBAPCILAR Levent , TAYLAN Ali , BILGIR Oktay , KOZACI Didem L. , YILDIZ Yasar , YUKSEL Arif , GUNAY Necati , AKKOC Nurullah
Published: December 2009

Aim:  Interleukin‐18 (IL‐18) and fetuin‐A have been implicated in atherosclerosis. Preliminary evidence suggests that ankylosing spondylitis (AS) is associated with an increased risk of atherosclerosis. The aim of the present study was to investigate possible abnormalities in IL‐18 and fetuin‐A levels in AS.

Methods:  Subjects without established cardiovascular (CV) risk factors were studied. Fasting glucose, serum lipids, high sensitive C‐reactive protein (hsCRP), erythrocyte sedimentation rate, IL‐18 and fetuin‐A were assessed. Patients were also evaluated with the Bath Ankylosing Spondylitis Metrology Index, Bath Ankylosing Spondylitis Functional Index, and the Bath Ankylosing Spondylitis Disease Activity Index.

Results:  Fourty‐five patients with AS (37.4 ± 9.7 years; 35M/10F) and 29 controls (35.5 ± 11.1 years; 21M/8F) were studied. Fetuin‐A levels were significantly higher in AS patients compared to controls (1023.5 ± 171.6 vs. 856.9 ± 207.9 μg/mL, P < 0.001). IL‐18 levels were also higher in the AS group but the difference was not significant (184 ± 186 vs. 140 ± 115, P = 0.1). Significant but weak correlations were found between fetuin‐A, IL‐18, hsCRP, low density lipoprotein cholesterol, and triglyceride levels (P < 0.05; r = 0.4, 0.3, 0.2, and 0.3 respectively). Comparison of subjects with respect to the treatment type, disease activity and history of peripheral arthritis yielded no difference regarding fetuin‐A and IL‐18 between groups.

Conclusion:  Fetuin‐A and IL‐18 levels seem to be increased in AS patients regardless of disease activity and treatment type.
The effects of an orally administered probiotic on sulfasalazine metabolism in individuals with rheumatoid arthritis: a preliminary study
Authors: LEE Hee Ji , WALLER Rosmary D. , STEBBINGS Simon , HIGHTON John , ORLOVICH David A. , SCHMIERER David , FAWCETT J. Paul
Published: December 2009

Aim: To carry out a pilot study to investigate the effect of short‐term oral probiotic administration on the metabolism of sulfasalazine (SSZ) in patients with rheumatoid arthritis (RA) stabilized on SSZ.

Methods: Twelve subjects with RA taking stable doses of SSZ for a minimum of 3 months prior to the study, received a probiotic preparation contained three strains of bacteria (1.8 × 109 CFU/day) twice daily for 1 week. Single point blood and 12‐h urine samples were taken before and after probiotic treatment and 3 weeks following discontinuation of probiotics, for determination of SSZ and its metabolites. The presence of the probiotic bacteria in the feces of patients was investigated by denaturing gradient gel electrophoresis (DGGE).

Results: Adverse events recorded were three instances of gastrointestinal disturbance and one flare of RA. Plasma and urinary levels of SSZ and its metabolites showed no statistically significant changes after probiotic administration and the incidence of gastrointestinal disturbance did not appear to be ascribed to higher sulfapyridine plasma levels. Probiotic‐specific DGGE bands were detected in the feces of some patients after the treatment period.

Conclusions: Short‐term treatment of RA patients with a multi‐strain probiotic did not significantly influence SSZ metabolism as has been demonstrated in animal models.
Beam induced deposition of platinum using a helium ion microscope
Authors: Sanford Colin A. , Stern Lewis , Barriss Louise , Farkas Lou , DiManna Mark , Mello Russ , Maas Diederik J. , Alkemade Paul F. A.
Published: December 2009

Helium ion microscopy is now a demonstrated practical technology that possesses the resolution and beam currents necessary to perform nanofabrication tasks, such as circuit edit applications. Due to helium’s electrical properties and sample interaction characteristics relative to gallium, it is likely that the properties and deposition characteristics of beam induced deposited films will be different than those produced using gallium focused ion beam technology. However, there is at this date very little literature discussing the use of helium beams for beam induced chemistry or characterization of the resulting films. In this article, the authors present initial results regarding the deposition of platinum using a helium ion microscope and a gaseous organometallic precursor. Within this work a Carl Zeiss ORION™ helium ion microscope was used along with an OmniGIS unit to deposit platinum while exploring a variety of controllable parameters such as beam current, beam overlap, and size of deposition.
Precision material modification and patterning with He ions
Authors: Bell David C. , Lemme Max C. , Stern Lewis A. , Marcus Charles M.
Published: December 2009

The authors report on the use of a helium ion microscope as a potential technique for precise nanopatterning. Combined with an automated pattern generation system, they demonstrate controlled etching and patterning of materials, giving precise command over the geometery of the modified nanostructure. After the determination of suitable doses, sharp edge profiles and clean etching of areas in materials were observed. In this article they present examples of patterning on SiO2 and graphene, which is particularly relevant. This technique could be an avenue for precise material modification for future graphene based device fabrication. The technique has the potential to revolutionize the way that very thin, one-atomic layer materials are modified in a controlled and predictable way.
Roles of secondary electrons and sputtered atoms in ion-beam-induced deposition
Authors: Chen Ping , Salemink Huub W. M. , Alkemade Paul F. A.
Published: December 2009

The authors report the results of investigating two models for ion-beam-induced deposition (IBID). These models describe IBID in terms of the impact of secondary electrons and of sputtered atoms, respectively. The yields of deposition, sputtering, and secondary electron emission, as well as the energy spectra of the secondary electrons were measured in situ during IBID using (CH3)3Pt(CPCH3) as functions of Ga+ ion incident angle (0°–45°) and energy (5–30 keV). The deposition yield and the secondary electron yield have the same angular dependences but very different energy dependences. It was also found that the deposition yield per secondary electron is very high (⪢10). However, within the investigated angle and energy ranges, the deposition yield is linearly related to the sputtering yield, the offset of which might be due to the contribution of primary ions. They conclude that the sputtered atom model describes IBID better than the secondary electron model.
Ion multibeam nanopatterning for photonic applications: Experiments and simulations, including study of precursor gas induced etching and deposition
Authors: Ebm Christoph , Platzgummer Elmar , Loeschner Hans , Eder-Kapl Stefan , Joechl Peter , Kuemmel Marco , Reitinger Ruediger , Hobler Gerhard , Koeck Anton , Hainberger Rainer , Wellenzohn Markus , Letzkus Florian , Irmscher Mathias
Published: December 2009

The capabilities of charged particle nanopatterning (CHARPAN) for photonic device fabrication are investigated. The CHARPAN tool is a proof-of-concept tool for a multi-ion beam system that the authors used to directly pattern photonic structures into both Si and Ni as well as for maskless exposure of hydrogen silsesquioxane resist. The realized structures have a regular array and show adequate roundness of the holes as well as little sidewall roughness. For the development and a better understanding of the processes they extended and used the IonShaper® simulation software. They could achieve excellent agreement between sputtering simulation and experiments. Furthermore, they developed a nonlocal recoil-based algorithm for the simulation of ion beam induced etching and deposition. Simulation results for three dimensional nanopatterning with this algorithm are presented.
Evaluation of chamber contamination in a scanning electron microscope
Authors: Roediger P. , Wanzenboeck H. D. , Hochleitner G. , Bertagnolli E.
Published: December 2009

In any scanning electron microscope (SEM) organic contamination of the vacuum chamber leads to undesired material deposition resulting in artifacts in imaging or compromises focused electron beam induced processes like etching (FEBIE) [S. Matsui and K. Mori, Appl. Phys. Lett 51, 1498 (1987)] or deposition (FEBID) [S. Matsui and K. Mori, J. Vac. Sci. Technol. B 4, 299 (1986); W. F. van Dorp and C. W. Hagen, J. Appl. Phys. 4, 081301 (2008)]. This effect can also be used on purpose as a method to evaluate the contamination level of a SEM. With a standardized process for controlled deposition from residual gas, a method to evaluate the contamination level of an electron microscope quantitatively and reproductively was developed. Additionally, this method not only allows monitoring the contamination level of a SEM over its lifetime. Also the impact of various deposition parameters on the extent of contamination deposition has been investigated systematically. This method also allows comparing the status of different tools. A comparison of three different SEM tools of different vendors and with different fields of application is demonstrated.
Toroidal spectrometer for signal detection in scanning ion/electron microscopes
Authors: Hoang H. Q. , Khursheed A.
Published: December 2009

This article presents a second-order focusing toroidal spectrometer/detection system for scanning ion/electron microscopes. The spectrometer, combined with a prefocusing electrostatic lens, is predicted to have relative energy resolutions of 0.02% and 0.088% for emission angular spreads of ±6° and ±10°, respectively, corresponding to transmittances of around 20% and 34%. Initial experimental backscattered electron (BSE) spectra were recorded with a prototype toroidal spectrometer functioning as an attachment unit inside a conventional scanning electron microscope (SEM). These results were used to quantify SEM BSE material contrast.
Understanding the base development mechanism of hydrogen silsesquioxane
Authors: Kim Jihoon , Chao Weilun , Griedel Brian , Liang Xiaogan , Lewis Mark , Hilken Dawn , Olynick Deirdre
Published: December 2009

The authors study the dissolution mechanism of hydrogen silsesquioxane in base solutions with the addition of chloride salts to elucidate the development mechanism. The reaction mechanisms are proposed based on the dissolution mechanism of quartz. Development kinetics suggests two dose-dependent development mechanisms. Considering ion sizes, both hydrated and nonhydrated, and ion exchange, they propose that a combination of a surface dominated reaction at higher doses and a matrix dominated reaction at lower doses accounts for the high development contrast with a NaOH base/NaCl salt mixture. The interplay between the hydrated and the nonhydrated ion sizes leads to higher contrast developers, such as tetramethyl ammonium hydroxide with NaCl.
Grazing incident small angle x-ray scattering: A metrology to probe nanopatterned surfaces
Authors: Hofmann T. , Dobisz E. , Ocko B. M.
Published: December 2009

Grazing incident small angle x-ray scattering (GISAXS) and transmission small angle x-ray scattering studies have been carried out on periodic patterns on silicon substrates in order to determine the average morphology and arrangement of the patterned features. The GISAXS pattern exhibited rods of scattering at Bragg positions, discrete and evenly spaced, in the surface plane. The scattered intensity modulations along each rod have been compared with simulated scattering from simple geometrical patterns to obtain quantitative information on the diameter, width, height, and sidewall inclination of the pillars and gratings. The results are in good agreement with real space images obtained with SEM and demonstrate that GISAXS is a powerful technique for characterizing nanoscale arrays used in patterned media, photonics structures, and electronics structures.
Design of a multiple-electron-beam imaging technique for surface inspection
Authors: Luo T. , Khursheed A. , Osterberg M. , Hoang H.
Published: December 2009

This article presents a multiple-electron-beam imaging technique, which is able to simultaneously process images from multiple scanning sources. The proposal is based on the detection of wide-angle BSEs, whose spectrum is predicted to be largely confined to a sharp elastic peak at the primary electron beam energy, which remains unaltered even if the incident beam is tilted. When electron sources of different energies are used to illuminate the sample, the energy of wide-angle BSEs will be confined close to their respective primary beam energies. The wide-angle scattered electrons are then subsequently energy filtered to obtain separate images, which are formed by parallel energy mode acquisition at the detector plane.
Understanding of hydrogen silsesquioxane electron resist for sub-5-nm-half-pitch lithography
Authors: Yang Joel K. W. , Cord Bryan , Duan Huigao , Berggren Karl K. , Klingfus Joseph , Nam Sung-Wook , Kim Ki-Bum , Rooks Michael J.
Published: December 2009

The authors, demonstrated that 4.5-nm-half-pitch structures could be achieved using electron-beam lithography, followed by salty development. They also hypothesized a development mechanism for hydrogen silsesquioxane, wherein screening of the resist surface charge is crucial in achieving a high initial development rate, which might be a more accurate assessment of developer performance than developer contrast. Finally, they showed that with a high-development-rate process, a short duration development of 15s was sufficient to resolve high-resolution structures in 15-nm-thick resist, while a longer development degraded the quality of the structures with no improvement in the resolution.
Understanding imaging modes in the helium ion microscope
Authors: Scipioni Larry , Sanford Colin A. , Notte John , Thompson Bill , McVey Shawn
Published: December 2009

Recent investigations are gaining us a better understanding of the nature of the beam-sample interactions in the helium ion microscope and what they mean for the image information provided. In secondary electron (SE) imaging, for example, the surface sensitivity is attributed to the low SE-II fraction. Voltage contrast imaging shows the ability to see both buried structures and to probe the conductance to ground of surface contacts. It is found, however, that the prominence of these two types of contrast varies oppositely with beam energy, yielding information about the nature of the interactions that gives rise to them. Transmission ion imaging can yield information about material density, atomic number, grain structure, and electronic structure. It is possible to capture the top-side SE signal, bright field signal, and dark field signal from a given sample simultaneously. The detection of diffraction contrast is under investigation.
Near neighbor averaging: A technique for improving image uniformity in aperture array lithography
Authors: Nasrullah A. , Smith D. , Sherlock T. , Ruchhoeft P. , Litvinov D.
Published: December 2009

Ion beam aperture array lithography was developed to rapidly form large arrays of periodic patterns whose shape is defined at the printing step. This is accomplished with a massive array of ion beamlets formed by exposing a stencil mask with a dense array of openings to a broad ion beam; these can be moved across the wafer surface to write the shape of the unit element with each beamlet. In this work, the authors demonstrate that the uniformity of the aperture array mask image can be significantly improved by averaging the exposure with images formed by the neighboring apertures. This reduces the tolerances for patterns in the stencil mask and allows for the correction of random defects that may occur during the mask fabrication process. To achieve this, each aperture image is formed as the sum of the images of itself and its neighbors. They demonstrate, through modeling and experiment, that this process can form images where the standard deviation of the openings has been reduced by a factor of 3 when averaging the exposure over nine neighboring apertures. They show that the size distribution scales inversely with the square root of the number of near neighbor exposures.
Identifying and addressing student difficulties with hydrostatic pressure
Authors: Loverude M. E. , Heron P. R. L. , Kautz C. H.
Published: December 2009

We describe an investigation of student learning of the concept of pressure in a static liquid. We document patterns of student answers and explanations in response to written and interview questions. We find that many undergraduate students fail to develop a correct understanding of pressure in this context. Many students have difficulty identifying the forces that act on a liquid and relating these forces to pressure. We describe the development and assessment of research-based instructional materials designed to address student difficulties with pressure and provide evidence that these materials can improve student understanding.
Two-electron atoms, ions, and molecules
Authors: Høgaasen Hallstein , Richard Jean-Marc , Sorba Paul
Published: December 2009

The quantum mechanics of two-electron systems is reviewed, starting with the ground state of the helium atom and heliumlike ions with central charge Z. The case of Z≥2 is rather straightforward. In contrast, for negative hydrogen ion with Z=1, the stability of H− cannot be achieved using a product of individual electron wavefunctions and requires explicit account of the anticorrelation among the two electrons. The wavefunction proposed by Chandrasekhar is revisited, where the permutation symmetry is first broken and then restored by a counterterm. More difficult problems can be studied using the same strategy such as the stability of hydrogenlike ions for any value of the proton-to-electron mass ratio M/m, the energy of the lowest spin-triplet state of helium and heliumlike ions, and the stability of the doubly excited hydrogen ion with unnatural parity. The positronium molecule, which was predicted years ago and discovered recently, can also be shown to be stable against spontaneous dissociation. Emphasis is placed on symmetry breaking, which can either spoil or improve the stability.
Rapid calculation of individual ion Madelung constants and their convergence to bulk values
Authors: Baker A. D. , Baker M. D.
Published: December 2009

The distinction between the single Madelung constant that characterizes bulk materials and the range of Madelung constants that exists for real (finite) materials is emphasized. Madelung constants are calculated using a fast algorithm to compute Coulomb sums. The weighted averages of the specific ion Madelung constants provide a measure of the electrostatic potential for any cluster of ions. The central ions’ Madelung constants in a succession of progressively larger structures with the same symmetry as the bulk converge rapidly to the bulk Madelung constant if all the precursors to the bulk are electrically neutral. If this condition is satisfied, convergence is faster than other methods and is simpler to implement than the classical Ewald method. Applications to surface science and to the conformations and energies of nanostructures are made possible by this approach.
Exploitation of symmetries for image reconstruction in linearized variable density diffraction tomography
Authors: Shi Daxin , Anastasio Mark A.
Published: December 2009

The problem of reconstructing an object’s weakly varying compressibility and density distributions in three-dimensional (3D) acoustic diffraction tomography is studied. Based on the Fourier diffraction projection theorem for acoustic media, it is demonstrated that the 3D Fourier components of an object’s compressibility and density distributions can be decoupled algebraically, thereby providing a method for separately reconstructing the distributions. This is facilitated by the identification and exploitation of tomographic symmetries and the rotational invariance of the imaging model. The developed reconstruction methods are investigated by use of computer- simulation studies. The application of the proposed image reconstruction strategy to other tomography problems is discussed.
Informational factors in identifying environmental sounds in natural auditory scenes
Authors: Leech Robert , Gygi Brian , Aydelott Jennifer , Dick Frederic
Published: December 2009

In a non-linguistic analog of the “cocktail-party” scenario, informational and contextual factors were found to affect the recognition of everyday environmental sounds embedded in naturalistic auditory scenes. Short environmental sound targets were presented in a dichotic background scene composed of either a single stereo background scene or a composite background scene created by playing different background scenes to the different ears. The side of presentation, time of onset, and number of target sounds were varied across trials to increase the uncertainty for the participant. Half the sounds were contextually congruent with the background sound (i.e., consistent with the meaningful real-world sound environment represented in the auditory scene) and half were incongruent. The presence of a single competing background scene decreased identification accuracy, suggesting an informational masking effect. In tandem, there was a contextual pop-out effect, with contextually incongruent sounds identified more accurately. However, when targets were incongruent with the real-world context of the background scene, informational masking was reduced. Acoustic analyses suggested that this contextual pop-out effect was driven by a mixture of perceptual differences between the target and background, as well as by higher-level cognitive factors. These findings indicate that identification of environmental sounds in naturalistic backgrounds is an active process that requires integrating perceptual, attentional, and cognitive resources.
Three dimensional finite element modeling of smart foam
Authors: Leroy Pierre , Atalla Noureddine , Berry Alain , Herzog Philippe
Published: December 2009

The “smart foam” concept and design originate from the combination of the passive dissipation capability of foam in the medium and high frequency ranges and the active absorption ability of piezoelectric actuator (generally polyvinylidene fluoride) in the low frequency range. This results into a passive/active absorption control device that can efficiently operate over a broad range of frequencies. In this paper, a full three dimensional finite element model of smart foam is presented including its experimental validation. The modeling tool uses quadratic poroelastic elements, as well as elastic, fluid, and piezoelectric elements. The weak integral formulation of the different media involved is presented with the associated coupling conditions. A simplified orthotropic model of poroelastic media is presented. To validate the developed model, a prototype of a smart foam has been realized and its passive absorption and radiation measured in an impedance tube and compared to predictions. The experimental validation demonstrates the validity of the model. This modeling tool constitutes a general platform to simulate and optimize various configurations of smart foams.
Passive cavitation imaging with ultrasound arrays
Authors: Salgaonkar Vasant A. , Datta Saurabh , Holland Christy K. , Mast T. Douglas
Published: December 2009

A method is presented for passive imaging of cavitational acoustic emissions using an ultrasound array, with potential application in real-time monitoring of ultrasound ablation. To create such images, microbubble emissions were passively sensed by an imaging array and dynamically focused at multiple depths. In this paper, an analytic expression for a passive image is obtained by solving the Rayleigh–Sommerfield integral, under the Fresnel approximation, and passive images were simulated. A 192-element array was used to create passive images, in real time, from 520-kHz ultrasound scattered by a 1-mm steel wire. Azimuthal positions of this target were accurately estimated from the passive images. Next, stable and inertial cavitation was passively imaged in saline solution sonicated at 520 kHz. Bubble clusters formed in the saline samples were consistently located on both passive images and B-scans. Passive images were also created using broadband emissions from bovine liver sonicated at 2.2 MHz. Agreement was found between the images and source beam shape, indicating an ability to map therapeutic ultrasound beams in situ. The relation between these broadband emissions, sonication amplitude, and exposure conditions are discussed.
Analytical modeling of piezoelectric ceramic transducers based on coupled vibration analysis with application to rectangular thickness poled plates
Authors: Aronov Boris S. , Bachand Corey L. , Brown David A.
Published: December 2009

The energy method for analyzing piezoelectric ceramic transducers [B. S. Aronov, J. Acoust. Soc. Am. 117, 210–220 (2005)] is applied to the treatment of transducers with mechanical systems that can be considered as two-dimensional. Analysis is made following the general outline of the theory of coupled vibration in two degrees-of-freedom systems and its extension in calculating the resonance frequencies of elastic bodies, as suggested by Giebe and Blechschmidt [Ann. Physik, Ser. 5 18, 417–485 (1933)]. The approach to the problem is illustrated with examples of piezoceramic rectangular thickness poled plates. The resonance frequencies and effective coupling coefficients are presented as functions of the plates’ aspect ratio.
Estimating the shell parameters of SonoVue® microbubbles using light scattering
Authors: Tu Juan , Guan Jingfeng , Qiu Yuanyuan , Matula Thomas J.
Published: December 2009

Experiments were performed to measure the dynamical response of individual SonoVue® microbubbles subjected to pulsed ultrasound. Three commonly used bubble dynamic models (i.e., Hoff’s, Sarkar’s, and linearized Marmottant’s models) were compared to determine the most appropriate model for fitting to the experimental data. The models were evaluated against published optical microscopy data. The comparison suggests that it is difficult to rank these models for lipid-shelled microbubbles undergoing small-amplitude oscillations, because under these conditions the shell parameters in these models are closely related. A linearized version of the Marmottant model was used to estimate the shell parameters (i.e., shear modulus and shear viscosity) of SonoVue® microbubbles from the experimental light scattering data, as a function of ambient microbubble radius. The SonoVue® microbubble shell elasticity and dilatational viscosity increase with ambient bubble radius, in agreement with previously published data. The results suggest that light scattering, used in conjunction with one of several popular bubble dynamics models, is effective at characterizing microbubble response and evaluating shell parameters.
Surface response of a fractional order viscoelastic halfspace to surface and subsurface sources
Authors: Meral F. Can , Royston Thomas J. , Magin Richard L.
Published: December 2009

Previous studies by the second author published in this journal focused on low audible frequency (40–400Hz) shear and surface wave motion in and on a viscoelastic material representative of biological tissue. Specific cases considered were that of surface wave motion on a halfspace caused by a finite rigid circular disk located on the surface and oscillating normal to it [Royston et al., J. Acoust. Soc. Am. 106, 3678–3686 (1999)] and compression, shear, and surface wave motion in a halfspace generated by a subsurface finite dipole [Royston et al., J. Acoust. Soc. Am. 113, 1109–1121 (2003)]. In both studies, a Voigt model of viscoelasticity was assumed in the theoretical treatment, which resulted in agreement between theoretical predictions and experimental measurements over a limited frequency range. In the present article, the linear viscoelastic assumption in these two prior works is revisited to consider a (still linear) fractional order Voigt model, where the rate-dependent damping component that is dependent on the first derivative of time is replaced with a component that is dependent on a fractional derivative of time. It is shown that in both excitation source configurations, the fractional order Voigt model assumption improves the match of theory to experiment over a wider frequency range (in some cases up to the measured range of 700Hz).
Measurement of characteristic impedance and wave number of porous material using pulse-tube and transfer-matrix methods
Authors: Sun Liang , Hou Hong , Dong Li-ying , Wan Fang-rong
Published: December 2009

The time domain implementation of the transfer-matrix method developed by Song and Bolton [J. Acoust. Soc. Am. 107, 1131–1154 (2000)] for measuring the characteristic impedance and wave number of porous materials is described in this paper. The so called Butterworth impulse is generated in a standing wave tube with a flat frequency response over a wide frequency range. With only two microphone measurements, the transfer matrix of porous layers can easily be determined through the calculation of complex amplitudes of incident, reflected, and transmitted pulses. The procedure has been used to measure the acoustical properties of a fiber material, and good agreement was found between measured acoustical properties and predicted results by Delany and Bazley [Appl. Acoust. 3, 105–116 (1971)] semiempirical formulas. Although the error associated with the sample-edge constraint still remains, the new method has a better frequency response as a result of the system calibration process, and the optimal inter-microphone distance is no longer required compared to the frequency domain implementation.
Comparison of three measurement techniques for the normal absorption coefficient of sound absorbing materials in the free field
Authors: Hirosawa Kunikazu , Takashima Kazuhiro , Nakagawa Hiroshi , Kon Makoto , Yamamoto Aki , Lauriks Walter
Published: December 2009

Three different techniques for evaluating the absorption coefficient of sound absorbing materials in free field conditions are discussed. One technique measures the acoustic impedance at one point nearby a specimen, the other two techniques evaluate the impedance from the transfer function of two sound pressures and two particle velocities at two points. These are called “PU-method,” “PP-method,” and “UU-method,” respectively. An iterative algorithm to estimate the acoustic impedance of the locally reactive specimen in the spherical wave field is also applied. First, the effect of receiver positions, specimen areas, and source heights to the measured normal absorption coefficient is investigated by the boundary element method. According to these investigations, the PU-method is most stable against the effect of specimen area, and the UU-method is easily affected by that effect. Closer source to the specimen distance is advantageous for the signal to noise ratio of these measurement techniques, but correction for the effect of the spherical wave field has to be applied. As a finding, the iterative algorithm works for all of three techniques. Finally, the PU-method is applied experimentally with a pressure-velocity sensor and a loudspeaker in a hemi-anechoic room. As a result, the calculated results have been verified.
Predictions of angle dependent tortuosity and elasticity effects on sound propagation in cancellous bone
Authors: Aygün Haydar , Attenborough Keith , Postema Michiel , Lauriks Walter , Langton Christian M.
Published: December 2009

The anisotropic pore structure and elasticity of cancellous bone cause wave speeds and attenuation in cancellous bone to vary with angle. Previously published predictions of the variation in wave speed with angle are reviewed. Predictions that allow tortuosity to be angle dependent but assume isotropic elasticity compare well with available data on wave speeds at large angles but less well for small angles near the normal to the trabeculae. Claims for predictions that only include angle-dependence in elasticity are found to be misleading. Audio-frequency data obtained at audio-frequencies in air-filled bone replicas are used to derive an empirical expression for the angle-and porosity-dependence of tortuosity. Predictions that allow for either angle dependent tortuosity or angle dependent elasticity or both are compared with existing data for all angles and porosities.
Ambient pressure sensitivity of microbubbles investigated through a parameter study
Authors: Andersen Klaus Scheldrup , Jensen Jørgen Arendt
Published: December 2009

Measurements on microbubbles clearly indicate a relation between the ambient pressure and the acoustic behavior of the bubble. The purpose of this study was to optimize the sensitivity of ambient pressure measurements, using the subharmonic component, through microbubble response simulations. The behavior of two microbubbles corresponding to two different contrast agents was investigated as a function of driving pulse and ambient overpressure pov. Simulations of Levovist using a rectangular driving pulse show an almost linear reduction in the subharmonic component as pov is increased. For a 20 cycle driving pulse, a reduction of 4.6 dB is observed when changing pov from 0 to 25 kPa. Increasing the pulse duration makes the reduction even clearer. For a pulse with 64 cycles, the reduction is 9.9 dB. This simulation is in good correspondence with measurement results presented in the literature. Further simulations of Levovist show that also the shape and the acoustic pressure of the driving pulse are very important factors. The best pressure sensitivity of Levovist was found to be 0.88 dB/kPa. For Sonazoid, a sensitivity of 1.14 dB/kPa has been found, although the reduction is not completely linear as a function of the ambient pressure.
Measurements and inversion of acoustic scattering from suspensions having broad size distributions
Authors: Moate Benjamin D. , Thorne Peter D.
Published: December 2009

Measurements are presented from a multi-frequency acoustic backscatter study of aqueous suspensions of irregularly shaped quartz sediments having broad particle size distributions. Using the backscattered sound from a homogenous suspension, measurements of the ensemble backscatter form function and ensemble normalized total scattering cross section were obtained. Three different size distribution types are examined; namely Gaussian, log-normal, and bi-modal distributions, each covering a range of particle sizes similar to those observed in sandy marine environments near the seabed. The measurements of ensemble scattering are compared with theoretical predictions, derived by integrating the intrinsic scattering properties of the sediments over the probability density functions of the size distributions used in the present study. The results show that the ensemble scattering parameters are significant functions of both the width and type of size distribution in suspension. The impact of errors in size distribution width on inversion predictions of both mean size and suspended concentration is also examined. The validity of the theoretical predictions is discussed, along with the implication of the inversion results for using acoustic backscatter data to measure suspended concentration and particle size in sandy marine environments.
The natural frequencies of microbubble oscillation in elastic vessels
Authors: Martynov Sergey , Stride Eleanor , Saffari Nader
Published: December 2009

A theoretical model for the dynamics of a bubble in an elastic blood vessel is applied to study numerically the effect of confinement on the free oscillations of a bubble. The vessel wall deformations are described using a lumped-parameter membrane-type model, which is coupled to the Navier–Stokes equations for the fluid motion inside the vessel. It is shown that the bubble oscillations in a finite-length vessel are characterized by a spectrum of frequencies, with distinguishable high-frequency and low-frequency modes. The frequency of the high-frequency mode increases with the vessel elastic modulus and, for a thin-wall vessel, can be higher than the natural frequency of bubble oscillations in an unconfined liquid. In the limiting case of an infinitely stiff vessel wall, the frequency of the low-frequency mode approaches the well-known solution for a bubble confined in a rigid vessel. In order to interpret the results, a simple two-degree-of-freedom model is applied. The results suggest that in order to maximize deposition of acoustic energy, a bubble confined in a long elastic vessel has to be excited at frequencies higher than the natural frequency of the equivalent unconfined bubble.
Perceptual and emotional categorization of sound
Authors: Bergman Penny , Sköld Anders , Västfjäll Daniel , Fransson Niklas
Published: December 2009

This paper investigates how different types of data from psychoacoustical experiments may be combined to render further knowledge about the mechanisms underlying sound perception. Two studies were conducted with auditory alerts of short duration. First, an experiment where participants rated the dissimilarity among the auditory alerts was performed. This resulted in a two-dimensional multi-dimensional scaling solution. Second, an experiment where participants evaluated the stimuli with semantic descriptors and rated their emotional reactions to the sounds was performed. The output of this experiment was a reduced set of underlying perceptual and emotional dimensions. The results of the two experiments were then integrated by the use of multi-dimensional perceptual unfolding and a set mediation analyses. The integrative analyses showed that part of the cognitive categorization of the semantic descriptors was mediated by the emotional reactions to the sounds. The results are discussed in relation to theories of auditory perception and emotional response categorization.
Geostatistical modeling of sound propagation: Principles and a field application experiment
Authors: Baume Olivier , Gauvreau Benoit , Bérengier Michel , Junker Fabrice , Wackernagel Hans , Chilès Jean-Paul
Published: December 2009

The assessment of noise sources for environmental purposes requires reliable methods for mapping. Numerical models are well adapted for sophisticated simulations and sensitivity analyses; however, real-time mapping of large frequency bands must be based on fast and acceptable computations and honor in situ measurements. In this paper, a real-time mapping procedure of noise exposure is proposed. The procedure is based on geostatistical modeling of spatial variations and applied to a case study taken from an experimental campaign, where a point source was placed on a flat meadow. An analytical approximation of the acoustic field was first computed with the Embleton model. The difference between this approximation and the actual measurements (Leq15min 1∕3-octave bands samples from 19 microphones spread over the meadow) showed spatial structure, which has been modeled with a variogram. Finally, the geostatistical technique of kriging with external drift provided an optimal interpolation of the acoustic field data while encapsulating the first approximation from the Embleton model. Systematic geostatistical inference and real-time mapping with the proposed procedure can be envisaged in simple cases.
The role of across-frequency processes in dichotic listening conditions
Authors: Nitschmann Marc , Verhey Jesko L. , Kollmeier Birger
Published: December 2009

In the bandwidening experiment with a diotic noise masker, an apparently wider critical bandwidth has often been reported when a dichotic signal (Sπ) is used instead of a diotic signal (So). Two competing across-channel processes were proposed to account for this apparently wider critical bandwidth: (i) A detrimental across-channel effect reducing the binaural masking-level difference (BMLD) for broadband maskers and (ii) a beneficial integration of information across channels for narrowband maskers. The two hypotheses result in different predictions of the BMLD in the notched-noise experiment: According to the first hypothesis, the change in BMLD with notch width is determined by the level-dependence of the BMLD for a narrowband masker centered at the signal frequency, whereas the second hypothesis predicts that it is determined by the level-dependence of the BMLD for a broadband masker. To test the hypotheses, masked thresholds of a diotic or dichotic 500-Hz signal were measured for a diotic notched-noise masker as a function of notch width. In addition, thresholds were measured for a diotic broadband and narrowband masker as a function of masker level. The data indicate that neither of the two hypotheses is able to predict the continuous decrease in the BMLD as the notch width increases.
Comparison of in-situ calibration methods for quantifying input to the middle ear
Authors: Lewis James D. , McCreery Ryan W. , Neely Stephen T. , Stelmachowicz Patricia G.
Published: December 2009

Sound pressure level in-situ measurements are sensitive to standing-wave pressure minima and have the potential to result in over-amplification with risk to residual hearing in hearing-aid fittings. Forward pressure level (FPL) quantifies the pressure traveling toward the tympanic membrane and may be a potential solution as it is insensitive to ear-canal pressure minima. Derivation of FPL is dependent on a Thevenin-equivalent source calibration technique yielding source pressure and impedance. This technique is found to accurately decompose cavity pressure into incident and reflected components in both a hard-walled test cavity and in the human ear canal through the derivation of a second sound-level measure termed integrated pressure level (IPL). IPL is quantified by the sum of incident and reflected pressure amplitudes. FPL and IPL were both investigated as measures of sound-level entering the middle ear. FPL may be a better measure of middle-ear input because IPL is more dependent on middle-ear reflectance and ear-canal conductance. The use of FPL in hearing-aid applications is expected to provide an accurate means of quantifying high-frequency amplification.
Angular and frequency spectral analysis of the ultrasonic backward beam displacement on a periodically grooved solid
Authors: Herbison Sarah W. , Declercq Nico F. , Breazeale Mack A.
Published: December 2009

The ultrasonic backward beam displacement, which has been shown to occur when a bounded beam is incident upon a periodically corrugated liquid-solid interface, is studied experimentally. This effect has been previously studied on a periodic water-brass interface at one particular frequency (6 MHz) and one corresponding angle of incidence (22.5°), but the question has remained whether it would also exist at other frequency and angle combinations. The knowledge of whether this phenomenon is a coincidence or whether it will occur for other frequency and angle combinations contributes to a better understanding of the interaction of ultrasound with periodic structures and diffraction effects, in particular. Potential applications exist in the study of phononic crystals and in the non-destructive evaluation of materials. The present work reports results from recent experiments on the same periodically grooved brass sample that was employed in the first investigations of this phenomenon. Through the examination of frequency spectra in the form of angular and classical spectrograms, the experiments reported here show the backward beam displacement to occur for multiple angles of incidence and frequencies. Furthermore, evidence is shown as to the exact cause of the backward beam displacement, namely, a backward propagating Scholte–Stoneley wave.
Determination of elastic constants of generally anisotropic inclined lamellar structure using line-focus acoustic microscopy
Authors: Kim Jin-Yeon , Rokhlin Stanislav I.
Published: December 2009

A methodology for measuring elastic constants of different phases in materials with lamellar microstructure by line-focus acoustic microscopy is developed. The material microstructure investigated is modeled by generally anisotropic multilayers arbitrarily inclined to the sample surface on which acoustic microscopy measurements are performed. To calculate surface acoustic wave (SAW) propagation in such structures quasi-static effective elastic constants are determined and compared with calculated frequency-dependent constants. As a model material, practically important, Ti–6Al–2Sn–4Zr–2Mo alloy is selected. Time-resolved line-focus acoustic microscopy experiments are performed on a Ti-6242 α/β single colony (Ti–6Al–2Sn–4Zr–2Mo alloy) and on a Ti–6Al α-phase single crystal for which elastic constants of different phases are determined using inversion of measured SAW velocities. To validate the experimental methodology, SAW velocities in an X-cut quartz crystal are measured as a function of sample orientation angle and compared with predictions based on the known elastic moduli of quartz.
Transmission loss of double panels filled with porogranular materials
Authors: Chazot Jean-Daniel , Guyader Jean-Louis
Published: December 2009

Sound transmission through hollow structures found its interest in several industrial domains such as building acoustics, automotive industry, and aeronautics. However, in practice, hollow structures are often filled with porous materials to improve acoustic properties without adding an excessive mass. Recently a lot of interest arises for granular materials of low density that can be an alternative to standard absorbing materials. This paper aims to predict vibro-acoustic behavior of double panels filled with porogranular materials by using the patch-mobility method recently published. Biot’s theory is a basic tool for the description of porous material but is quite difficult to use in practice, mostly because of the solid phase characterization. The original simplified Biot’s model (fluid-fluid model) for porogranular material permitting a considerable reduction in data necessary for calculation has been recently published. The aim of the present paper is to propose a model to predict sound transmission through a double panel filled with a porogranular material. The method is an extension of a previous paper to take into account the porogranular material through fluid-fluid Biot’s model. After a global overview of the method, the case of a double panel filled with expanded polystyrene beads is studied and a comparison with measurements is realized.
Speech identification in noise: Contribution of temporal, spectral, and visual speech cues
Authors: Kim Jeesun , Davis Chris , Groot Christopher
Published: December 2009

This study investigated the degree to which two types of reduced auditory signals (cochlear implant simulations) and visual speech cues combined for speech identification. The auditory speech stimuli were filtered to have only amplitude envelope cues or both amplitude envelope and spectral cues and were presented with/without visual speech. In Experiment 1, IEEE sentences were presented in quiet and noise. For in-quiet presentation, speech identification was enhanced by the addition of both spectral and visual speech cues. Due to a ceiling effect, the degree to which these effects combined could not be determined. In noise, these facilitation effects were more marked and were additive. Experiment 2 examined consonant and vowel identification in the context of CVC or VCV syllables presented in noise. For consonants, both spectral and visual speech cues facilitated identification and these effects were additive. For vowels, the effect of combined cues was underadditive, with the effect of spectral cues reduced when presented with visual speech cues. Analysis indicated that without visual speech, spectral cues facilitated the transmission of place information and vowel height, whereas with visual speech, they facilitated lip rounding, with little impact on the transmission of place information.