bluuebunny/crossref_metadata_2025 huggingface dataset:
TH‐C‐304A‐04: Simultaneous Delineation of Bladder and Prostate From 3D CT: An Optimal Graph‐Theoretic Approach
Authors: Song Q , Wu X , Buatti J , Smith M , Sonka M
Published: April 2010

Introduction Precise target delineation is critical for a successful 3‐D radiotherapy treatment planning for prostate cancer treatment. Automatic segmentation techniques are urgently needed due to large amounts of 3‐D image data that require increased time for manually contouring. We report a novel segmentation method for simultaneous 3‐D surface detection of bladder and prostate, incorporating both edge and shape information. Our method is the first attempt to employ an arc‐weighted graph‐based representation for simultaneous surface detection, which delivers a globally optimal solution in low‐order polynomial time. Method and Material The core of our approach is to represent segmentation problem using an arc‐weighted graph, which permits a wider spectrum of constraints into 3‐D graph‐theoretic approach. Hard surface interacting constraints are enforced in interacting regions to preserve geometric relationships between partially interacting boundary surfaces of prostate and bladder. Soft smoothness shape compliance is further employed to incorporate shape information. Two globally mutually interacting optimal surfaces are then computed by solving a maximum flow problem. Testing the approach was accomplished on 13 CT data sets from different patients. Computed results were compared with expert‐traced standard. Results Our method yielded high‐quality segmentation, despite of the low saliency of CT images. The average probability of correct detection was 0.958±0.024 for bladder and 0.852±0.046 for prostate. The average probability of false detection was 0.115±0.062 for bladder and 0.136±0.045 for prostate. The unsigned surface distance error was 1.04±1.00mm for bladder and 1.38±1.08mm for prostate. The percentage of expert‐defined surface points with less than 5mm from our computed surface was 99% for bladder and 98.6% for prostate. Conclusion We develop a novel segmentation method for simultaneous detection of bladder and prostate. A sub‐voxel accuracy was achieved, which demonstrates the promise of our algorithm.
TH‐C‐304A‐09: Semi‐Automatic Respiratory Motion Correction for Liver CT Perfusion
Authors: Jensen N , Lock M , Kozak R , Carnes G , Chen X , Chen J , Wong E , Lee T
Published: April 2010

Purpose: To develop and validate a semi‐automatic algorithm for correcting respiratory motion in a free breathing dynamic CT scan for perfusion imaging. Method and Materials: The CT perfusion protocol allowed the patients to breath freely, imaging two adjacent 4 cm volumes of liver alternatingly using the axial shuttle mode. Each 4 cm section was imaged 40 times during 2 minutes with 30–40 ml of contrast agent injected at a rate of 4 ml/s beginning approximately 10 seconds into the scan. A semi‐automatic algorithm has been implemented to sort the reconstructed CT images. One reference image from each 4 cm section is selected and several 40×40 voxels regions of interest are placed around the edge of the liver to create a binary mask. Every image in the scan was then filtered with the binary mask and cross‐correlated with the reference image ‐ with the maximum correlation coefficient indicating the best match. The method was first validated using a motion phantom with both sinusoidal and irregular breathing patterns. The method has also been applied to15 patient scans ‐ with manual sorting based on contour matching being the gold standard. Results: For the sinusoidal motion phantom, the algorithm reproduced the predicted period and amplitude. In the phantom study with irregular breathing‐pattern the algorithm matched the manual sorting within ±1.25 mm. The automatic algorithm matched the gold standard within ±2.5 mm in 91% of all images in patient scans. In patient‐scans with detected peak‐to‐peak breathing amplitude of 15 mm or less the algorithm matched the manual sorting within ±2.5 mm in 93% of cases. Conclusions: The semi‐automatic respiratory motion correction algorithm has been validated in motion phantom scans and 15 patient‐scans. The algorithm improved sorting efficiency significantly, reducing a typical sorting time from 2 hours to less than 6 minutes per patient.
TH‐C‐210A‐01: Perfusion‐CT of the Brain: Stroke, TBI and Beyond
Authors: Wintermark M
Published: April 2010

Perfusion computed tomography (PCT) is an imaging technique that allows rapid, noninvasive, quantitative evaluation of cerebral perfusion by generating maps of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). The concepts behind this imaging technique were developed in the 80s, but its widespread clinical use was allowed by the recent introduction of rapid, large‐coverage multidetector‐raw CT scanners. Key clinical applications for PCT include the diagnosis of cerebral ischemia and infarction, and evaluation of vasospasm after subarachnoid hemorrhage. PCT measurements of cerebrovascular reserve after acetazolamide challenges in patients with vascular stenoses permit evaluation of candidacy for bypass surgery and endovascular treatment. PCT has also been used to assess cerebral perfusion after head trauma and microvascular permeability in the setting of intracranial neoplasm. Some controversy exists regarding this technique, including questions regarding correct selection of an input vessel, the accuracy of quantitative results, and the reproducibility of results. This presentation will provide an overview of PCT, including details of technique, major clinical applications, and limitations.
TH‐D‐BRD‐01: New Developments in The Computational Environment for Radiotherapy Research (CERR) Software System
Authors: Apte A , Khullar D , Wu Y , Deasy J
Published: April 2010

Purpose: CERR continues to be used across the world for radiotherapy research, and was downloaded over 1,000 times in the last year. We present recent improvements and changes to the system in response to user requests and research needs. Methods: New developments in the last year include: (1) integration of more powerful image registration tools (a multi‐scale demons algorithm), (2) the development of an extensive plan robustness analysis module (used to statistically simulate the effect of random, systematic, and contouring variations over a course of treatment), (3) generalizations to the java‐based DICOM input and output, (4) documentation now available via an extensive wiki page, and (5) a new tool that indicates the location of cold spots in a target volume by plotting the distance to the edge of a target volume for each voxel below a user‐selected dose threshold. Results: The image registration module has been stabilized and is being used extensively. The plan robustness module provides the statistical effect on DVH curves of presumed uncertainties. These ‘dose‐distance histograms’ give the user a simple graphical method for understanding the location of cold spots in target volumes. Documentation is now much more extensive. Conclusion: The updates to CERR will enhance user experience in using image registration and plan QA to validate treatment plan.

Partially supported by NIH grants R01 CA11820 and R01 CA85181.
TH‐D‐BRD‐02: Convolution‐Superposition Dose Calculations with GPUs
Authors: Hissoiny S , Ozell B , Després P
Published: April 2010

Purpose: To study the impact in terms of execution time and accuracy of using graphics hardware for calculating the dose in a treatment planning system. The architecture of Graphics Processing Units (GPU) is well suited for numerical tasks that are intrinsically parallel, such as dose calculations. Method and Materials: This work was made within the framework of PlanUNC, or PLUNC, a treatment planning system developed and maintained by the Department of Radiation Oncology of the University of North Carolina at Chapel Hill for research and development purposes. The objective was to transparently integrate a GPU dose calculation engine to PLUNC. The CUDA platform from NVIDIA was used for the GPU implementation. A convolution/superposition (CS) dose calculation algorithm was ported by developing programs (called kernels) that are executed on the GPU. Firstly, the CS engine of PLUNC was directly ported to the GPU, with the original code preserved as much as possible. Secondly, parts of the original algorithm were redesigned to better exploit the massively parallel architecture of GPUs. The numerical experiments were conducted with a NVIDIA GeForce GTX280 and an Intel Q6600 CPU. Results: Acceleration factors of 10× to 20× were achieved with the GPU implementation relative to the CPU version with the direct port of the CS algorithm. The numerical accuracy of the results was preserved with the GPU implementation. A 40× acceleration factor was obtained for the TERMA calculation subroutine, which was rewritten with the GPU architecture in mind. These acceleration factors were sufficient to significantly improve the responsiveness of the PLUNC graphical interface. Conclusion: This work demonstrates the potential of graphics hardware for dose calculation in treatment planning systems. This could in turn have a significant impact on optimization strategies for complex delivery techniques such as IMRT.

Research sponsored by Varian Medical Systems, Inc.
TH‐D‐BRD‐05: Replacement for Generalized Equivalent Dose in Phenomenological NTCP Models
Authors: Fatyga M , Williamson J
Published: April 2010

Purpose: phenomenological normal tissue complications probability (NTCP) models use generalized equivalent uniform dose (gEUD) as a summary measure which converts an inhomogeneous dose distribution into an “equivalent” uniform dose. We have investigated adapting gEUD models to brachytherapy dose distributions which are characterized by small focal hotspots. We have found that small hotspots dominate the behavior of gEUD measure. As it is unlikely that clinical NTCP values are determined to this extent by small focal hotspots, we have developed an alternative to gEUD‐based dose‐volume histogram reduction for adapting the phenomenological NTCP models to combined external‐beam and brachytherapy treatments. Our revised metric allows for local saturation in biological effectiveness in volume‐limited high‐dose regions. Materials & Methods: Three summary measures were computed on rectal DVHs. The gBEUD is an equivalent of gEUD, but with the physical dose replaced by biologically equivalent dose (BED). The tESD and vESD measures compute ESD index (equivalent uniform dose leading to the same cell survival fraction as the inhomogeneous dose distribution) on high BED portions of rectal DVHs. The tESD measure uses common BED threshold for all DVHs, which becomes an adjustable parameter of the measure. The vESD measure uses common fraction of the rectal volume as an adjustable parameter, and thus computes a BED threshold for each DVH. Properties of the three measures are compared. A database of 9 prostate patients with 7‐field IMRT boost plans and HDR brachytherapy boost plans delivering biologically equivalent D98 doses were used for the study. Results: For 6 of the 9 patients the gBEUD increased by approximately 100% due to doses confined to volumes <1% of the organ volume. The gEUD/gBEUD measures could be replaced by ESD based metrics, which explicitly incorporate saturation of biological effectiveness of high doses.

Acknowledgments: Supported by NIH Grant P01 CA11602.
Sound radiation from a resilient spherical cap on a rigid sphere
Authors: Aarts Ronald M. , Janssen Augustus J. E. M.
Published: April 2010

It has been argued that the sound radiation of a loudspeaker is modeled realistically by assuming the loudspeaker cabinet to be a rigid sphere with a resilient spherical cap. Series expansions, valid in the whole space outside the sphere, for the pressure due to a harmonically excited cap with an axially symmetric velocity distribution are presented. The velocity profile is expanded in functions orthogonal on the cap, rather than on the whole sphere. As a result, only a few expansion coefficients are sufficient to accurately describe the velocity profile. An adaptation of the standard solution of the Helmholtz equation to this particular parametrization is required. This is achieved by using recent results on argument scaling of orthogonal (Zernike) polynomials. The approach is illustrated by calculating the pressure due to certain velocity profiles that vanish at the rim of the cap to a desired degree. The associated inverse problem, in which the velocity profile is estimated from pressure measurements around the sphere, is also feasible as the number of expansion coefficients to be estimated is limited. This is demonstrated with a simulation.
One-dimensional transport equation models for sound energy propagation in long spaces: Simulations and experiments
Authors: Jing Yun , Xiang Ning
Published: April 2010

In this paper, the accuracy and efficiency of the previously discussed one-dimensional transport equation models [Y. Jing et al., J. Acoust. Soc. Am. 127, 2312–2322 (2010)] are examined both numerically and experimentally. The finite element method is employed to solve the equations. Artificial diffusion is applied in the numerical implementation to suppress oscillations of the solution. The transport equation models are then compared with the ray-tracing based method for different scenarios. In general, they are in good agreement, and the transport equation models are substantially less time consuming. In addition, the two-group model is found to yield more accurate results than the one-group model for the tested cases. Lastly, acoustic experimental results obtained from a 1:10 long room scale-model are used to verify the transport equation models. The results suggest that the transport equation models are able to accurately model the sound field in a long space.
Multiple signal classification method for detecting point-like scatterers embedded in an inhomogeneous background medium
Authors: Chen Xudong
Published: April 2010

The multiple signal classification (MUSIC) type method has been widely used to detect point-like scatterers embedded in a homogeneous background medium. This paper extends the MUSIC-type method to the detection of point-like scatterers that are embedded in an inhomogeneous background. Although the background Green’s function at each test point is not directly available in inhomogeneous background scenario, this paper proposes an approach, based on the finite element method, to simultaneously obtain the Green’s function at all test points. Numerical simulations illustrate the efficacy of the proposed theory and algorithm presented in this paper, and some interesting observations, which are absent in homogeneous background scenario, are highlighted and discussed.
Adaptive passive fathometer processing
Authors: Siderius Martin , Song Heechun , Gerstoft Peter , Hodgkiss William S. , Hursky Paul , Harrison Chris
Published: April 2010

Recently, a technique has been developed to image seabed layers using the ocean ambient noise field as the sound source. This so called passive fathometer technique exploits the naturally occurring acoustic sounds generated on the sea-surface, primarily from breaking waves. The method is based on the cross-correlation of noise from the ocean surface with its echo from the seabed, which recovers travel times to significant seabed reflectors. To limit averaging time and make this practical, beamforming is used with a vertical array of hydrophones to reduce interference from horizontally propagating noise. The initial development used conventional beamforming, but significant improvements have been realized using adaptive techniques. In this paper, adaptive methods for this process are described and applied to several data sets to demonstrate improvements possible as compared to conventional processing.
Statistical properties of kinetic and total energy densities in reverberant spaces
Authors: Jacobsen Finn , Molares Alfonso Rodríguez
Published: April 2010

Many acoustical measurements, e.g., measurement of sound power and transmission loss, rely on determining the total sound energy in a reverberation room. The total energy is usually approximated by measuring the mean-square pressure (i.e., the potential energy density) at a number of discrete positions. The idea of measuring the total energy density instead of the potential energy density on the assumption that the former quantity varies less with position than the latter goes back to the 1930s. However, the phenomenon was not analyzed until the late 1970s and then only for the region of high modal overlap, and this analysis has never been published. Moreover, until fairly recently, measurement of the total sound energy density required an elaborate experimental arrangement based on finite-difference approximations using at least four amplitude and phase matched pressure microphones. With the advent of a three-dimensional particle velocity transducer, it has become somewhat easier to measure total rather than only potential energy density in a sound field. This paper examines the ensemble statistics of kinetic and total sound energy densities in reverberant enclosures theoretically, experimentally, and numerically.
Models for wave propagation in two-dimensional random composites: A comparative study
Authors: Kim Jin-Yeon
Published: April 2010

This paper provides a set of benchmark results on existing theoretical models for wave propagation in two-dimensional composite materials. This comparative study is motivated to investigate the reason why results from an accurate ultrasonic measurement often significantly contradict theoretical predictions. Eight different models are evaluated with their numerically calculated effective wave speeds and coherent attenuations. For computational simplicity, the problem of horizontal shear wave propagation in an elastic matrix containing parallel circular cylinders is considered. Numerical calculations are conducted for different composites in wide ranges of material properties, volume concentration, and frequency. Some of the numerical results are compared with experimental data. Judgments are made based on fundamental theoretical and physical criteria as well as relative agreements in the numerical results, and then possible causes of failures are discussed. The effect of microstructure, potentially as a major source of the observed disagreements between models, is also discussed.
Effect of lithotripter focal width on stone comminution in shock wave lithotripsy
Authors: Qin Jun , Simmons W. Neal , Sankin Georgy , Zhong Pei
Published: April 2010

Using a reflector insert, the original HM-3 lithotripter field at 20 kV was altered significantly with the peak positive pressure (p+) in the focal plane increased from 49 to 87 MPa while the −6 dB focal width decreased concomitantly from 11 to 4 mm. Using the original reflector, p+ of 33 MPa with a −6 dB focal width of 18 mm were measured in a pre-focal plane 15-mm proximal to the lithotripter focus. However, the acoustic pulse energy delivered to a 28-mm diameter area around the lithotripter axis was comparable (∼120 mJ). For all three exposure conditions, similar stone comminution (∼70%) was produced in a mesh holder of 15 mm after 250 shocks. In contrast, stone comminution produced by the modified reflector either in a 15-mm finger cot (45%) or in a 30-mm membrane holder (14%) was significantly reduced from the corresponding values (56% and 26%) produced by the original reflector (no statistically significant differences were observed between the focal and pre-focal planes). These observations suggest that a low-pressure/broad focal width lithotripter field will produce better stone comminution than its counterpart with high-pressure/narrow focal width under clinically relevant in vitro comminution conditions.
Spatial location influences vocal interactions in bullfrog choruses
Authors: Bates Mary E. , Cropp Brett F. , Gonchar Marina , Knowles Jeffrey , Simmons James A. , Simmons Andrea Megela
Published: April 2010

A multiple sensor array was employed to identify the spatial locations of all vocalizing male bullfrogs (Rana catesbeiana) in five natural choruses. Patterns of vocal activity collected with this array were compared with computer simulations of chorus activity. Bullfrogs were not randomly spaced within choruses, but tended to cluster into closely spaced groups of two to five vocalizing males. There were nonrandom, differing patterns of vocal interactions within clusters of closely spaced males and between different clusters. Bullfrogs located within the same cluster tended to overlap or alternate call notes with two or more other males in that cluster. These near-simultaneous calling bouts produced advertisement calls with more pronounced amplitude modulation than occurred in nonoverlapping notes or calls. Bullfrogs located in different clusters more often alternated entire calls or overlapped only small segments of their calls. They also tended to respond sequentially to calls of their farther neighbors compared to their nearer neighbors. Results of computational analyses showed that the observed patterns of vocal interactions were significantly different than expected based on random activity. The use of a multiple sensor array provides a richer view of the dynamics of choruses than available based on single microphone techniques.
An analytical comparison of ultrasonic array imaging algorithms
Authors: Velichko Alexander , Wilcox Paul D.
Published: April 2010

In the paper different techniques for post-processing data from an ultrasonic transducer array are considered. First, a mathematical model of the transmit-receive array data is developed. Then based on this model three imaging methods are formulated: the total focusing method, the wavenumber algorithm, and the back-propagation method. Although these methods are conceptually different and use different approximations they can all be expressed in the form of a linear superposition of transmit-receive signals in the frequency domain with some focusing coefficients. The equivalent coefficients for each processing algorithm are derived, and difference between approaches is discussed. It is shown that in the general case the most appropriate imaging method is the back-propagation method, which is based on the back-propagation of the angular spectrum of transmit-receive signals. The relative performance of the imaging methods is illustrated using simulated and experimental data.
Acoustic characteristics of phonation in “wet voice” conditions
Authors: Murugappan Shanmugam , Boyce Suzanne , Khosla Sid , Kelchner Lisa , Gutmark Ephraim
Published: April 2010

A perceptible change in phonation characteristics after a swallow has long been considered evidence that food and/or drink material has entered the laryngeal vestibule and is on the surface of the vocal folds as they vibrate. The current paper investigates the acoustic characteristics of phonation when liquid material is present on the vocal folds, using ex vivo porcine larynges as a model. Consistent with instrumental examinations of swallowing disorders or dysphagia in humans, three liquids of different Varibar viscosity (“thin liquid,” “nectar,” and “honey”) were studied at constant volume. The presence of materials on the folds during phonation was generally found to suppress the higher frequency harmonics and generate intermittent additional frequencies in the low and high end of the acoustic spectrum. Perturbation measures showed a higher percentage of jitter and shimmer when liquid material was present on the folds during phonation, but they were unable to differentiate statistically between the three fluid conditions. The finite correlation dimension and positive Lyapunov exponent measures indicated that the presence of materials on the vocal folds excited a chaotic system. Further, these measures were able to reliably differentiate between the baseline and different types of liquid on the vocal folds.
Estimation of seismic velocities of upper oceanic crust from ocean bottom reflection loss data
Authors: Dong Hefeng , Chapman N. Ross , Hannay David E. , Dosso Stan E.
Published: April 2010

This paper describes a Bayesian inversion of acoustic reflection loss versus angle measurements to estimate the compressional and shear wave velocities in young uppermost oceanic crust, Layer 2A. The data were obtained in an experiment on the thinly sedimented western flank of the Endeavor segment of the Juan de Fuca Ridge, using a towed horizontal hydrophone array and small explosive charges as sound sources. Measurements were made at three sites at increasing distance from the ridge spreading center to determine the effect of age of the crust on seismic velocities. The inversion used reflection loss data in a 1/3-octave band centered at 16 Hz. The compressional and shear wave velocities of the basalt were highly sensitive parameters in the inversion. The compressional wave velocity increased from 2547±30 to 2710±18 m/s over an age span of 1.4 million years (Ma) from the spreading center, an increase of 4.5±1.0%/Ma. The basalt shear wave velocity increased by nearly a factor of 2, from ∼725 to 1320 m/s over the same age span. These results show a decreasing trend of Poisson’s ratio with age, from a value of 0.46 at the youngest site closest to the ridge axis.
Limiting factors in acoustic separation of carbon particles in air
Authors: Karpul David , Tapson Jonathan , Rapson Michael , Jongens Adrian , Cohen Gregory
Published: April 2010

Particles suspended in a fluid that is exposed to an acoustic standing wave experience a time-averaged force that drives them to either the pressure nodes or anti-nodes of the wave. Several filter designs have been successfully implemented using this force to filter small particles in liquids with low flow rates and small cross-sectional areas. It has been suggested that the filtration of small solid particles out of a gas, such as carbon in air (smoke), would be a possible application of acoustic standing wave based particle separation. This study shows the limiting factors, in both power requirements and design factors, of an acoustic filter designed for filtering smoke particles across large cross-sectional areas. It is shown that while filtration is possible, the power needed is impractical. It is also shown that operating the filter within certain settling time parameters optimizes the energy usage of the filter.
The effect of onset asynchrony on relative weights in profile analysis
Authors: Qian Jinyu , Richards Virginia M.
Published: April 2010

Decision weights were estimated in a profile analysis task to determine whether onset asynchronies between the signal component and the nonsignal components encourage the segregation of the signal relative to the other components. The signal component onset was either synchronous or asynchronous with respect to the nonsignal components. In the asynchronous conditions, thresholds were higher and the decision weights were less efficient than in the synchronous conditions. These data are largely consistent with a segregation hypothesis: onset asynchrony encourages subjects to shift strategies from one of spectral shape discrimination toward one of intensity discrimination.
An acoustic microscopy technique to assess particle size and distribution following needle-free injection
Authors: Condliffe Jamie , Schiffter Heiko A. , Cleveland Robin O. , Coussios Constantin-C.
Published: April 2010

Needle-free injection is a novel technique for transdermal drug and vaccine delivery, the efficacy of which depends on the number density and mean penetration depth of particles beneath the skin. To date, these parameters have been assessed optically, which is time-consuming and unsuitable for use in vivo. The present work describes the development of a scanning acoustic microscopy technique to map and size particle distributions following injection. Drug particles were modeled using a polydisperse distribution of polystyrene spheres, mean diameter 30.0 μm, and standard deviation 16.7 μm, injected into agar-based tissue-mimicking material, and later, as polydisperse stainless steel spheres, mean diameter 46.0 μm, and standard deviation 13.0 μm, injected both into agar and into porcine skin. A focused broadband immersion transducer (10–75 MHz), driven in pulse-echo mode, was scanned over the surface of the injected samples. Recorded echo signals were post-processed to deduce particle penetration depth (30–300 μm). Furthermore, post-injection size distribution of the spheres was calculated using a novel, automated spectral analysis technique. Experimental results were validated optically and found to predict penetration depth and particle size accurately. The availability of simultaneous particle penetration depth and particle size information makes it possible for the first time to optimize particle design for specific drug delivery applications.
Auditory temporal-order processing of vowel sequences by young and elderly listeners
Authors: Fogerty Daniel , Humes Larry E. , Kewley-Port Diane
Published: April 2010

This project focused on the individual differences underlying observed variability in temporal processing among older listeners. Four measures of vowel temporal-order identification were completed by young (N=35; 18–31 years) and older (N=151; 60–88 years) listeners. Experiments used forced-choice, constant-stimuli methods to determine the smallest stimulus onset asynchrony (SOA) between brief (40 or 70 ms) vowels that enabled identification of a stimulus sequence. Four words (pit, pet, pot, and put) spoken by a male talker were processed to serve as vowel stimuli. All listeners identified the vowels in isolation with better than 90% accuracy. Vowel temporal-order tasks included the following: (1) monaural two-item identification, (2) monaural four-item identification, (3) dichotic two-item vowel identification, and (4) dichotic two-item ear identification. Results indicated that older listeners had more variability and performed poorer than young listeners on vowel-identification tasks, although a large overlap in distributions was observed. Both age groups performed similarly on the dichotic ear-identification task. For both groups, the monaural four-item and dichotic two-item tasks were significantly harder than the monaural two-item task. Older listeners’ SOA thresholds improved with additional stimulus exposure and shorter dichotic stimulus durations. Individual differences of temporal-order performance among the older listeners demonstrated the influence of cognitive measures, but not audibility or age.
Wavefield extraction using multi-channel chirplet decomposition
Authors: Le Touzé Grégoire , Cristini Paul , Favretto-Cristini Nathalie , Blanco Jacques
Published: April 2010

In acoustical and seismic fields, wavefield extraction has always been a crucial issue to solve inverse problem. Depending on the experimental configuration, conventional methods of wavefield decomposition might no longer likely to hold. In this paper, an original approach is proposed based on a multichannel decomposition of the signal into a weighted sum of elementary functions known as chirplets. Each chirplet is described by physical parameters and the collection of chirplets makes up a large adaptable dictionary, so that a chirplet corresponds unambiguously to one wave component.
Benefits of knowing who, where, and when in multi-talker listening
Authors: Kitterick Pádraig T. , Bailey Peter J. , Summerfield A. Quentin
Published: April 2010

The benefits of prior information about who would speak, where they would be located, and when they would speak were measured in a multi-talker spatial-listening task. On each trial, a target phrase and several masker phrases were allocated to 13 loudspeakers in a 180° arc, and to 13 overlapping time slots, which started every 800 ms. Speech-reception thresholds (SRTs) were measured as the level of target relative to masker phrases at which listeners reported key words at 71% correct. When phases started in pairs all three cues were beneficial (“who” 3.2 dB, “where” 5.1 dB, and “when” 0.3 dB). Over a range of onset asynchronies, SRTs corresponded consistently to a signal-to-noise ratio (SNR) of −2 dB at the start of the target phrase. When phrases started one at a time, SRTs fell to a SNR of −8 dB and were improved significantly, but only marginally, by constraining “who” (1.9 dB), and not by constraining “where” (1.0 dB) or “when” (0.01 dB). Thus, prior information about “who,” “where,” and “when” was beneficial, but only when talkers started speaking in pairs. Low SRTs may arise when talkers start speaking one at a time because of automatic orienting to phrase onsets and/or the use of loudness differences to distinguish target from masker phrases.
The origin of binaural interaction in the modulation domain
Authors: Sek Aleksander , Glasberg Brian R. , Moore Brian C. J.
Published: April 2010

The purpose of these experiments was to assess whether the detection of diotic 5 Hz “probe” modulation of a 4000 Hz sinusoidal carrier was influenced by binaural interaction of “masker” modulators presented separately to each ear and applied to the same carrier. A 50 Hz masker modulator was applied to one ear and the masker modulator applied to the other ear had a frequency of 55 or 27.5 Hz. The starting phase of the masker modulators was fixed, and the starting phase of the probe modulator was varied. For both pairs of masker modulators, the threshold for detecting the probe modulation varied slightly but significantly with probe starting phase. Further experiments measuring probe detectability as a function of probe modulation depth did not provide clear evidence to support the idea that the internal representations of the masker modulators interacted binaurally to produce a weak distortion component in the internal representation of the modulation at a 5 Hz frequency. Also, the obtained phase effects were not correctly predicted using a model based on short-term loudness fluctuations.
Measurement of hearing aid internal noise
Authors: Lewis James D. , Goodman Shawn S. , Bentler Ruth A.
Published: April 2010

Hearing aid equivalent input noise (EIN) measures assume the primary source of internal noise to be located prior to amplification and to be constant regardless of input level. EIN will underestimate internal noise in the case that noise is generated following amplification. The present study investigated the internal noise levels of six hearing aids (HAs). Concurrent with HA processing of a speech-like stimulus with both adaptive features (acoustic feedback cancellation, digital noise reduction, microphone directionality) enabled and disabled, internal noise was quantified for various stimulus levels as the variance across repeated trials. Changes in noise level as a function of stimulus level demonstrated that (1) generation of internal noise is not isolated to the microphone, (2) noise may be dependent on input level, and (3) certain adaptive features may contribute to internal noise. Quantifying internal noise as the variance of the output measures allows for noise to be measured under real-world processing conditions, accounts for all sources of noise, and is predictive of internal noise audibility.
Combining information across frequency regions in fundamental frequency discrimination
Authors: Gockel Hedwig E. , Carlyon Robert P. , Plack Christopher J.
Published: April 2010

Sensitivity to fundamental frequency (F0) differences was measured for two complex tones, A and B, which had the same F0 but were filtered into two different frequency regions. Tones were presented either alone or together. A signal-detection analysis was used to predict effects of combining F0 information across frequency regions. For 400-ms tones containing only unresolved harmonics, the first experiment showed that performance (in terms of d′) for the combined presentation was better than for the isolated tones but was not optimal (assuming independent channels and noises) and was independent of the relative timing of pulses in the envelopes of tones A and B (varied by changing the starting phase of components of tone B relative to those of tone A). The nonoptimal performance was shown not to be due to peripheral masking (experiment II), or to listeners paying attention mainly to one frequency region (experiment III), nor was it specific to conditions where all harmonics were unresolved (experiment IV). In contrast, optimal performance in F0 discrimination for combined presentation was observed for 50-ms tones (experiment V). The results may reflect the limited ability of the human auditory system to integrate information simultaneously in the time and the frequency domains.
The loudness of sounds whose spectra differ at the two ears
Authors: Glasberg Brian R. , Moore Brian C. J.
Published: April 2010

Moore and Glasberg [(2007). J. Acoust. Soc. Am. 121, 1604–1612] developed a model for predicting the loudness of dichotic sounds. The model gave accurate predictions of data in the literature, except for an experiment of Zwicker and Zwicker [(1991). J. Acoust. Soc. Am. 89, 756–764], in which sounds with non-overlapping spectra were presented to the two ears. The input signal was noise with the same intensity in each critical band (bark). This noise was filtered into 24 bands each 1 bark wide. The bands were then grouped into wider composite bands (consisting of 1, 2, 4, or 12 successive sub-bands) and each composite band was presented either to one ear or the other. Loudness estimates obtained using a scaling procedure decreased somewhat as the number of composite bands increased (and their width decreased), but the predictions of the model showed the opposite pattern. This experiment was similar to that of Zwicker and Zwicker, except that the widths of the bands were based on the ERBN-number scale, and a loudness-matching procedure was used. The pattern of the results was consistent with the predictions of the model, showing an increase in loudness as the number of composite bands increased and their spacing decreased.
A generalization of the membrane-plate analogy to non-homogeneous polygonal domains consisting of homogeneous subdomains
Authors: Filipich Carlos P. , Rosales Marta B.
Published: April 2010

The well-known membrane-plate analogy that relates the natural frequencies when dealing with polygonal homogeneous domains is herein extended to non-homogeneous systems comprised of homogeneous subdomains. The analogy is generalized and demonstrated and it is shown that certain restrictions among the frequency parameters of the membranes and plates arise. Several examples of membranes and plates with interfaces separating areas with different material properties are numerically solved with different approaches. The subdomains are separated by straight, curved, and closed line interfaces. It is shown that the analogy is verified provided that the restrictions are satisfied. The analogy is first demonstrated and presented as a practical methodology to find the natural frequencies of membranes knowing the corresponding ones of the plates or vice versa. Second, the plate and membrane vibration problems, governed by the bi-Laplacian and Laplacian differential operators, respectively, can be solved without distinction, though under certain conditions, i.e., solve one of them and deduce the other using the analogy. Various numerical examples validate the analogy.
Comments on “On pore fluid viscosity and the wave properties of saturated granular materials including marine sediments” [J. Acoust. Soc. Am. 122, 1486–1501 (2007)]
Authors: Chotiros Nicholas P. , Isakson Marcia J.
Published: April 2010

The ability of the grain shearing (GS) and viscous grain shearing (VGS) models to relate geophysical and acoustic properties is tested by a method based on the claimed tight coupling between compressional and shear wave speeds and attenuations, which allows the test result to be quantified in a single parameter. The VGS model is claimed to provide a better fit to the measured sound speed and attenuation in sandy sediments below 10 kHz. In situ measurements of wave speeds and attenuations from the Sediment Acoustics Experiment 1999 (SAX99) and published laboratory measurements by Prasad and Meissner [Geophysics 57, 710–719 (1992)] on a number of sand samples were used to test the models. By this metric, the SAX99 data show that the VGS model is no better than the original GS model because the improved agreement of compressional wave speeds at low frequencies is achieved at the expense of gross overestimation of the shear wave attenuation. When applied to the measurements by Prasad and Meissner, it is shown that the GS models are not applicable at any significant confining pressures, and at zero pressure they may only be applicable to a small subset of the sand samples.
8-kHz bottom backscattering measurements at low grazing angles in shallow water
Authors: La Hyoungsul , Choi Jee Woong
Published: April 2010

8-kHz bottom backscattering measurements at low grazing angles (6°–31°) are presented. The experiment was performed at a very shallow water site with a silty bottom on the south coast of Korea. Backscattering strengths between −42 and −30 dB were obtained and were compared to a theoretical backscattering model and Lambert’s law. The fit of the theoretical model to the measurements suggests that sediment volume scattering is dominant over scattering from bottom interface roughness. Combining these results with previous measurements found in the published literature implies that backscattering strengths from silty sediment increase slightly as the frequency increases.
Influence of viscoelastic and viscous absorption on ultrasonic wave propagation in cortical bone: Application to axial transmission
Authors: Naili Salah , Vu Mai-Ba , Grimal Quentin , Talmant Maryline , Desceliers Christophe , Soize Christian , Haïat Guillaume
Published: April 2010

Cortical bone and the surrounding soft tissues are attenuating and heterogeneous media, which might affect the signals measured with axial transmission devices. This work aims at evaluating the effect of the heterogeneous acoustic absorption in bone and in soft tissues on the bone ultrasonic response. Therefore, a two-dimensional finite element time-domain method is derived to model transient wave propagation in a three-layer medium composed of an inhomogeneous transverse isotropic viscoelastic solid layer, sandwiched between two viscous fluid layers. The model couples viscous acoustic propagation in both fluid media with the anisotropic viscoelastic response of the solid. A constant spatial gradient of material properties is considered for two values of bone thicknesses (0.6 and 4 mm). In the studied configuration, absorption in the surrounding fluid tissues does not affect the results, whereas bone viscoelastic properties have a significant effect on the first arriving signal (FAS) velocity. For a thin bone, the FAS velocity is governed by the spatially averaged bone properties. For a thick bone, the FAS velocity may be predicted using a one-dimensional model.
AAA+ Proteins RUVBL1 and RUVBL2 Coordinate PIKK Activity and Function in Nonsense-Mediated mRNA Decay
Authors: Izumi Natsuko , Yamashita Akio , Iwamatsu Akihiro , Kurata Rie , Nakamura Hiroki , Saari Bonnie , Hirano Hisashi , Anderson Philip , Ohno Shigeo
Published: April 2010

Two ATPases regulate molecular complexes that ensure genome integrity and accurate gene expression.
Tailor-Made Tumor
Authors: Zahn Laura M.
Published: April 2010

Transcriptionally different expression occurs between infected maize tissues and the corn smut infecting these tissues.
Flower Power
Authors: Hines Pamela J.
Published: April 2010

The master transcription factor APETALA1 dynamically regulates a complex genetic network to guide flower development.
A Trojan Horse for Parkinson’s Disease
Authors: Hu Yi , Tong Youren
Published: April 2010

Inhibition of the kinase activity of LRRK2 may be neuroprotective.
Science Translational Medicine
Podcast: 7 April 2010
Authors: FitzGerald Garret A. , Travis Kate
Published: April 2010

A conversation about the Commentary published in the 7 April 2010 issue of
Science Translational Medicine
.
Airway PI3K Pathway Activation Is an Early and Reversible Event in Lung Cancer Development
Authors: Gustafson Adam M. , Soldi Raffaella , Anderlind Christina , Scholand Mary Beth , Qian Jun , Zhang Xiaohui , Cooper Kendal , Walker Darren , McWilliams Annette , Liu Gang , Szabo Eva , Brody Jerome , Massion Pierre P. , Lenburg Marc E. , Lam Stephen , Bild Andrea H. , Spira Avrum
Published: April 2010

A cancer-associated signaling pathway is reversibly activated in the normal airways of smokers before they develop lung cancer, presenting an opportunity for preventive therapy.
Mom's Diet and Baby's Appetite
Authors: Bremer Andrew A.
Published: April 2010

Maternal diet affects the expression of fetal hormones that influence feeding behavior.
Does Cancer Know Which Way Is Up?
Authors: Hansel Donna E.
Published: April 2010

Microdeletions in polarity genes occur in a subset of cancers.
Engineering Cyanobacteria To Synthesize and Export Hydrophilic Products
Authors: Niederholtmeyer Henrike , Wolfstädter Bernd T. , Savage David F. , Silver Pamela A. , Way Jeffrey C.
Published: April 2010

Metabolic engineering of cyanobacteria has the advantage that sunlight and CO2are the sole source of energy and carbon for these organisms. However, as photoautotrophs, cyanobacteria generally lack transporters to move hydrophilic primary metabolites across membranes. To address whether cyanobacteria could be engineered to produce and secrete organic primary metabolites,Synechococcus elongatusPCC7942 was engineered to express genes encoding an invertase and a glucose facilitator, which mediated secretion of glucose and fructose. Similarly, expression of lactate dehydrogenase- and lactate transporter-encoding genes allowed lactate accumulation in the extracellular medium. Expression of the relevant transporter was essential for secretion. Production of these molecules was further improved by expression of additional heterologous enzymes. Sugars secreted by the engineered cyanobacteria could be used to supportEscherichia coligrowth in the absence of additional nutrient sources. These results indicate that cyanobacteria can be engineered to produce and secrete high-value hydrophilic products.
Broad-Host-Range Plasmids for Red Fluorescent Protein Labeling of Gram-Negative Bacteria for Use in the Zebrafish Model System
Authors: Singer John T. , Phennicie Ryan T. , Sullivan Matthew J. , Porter Laura A. , Shaffer Valerie J. , Kim Carol H.
Published: April 2010

To observe real-time interactions between green fluorescent protein-labeled immune cells and invading bacteria in the zebrafish (
Danio rerio
), a series of plasmids was constructed for the red fluorescent protein (RFP) labeling of a variety of fish and human pathogens. The aim of this study was to create a collection of plasmids that would express RFP pigments both constitutively and under
tac
promoter regulation and that would be nontoxic and broadly transmissible to a variety of Gram-negative bacteria. DNA fragments encoding the RFP dimeric (d), monomeric (m), and tandem dimeric (td) derivatives d-Tomato, td-Tomato, m-Orange, and m-Cherry were cloned into the IncQ-based vector pMMB66EH in
Escherichia coli.
Plasmids were mobilized into recipient strains by conjugal mating. Pigment production was inducible in
Escherichia coli
,
Pseudomonas aeruginosa
,
Edwardsiella tarda
, and
Vibrio
(
Listonella
)
anguillarum
strains by isopropyl-β-
d
-thiogalactopyranoside (IPTG) treatment. A spontaneous mutant exconjugant of
P. aeruginosa
PA14 was isolated that expressed td-Tomato constitutively. Complementation analysis revealed that the constitutive phenotype likely was due to a mutation in
lacI
q
carried on pMMB66EH. DNA sequence analysis confirmed the presence of five transitions, four transversions, and a 2-bp addition within a 14-bp region of
lacI.
Vector DNA was purified from this constitutive mutant, and structural DNA sequences for RFP pigments were cloned into the constitutive vector. Exconjugants of
P. aeruginosa
,
E. tarda
, and
V. anguillarum
expressed all pigments in an IPTG-independent fashion. Results from zebrafish infectivity studies indicate that RFP-labeled pathogens will be useful for the study of real-time interactions between host cells of the innate immune system and the infecting pathogen.