bluuebunny/crossref_metadata_2025 huggingface dataset:
Pathogenesis, diagnosis and treatment of systemic amyloidosis
Authors: Pepys M. B.
Published: July 2002

Amyloidosis is a disorder of protein folding in which normally soluble proteins are deposited as abnormal, insoluble fibrils that disrupt tissue structure and cause disease. Although about 20 different unrelated proteins can form amyloid fibrilsin vivo, all such fibrils share a common cross–β core structure. Some natural wild–type proteins are inherently amyloidogenic, form fibrils and cause amyloidosis in old age or if present for long periods at abnormally high concentration. Other amyloidogenic proteins are acquired or inherited variants, containing amino–acid substitutions that render them unstable so that they populate partly unfolded states under physiological conditions, and these intermediates then aggregate in the stable amyloid fold. In addition to the fibrils, amyloid deposits always contain the non–fibrillar pentraxin plasma protein, serum amyloid P component (SAP), because it undergoes specific calcium–dependent binding to amyloid fibrils. SAP contributes to amyloidogenesis, probably by stabilizing amyloid fibrils and retarding their clearance. Radiolabelled SAP is an extremely useful, safe, specific, non–invasive, quantitative tracer for scintigraphic imaging of systemic amyloid deposits. Its use has demonstrated that elimination of the supply of amyloid fibril precursor proteins leads to regression of amyloid deposits with clinical benefit. Current treatment of amyloidosis comprises careful maintenance of impaired organ function, replacement of end–stage organ failure by dialysis or transplantation, and vigorous efforts to control underlying conditions responsible for production of fibril precursors. New approaches under development include drugs for stabilization of the native fold of precursor proteins, inhibition of fibrillogenesis, reversion of the amyloid to the native fold, and dissociation of SAP to accelerate amyloid fibril clearancein vivo.
Rhythms of differentiation and diacylglycerol in
Neurospora
Authors: Lakin-Thomas Patricia L. , Van D. Gooch , Ramsdale Mark
Published: July 2002

Although the fungus
Neurospora crassa
is a relatively simple lower eukaryote, its circadian system may be more complex than previously thought. In this paper we review evidence suggesting that there may be several output pathways coupled in complex ways to a single oscillator, or that there may be more than one oscillator driving independent output pathways. We have described two new rhythms in
Neurospora
that are not tightly coupled to the rhythm of conidiation bands that is the standard assay for the state of the
Neurospora
circadian clock. The first is a rhythm in the timing of differentiation, i.e. the production of aerial hyphae and spores. Large regions of the mycelium differentiate synchronously, as if responding to a spatially widespread signal. This rhythm may be distinct from the timer that sets the determination switch controlling the spatial pattern of conidiation bands. The second new rhythm is an oscillation in the levels of the neutral lipid diacylglycerol (DAG). This rhythm is found in all regions of a colony and is not always in phase with the rhythm of conidiation bands. The DAG rhythm shares some characteristics with the differentiation rhythm and has the potential to act as the signal that induces rhythmic differentiation.
Expression Profiles of 290 ESTs Mapped to Chromosome 3 in Human Epithelial Ovarian Cancer Cell Lines Using DNA Expression Oligonucleotide Microarrays
Authors: Manderson Emily N. , Mes-Masson Anne-Marie , Novak Jaroslav , Lee Peter D. , Provencher Diane , Hudson Thomas J. , Tonin Patricia N.
Published: July 2002

We have investigated previously the utility of oligonucleotide expression microarray technology in an analysis of four spontaneously transformed epithelial ovarian cancer (EOC) cell lines, TOV-21G, TOV-81D, OV-90, and TOV-112D. Here, we examine the expression of 290 expressed sequence tags (ESTs) that map to human chromosome 3 in a primary culture derived from normal ovarian surface epithelium (NOSE), NOV-31, and the four spontaneously transformed EOC cell lines. One of these cell lines, OV-90, harbors a deletion of an entire chromosome 3p arm. Whereas the most aggressive cell lines (OV-90, TOV-112D, and TOV-21G) exhibited the highest levels of expression, assessed by the mean of expression values of all ESTs, OV-90 showed the lowest mean of expression of ESTs that map to the 3p arm in comparison with TOV-112D and TOV-21G. This difference in expression profile of 3p ESTs in OV-90 is also reflected in the ratio of expression of ESTs on 3p versus the 3q arm and in that the expression values of ESTs that map to 3p were more often lower than higher in OV-90 in two-way comparisons with NOV-31, TOV-21G, and TOV-112D. The loss of a 3p arm does not affect the pattern of differential expression in analyses based on the range of numeric expression values of each EST or fold differences in expression for each EST in comparison with NOV-31. However, 25 differentially expressed ESTs were identified on the basis of threefold differences in expression values between NOV-31 and any EOC cell line; and six of these ESTs were differentially expressed uniquely in OV-90. The investigation of these ESTs could facilitate the identification of novel chromosome 3 genes implicated in ovarian tumorigenesis.
Whole Genome Comparison of Campylobacter jejuni Human Isolates Using a Low-Cost Microarray Reveals Extensive Genetic Diversity
Authors: Dorrell Nick , Mangan Joseph A. , Laing Kenneth G. , Hinds Jason , Linton Dennis , Al-Ghusein Hasan , Barrell Bart G. , Parkhill Julian , Stoker Neil G. , Karlyshev Andrey V. , Butcher Philip D. , Wren Brendan W.
Published: July 2002

Campylobacter jejuni is the leading cause of bacterial food-borne diarrhoeal disease throughout the world, and yet is still a poorly understood pathogen. Whole genome microarray comparisons of 11C. jejuni strains of diverse origin identified genes in up to 30 NCTC 11168 loci ranging from 0.7 to 18.7 kb that are either absent or highly divergent in these isolates. Many of these regions are associated with the biosynthesis of surface structures including flagella, lipo-oligosaccharide, and the newly identified capsule. Other strain-variable genes of known function include those responsible for iron acquisition, DNA restriction/modification, and sialylation. In fact, at least 21% of genes in the sequenced strain appear dispensable as they are absent or highly divergent in one or more of the isolates tested, thus defining 1300 C. jejuni core genes. Such core genes contribute mainly to metabolic, biosynthetic, cellular, and regulatory processes, but many virulence determinants are also conserved. Comparison of the capsule biosynthesis locus revealed conservation of all the genes in this region in strains with the same Penner serotype as strain NCTC 11168. By contrast, between 5 and 17 NCTC 11168 genes in this region are either absent or highly divergent in strains of a different serotype from the sequenced strain, providing further evidence that the capsule accounts for Penner serotype specificity. These studies reveal extensive genetic diversity amongC. jejuni strains and pave the way toward identifying correlates of pathogenicity and developing improved epidemiological tools for this problematic pathogen.
Contrast‐detail analysis for detection and characterization with near‐infrared diffuse tomography
Authors: Pogue Brian W. , Willscher Claire , McBride Troy O. , Österberg Ulf L. , Paulsen Keith D.
Published: July 2002

Near‐infrared (NIR) diffuse tomography is emerging as a medical imaging modality for obtaining information related to tissue hemoglobin concentration and oxygen saturation and may be used for characterizing diseased tissues such as breast cancer. The optimal methodology for NIR image reconstruction remains an ongoing research problem with several new approaches being demonstrated in recent years. However, a comparison of reconstruction methods is problematic because tools for the objective assessment of image quality have yet to be clearly defined for this type of nonlinear reconstruction problem. Contrast‐detail analysis has become an accepted assessment tool to quantify x‐ray mammography image quality, and in this study it has been applied to a prototype NIR diffuse tomography system that is being evaluated for breast cancer characterization. The minimum detectable levels of contrast have been defined for different sizes of objects, and the minimum contrasts which can be accurately reconstructed have also been determined for the same object sizes. In general, objects 8 mm and larger in diameter can be accurately reconstructed and detected for most absorption contrasts which are observed in human tissues (i.e., greater than 1% contrast in absorption). Objects as small as 2 mm can be detected with high contrast (i.e., near 100%), but cannot be accurately reconstructed. Within the size range of 2 mm to 8 mm, there is an inverse correlation between contrast and detail size which is characteristic of the total noise in the system. This analysis provides an objective method for assessing detection and characterization limits and can be applied to future improvements in hardware system architecture as well as reconstruction algorithms.
Geometric analysis of light‐field position of a multileaf collimator with curved ends
Authors: Boyer Arthur L. , Li Shidong
Published: July 2002

The purpose of this work was to analyze the difference between the light‐field edge and the radiation field edge produced by multileaf collimator (MLC) leaves that are constructed with rounded ends. A formula was derived using three‐dimensional geometry predicting the location of the ideal point‐source light‐field edge relative to the geometric projection of the tip of the rounded leaf end. The theoretical edge of the radiation field for a point source was also calculated along the projection of a chord whose length was one Half‐Value Thickness (HVT). Analytic solutions were found for the radiation‐field edge and the transmission penumbra. The displacement of the light‐field edge relative to the projection of the leaf tip varied from 0 mm for the leaf tip projected onto the central axis to approximately 3.2 mm for the leaf tip projected to 20 cm off the central axis. The light‐field edge was always displaced into the unblocked area. The location of the projection of the 1 HVT chord was displaced from the light‐field edge by a small and essentially constant distance (approximately 0.3 mm) for all field sizes. The transmission penumbra (80%–20%) was about 1.2 mm for all leaf positions. The calibration of the leaf position must account for the nonlinear relationship between the leaf‐tip projection and the light‐field (or radiation‐field) edge.
A genetic algorithm‐based method for optimizing the performance of a computer‐aided diagnosis scheme for detection of clustered microcalcifications in mammograms
Authors: Anastasio Mark A. , Yoshida Hiroyuki , Nagel Rufus , Nishikawa Robert M. , Doi Kunio
Published: July 2002

Computer‐aided diagnosis (CAD) schemes have the potential of substantially increasing diagnostic accuracy in mammography by providing the advantages of having a second reader. Our laboratory has developed a CAD scheme for detecting clustered microcalcifications in digital mammograms that is being tested clinically at the University of Chicago Hospitals. Our CAD scheme contains a large number of parameters such as filter weights, threshold levels, and region of interest (ROI) sizes. The choice of these parameter values determines the overall performance of the system and thus must be carefully set. Unfortunately, when the number of parameters becomes large, it is very difficult to obtain the optimal performance, especially when the values of the parameters are correlated with each other. In this study, we address the problem of identifying the optimal overall performance by developing an automated method for the determination of the parameter values that maximize the performance of a mammographic CAD scheme. Our method utilizes a genetic algorithm to search through the possible parameter values, and provides the set of parameters that minimize a cost function which measures the performance of the scheme. Using a database of 89 digitized mammograms, our method demonstrated that the sensitivity of our CAD scheme can be increased from 80% to 87% at a false positive rate of 1.0 per image. We estimate the average performance of our CAD scheme on unknown cases by performing jackknife tests; this was previously not feasible when the parameters of the CAD scheme were determined in a nonautomated manner.
Optical CT reconstruction of 3D dose distributions using the ferrous–benzoic–xylenol (FBX) gel dosimeter
Authors: Kelly R. G. , Jordan K. J. , Battista J. J.
Published: July 2002

In recent years, magnetic‐resonance imaging of gelatin doped with the Fricke solution has been applied to the direct measurement of three‐dimensional (3D) radiation dose distributions. However, the 3D dose distribution can also be imaged more economically and efficiently using the method of optical absorption computed tomography. This is accomplished by first preparing a gelatin matrix containing a radiochromic dye and mapping the radiation‐induced local change in the optical absorption coefficient. Ferrous–Benzoic–Xylenol (FBX) was the dye of choice for this investigation. The complex formed by and xylenol orange exhibits a linear change in optical attenuation with radiation dose in the range between 0 and 1000 cGy, and the local concentration of this complex can be probed using a green laser light (λ=543.5 nm). An optical computed tomography (CT) scanner was constructed analogous to a first‐generation x‐ray CT scanner, using a He–Ne laser, photodiodes, and rotation–translation stages controlled by a personal computer. The optical CT scanner itself can reconstruct attenuation coefficients to a baseline accuracy of 2% while yielding dose images accurate to within 5% when other uncertainties are taken into account. Optical tomography is complicated by the reflection and refraction of light rays in the phantom materials, producing a blind spot in the transmission profiles which, results in a significant dose artifact in the reconstructed images. In this report we develop corrections used to reduce this artifact and yield accurate dosimetric maps. We also report the chemical reaction kinetics, the dose sensitivity and spatial resolution (<1 mm3) obtained by optical absorption computed tomography. The article concludes with sample dose distributions produced by “cross‐field” 6 MV x‐ray beams, including a radiosurgery example.
Near‐infrared study of fluctuations in cerebral hemodynamics during rest and motor stimulation: Temporal analysis and spatial mapping
Authors: Toronov Vlad , Franceschini Maria Angela , Filiaci Mattia , Fantini Sergio , Wolf Martin , Michalos Antonios , Gratton Enrico
Published: July 2002

We have noninvasively studied the motor cortex hemodynamics in human subjects under rest and motor stimulation conditions using a multichannel near‐infrared tissue spectrometer. Our instrument measures optical maps of the cerebral cortex at two wavelengths (758 and 830 nm), with an acquisition time of 160 ms per map. We obtained optical maps of oxy‐ and deoxy‐hemoglobin concentration changes in terms of amplitudes of folding average, power spectrum and coherence at the stimulation repetition frequency, and the phase synchronization index. Under periodic motor stimulation conditions, we observed coherence and frequency or phase synchronization of the local hemodynamic changes with stimulation. Our main findings are the following: (1) The amplitude of the hemodynamic response to the motor stimulation is comparable to the amplitude of the fluctuations at rest. (2) The spatial patterns of the oxy‐ and deoxy‐hemoglobin responses to the stimulation are different. (3) The hemodynamic response to stimulation shows a spatial localization and a level of phase synchronization with the motor stimulation that depends on the stimulation period.
High resolution computed tomography and MRI for monitoring lung tumor growth in mice undergoing radioimmunotherapy: Correlation with histology
Authors: Kennel Stephen J. , Davis Ila A. , Branning John , Pan Hongjun , Kabalka George W. , Paulus Michael J.
Published: July 2002

A model lung tumor system has been developed in mice for the evaluation of vascular targeted radioimmunotherapy. In this model, EMT‐6 mammary carcinoma tumors growing in the lung are treated with an alpha particle emitter, which is targeted to lung blood vessels using a monoclonal antibody. Smaller tumors in diameter) are cured, but larger tumors undergo a period of regression and then regrow and ultimately prove lethal. The goal of this work was to determine if external imaging with MRI or CT could be used routinely to monitor the growth/ regression of lung tumors in live mice. To attempt to evaluate individual tumors in vivo, animals were initially imaged with magnetic resonance imaging (MRI). High resolution MRI images could be obtained only after sacrifice when lungs were not moving. In contrast, high resolution computed tomography (CT) produced evaluable images from anesthetized animals. Serial CT images (up to 5/animal) were collected over a 17 day period of tumor growth and treatment. When tumored animals became moribund, animals were sacrificed and lungs were inflated with fixative, embedded in paraffin, and then sectioned serially to compare the detection of tumors by high resolution CT with detection by histology. CT proved most useful in detecting lung tumors located in the hilar area and least useful in detecting serosal surface and anterior lobe tumor foci. Overall, CT images of live animals revealed tumors in of cases detected in histologic serial sections when relatively few tumors were present per lung. Detection of lesions and their resolution post therapy were complicated due to residual hemorrhagic, regressing tumor nodules and the development of lung edema both of which appeared as high density areas in the CT scans. We conclude that the microCT method used could identify some lung tumors as small as 100 μm in diameter; however, no concrete evaluation of therapy induced regression of the tumors could be made with CT analyses alone.
Radiochromic film dosimetry of a low energy proton beam
Authors: Piermattei A. , Miceli R. , Azario L. , Fidanzio A. , delle Canne S. , De Angelis C. , Onori S. , Pacilio M. , Petetti E. , Raffaele L. , Sabini M. G.
Published: July 2002

In this work some dosimetric characteristics of MD‐55‐2 GafChromic films were studied in a low energy proton beam (21.5 MeV) directly in a water phantom. The nonlinearity of the optical density was quantified by a factor A correction factor that accounts for optical density dependence on the energy, was empirically determined. The effects of detector thickness in depth dose measurements and of the film orientation with respect to beam direction were investigated. The results show that the MD‐55‐2 films provide dose measurements with the films positioned perpendicularly to the proton beam. A dosimetric formalizm is proposed to determine the dose to water at depth d, with films oriented perpendicularly to the beam axis. This formalism uses a calibration factor of the radiochromic film determined directly on the proton beam at a reference depth in water, and the factor, that takes into account the nonlinearity of the calibration curve and the factor that, in turn takes into account the change of proton beam energy in water. The MD‐55‐2 films with their high spatial resolution and the quasiwater equivalent material are attractive, positioned perpendicularly along the beam axis, for the absolute dose determination of very small beam sizes and modulated proton beams.
Physics and Biology: Bio-plasma physics
Authors: Uehara Mituo , Sakane Kumiko K. , Maciel Homero S. , Urruchi Wilfredo I.
Published: July 2002

The purpose of this paper is to show that plasma physics can be useful in the investigation of the physical properties of living cells. Concepts like charge neutrality, Debye length, and double layer are very useful to explain the electrical properties of a cellular membrane. It is hoped that examples of physics applications to biology can be useful in giving students of physics courses new motivations to study physics and to carry out interdisciplinary studies. This paper can be easily understood by students of physics courses with no previous knowledge of plasma physics or biology.
Acoustic impedances at the oval window, and sound pressure transformation of the middle ear in Norwegian cattle
Authors: Kringlebotn Magne
Published: July 2002

In 15 cadaver ears from Norwegian cattle, sound pressure transfer functions have been measured (1) for sound input to the tympanic membrane, (2) for sound input to the oval window with the footplate in place, but with the ossicular chain removed, and (3) for sound input to the oval window with also the footplate removed. The output pressure was measured in an enclosure cemented to the round window. The data allow calculation of equivalent sound pressures at the input positions, as well as the acoustic input impedances at the oval window with intact footplate, Zsc, and with the footplate removed, Zc. The difference Zs=Zsc−Zc is the acoustic impedance contribution of the footplate and annular ligament. Zsc is mainly determined by the stiffness of the annular ligament at low frequencies, and by the cochlear input impedance Zc at higher frequencies. Zc is predominately resistive, a minor reactive part at low frequencies is attributed to the stiffness of the round window membrane. Zs and Zc are equal in magnitude at about 0.4 kHz. Rather close RLC fits have been obtained for all the three impedances, Zsc, Zs, and Zc. The fitted values for the resistive parts of Zsc and Zc are 62.9 and 58.2 acoustic GΩ, respectively. The relatively small difference, 4.7 GΩ, is attributed to the resistance of the annular ligament. The fitted resistance of Zs is somewhat larger, 8.6 GΩ, but is anyway of minor importance relative to the dynamic stiffness of the annular ligament. This stiffness depends on the static pressure difference across the footplate. Each of the averaged Zsc corresponds to minimum stiffness. The fitted acoustic compliance is 6.89×10−15 m3/Pa. The acoustic inertance plays a minor role. It is attributed to the mass of the footplate and the co-vibrating liquid in the inner ear, and has a fitted value of 4.7×105 Pa s2/m3. A sound pressure at the eardrum is equivalent to a larger pressure at the footplate, about 16 dB larger at frequencies below 100 Hz, increasing to about 30 dB at 10 kHz. In the vestibulum at the inner side of the footplate, the sound pressure at 20 Hz is about 20 dB below the equivalent pressure at the outer side. The two pressures approach toward higher frequencies, and above 1 kHz they are nearly equal.
Localization of multiple sound sources with two microphones
Authors: Liu Chen , Wheeler Bruce C. , O’Brien William D. , Bilger Robert C. , Lansing Charissa R. , Feng Albert S.
Published: July 2002

This paper presents a two-microphone technique for localization of multiple sound sources. Its fundamental structure is adopted from a binaural signal-processing scheme employed in biological systems for the localization of sources using interaural time differences (ITD). The two input signals are transformed to the frequency domain and analyzed for coincidences along left/right-channel delay-line pairs. The coincidence information is enhanced by a nonlinear operation followed by a temporal integration. The azimuths of the sound sources are estimated by integrating the coincidence locations across the broadband of frequencies in speech signals (the “direct” method). Further improvement is achieved by using a novel “stencil” filter pattern recognition procedure. This includes coincidences due to phase delays of greater than 2π, which are generally regarded as ambiguous information. It is demonstrated that the stencil method can greatly enhance localization of lateral sources over the direct method. Also discussed and analyzed are two limitations involved in both methods, namely missed and artifactual sound sources. Anechoic chamber tests as well as computer simulation experiments showed that the signal-processing system generally worked well in detecting the spatial azimuths of four or six simultaneously competing sound sources.
Time-reversing array retrofocusing in noisy environments
Authors: Khosla Sunny R. , Dowling David R.
Published: July 2002

Acoustic time reversal is a robust means of retrofocusing acoustic energy, in both time and space, to the original sound-source location. However, noise may limit the performance of a time-reversing array (TRA) at long source–array ranges, or when the original-source or TRA-element power levels are low. The operation of a TRA requires two steps (reception and transmission) so both TRA-broadcast noise and ambient noise must be taken into account. In this paper, predictions are made for how a simple omnidirectional noise field influences the probability that the signal amplitude from a narrow-band TRA will exceed the noise at the TRA’s retrofocus. A general formulation for the probability of TRA retrofocusing, which can be used for TRA design, is developed that includes: the variance of the noise field, the original source strength, the TRA’s element output power, the number of TRA elements (N), and the propagation characteristics of the environment. This formulation predicts that a TRA’s array gain (in dB) at the retrofocus may be as high as +10 log10(N) to +20 log10(N) depending on the relative strengths of the original source and the TRA’s elements. Monte Carlo simulations in both a free-space environment and a shallow-ocean sound-channel environment compare well to this probability formulation even when simple approximate parametric relationships for the appropriate Green’s functions are used. The dominant deviation between theory and simulation in the sound channel is caused by acoustic absorption.
Acoustic streaming induced by ultrasonic flexural vibrations and associated enhancement of convective heat transfer
Authors: Loh Byoung-Gook , Hyun Sinjae , Ro Paul I. , Kleinstreuer Clement
Published: July 2002

Acoustic streaming induced by ultrasonic flexural vibrations and the associated convection enhancement are investigated. Acoustic streaming pattern, streaming velocity, and associated heat transfer characteristics are experimentally observed. Moreover, analytical analysis based on Nyborg’s formulation is performed along with computational fluid dynamics (CFD) simulation using a numerical solver CFX 4.3. Two distinctive acoustic streaming patterns in half-wavelength of the flexural vibrations are observed, which agree well with the theory. However, acoustic streaming velocities obtained from CFD simulation, based on the incompressible flow assumption, exceed the theoretically estimated velocity by a factor ranging from 10 to 100, depending upon the location along the beam. Both CFD simulation and analytical analysis reveal that the acoustic streaming velocity is proportional to the square of the vibration amplitude and the wavelength of the vibrating beam that decreases with the excitation frequency. It is observed that the streaming velocity decreases with the excitation frequency. Also, with an open-ended channel, a substantial increase in streaming velocity is observed from CFD simulations. Using acoustic streaming, a temperature drop of 40 °C with a vibration amplitude of 25 μm at 28.4 kHz is experimentally achieved.
Determination of elastic moduli of rock samples using resonant ultrasound spectroscopy
Authors: Ulrich TJ , McCall K. R. , Guyer R. A.
Published: July 2002

Resonant ultrasound spectroscopy (RUS) is a method whereby the elastic tensor of a sample is extracted from a set of measured resonance frequencies. RUS has been used successfully to determine the elastic properties of single crystals and homogeneous samples. In this paper, we study the application of RUS to macroscopic samples of mesoscopically inhomogeneous materials, specifically rock. Particular attention is paid to five issues: the scale of mesoscopic inhomogeneity, imprecision in the figure of the sample, the effects of low Q, optimizing the data sets to extract the elastic tensor reliably, and sensitivity to anisotropy. Using modeling and empirical testing, we find that many of the difficulties associated with using RUS on mesoscopically inhomogeneous materials can be mitigated through the judicious choice of sample size and sample aspect ratio.
A computerized adaptive testing system for speech  discrimination measurement: The Speech Sound Pattern Discrimination Test
Authors: Bochner Joseph , Garrison Wayne , Palmer Linda , MacKenzie Douglas , Braveman Amy
Published: July 2002

A computerized, adaptive test-delivery system for the measurement of speech discrimination, the Speech Sound Pattern Discrimination Test, is described and evaluated. Using a modified discrimination task, the testing system draws on a pool of 130 items spanning a broad range of difficulty to estimate an examinee’s location along an underlying continuum of speech processing ability, yet does not require the examinee to possess a high level of English language proficiency. The system is driven by a mathematical measurement model which selects only test items which are appropriate in difficulty level for a given examinee, thereby individualizing the testing experience. Test items were administered to a sample of young deaf adults, and the adaptive testing system evaluated in terms of respondents’ sensory and perceptual capabilities, acoustic and phonetic dimensions of speech, and theories of speech perception. Data obtained in this study support the validity, reliability, and efficiency of this test as a measure of speech processing ability.
Simultaneous acoustic and microwave backscattering from the sea surface
Authors: Dahl Peter H. , Plant William J. , Nützel Bernd , Schmidt Anke , Herwig Heinz , Terray Eugene A.
Published: July 2002

Simultaneous and coincident measurements of acoustic and microwave backscatter from the air/sea interface were obtained during Phase II of the SAXON-FPN experiment in December 1992 and again in March 1993. The acoustic and microwave grazing angles were both set to 17°, and the wavelengths were matched, being set to 2.14, 3.00, and 5.66 cm, corresponding to, respectively, acoustic frequencies of 26.5, 50, and 70 kHz and microwave frequencies of 5.3, 10, and 14 GHz. Backscattering cross sections normalized by ensonified area for the acoustic (σ0a) and microwave (σ0m) returns were determined, and their dependence on wind speed was investigated. The acoustic scattering strength is defined as 10 log10(σ0a) and the microwave scattering strength is defined as 10 log10(σ0m)−10 log10(4π). The results of these experiments show that the two scattering strengths are comparable at wind speeds below about 3 m/s but that the acoustic scattering strength increases much faster than the microwave scattering strength with increasing wind speed until reaching saturation. If these wind-speed dependencies are represented by a power law, Un, then n is 5–6 for σ0a and 2–4 for σ0m for wind speeds between 2 and 7 m/s. This difference is ascribed to the effect of bubbles on the acoustic backscatter. The more rapid increase of σ0a compared to σ0m implies that for our 17° grazing angle acoustic scattering from the surface is negligible at all but the lowest wind speeds. Therefore a simple model is used for bubble scattering to fit the acoustic data as a function of wind speed for all three acoustic frequencies. The bubble densities required to fit the data agree well with previous measurements of near-surface bubble distributions. The model predicts an overshoot of the acoustic scattering strength (above the saturation level) at moderate wind speeds which is clearly seen in the data at 26.5 and 70 kHz. Finally, a composite surface scattering model is utilized for the pure surface scattering component along with the bubble model to predict the wind-speed dependence of the acoustic scattering strength at a 45° grazing angle and compare the results with earlier measurements.
The influence of different timbre attributes on the perceptual segregation of complex-tone sequences
Authors: Singh Punita G. , Bregman Albert S.
Published: July 2002

Spectral factors such as differences in harmonic content are powerful cues in the perceptual organization of tone sequences. Temporal features such as rise time, however, have been shown to be poor cues [W. M. Hartmann and D. Johnson, Mus. Perc. 9, 155–184 (1991)]. The relative influence of these timbral features on perceptual segregation was investigated. Complex tones were sequenced in a repeating ABA- “gallop” format, under four conditions in which tones A and B had the same or different timbres as defined by differences in numbers of harmonics and temporal-envelope features. A sequence started with A and B tones at the same F0. The F0 difference between A and B then increased over the course of a trial, until a listener terminated the trial indicating perceptual segregation into sub-sequences comprising A and B tones, respectively. The F0 difference required to reach this crossover point of segregation provided a measure of the efficacy of stimulus features of A and B as cues for perceptual organization. Sequences combining differences in harmonic structure and temporal envelope required the smallest F0 change for segregation. Sequences of tones with the same harmonic structure and temporal envelope required larger changes in F0, while the other conditions fell in the middle of this range. The F0-tracking method used in this study facilitates measurement of the relative contribution of different stimulus features to stream segregation. It also holds potential as a tool using the point of segregation as a measure of the magnitude of timbre differences brought about by different physical features of sounds.
Interference effects in short-term memory for timbre
Authors: Starr Gary E. , Pitt Mark A.
Published: July 2002

Four experiments investigated memory for timbre using the interpolated-tone paradigm [Deutsch, Science 168, 1604–1605 (1970)], in which participants discriminate pairs of tones (standard and comparison) separated by intervening (interpolated) tones. Interpolated tones varied from the standard tone in spectral similarity (within-dimensional variation), fundamental frequency (cross-dimensional variation), and repetition frequency. While the latter two variables had negligible effects on timbre memory, interference with timbre memory increased with the spectral similarity of the interpolated tones to the standard tone. The findings closely parallel those found for pitch memory, and suggest that memory interference depends on perceptual similarity in both cases.
Otoreflectance of the cochlea and middle ear
Authors: Keefe Douglas H.
Published: July 2002

Otoreflectance refers to acoustic pressure reflectance measurements in the ear canal, by the use of a leak-free insertion of a probe assembly, in the frequency or time domain over a range of two or more stimulus levels. Otoreflectance includes an iso-level response indicative of the forward transfer of acoustic energy into the middle ear, and nonlinear responses indicative of the acoustic energy reflected back from the cochlea. The nonlinear otoreflectance decouples the reflected energy in an evoked otoacoustic emission (OAE) from its subsequent re-reflected energy due to the presence of the ear-canal probe. Nonlinear otoreflectance responses are extremely sensitive to probe distortion, and a double-evoked (2E) technique, previously used in evoked (OAE) measurements, is adapted for otoreflectance to solve the distortion problem. Results are obtained using a 2E stimulus set containing a set of three click stimuli delivered through a pair of sources. The corresponding sets of three pressure responses are acquired in a calibration tube, and in the ear canal, and a set of three iso-level ear-canal reflectances is calculated. An evoked OAE can be decomposed into a otoacoustic reflected pressure (ORP), and a nonlinear otoreflectance is defined by the ratio of the ORP to the initial pressure spectrum. Otoreflectance provides simultaneous measurements of middle-ear and cochlear responses, and has potential, as yet untested, for application to clinical tests for hearing impairments.
Separation of current and sound speed in the effective refractive index for a turbulent environment using reciprocal acoustic transmission
Authors: Di Iorio Daniela , Farmer David M.
Published: July 2002

Here a high-frequency acoustic experiment through a turbulent flow in Cordova Channel is described which is specifically designed to measure the contribution of scalar and vector fluctuations to the total scattered signal over a 48-h period. The effective refractive index fluctuations are determined by both the random changes in sound speed (scalars) and the random motion of the medium (vectors), and so in this paper it is demonstrated that reciprocal acoustic transmission is a technique which unambiguously separates their effects. The effective refractive index structure parameter, Cηeff2 is defined as the sum of scalar Cηs2 and vector Cηv2 contributions through the equation Cηs2+11/6Cηv2. The effective refractive index structure parameter is also measured from the forward propagation acoustical scintillation variances, thus providing an independent check on the interpretation.
Thermoacoustic streaming in a resonant channel: The time-averaged temperature distribution
Authors: Gopinath Ashok , Tait Nicole L. , Garrett Steven L.
Published: July 2002

The problem of thermoacoustic streaming in a plane parallel resonant channel, representative of the stack in a thermoacoustic engine, has been developed in a general dimensionless form. The utility of such a formulation and its wide ranging applicability to different solid–fluid combinations is demonstrated by which a consistent account of all the energy-exchange mechanisms can be made. Certain (wide-gap, thick-wall) simplifications are initially made to arrive at more manageable forms of the time-averaged temperature distributions of interest in both the fluid gap, and the channel walls. These simplifications clarify the origin of the thermoacoustic effect and provide a description of the responsible physical mechanisms based on which the validity of the “bucket-brigade” model is examined. The unexpected role of a little-known second-order thermal expansion coefficient is pointed out. It is shown that the conjugate wall–fluid coupling is crucial in yielding the large time-averaged axial temperature gradients that can be induced in the channel. In particular, the heat transfer rates at the ends of the channel are found to play an important role in determining the magnitude of these time-averaged gradients. The more general and practically useful case of arbitrary channel gap widths is also treated and it is found that for ideal gas working fluids there is an optimum channel gap width for which the axial thermal stratification in the channel is maximized. A comparison of the predictions from this study with available experimental data shows very good agreement.
Physics of acoustic cavitation in liquids: H. G. Flynn’s review 35 years later
Authors: Prosperetti A.
Published: July 2002

In 1964 Hugh G. Flynn published in Vol. I, Part B of the series Physical Acoustics, edited by W. P. Mason (Academic Press), a long review article by the title ‘‘Physics of Acoustic Cavitation in Liquids.’’ This was the first comprehensive review of the topic and has had a enormous influence on the field, serving as an introduction to cavitation and bubble dynamics for at least two generations of researchers (including the present author). A summary of that work will be presented in the light of subsequent developments and the present understanding of the cavitation phenomena. [Work supported by NASA.]
Evaluation of interior car sound with a new specific semantic differential design
Authors: Hempel Thomas , Chouard Nicolas
Published: July 2002

In an accompanying contribution [see Chouard and Hempel, ‘‘A semantic differential design especially developed for the evaluation of interior car sounds’’] the development of a semantic differential design based on a verbal space adapted to the description of interior car sounds was presented. In this contribution, this is used in semantic differential tests in order to characterize the interior car sound of eight different cars presented at the same loudness. Results of polarity profiles as well as factor analysis and cluster analysis on the set of cars are presented. Advantages and drawbacks of the method are discussed from the point of view of the experimenter.
Azimuthal dependence of Bragg scattering from the ocean surface
Authors: Hayek C. Scott , Schurman Iman W. , Sweeney John H. , Boyles C. Allan
Published: July 2002

Frequency selective scattering of water-borne acoustic waves by the rough sea surface (Bragg scattering) has been observed, in particular during the Critical Sea Test series. The directional nature of the gravity wave spectrum observed by Mitsiyasu, Donelan, Banner and others implies that the interface scattering will be directional, that is, depend upon azimuth relative to the receiver. During the ocean exercise Critical Sea Test 4, Bragg scattering was observed at 250 Hz over a wide range of azimuths using a linear hydrophone array with approximately one degree azimuthal resolution. The amplitude of the Bragg scattering and its dependence on azimuth closely matched model predictions based on the Donelan 2-D wave spectrum, first-order perturbation theory and a normal mode reverberation model.
A microcosm of musical expression. III. Contributions of timing and dynamics to the aesthetic impression of pianists’ performances of the initial measures of Chopin’s Etude in E Major
Authors: Repp Bruno H.
Published: July 2002

Four judges repeatedly assessed the overall aesthetic quality of more than 100 recorded performances of the opening of Chopin’s Etude in E major on a 10-point scale. The judgments, which exhibited reasonable reliability and modest intercorrelations, were entered into regression analyses with 16 independent variables derived from earlier objective analyses of the expressive timing and dynamics of the performances [Repp, J. Acoust. Soc. Am. 104, 1085–1100 (1998); 105, 1972–1988 (1999)]. Only between 9% and 18% of the variance in the judges’ ratings was accounted for. By contrast, timing variables accounted for 53% of the variance in one judge’s ratings of synthesized performances that varied in timing only and mimicked the timing patterns of the original performances. These results indicate, first, that the aesthetic impression of the original recordings rested primarily on aspects other than those measured (such as texture, tone, or aspects of timing and dynamics that eluded the earlier analyses) and, second, that very different patterns of timing and dynamics are aesthetically acceptable for the same music, provided that other, aesthetically more crucial performance aspects are present.
Suprasegmental and segmental timing models in Mandarin Chinese and American English
Authors: van Santen Jan P. H. , Shih Chilin
Published: July 2002

This paper formalizes and tests two key assumptions of the concept of suprasegmental timing: segmental independence and suprasegmental mediation. Segmental independence holds that the duration of a suprasegmental unit such as a syllable or foot is only minimally dependent on its segments. Suprasegmental mediation states that the duration of a segment is determined by the duration of its suprasegmental unit and its identity, but not directly by the specific prosodic context responsible for suprasegmental unit duration. Both assumptions are made by various versions of the isochrony hypothesis [I. Lehiste, J. Phonetics 5, 253–263 (1977)], and by the syllable timing hypothesis [W. Campbell, Speech Commun. 9, 57–62 (1990)]. The validity of these assumptions was studied using the syllable as suprasegmental unit in American English and Mandarin Chinese. To avoid unnatural timing patterns that might be induced when reading carrier phrase material, meaningful, nonrepetitive sentences were used with a wide range of lengths. Segmental independence was tested by measuring how the average duration of a syllable in a fixed prosodic context depends on its segmental composition. A strong association was found; in many cases the increase in average syllabic duration when one segment was substituted for another (e.g., bin versus pin) was the same as the difference in average duration between the two segments (i.e., [b] versus [p]). Thus, the [i] and [n] were not compressed to make room for the longer [p], which is inconsistent with segmental independence. Syllabic mediation was tested by measuring which locations in a syllable are most strongly affected by various contextual factors, including phrasal position, within-word position, tone, and lexical stress. Systematic differences were found between these factors in terms of the intrasyllabic locus of maximal effect. These and earlier results obtained by van Son and van Santen [R. J. J. H van Son and J. P. H. van Santen, “Modeling the interaction between factors affecting consonant duration,” Proceedings Eurospeech-97, 1997, pp. 319–322] showing a three-way interaction between consonantal identity (coronals vs labials), within-word position of the syllable, and stress of surrounding vowels, imply that segmental duration cannot be predicted by compressing or elongating segments to fit into a predetermined syllabic time interval. In conclusion, while there is little doubt that suprasegmental units play important predictive and explanatory roles as phonological units, the concept of suprasegmental timing is less promising.
Beam profile measurements and simulations for ultrasonic transducers operating in air
Authors: Benny Graham , Hayward Gordon , Chapman Roy
Published: July 2002

This paper outlines a method that has been implemented to predict and measure the acoustic radiation generated by ultrasonic transducers operating into air in continuous wave mode. Commencing with both arbitrary surface displacement data and radiating aperture, the transmitted pressure beam profile is obtained and includes simulation of propagation channel attenuation and where necessary, the directional response of any ultrasonic receiver. The surface displacement data may be derived directly, from laser measurement of the vibrating surface, or indirectly, from finite element modeling of the transducer configuration. To validate the approach and to provide experimental measurement of transducer beam profiles, a vibration-free, draft-proof scanning system that has been installed within an environmentally controlled laboratory is described. A comparison of experimental and simulated results for piezoelectric composite, piezoelectric polymer, and electrostatic transducers is then presented to demonstrate some quite different airborne ultrasonic beam-profile characteristics. Good agreement between theory and experiment is obtained. The results are compared with those expected from a classical aperture diffraction approach and the reasons for any significant differences are explained.