bluuebunny/crossref_metadata_2025 huggingface dataset:
Lack of Correlation between Activation of Jun–NH2-terminal Kinase and Induction of Apoptosis after Detachment of Epithelial Cells
Authors: Khwaja Asim , Downward Julian
Published: July 2002

Detachment of epithelial cells from the extracellular matrix leads to induction of programmed cell death, a process that has been termed “anoikis.” It has been reported recently that detachment of MDCK cells from matrix results in activation of Jun–NH2-terminal kinases (JNKs) and speculated that these stress activated protein kinases play a causal role in the induction of anoikis (Frisch, S.M., K. Vuori, D. Kelaita, and S. Sicks. 1996. J. Cell Biol. 135:1377–1382). We report here that although JNK is activated by detachment of normal MDCK cells, study of cell lines expressing activated signaling proteins usually controlled by Ras shows that stimulation of JNK fails to correlate with induction of anoikis. Activated phosphoinositide 3-OH kinase and activated PKB/Akt protect MDCK cells from detachment-induced apoptosis without suppressing JNK activation. Conversely, activated Raf and dominant negative SEK1, a JNK kinase, attenuate detachment-induced JNK activation without protecting from apoptosis. zVAD-fmk, a peptide inhibitor of caspases, prevents MDCK cell anoikis without affecting JNK activation. p38, a related stress-activated kinase, is also stimulated by detachment from matrix, but inhibition of this kinase with SB 203580 does not protect from anoikis. It is therefore unlikely that either JNK or p38 play a direct role in detachment-induced programmed cell death in epithelial cells.
An Epidermal Plakin That Integrates Actin and Microtubule Networks at Cellular Junctions
Authors: Karakesisoglou Iakowos , Yang Yanmin , Fuchs Elaine
Published: July 2002

Plakins are cytoskeletal linker proteins initially thought to interact exclusively with intermediate filaments (IFs), but recently were found to associate additionally with actin and microtubule networks. Here, we report on ACF7, a mammalian orthologue of the Drosophila kakapo plakin genetically involved in epidermal–muscle adhesion and neuromuscular junctions. While ACF7/kakapo is divergent from other plakins in its IF-binding domain, it has at least one actin (Kd = 0.35 μM) and one microtubule (Kd ∼6 μM) binding domain. Similar to its fly counterpart, ACF7 is expressed in the epidermis. In well spread epidermal keratinocytes, ACF7 discontinuously decorates the cytoskeleton at the cell periphery, including microtubules (MTs) and actin filaments (AFs) that are aligned in parallel converging at focal contacts. Upon calcium induction of intercellular adhesion, ACF7 and the cytoskeleton reorganize at cell–cell borders but with different kinetics from adherens junctions and desmosomes. Treatments with cytoskeletal depolymerizing drugs reveal that ACF7's cytoskeletal association is dependent upon the microtubule network, but ACF7 also appears to stabilize actin at sites where microtubules and microfilaments meet. We posit that ACF7 may function in microtubule dynamics to facilitate actin–microtubule interactions at the cell periphery and to couple the microtubule network to cellular junctions. These attributes provide a clear explanation for the kakapo mutant phenotype in flies.
The kinetically dominant assembly pathway for centrosomal asters in Caenorhabditis elegans is γ-tubulin dependent
Authors: Hannak Eva , Oegema Karen , Kirkham Matthew , Gönczy Pierre , Habermann Bianca , Hyman Anthony A.
Published: July 2002

γ-Tubulin–containing complexes are thought to nucleate and anchor centrosomal microtubules (MTs). Surprisingly, a recent study (Strome, S., J. Powers, M. Dunn, K. Reese, C.J. Malone, J. White, G. Seydoux, and W. Saxton. Mol. Biol. Cell. 12:1751–1764) showed that centrosomal asters form in Caenorhabditis elegans embryos depleted of γ-tubulin by RNA-mediated interference (RNAi). Here, we investigate the nucleation and organization of centrosomal MT asters in C. elegans embryos severely compromised for γ-tubulin function. We characterize embryos depleted of ∼98% centrosomal γ-tubulin by RNAi, embryos expressing a mutant form of γ-tubulin, and embryos depleted of a γ-tubulin–associated protein, CeGrip-1. In all cases, centrosomal asters fail to form during interphase but assemble as embryos enter mitosis. The formation of these mitotic asters does not require ZYG-9, a centrosomal MT-associated protein, or cytoplasmic dynein, a minus end–directed motor that contributes to self-organization of mitotic asters in other organisms. By kinetically monitoring MT regrowth from cold-treated mitotic centrosomes in vivo, we show that centrosomal nucleating activity is severely compromised by γ-tubulin depletion. Thus, although unknown mechanisms can support partial assembly of mitotic centrosomal asters, γ-tubulin is the kinetically dominant centrosomal MT nucleator.
Behavior of  Visceral Leishmania donovani in an Experimentally Induced T Helper Cell 2 (Th2)-Associated Response Model
Authors: Murray Henry W. , Hariprashad June , Coffman Robert L.
Published: July 2002

Although implicated in the clinical expression of human visceral leishmaniasis, a disease-exacerbating T helper cell 2 (Th2)-associated immune response involving interleukin-4 (IL-4) and/ or IL-10 is not readily detectable in experimental visceral infection. To overcome this obstacle to analyzing visceral Leishmania donovani in this relevant immunopathogenetic environment, we sought a model in which a Th2 response induces noncuring infection. Four initial approaches were tested primarily in BALB/c mice which control intracellular L. donovani via an IL-12– and interferon-γ (IFN-γ)–dependent Th1 mechanism: (a) modifying the cytokine milieu when the parasite is first encountered (treatment with exogenous IL-4 or anti–IL-12), (b) providing sustained endogenous exposure to a Th2 cytokine (infection of IL-4 transgenic mice), (c) increasing the parasite challenge inoculum, and (d) injecting heat-killed L. major promastigotes (HKLMP) to induce a cross-reactive Th2 response to live L. donovani. Only the last approach generated a functional Th2-type response that induced disease exacerbation accompanied by inhibition of tissue granuloma assembly. In HKLMP-primed BALB/c mice, prophylaxis with anti–IL-4, anti–IL-10, or exogenous IL-12 (but not IFN-γ) readily restored resistance. In primed mice with established visceral infection, treatment with either IL-12 or IFN-γ also successfully induced antileishmanial activity. The results in this model (a) suggest that rather than acting alone, IL-4 and IL-10 may act in concert to prevent acquisition of resistance to L. donovani, (b) reemphasize the capacity of IL-12 to reverse early Th2-related effects, and (c) demonstrate that Th1 cytokines (IL-12, IFN-γ) have therapeutic action in an established systemic infection despite the presence of a disease-exacerbating Th2-type response.
T Cell Receptor (TCR)-induced Death of Immature CD4+CD8+ Thymocytes by Two Distinct Mechanisms Differing in Their Requirement for CD28 Costimulation: Implications for Negative Selection in the Thymus
Authors: Punt Jennifer A. , Havran Wendy , Abe Ryo , Sarin Apurva , Singer Alfred
Published: July 2002

Negative selection is the process by which the developing lymphocyte receptor repertoire rids itself of autoreactive specificities. One mechanism of negative selection in developing T cells is the induction of apoptosis in immature CD4+CD8+ (DP) thymocytes, referred to as clonal deletion. Clonal deletion is necessarily T cell receptor (TCR) specific, but TCR signals alone are not lethal to purified DP thymocytes. Here, we identify two distinct mechanisms by which TCR-specific death of DP thymocytes can be induced. One mechanism requires simultaneous TCR and costimulatory signals initiated by CD28. The other mechanism is initiated by TCR signals in the absence of simultaneous costimulatory signals and is mediated by subsequent interaction with antigen-presenting cells. We propose that these mechanisms represent two distinct clonal deletion strategies that are differentially implemented during development depending on whether immature thymocytes encounter antigen in the thymic cortex or thymic medulla.
Stretch-induced Calcium Release in Smooth Muscle
Authors: Ji Guangju , Barsotti Robert J. , Feldman Morris E. , Kotlikoff Michael I.
Published: July 2002

Smooth muscle cells undergo substantial increases in length, passively stretching during increases in intraluminal pressure in vessels and hollow organs. Active contractile responses to counteract increased transmural pressure were first described almost a century ago (Bayliss, 1902) and several mechanisms have been advanced to explain this phenomenon. We report here that elongation of smooth muscle cells results in ryanodine receptor–mediated Ca2+ release in individual myocytes. Mechanical elongation of isolated, single urinary bladder myocytes to ∼120% of slack length (ΔL = 20) evoked Ca2+ release from intracellular stores in the form of single Ca2+ sparks and propagated Ca2+ waves. Ca2+ release was not due to calcium-induced calcium release, as release was observed in Ca2+-free extracellular solution and when free Ca2+ ions in the cytosol were strongly buffered to prevent increases in [Ca2+]i. Stretch-induced calcium release (SICR) was not affected by inhibition of InsP3R-mediated Ca2+ release, but was completely blocked by ryanodine. Release occurred in the absence of previously reported stretch-activated currents; however, SICR evoked calcium-activated chloride currents in the form of transient inward currents, suggesting a regulatory mechanism for the generation of spontaneous currents in smooth muscle. SICR was also observed in individual myocytes during stretch of intact urinary bladder smooth muscle segments. Thus, longitudinal stretch of smooth muscle cells induces Ca2+ release through gating of RYR. SICR may be an important component of the physiological response to increases in luminal pressure in smooth muscle tissues.
Taimanov’s surface evolution and Bäcklund transformations for curves
Authors: Garay Oscar , Langer Joel
Published: July 2002

Taimanov’s evolution of conformally parametrized surfaces in Euclidean space by the modified Novikov-Veselov equation is interpreted here (in the revolution case) using hyperbolic geometry and Bäcklund transformations for curves.
Super‐global distortion correction for a rotational C‐arm x‐ray image intensifier
Authors: Liu Ruijie Rachel , Rudin Stephen , Bednarek Daniel R.
Published: July 2002

Image intensifier (II) distortion changes as a function of C‐arm rotation angle because of changes in the orientation of the II with the earth's or other stray magnetic fields. For cone‐beam computed tomography (CT), distortion correction for all angles is essential. The new super‐global distortion correction consists of a model to continuously correct II distortion not only at each location in the image but for every rotational angle of the C arm. Calibration bead images were acquired with a standard C arm in 9 in. II mode. The super‐global (SG) model is obtained from the single‐plane global correction of the selected calibration images with given sampling angle interval. The fifth‐order single‐plane global corrections yielded a residual rms error of 0.20 pixels, while the SG model yielded a rms error of 0.21 pixels, a negligibly small difference. We evaluated the accuracy dependence of the SG model on various factors, such as the single‐plane global fitting order, SG order, and angular sampling interval. We found that a good SG model can be obtained using a sixth‐order SG polynomial fit based on the fifth‐order single‐plane global correction, and that a 10° sampling interval was sufficient. Thus, the SG model saves processing resources and storage space. The residual errors from the mechanical errors of the x‐ray system were also investigated, and found comparable with the SG residual error. Additionally, a single‐plane global correction was done in the cylindrical coordinate system, and physical information about pincushion distortion and S distortion were observed and analyzed; however, this method is not recommended due to a lack of calculational efficiency. In conclusion, the SG model provides an accurate, fast, and simple correction for rotational C‐arm images, which may be used for cone‐beam CT.
Correction for geometric image distortion in the x‐ray imaging chain: Local technique versus global technique
Authors: Gronenschild Ed
Published: July 2002

The local technique to correct for geometric image distortion in the x‐ray imaging chain has been implemented and compared with the global correction technique reported previously. Three local correction models were considered, all applied locally within each quadrilateral cell bounded by four adjacent points on a distorted 1.0 cm spaced rectilinear calibration grid. Model 1 uses bilinear interpolation between the correction vectors derived at the four vertices. In Models 2 and 3 a polynomial mapping from distorted to undistorted positions is applied, with Model 2 representing a linear six‐parameter correction and Model 3 a nonlinear eight‐parameter correction. Both techniques have been analyzed in depth concerning their accuracy. To this end, experimental (35 mm cine film and online video) and computer simulated distorted images of the calibration grid were used. Both radial and sigmoidal distortions were considered in the simulations. The main results are summarized as follows. The accuracy of the local technique depends upon the position within each quadrilateral cell and upon the local direction of the distortion gradient, contrary to the global technique. The accuracy of the local technique decreases with increasing radial as well as sigmoidal distortion. For the global technique only the latter dependency applies. The relationship of the accuracy with the pixel size is different for all models. Finally, the local technique is more sensitive to noise than the global technique. The reproducibility of the correction methods has been evaluated by means of imaging the calibration grid in various orientations with respect to the input screen of the image intensifier. The local technique turns out to reproduce a factor of 4–10 worse than the global technique. In summary, Model 1 is the worst method in all respects, whereas Model 3 is slightly better than Model 2. However, the global technique is to be preferred because it outperforms the local technique on all relevant issues.
A computational analysis of sonic booms penetrating a realistic ocean surface
Authors: Rochat Judith L. , Sparrow Victor W.
Published: July 2002

The last decade has seen a revival of sonic boom research, a direct result of the projected market for a new breed of supersonic passenger aircraft, its design, and its operation. One area of the research involves sonic boom penetration into the ocean, one concern being the possible disturbance of marine mammals from the noise generated by proposed high-speed civil transport (HSCT) flyovers. Although theory is available to predict underwater sound levels due to a sonic boom hitting a homogeneous ocean with a flat surface, theory for a realistic ocean, one with a wavy surface and bubbles near the surface, is missing and will be presented in this paper. First, reviews are given of a computational method to calculate the underwater pressure field and the effects of a simple wavy ocean surface on the impinging sonic boom. Second, effects are described for the implementation of three additional conditions: a sonic boom/ocean “wavelength” comparison, complex ocean surfaces, and bubbles near the ocean surface. Overall, results from the model suggest that the realistic ocean features affect the penetrating proposed HSCT sonic booms by modifying the underwater sound-pressure levels only about 1 decibel or less.
Measurement of auditory temporal processing using modified masking period patterns
Authors: Eddins David A.
Published: July 2002

A common metric of auditory temporal processing is the difference in the threshold for a pure-tone signal masked by either unmodulated or amplitude-modulated noise. This technique may be viewed as a modification of the masking period pattern technique. Such measurements have been proposed as an efficient means of estimating auditory temporal resolution in a clinical setting, although in many cases threshold differences may reflect additional spectro-temporal processes. The primary purpose of the present experiment was to examine interactions among signal frequency and masker bandwidth and the effects of modulation frequency on modified masking period patterns. The results revealed unmodulated–modulated threshold differences that increased with increasing masker bandwidth and decreased with increasing modulation frequency. There was little effect of signal frequency for narrow-band noise maskers that were equal in absolute bandwidth across frequency. However, unmodulated−modulated threshold differences increased substantially with increasing signal frequency for bandwidths proportional to the signal frequency and for wideband maskers. Although the results are interpreted in terms of a combination of both within-channel and across-channel cues, the specific contributions of these cues in particular conditions are difficult to ascertain. Because modified masking period patterns depend strongly upon a number of specific stimulus parameters, and because it is difficult to determine with any precision the underlying perceptual processes, this technique is not recommended for use as a clinical measure of auditory temporal processing.
Vowel formant discrimination II: Effects of stimulus uncertainty, consonantal context, and training
Authors: Kewley-Port Diane
Published: July 2002

This study is one in a series that has examined factors contributing to vowel perception in everyday listening. Four experimental variables have been manipulated to examine systematical differences between optimal laboratory testing conditions and those characterizing everyday listening. These include length of phonetic context, level of stimulus uncertainty, linguistic meaning, and amount of subject training. The present study investigated the effects of stimulus uncertainty from minimal to high uncertainty in two phonetic contexts, /V/ or /bVd/, when listeners had either little or extensive training. Thresholds for discriminating a small change in a formant for synthetic female vowels /I,ɛ,æ,ɑ,ʌ,o/ were obtained using adaptive tracking procedures. Experiment 1 optimized extensive training for five listeners by beginning under minimal uncertainty (only one formant tested per block) and then increasing uncertainty from 8-to-16-to-22 formants per block. Effects of higher uncertainty were less than expected; performance only decreased by about 30%. Thresholds for CVCs were 25% poorer than for isolated vowels. A previous study using similar stimuli [Kewley-Port and Zheng, J. Acoust. Soc. Am. 106, 2945–2958 (1999)] determined that the ability to discriminate formants was degraded by longer phonetic context. A comparison of those results with the present ones indicates that longer phonetic context degrades formant frequency discrimination more than higher levels of stimulus uncertainty. In experiment 2, performance in the 22-formant condition was tracked over 1 h for 37 typical listeners without formal laboratory training. Performance for typical listeners was initially about 230% worse than for trained listeners. Individual listeners’ performance ranged widely with some listeners occasionally achieving performance similar to that of the trained listeners in just one hour.
Sonic booms of space shuttles approaching Edwards Air Force Base, 1988–1993
Authors: Young Robert W.
Published: July 2002

From 1988 to 1993 13 sonic booms of space shuttles approaching Edwards Air Force Base were measured at a site 10 miles west of EAFB, with one to seven different sound level meters for each measurement. Results from five of these measurements are here presented. Maximum differences in measured levels between instruments for the same flight varied from 0 to 6 dB depending on the measurement descriptor and model of sound level meter. The average difference between predicted and measured values was 0.7±1.5 dB. For sound level meters with adequate bandwidth the waveforms measured varied from a near perfect N-wave to a more distorted form reflecting the influence of the varying condition of the atmosphere during propagation to the ground.
Comment on “Corrections to Foldy’s effective medium theory for propagation in bubble clouds and other collections of very small scatterers” [J. Acoust. Soc. Am. 105, 2149–2154 (1999)]
Authors: Feuillade C.
Published: July 2002

Criticisms made by Henyey of my article “The attenuation and dispersion of sound in water containing multiply interacting air bubbles” [J. Acoust. Soc. Am. 99, 3412–3430 (1996)] are refuted. The first two criticisms are based upon misunderstandings and misreadings of my article. The third criticism, based upon an unjustifiable comparison between theories designed for dissimilar physical cases, is irrelevant. My theory is designed to apply to high volume fraction, strong resonator cases where Foldy’s scattering theory has been unable to satisfactorily explain experimental data. Henyey notes that his theory is applicable to low volume fraction and/or weak scatterer cases. Any overlap in the ranges of the two theories appears negligible for practical purposes.
Reply to “Comment on ‘Corrections to Foldy’s effective medium theory for propagation in bubble clouds and other collections of very small scatterers’ ” [J. Acoust. Soc. Am. 111, 1552–1555 (2002)]
Authors: Henyey Frank S.
Published: July 2002

Response is made to Feuillade’s comments [J. Acoust. Soc. Am. 111, 1552–1555 (2002)]. After discussing the care needed in formulating self-consistent physical theories to avoid multiple counting of scattering contributions, I show that Feuillade [J. Acoust. Soc. Am. 99, 3412–3430 (1996)] did not avoid that multiple counting, and made a number of further mistakes. I show (as Foldy showed over half a century ago) that by making the primary assumption made by Feuillade, and avoiding the multiple counting, the theory can be solved with no further assumptions, and Foldy’s result is obtained. My paper [J. Acoust. Soc. Am. 105, 2149–2154 (1999)] constructed a self-consistent method which avoids an expansion in a parameter that is often large, and results in an expansion in a parameter which is large much less often. I showed that the lowest order of the resulting expansion duplicates Foldy, and the next order gives an expression which Sangani previously obtained, but in a less rigorous way.
Synchrony capture hypothesis fails to account for effects of amplitude on voicing perception
Authors: Lotto Andrew J. , Kluender Keith R.
Published: July 2002

Kluender et al. [J. Acoust. Soc. Am. 97, 2552–2567 (1995)] reported that overall stimulus amplitude affects perception of the voicing contrast in syllable-initial stops as a function of frequency separation between the first formant (F1) and higher formants (F2, F3). These results were offered as support for a hypothesis that [−voice] could be signaled by a shift in the temporal pattern of neural firing from synchronizing to energy at frequencies of F2 and F3 to synchronizing to energy near F1. Several predictions from this “synchrony capture hypothesis” were tested in the current study. In all cases the hypothesis was not supported. Effect of stimulus amplitude (increased voiceless responses with higher amplitude) was maintained when there was no cutback in F1 or when F2 and F1 energy bands were presented dichotically. In further tests of the hypothesis, voice–voiceless series were created that maintained periodic energy throughout the syllable (with F1 cutback signaling voicing). Energy just below the frequency of F2 and energy above F1 were presented dichotically. Thus, at the periphery there was no competition between frequencies near F2 and lower frequencies. In contrast to predictions of the “synchrony capture hypothesis,” overall amplitude still had an effect on voice–voiceless identifications.
Subjective evaluation of temporal fluctuation of sound source and sound field
Authors: Atagi Junko
Published: July 2002

Physical properties and subjective evaluation of the tiime-variant sound field were investigated. Physical properties were analyzed by the autocorrelation function (ACF). Three temporal factors are extracted from the ACF: (i) effective duration, τe, which is ten-percentile delay of the envelope of the ACF; (ii) the delay of the first peak of the ACF, τ1; and (iii) its amplitude, φ1. The results showed that the physical properties of the time-variant sound field are identified by τe and the envelope of the ACF of the sound field. In the second part, physical properties and subjective annoyance of traffic noise were investigated. It was found that the physical properties are identified by the temporal factors τ1 and τe of the traffic noise. Paired-comparison tests on subjective annoyance of the traffic noise were also conducted. It was found that the subjective annoyance is associated with the temporal factors τ1 and τe of the traffic noise.

Thesis advisor: Yoichi Ando

Copies of this thesis written in English can be obtained from Junko Atagi, 6813 Mosonou, Saijo-cho, Higashi-Hiroshima 739-0024, Japan. E-mail address: atagi\@urban.ne.jp.
Spectral integration of synchronous and asynchronous cues to consonant identification
Authors: Hall Joseph W. , Buss Emily , Grose John H.
Published: July 2002

When speech is presented at poor speech-to-masker ratios, the listener may momentarily receive some spectral regions of the signal at more favorable ratios than other regions. These optimal spectral regions may vary dynamically as a function of time. It is therefore of interest to determine how well listeners utilize cues from different spectral regions that occur asynchronously as opposed to synchronously across frequency. Here, we examined masked identification of consonants under various conditions of 10-Hz square-wave modulation of the speech material. Speech from 100–10000 Hz was divided into either 2, 4, 8, or 16 contiguous bands. In one set of conditions, bands were amplitude modulated coherently, while in the other, even and odd bands were modulated 180 degrees out of phase. These conditions, along with further conditions employing only modulated even or odd bands, allowed performance to be compared between synchronous and asynchronous presentation. This approach is similar to a published checkerboard masking study in which the noise rather than the speech was modulated [Howard-Jones and Rosen, J. Acoust. Soc. Am. 93, 2915–2922]. Preliminary data suggest that many listeners are able to utilize asynchronous speech cues efficiently in all of the band number conditions examined. [Work supported by NIDCD (5R01DC000418).]
Perception and psychological evaluation for visual and auditory environment based on the correlation mechanisms
Authors: Fujii Kenji
Published: July 2002

In this dissertation, the correlation mechanism in modeling the process in the visual perception is introduced. It has been well described that the correlation mechanism is effective for describing subjective attributes in auditory perception. The main result is that it is possible to apply the correlation mechanism to the process in temporal vision and spatial vision, as well as in audition. (1) The psychophysical experiment was performed on subjective flicker rates for complex waveforms. A remarkable result is that the phenomenon of missing fundamental is found in temporal vision as analogous to the auditory pitch perception. This implies the existence of correlation mechanism in visual system. (2) For spatial vision, the autocorrelation analysis provides useful measures for describing three primary perceptual properties of visual texture: contrast, coarseness, and regularity. Another experiment showed that the degree of regularity is a salient cue for texture preference judgment. (3) In addition, the autocorrelation function (ACF) and inter-aural cross-correlation function (IACF) were applied for analysis of the temporal and spatial properties of environmental noise. It was confirmed that the acoustical properties of aircraft noise and traffic noise are well described. These analyses provided useful parameters extracted from the ACF and IACF in assessing the subjective annoyance for noise.

Thesis advisor: Yoichi Ando

Copies of this thesis written in English can be obtained from Junko Atagi, 6813 Mosonou, Saijo-cho, Higashi-Hiroshima 739-0024, Japan. E-mail address: atagi\@urban.ne.jp.
Multidimensional scaling of complex sounds by school-aged children and adults
Authors: Allen Prudence , Bond Cheryl-Ann
Published: July 2002

A paired-comparisons procedure was used to evaluate the processing of complex, nonspeech sounds by 7- and 10-year-old children and adults. Stimuli were brief duration and included pure tones, harmonic complexes, and bands of noise. From their similarity ratings, a three-dimensional multidimensional scaling solution was derived. Results suggested that listeners classified the stimuli into clusters based upon periodicity and the number of spectral peaks. Within each cluster, the stimuli were ordered according to frequency. Because individual differences in the overall weightings of features were large, separate solutions were derived for two subgroups of listeners, formed based upon similarities in the pattern of dimension weights obtained in the group analysis. One subgroup, for whom the full group analysis captured a large proportion of the variance in the ratings, included the adults, many of the 10-year-olds, and a few of the 7-year-olds. The solution derived for this subgroup suggested that spectral and temporal information were weighted equally and integrated into all dimension weights. Frequency information was coded but given less weight and was not used for stimulus classification. A second subgroup of listeners included most of the 7-year-old and some of the 10-year-old children. Examination of their data suggested that they relied heavily on an analysis of the signals according to periodicity as was reflected in their temporal fine structure. Also encoded but of lesser importance were aspects of spectral shape and absolute frequency.
Use of the fast field program for predicting diffraction of sound by curved surfaces
Authors: Chambers James P. , Raspet Richard , Berthelot Yves H. , White Michael J.
Published: July 2002

The fast field program (FFP) is a powerful tool for solving outdoor sound propagation problems in stratified atmospheres. It is shown here to be equally powerful for solving for the propagation of sound over curved surfaces of finite impedance. Results from scale model experiments are in excellent agreement with the FFP calculation in the deep shadow, penumbra, and bright zone behind the surface. The results are also compared with Berry and Daigle’s creeping wave series [J. Acoust. Soc. Am. 83, 2047–2058 (1988)]. The FFP calculation and creeping wave series yield identical results in the deep shadow. In the penumbra and bright zone behind the curved surface the FFP is in slightly better agreement with the data than the creeping wave series, although the differences are typically 1 dB or less which is comparable to the experimental error. The improvement is due to the more accurate sound speed profile and coordinate mapping used rather than to any differences in the computational method.
Vibration monitoring of slotted beams using an analytical model
Authors: Man XiuTing C. , Finch Robert D. , Jansen Ben H.
Published: July 2002

This paper reports part of a research program aimed at developing the scientific basis for vibration monitoring in rapid and automatic global inspection of structures for faults. Slotted steel beams in various conditions were used as experimental samples. A mathematical model of the slotted beam’s vibration was solved using a perturbation method. Relationships between the defect parameters and the vibration signature showed a strong dependence of the modal frequency on the slot characteristics, including location and size. The method is computationally efficient, robust and could be used for on-line signal processing. The experimental modal parameters were determined from the mobility function calculated from the excitation and response signals. The modal frequencies and their shifts were then used to quantify the slot. A test of 11 beams with various conditions demonstrated that the slot can be characterized inversely. Frequency shift contours which were numerically calculated from the analytical model were used to do this. The slot locations were assessed with great accuracy, although the slot depths were estimated to be larger than the actual values, due to the limitation of the perturbation method.
On the measurement of residual stress through changes in critical angle
Authors: Ditri John J.
Published: July 2002

The critical angle method of measuring residual stresses in materials, sometimes referred to as critical angle reflectivity, has been reexamined with an emphasis on improving the sensitivity of the technique by a judicious choice of reference material. The sensitivity of the critical angle to prestress level was found to be dependent upon the ratio of phase velocities of the incident wave to that of the critically refracted wave in an unstressed medium. The sensitivity is shown to increase monotonically as this ratio approaches unity. Some numerical results are tabulated for the expected change in critical angle per MPa of prestress for various reference/prestressed material combinations for various materials of industrial interest.
The acoustic finite integration technique for waves of cylindrical symmetry (CAFIT)
Authors: Peiffer A. , Köhler B. , Petzold S.
Published: July 2002

Many ultrasonic nondestructive testing applications have cylindrical geometries. Examples involve the excitation of ultrasound by cylindrical piezoelectic probes or by laser, x rays, electron beams [A. C. Tam, Rev. Mod. Phys. 58, 381–431 (1986)], or ion beams [L. Sulak et al., Nucl. Instrum. Methods 161, 203–217 (1979)]. Thus, calculations of cylindrical wave propagation are important for a better understanding and interpretation of many testing situations. This paper deals with the AFIT Code or finite volume method for numerical simulation of sound propagation in fluids adapted to cylindrical geometries (CAFIT). A comparison is made with standard difference-equations techniques also utilized for cylindrical geometries. Two examples are dealt with: (1) The sound generation by a high energy beam of heavy ions stopping in water; (2) the multimode sound propagation in a medical doppler injection device excited by a disk probe.
Propagation of sound in a turbulent medium. II. Spherical waves
Authors: Ostashev V. E. , Gerdes Frank , Mellert Volker , Wandelt Ralf
Published: July 2002

Formulas for the statistical moments of a spherical sound wave propagating in a medium with arbitrary (anisotropic) spectra of temperature and medium velocity fluctuations are obtained. These statistical moments are: the variances of log-amplitude and phase fluctuations, the correlation functions of log-amplitude and phase fluctuations, the mean sound field, and the coherence function of the sound field. Then, the statistical moments of a spherical sound wave are calculated analytically and numerically for Gaussian spectra of temperature and medium velocity fluctuations. It is shown that the temperature and medium velocity contributions to these statistical moments can differ not only quantitatively but also qualitatively. The useful relationships between the statistical moments of spherical and plane waves propagating in a moving random medium are derived. Some of the theoretical results obtained are compared with experimental data from the literature on sound propagation through the turbulent atmosphere.
The variation of modal wave numbers with geoacoustic parameters in layered media
Authors: Kessel Ronald T.
Published: July 2002

Analytic expressions are derived for the variation of modal wave numbers due to variations in five basic properties of a layered environment: the compressional wave speed, shear wave speed, density, and thickness of any layer, and the depth of an interface between layers. Both fluid and solid layers are permitted. The layers may absorb energy, and the modal wave numbers and their variations are generally complex valued. The analytic expressions provide an efficient way to linearize the relation between the modal wave numbers and many geoacoustic parameters, for use in field sensitivity studies, range-dependent propagation models, partially linearized matched-field inversion schemes, and in the study of modes generally.
Utilization of coupling effects in compensator design for structural acoustic systems
Authors: Banks H. T. , Demetriou M. A. , Smith R. C.
Published: July 2002

The quantification and utilization of coupling effects in a prototypical structural acoustic system are examined in this paper. In typical systems, the coupling mechanisms are manifested in two ways. The first leads to the transfer of energy from an ambient field to an adjacent structure and is often responsible for exogenous structural excitation. The second involves the transfer of energy from the vibrating structure to an adjacent field. This is the source of structure-borne noise and is ultimately the mechanism through which structural actuators are utilized to attenuate noise. The examples presented here demonstrate that in fully coupled systems, both mechanisms should be incorporated to accurately model system dynamics. The examples also illustrate advantages and limitations of compensators which utilize the accurate modeling of the structural coupling.
Masking by sinusoidally amplitude-modulated tonal maskers
Authors: Gregan Melanie J. , Bacon Sid P. , Lee Jungmee
Published: July 2002

In experiment 1, masking patterns were obtained with a tonal masker that was sinusoidally amplitude modulated (SAM) at a rate of 8 Hz and a depth (m) of 1.0. The signal was centered at a masker peak or masker valley. Masker frequency (fm) was 750, 1350, or 2430 Hz, and signal frequency (fs) ranged from 0.8 to 1.62 fm. Thresholds were generally higher for a signal in a masker peak than in a masker valley. The magnitude of this peak-to-valley (PV) difference was governed by fs/fm, rather than by fs, and was largest for fs>fm. The PV differences were smallest at the lowest fm, at least when fs>fm. In experiment 2, growth-of-masking functions were measured (fm=1350 Hz, fs=1.44fm). The masker was modulated at a depth (m) of 1.0, 0.75, or 0.50. These thresholds were compared with those obtained with an unmodulated masker in forward or simultaneous masking. The comparisons suggest that thresholds for a signal at a peak of an 8-Hz SAM masker are due to simultaneous masking, while those in a valley are due primarily to forward masking when m=1.0 or simultaneous masking when m=0.75 or 0.50. For these masker depths, the PV difference first increased but then decreased as masker level increased from 60 to 90 dB SPL. This was a consequence of the slope of the masking function for peak placement changing from a value greater than 2.0 to a value of 1.0 at the highest signal levels (an effect that was also observed with the unmodulated simultaneous masker), a result that may be understood in terms of basilar membrane nonlinearity.
Auditory continuity and loudness computationa)
Authors: McAdams Stephen , Botte Marie-Claire , Drake Carolyn
Published: July 2002

Sequences composed of alternating bursts of different levels with no silences separating them can give rise to a perception of a continuous sound upon which is superimposed an intermittent stream. These experiments sought to determine how the perceived loudness of the intermittent stream depends on the level difference between higher-level and lower-level bursts in the sequence in cases in which continuity is either heard or not heard. In the main experiment, listeners were asked to adjust the level of continuous or intermittent comparison sequences to match the loudness of components that appeared to be either continuous or intermittent in an alternating-level reference sequence, thus urging them to focus on the two-stream percept. Loudness matches of the continuous comparison stimulus were close to physical levels of the lower-level bursts, whereas matches of the intermittent comparison stimulus were well below the physical levels of higher-level bursts. These results are discussed in terms of Bregman’s [Auditory Scene Analysis (MIT, Cambridge, MA, 1990)] “old-plus-new” hypothesis: The loudness of the intermittent stream should result from the subtraction of the lower level from the higher level under the assumption that the higher-level burst represents a simultaneous mixture of sounds including the continuation of the lower-level burst. Additional experiments verified that, in the absence of the continuity phenomenon, matched levels were very close to the physical levels and that matches to fixed-level continuous and intermittent sequences were precise. The matching results from the main experiment support predictions of neither classical loudness models that do not take auditory organization processes into account nor schema-based models that presume a selection of information from the higher-level burst that does not affect the perceptual content of this burst. The matched levels fell between predictions of models based on subtraction of acoustic pressure and acoustic power, but were very different from subtraction of loudness measured in sones, suggesting that loudness is computed subsequent to auditory organization processes.
Time-average temperature distribution in a circular thermoacoustic pore
Authors: Mozurkewich George
Published: July 2002

The time-average temperature distribution in a thermoacoustic pore, such as one pore of a thermoacoustic stack, is calculated. The analysis applies to straight pores of arbitrary shape but is limited to the acoustic and short-stack approximations. A partial differential equation for temperature is found by applying conservation of energy to the standard expression for time-average energy flux. Previous solutions for parallel-plate pores [G. Mozurkewich, J. Acoust. Soc. Am. 103, 380–388 (1998)] are extended to pores of circular section. A heat-transfer coefficient is defined by h1=q(z)/ΔT(z), where q is the rate of heat transfer into the pore interior per unit area of pore wall, ΔT is the temperature difference between pore wall and pore centerline, and z is the axial coordinate. This coefficient is independent of z provided z is not too close to an end of the pore. Results will be given for the shapes of the radial eigenfunctions and for the variations of eigenvalues and h1 with pore size and Prandtl number.
Perception of roughness in harmonic multitones
Authors: Dobrucki Andrzej B. , Kin Maurycy J.
Published: July 2002

This paper presents results and problems of perception of mixed modulation (MM) in harmonic multitone for higher modulating frequencies (70 and 200 Hz), and a 5-harmonics complex. Results indicated that perception of frequency modulation at the presence of the threshold values of amplitude modulation is different than the perception of amplitude modulation at the presence of the threshold values of frequency modulation. It means that two mechanisms of perception for these kinds of modulation exist. It turns out that for perception of this kind of modulation, the hearing system uses two sidebands produced by modulation process, but the high sideband seems to be more important than the low one. Another phenomenon is the perceptual grouping mechanism: for some of the modulated partials MM can be perceived as an additional pitch occurring in multitones, which usually is out of tune for fundamental frequency of the complex. The summation of the partials in one critical band takes place, which suggests that a specific pitch for that partial could be changed and this is a simple way to detect these simultaneous fast changes in the amplitude and frequency of the modulated components from the musical point of view.
A new model for binaural signal detection
Authors: Breebaart Jeroen , van de Par Steven , Kohlrausch Armin
Published: July 2002

Most present-day binaural models make use of coincidence detectors following an internal delay, so-called crosscorrelation models. We present a new modeling approach based on a subtractive mechanism as found in excitatory–inhibitory type neurons in the auditory pathway. This approach transforms, for each auditory filter, time-domain waveforms into a time-varying two-dimensional activity pattern, where each unit within that pattern has a characteristic interaural time delay and intensity difference. Limits of resolution are modeled by adding the same amount of internal noise to each unit. From this activity pattern, several features of the stimulus can be extracted, such as the apparent lateralization and the presence of a test signal within a masker. For modeling binaural detection it is assumed that a test signal must induce a significant change within the internal representation in order to be detectable. Depending on the condition, detection is limited by internal noise (NoSπ) or by external fluctuations (NρSπ, ρ≤0.95). This model can be used as an artificial observer in the same way as described by Dau et al. [J. Acoust. Soc. Am. 99, 3615–3622 (1996)] for monaural signals.
Further evidence for the influence of peripheral compression on binaural detection
Authors: van de Par Steven , Kohlrausch Armin
Published: July 2002

Binaural detection at high frequencies depends on the envelope statistics of the masker. Van de Par and Kohlrausch [J. Acoust. Soc. Am. 101, 3104 (1997)] proposed that this results from the compressive response of the basilar membrane which can be shown to reduce interaural intensity differences (IIDs) strongest in stimuli with flat masker envelopes. To further test the effect of compression, the same experiment was repeated at 500 Hz. Results show that binaural detection at low frequencies is much less dependent on masker envelope statistics as compared to high frequencies. This was expected because at low frequencies, besides IIDs, interaural time delays can be used for signal detection, which are not affected by compression. In addition, psychometric functions for the discrimination between 4-kHz NoSo and NoSπ stimuli were measured as a function of the S/N ratio for stimuli of 20 and 65 dB SPL using a 250-Hz-wide masker. The psychometric functions were rather symmetric around a 0 dB S/N ratio at low SPLs, but asymmetric at 65 dB SPL favoring discrimination at a negative S/N ratio. Such an asymmetry at high stimulus levels is predicted, if the detection cue is a change in the interaural correlation of the compressed envelopes.
Reflectance measurements of the contralateral acoustic reflex input–output function
Authors: Feeney M. Patrick , Keefe Douglas H.
Published: July 2002

Available data suggest that the acoustic reflex reduces the transmission of sound through the middle ear in humans at frequencies below 1000 Hz. Wideband (0.2 to 10 kHz) reflectance, complex admittance, and absorbed power were used to measure the input–output function of the contralateral acoustic reflex in four adults. Broadband noise was used as a reflex activator. Measurements were taken at reflex threshold and in 5-dB increments above up to 112 dB SPL in one subject. The power transmission loss grew approximately 2.5 dB for every 5-dB increase in the activator above reflex threshold. Admittance measurements generally mirrored these changes below 1000 Hz with decreases in equivalent volume, conductance, and complex admittance. There was an increase in admittance with the acoustic reflex at frequencies from 1000 to 4000 Hz in agreement with Rabinowitz [Ph.D. thesis, MIT, 1977]. An unexpected decrease in energy reflectance was observed for one subject in a notch centered at 5600 Hz, near the zero crossing for equivalent volume, which suggests that the activation of the acoustic reflex increased the power delivered to the middle ear at that frequency. [Work supported by Ohio University Research Committee Grant No. 97-14, Ohio University CHHS SA Award, and NIH Grant No. DC00520.]