bluuebunny/crossref_metadata_2025 huggingface dataset:
Interactions between Ras1, dMyc, and dPI3K signaling in the developing Drosophila wing
Authors: Prober David A. , Edgar Bruce A.
Published: September 2002

The Ras GTPase links extracellular signals to intracellular mechanisms that control cell growth, the cell cycle, and cell identity. An activated form of Drosophila Ras (RasV12) promotes these processes in the developing wing, but the effector pathways involved are unclear. Here, we present evidence indicating that RasV12 promotes cell growth and G1/S progression by increasing dMyc protein levels and activating dPI3K signaling, and that it does so via separate effector pathways. We also show that endogenous Ras is required to maintain normal levels of dMyc, but not dPI3K signaling during wing development. Finally, we show that induction of dMyc and regulation of cell identity are separable effects of Raf/MAPK signaling. These results suggest that Ras may only affect PI3K signaling when mutationally activated, such as in RasV12-transformed cells, and provide a basis for understanding the synergy between Ras and other growth-promoting oncogenes in cancer.
A systematic study of water-filled submerged elastic spherical shells and the resolution of elastic- and water-included resonances
Authors: Werby Michael F. , Überall Herbert
Published: September 2002

Water-filled elastic shells present more complicated backscattered echoes when compared to evacuated shells and are less well understood. The objective here is to determine and explain features peculiar to such objects and to use these features to aid in object characterization. Towards that end, an acoustic background suitable for such targets in conjunction with “residual” partial wave analysis obtained from subtracting the background from the elastic response is used. This analysis is aided by the determination and comparison of plate modes and resonance locations of evacuated unloaded, evacuated loaded, and loaded water-filled shells. Analysis of water-filled shells suggests that there exist isolated narrow, uniformly spaced eigenmodes in addition to the elastic modes. The broader elastic modes appear split in comparison to their unloaded counterparts. Otherwise, the elastic modes are not greatly affected by the included eigenmodes. The isolated (included) eigenmodes are extremely well modeled by a water inclusion in an infinite elastic matrix composed of the elastic shell material. The splitting of elastic modes proves to be due to interference of the included eigenmodes and the elastic body resonances. This leads to what appear to be separate branches of dispersion curves related to the elastic modes. Because of the numerous and usually evenly spaced included eigenmodes, dispersion curves are dominated by the abundance of these modes. A clear picture of the physical processes emerges from this analysis that explains all features of this event. Simple sets of rules that lead to tractable calculations are introduced that facilitate analysis of this interesting physical process.
Early pitch-shift response is active in both steady and dynamic voice pitch control
Authors: Burnett Theresa A. , Larson Charles R.
Published: September 2002

When air conducted auditory feedback pitch is experimentally shifted upward or downward during steady phonation, voice pitch changes in response. The first pitch change is an automatic deflection opposite in direction to the feedback shift. It appears to help stabilize voice pitch by counteracting unintended changes. But what happens during an intended pitch change? If the purpose of the first pitch-shift response is to stabilize voice pitch around a fixed target, it should be suppressed during voluntary pitch changes. Alternatively, if the pitch-shift response is a general process of voice control it should be modified during intended pitch changes to bring production in line with the desired output. Auditory feedback pitch was shifted during steady pitch and upward glissando vocalizations by thirty trained singers. Contrary to the “steady-specific” hypothesis, pitch-shift responses occurred during dynamic pitch vocalizations. Responses were comparable in direction, peak time, and slope, but had significantly longer latency and smaller magnitude than responses elicited during steady note phonation. Results indicate that the early pitch-shift response is a general component of voice control that serves to automatically bring phonation pitch into agreement with an intended target, whether that target is constant or changing in time.
Acoustic characteristics of twin jets
Authors: He F. , Zhang X. W.
Published: September 2002

Experiments were conducted to investigate the acoustic characteristics of underexpanded supersonic twin jets in different azimuthal measurement planes. Compared with two independent jets, the twin jets produced additional noise due to the enhanced mixing and entrainment. The larger pressure ratio for switching from the axisymmetric mode to the helical mode led to lower noise levels at 90° than for two independent jets. For pressure ratios greater than 5.00, the noise reduction was due to cessation of screeching of the twin jets while screeching of a single jet was still detected. The apparent shielding phenomenon was measured for the screech helical mode. The screech tone intensities were attenuated largely due to the shielding effects. The noise reductions due to shielding were obtained over a wide range of pressure ratios relative to the sum of two independent jets.
Responses of partially immersed elastic structures using a symmetric formulation for coupled boundary element and finite element methods
Authors: Chen Pei-Tai , Lin Chorng-Shyan , Yang Tachung
Published: September 2002

Using a coupled BEM/FEM, this work describes a numerical method to compute the response and acoustic radiation for structures partially immersed in fluid. The structures and their responses are assumed to be symmetric about a symmetric plane. A symmetric complex matrix derived from the BEM and a reciprocal principle for surface acoustics is also used to represent the acoustic loading against the structures. In addition, selecting a proper Green’s function based on image source method satisfies the boundary conditions of pressure release on the fluid surface and null normal velocity on the symmetric plane. Moreover, a boundary integral equation emerges when the field point approaches the structural surface where the normal derivative of the Green’s function over partial, infinitesimal spheres is evaluated. These limiting values depend on locations of the field point on the surface. Owing to the symmetry of the acoustic loading matrix, the matrix for the coupled BEM/FEM is a banded, symmetric one, thereby allowing us to employ a variable banded storage method and invert of the matrix. Doing so markedly increases computational efficiency. Furthermore, an analytical solution of a spherical thin shell with the lower semi-sphere immersed in water is carried out by characteristic function expansions for shell equation and acoustic loading. These analytical solutions compare with the results obtained from the proposed numerical method. A good correlation for low frequencies is obtained and minor discrepancies are observed with an increasing frequency.
Auditory brainstem responses in adult budgerigars (Melopsittacus undulatus)
Authors: Brittan-Powell Elizabeth F. , Dooling Robert J. , Gleich Otto
Published: September 2002

The auditory brainstem response (ABR) was recorded in adult budgerigars (Melopsittacus undulatus) in response to clicks and tones. The typical budgerigar ABR waveform showed two prominent peaks occurring within 4 ms of the stimulus onset. As sound-pressure levels increased, ABR peak latency decreased, and peak amplitude increased for all waves while interwave interval remained relatively constant. While ABR thresholds were about 30 dB higher than behavioral thresholds, the shape of the budgerigar audiogram derived from the ABR closely paralleled that of the behavioral audiogram. Based on the ABR, budgerigars hear best between 1000 and 5700 Hz with best sensitivity at 2860 Hz—the frequency corresponding to the peak frequency in budgerigar vocalizations. The latency of ABR peaks increased and amplitude decreased with increasing repetition rate. This rate-dependent latency increase is greater for wave 2 as indicated by the latency increase in the interwave interval. Generally, changes in the ABR to stimulation intensity, frequency, and repetition rate are comparable to what has been found in other vertebrates.
Rules for controlling low-dimensional vocal fold models with muscle activation
Authors: Titze Ingo R. , Story Brad H.
Published: September 2002

A low-dimensional, self-oscillation model of the vocal folds is used to capture three primary modes of vibration, a shear mode and two compressional modes. The shear mode is implemented with either two vertical masses or a rotating plate, and the compressional modes are implemented with an additional bar mass between the vertically stacked masses and the lateral boundary. The combination of these elements allows for the anatomically important body-cover differentiation of vocal fold tissues. It also allows for reconciliation of lumped-element mechanics with continuum mechanics, but in this reconciliation the oscillation region is restricted to a nearly rectangular glottis (as in all low-dimensional models) and a small effective thickness of vibration (<3 mm). The model is controlled by normalized activation levels of the cricothyroid (CT), thyroarytenoid (TA), lateral cricoarytenoid (LCA), and posterior cricoarytenoid (PCA) muscles, and lung pressure. An empirically derived set of rules converts these muscle activities into physical quantities such as vocal fold strain, adduction, glottal convergence, mass, thickness, depth, and stiffness. Results show that oscillation regions in muscle activation control spaces are similar to those measured by other investigations on human subjects.
A full 3D plane-wave-expansion model for 1-3 piezoelectric composite structures
Authors: Wilm Mikaël , Ballandras Sylvain , Laude Vincent , Pastureaud Thomas
Published: September 2002

The plane-wave-expansion (PWE) approach dedicated to the simulation of periodic devices has been extended to 1-3 connectivity piezoelectric composite structures. The case of simple but actual piezoelectric composite structures is addressed, taking piezoelectricity, acoustic losses, and electrical excitation conditions rigorously into account. The material distribution is represented by using a bidimensional Fourier series and the electromechanical response is simulated using a Bloch–Floquet expansion together with the Fahmy–Adler formulation of the Christoffel problem. Application of the model to 1-3 connectivity piezoelectric composites is reported and compared to previously published analyses of this problem.
A measurement method of the flow rate in a pipe using a microphone array
Authors: Kim Yong-Beum , Kim Yang-Hann
Published: September 2002

A method of measuring the flow rate in a pipe is proposed. The method utilizes one-dimensional acoustic pressure signals that are generated by a loud speaker. A microphone array mounted flush with the inner pipe wall is used to measure the signals. A formula for the flow rate, which is a function of the change of wave number, is derived from a simple mathematical model of sound field in the pipe conveying a viscous fluid. The change of the wave number, which is one of the results caused by flow, is estimated from the recursive relation among the measured microphone array signals. Since measurement errors, due to extraneous measurement noise and mismatch of response characteristics between microphones, exist in the estimated flow rate, a method of compensating the errors is proposed. By using this measurement method, the flow rate can be obtained more accurately than that of our previous method. To verify applicability of the measurement method, numerical simulation and experiments are performed. The estimated flow rates are within 5% error bound.
Limitations on rate discrimination
Authors: Carlyon Robert P. , Deeks John M.
Published: September 2002

We investigated the limits of temporal pitch processing under conditions where the place and rate of stimulation on the basilar membrane were independent. Stimuli were harmonic complexes passed through a fixed bandpass filter and resembled filtered pulse trains. The task was to detect a difference in F0. When the harmonics were filtered between 3900–5400 Hz, presented monaurally, and summed in sine phase, subjects could perform the task at all F0s studied. However, when the pulse rate was doubled by summing components in alternating phase, thresholds increased with increasing F0 until the task was impossible at F0=300 Hz (pulse rate=600 pps). Thresholds improved again at higher F0s, presumably because some harmonics became resolved. The F0 at which this breakdown occurred decreased when the complexes were filtered into a lower frequency region, and increased when they were filtered into a higher region. In the highest region tested (7800–10 800 Hz), all listeners could detect an increase of less than about 20% re: a pulse rate of 600 pps for alternating-phase complexes. Presenting a copy of the standard (lower-F0) stimulus to the contralateral ear during all intervals of a forced-choice trial improved performance markedly under conditions where monaural rate discrimination was very poor. This showed that temporal information is present in the auditory nerve that is unavailable to the temporal pitch mechanism, but which is accessible when a binaural cue is available. The results are compared to the inability of most cochlear implantees to detect increases in the rate of electrical pulse trains above about 300 pps. It is concluded that this inability is unlikely to result entirely from a central pitch limitation, because, with analogous acoustic stimulation, normal listeners can perform the task at substantially higher rates.
Stable recursive algorithm for elastic wave propagation in layered anisotropic media: Stiffness matrix method
Authors: Rokhlin S. I. , Wang L.
Published: September 2002

An efficient recursive algorithm, the stiffness matrix method, has been developed for wave propagation in multilayered generally anisotropic media. This algorithm has the computational efficiency and simplicity of the standard transfer matrix method and is unconditionally computationally stable for high frequency and layer thickness. In this algorithm, the stiffness (compliance) matrix is calculated for each layer and recursively applied to generate a stiffness (compliance) matrix for a layered system. Next, reflection and transmission coefficients are calculated for layered media bounded by liquid or solid semispaces. The results show that the method is stable for arbitrary number and thickness of layers and the computation time is proportional to the number of layers. It is shown both numerically and analytically that for a thick structure the solution approaches the solution for a semispace. This algorithm is easily adaptable to laminates with periodicity, such as multiangle lay-up composites. The repetition and symmetry of the unit cell are naturally incorporated in the recursive scheme. As an example the angle beam time domain pulse reflections from fluid-loaded multilayered composites have been computed and compared with experiment. Based on this method, characteristic equations for Lamb waves and Floquet waves in periodic media have also been determined.
Temporal weighting in sound localization
Authors: Stecker G. Christopher , Hafter Ervin R.
Published: September 2002

The dynamics of sound localization were studied using a free-field direct localization task (pointing to sound sources) and an observer-weighting analysis that assessed the relative influence of each click in a click-train stimulus. In agreement with previous studies of the precedence effect and binaural adaptation, weighting functions showed increased influence of the onset click when the interclick interval (ICI) was short (<5 ms). For longer ICIs, all clicks in a train contributed roughly the same amount to listeners’ localization responses. Finally, when a short gap was introduced in the middle of a train, the influence of the click immediately following the gap increased, in agreement with the “restarting” results obtained by Hafter and Buell [J. Acoust. Soc. Am. 88, 806–812 (1990)].
Broadband transmission noise reduction of smart panels featuring piezoelectric shunt circuits and sound-absorbing material
Authors: Kim Jaehwan , Lee Joong-Kuen
Published: September 2002

The possibility of a broadband noise reduction of piezoelectric smart panels is experimentally studied. A piezoelectric smart panel is basically a plate structure on which piezoelectric patches with electrical shunt circuits are mounted and sound-absorbing material is bonded on the surface of the structure. Sound-absorbing material can absorb the sound transmitted at the midfrequency region effectively while the use of piezoelectric shunt damping can reduce the transmission at resonance frequencies of the panel structure. To be able to reduce the sound transmission at low panel resonance frequencies, piezoelectric damping using the measured electrical impedance model is adopted. A resonant shunt circuit for piezoelectric shunt damping is composed of resistor and inductor in series, and they are determined by maximizing the dissipated energy through the circuit. The transmitted noise-reduction performance of smart panels is tested in an acoustic tunnel. The tunnel is a square cross-sectional tube and a loudspeaker is mounted at one side of the tube as a sound source. Panels are mounted in the middle of the tunnel and the transmitted sound pressure across panels is measured. When an absorbing material is bonded on a single plate, a remarkable transmitted noise reduction in the midfrequency region is observed except for the fundamental resonance frequency of the plate. By enabling the piezoelectric shunt damping, noise reduction is achieved at the resonance frequency as well. Piezoelectric smart panels incorporating passive absorbing material and piezoelectric shunt damping is a promising technology for noise reduction over a broadband of frequencies.
On the existence of subresonance generated in a one-dimensional chain of identical spheres
Authors: Hladky-Hennion Anne-Christine , Cohen-Tenoudji Frédéric , Devos Arnaud , de Billy Michel
Published: September 2002

In this paper, the propagation of short compressional pulses through a one-dimensional chain of identical spherical beads is analyzed. First, a single sphere is studied. Then, an infinite chain of identical spheres is considered. Finally, a finite linear chain can be seen as a particular case of an infinite chain. It shows the existence of allowed and forbidden frequency bands. In the case of a finite chain of spheres, discrete resonance frequencies are excited and may be identified as “subresonance” of modes observed with a single sphere. We also analyze how the coupling between two adjacent spheres and the number of beads in the chain, modify the degeneracy of the stationary states. Finally, the theoretical results are qualitatively verified with experimental data obtained with the “resonant sphere technique.”
The effect of internal point masses on the radiation of a ribbed cylindrical shell
Authors: Marcus Martin H. , Houston Brian H.
Published: September 2002

A finite element analysis is performed on a submerged cylindrical shell with internal frames and point masses attached to the frames. A point force on the shell is shown to excite resonances of the frames. Without the point masses, most of these resonances are evanescent and do not radiate to the far field. With the point masses, the high circumferential order resonances couple with those at low circumferential order with the result of increasing radiation to the far field. In this investigation, the radiation increase is about 10 dB over a broad frequency range (1.5 to 3 times the ring resonance).
Enhancing sensitivity to interaural delays at high frequencies by using “transposed stimuli”
Authors: Bernstein Leslie R. , Trahiotis Constantine
Published: September 2002

It is well-known that thresholds for ongoing interaural temporal disparities (ITDs) at high frequencies are larger than threshold ITDs obtained at low frequencies. These differences could reflect true differences in the binaural mechanisms that mediate performance. Alternatively, as suggested by Colburn and Esquissaud [J. Acoust. Soc. Am. Suppl. 1 59, S23 (1976)], they could reflect differences in the peripheral processing of the stimuli. In order to investigate this issue, threshold ITDs were measured using three types of stimuli: (1) low-frequency pure tones; (2) 100% sinusoidally amplitude-modulated (SAM) high-frequency tones, and (3) special, “transposed” high-frequency stimuli whose envelopes were designed to provide the high-frequency channels with information similar to that available in low-frequency channels. The data and their interpretation can be characterized by two general statements. First, threshold ITDs obtained with the transposed stimuli were generally smaller than those obtained with SAM tones and, at modulation frequencies of 128 and 64 Hz, were equal to or smaller than threshold ITDs obtained with their low-frequency pure-tone counterparts. Second, quantitative analyses revealed that the data could be well accounted for via a model based on normalized interaural correlations computed subsequent to known stages of peripheral auditory processing augmented by low-pass filtering of the envelopes within the high-frequency channels of each ear. The data and the results of the quantitative analyses appear to be consistent with the general ideas comprising Colburn and Esquissaud’s hypothesis.
Wave selection using a magnetomechanical sensor in a solid cylinder
Authors: Lee Hocheol , Kim Yoon Young
Published: September 2002

Magnetomechanical sensors have received much attention in recent years. However, investigations on the rejection of unwanted wave modes and thus the selection of a desired mode have not been reported. The purpose of this investigation is to present a technique to select only a desired wave mode in a solid ferromagnetic cylinder using a magnetomechanical sensor. To achieve this goal, we propose some bias magnet configurations for each of which either longitudinal or flexural waves alone can be extracted. A simplified theory relating bias magnet arrangement and measured wave modes is developed. Several experimental results confirm the validity of the present investigation.
A quasiarticulatory approach to controlling acoustic source parameters in a Klatt-type formant synthesizer using HLsyn
Authors: Hanson Helen M. , Stevens Kenneth N.
Published: September 2002

The HLsyn speech synthesizer uses models of the vocal tract to map higher-level quasiarticulatory parameters to the acoustic parameters of a Klatt-type formant synthesizer. The benefits of this system are several. In addition to requiring a relatively small number of parameters, the HLsyn model includes constraints on source–filter relations that occur naturally during speech production. Such constraints help to prevent combinations of sources and filter that are impossible to achieve with the human vocal tract. Thus, HLsyn could lead to reductions in the complexity of formant synthesis and result in better quality synthesis. HLsyn can also be a useful tool for speech-science education and speech research. This paper focuses on the generation of acoustic sources in HLsyn. Described in detail are the equations and methods used to estimate Klatt-type source parameters from HLsyn parameters. Several examples illustrating the generation of source parameters for obstruents (voiced and voiceless) and sonorants are provided. Future papers will describe the filtering components of HLsyn.
The intelligibility of speech with “holes'’ in the spectrum
Authors: Kasturi Kalyan , Loizou Philipos C. , Dorman Michael , Spahr Tony
Published: September 2002

The intelligibility of speech having either a single “hole” in various bands or having two “holes” in disjoint or adjacent bands in the spectrum was assessed with normal-hearing listeners. In experiment 1, the effect of spectral “holes” on vowel and consonant recognition was evaluated using speech processed through six frequency bands, and synthesized as a sum of sine waves. Results showed a modest decrease in vowel and consonant recognition performance when a single hole was introduced in the low- and high-frequency regions of the spectrum, respectively. When two spectral holes were introduced, vowel recognition was sensitive to the location of the holes, while consonant recognition remained constant around 70% correct, even when the middle- and high-frequency speech information was missing. The data from experiment 1 were used in experiment 2 to derive frequency-importance functions based on a least-squares approach. The shapes of the frequency-importance functions were found to be different for consonants and vowels in agreement with the notion that different cues are used by listeners to identify consonants and vowels. For vowels, there was unequal weighting across the various channels, while for consonants the frequency-importance function was relatively flat, suggesting that all bands contributed equally to consonant identification.
A novel cavitation probe design and some preliminary measurements of its application to megasonic cleaning
Authors: Ferrell Gary W. , Crum Lawrence A.
Published: September 2002

Cavitation is an effective physical mechanism for concentrating mechanical energy. Accordingly, it has wide applications in such diverse fields as sonochemistry, in which chemical reactions are initiated or accelerated, or in the electronic component cleaning industry in which particles (and other materials) are removed from surfaces. However, devices designed to act as cavitation monitors have had little success, partly because their intrusiveness often affects the cavitation field itself. Presented here is a brief description of a unique cavitation monitor that utilizes the phenomenon of sonoluminescence as an indirect quantifier of cavitation. It appears to work efficiently over a broad range of acoustic field intensities and its application to megasonic cleaning has provided interesting and valuable insights into this technology.
Wave propagation in a solid cylinder of arbitrary cross-section immersed in fluid
Authors: Venkatesan M. , Ponnusamy P.
Published: September 2002

The problem of wave propagation in a solid cylinder of arbitrary cross-section immersed in fluid is studied using the Fourier expansion collocation method. The frequency equations are obtained for longitudinal and flexural vibrations and are studied numerically for elliptic and cardioidal cylinders and are presented in the tabular form and also in the graphical form. The general theory can be used to study any kind of cylinder with proper geometric relations.
Factors underlying the speech-recognition performance of elderly hearing-aid wearers
Authors: Humes Larry E.
Published: September 2002

This paper reports the aided and unaided speech-recognition scores from a group of 171 elderly hearing-aid wearers. All hearing-aid wearers were fit with identical instruments (linear Class-D amplifiers with output-limiting compression) and evaluated with a standard protocol. In addition to including multiple measures of speech recognition, an extensive set of physiological and perceptual measures of auditory function, as well as general measures of cognitive function, were completed prior to the hearing-aid fitting. Comparison of the results from this study to available norms suggested that this group of participants was fairly typical or representative for their hearing loss and age. Approaches to the prediction of general speech-recognition performance that were examined included methods based on an acoustical index, the Speech Intelligibility Index (SII), and others based on linear-regression statistical analysis. The latter approach proved to be the most successful, accounting for about two-thirds of the variance in speech-recognition performance, with the primary predictive factors being measures of hearing loss and cognitive function.
Estimation of sound power of baffled planar sources using radiation matrices
Authors: Bai Mingsian R. , Tsao Mingchun
Published: September 2002

A technique is presented in this paper for the analysis of acoustic radiation of baffled planar sources. This method is based on the concept of the radiation matrix which is a representation of the sound field radiated by complex sources. Both sound power and far-field pressure can be estimated using this method. Numerical simulation and experimental investigation were carried out to verify the proposed method. In comparison with the conventional pressure-based method ISO 3745, the proposed technique produced more accurate estimation of sound power. With comparable number of measuring positions as the conventional methods, the proposed approach does not require special measuring environments. Computation complexity can be significantly reduced if only dominant radiation modes in the low-frequency range are retained. Estimation of far-field pressure can also be obtained using the proposed method.
Phenomenological model of propagation of the elastic waves in a fluid-saturated porous solid with nonzero boundary slip velocity
Authors: Tsiklauri David
Published: September 2002

It is known that a boundary slip velocity starts to play an important role when the length scale over which the fluid velocity changes approaches the slip length, i.e., when the fluid is highly confined, for example, fluid flow through porous rock or blood vessel capillaries. Zhu and Granick [Phys. Rev. Lett. 87, 096105 (2001)] have recently experimentally established the existence of a boundary slip in a Newtonian liquid. They reported typical values of the slip length of the order of few micrometers. In this light, the effect of introduction of the boundary slip into the theory of propagation of elastic waves in a fluid-saturated porous medium formulated by Biot [J. Acoust. Soc. Am. 28, 179–191 (1956)] is investigated. Namely, the effect of introduction of boundary slip upon the function F(κ) that measures the deviation from Poiseuille flow friction as a function of frequency parameter κ is studied. By postulating phenomenological dependence of the slip velocity upon frequency, notable deviations in the domain of intermediate frequencies in the behavior of F(κ) are introduced with the incorporation of the boundary slip into the model. It is known that F(κ) crucially enters Biot’s equations, which describe dynamics of fluid-saturated porous solid. Thus, consequences of the nonzero boundary slip by calculating the phase velocities and attenuation coefficients of both rotational and dilatational waves with the variation of frequency are investigated. The new model should allow one to fit the experimental seismic data in circumstances when Biot’s theory fails, as the introduction of phenomenological dependence of the slip velocity upon frequency, which is based on robust physical arguments, adds an additional degree of freedom to the model. In fact, it predicts higher than the Biot’s theory values of attenuation coefficients of the both rotational and dilatational waves in the intermediate frequency domain, which is in qualitative agreement with the experimental data. Therefore, the introduction of the boundary slip yields threefold benefits: (1) better agreement of theory with experimental data since the parametric space of the model is larger (includes effects of boundary slip); (2) the possibility to identify types of porous medium and physical situations where boundary slip is important; and (3) constrain model parameters that are related to the boundary slip.
Loudness enhancement: Induced loudness reduction in disguise? (L)
Authors: Scharf Bertram , Buus Søren , Nieder Bärbel
Published: September 2002

Two opposite sequential loudness effects concern the effect of a stronger Tone 1 on the loudness of a subsequent weaker Tone 2, as assessed by loudness matches with Tone 3. Loudness enhancement is reported when Tone 1 precedes Tone 2 by 50 to 100 ms. Loudness recalibration (or induced loudness reduction) is obtained for delays of about 1 s. This letter argues that what appears as an enhancement of Tone 2’s loudness is, in fact, an induced reduction of Tone 3’s loudness, which occurs because Tones 1 and 3 are at the same frequency. Preliminary experiments support this analysis.
Interaural level differences and the level-meter model
Authors: Hartmann William M. , Constan Zachary A.
Published: September 2002

The interaural level difference (ILD) plays a significant role in sound localization. However, the definition of ILD for noise is open to some interpretation because it is not obvious how to deal with the inevitable level fluctuations. In this article, the ILD is interpreted as an energylike (time-integrated) measure of stimulus level, independent of other stimulus details—particularly interaural correlation. This concept is called the “level-meter model.” The model was tested by measuring human ILD thresholds for noise stimuli that were interaurally correlated, or anticorrelated, or uncorrelated. An additional test (not involving lateralization) measured the threshold for level discrimination based on loudness. According to the level-meter model, all four thresholds should be the same. The experimental results showed that the predictions of the level-meter model held good to within about half a dB, although thresholds for level discrimination were systematically higher than ILDs. Among the ILDs themselves, thresholds were slightly higher for uncorrelated noise. The latter result could be explained by replacing the level-meter model with a loudness-meter model, incorporating temporal integration. The same model accounted for the bandwidth dependence of the threshold.
Remote measurement of material properties from radiation force induced vibration of an embedded sphere
Authors: Chen Shigao , Fatemi Mostafa , Greenleaf James F.
Published: September 2002

A quantitative model is presented for a sphere vibrated by two ultrasound beams of frequency ω1 and ω2. Due to the interference of two sound beams, the radiation force has a dynamic component of frequency ω2−ω1. The radiation impedance and mechanical impedance of the sphere are then used to compute the vibration speed of the sphere. Vibration speed versus vibration frequency is measured by laser vibrometer on several spheres, both in water and in gel phantom. These experimental results are used to verify the model. This method can be used to estimate the material properties of the medium (e.g., shear modulus) surrounding the sphere.
Characterization of tissue microstructure using ultrasonic backscatter: Theory and technique for optimization using a Gaussian form factor
Authors: Oelze Michael L. , Zachary James F. , O’Brien William D.
Published: September 2002

Characterization of tissue microstructure through ultrasonic backscatter is hypothesized to aid in detection and classification of diseased tissues. Radio frequency signals backscattered from tissues can be modeled according to the assumed shape, size, and distribution of scatterers in tissues. Power spectra of rf backscattered signals describe the frequency dependence of scatterers. Experimental measurements of ultrasonic backscatter from spontaneous mammary tumors in rats are obtained over the frequency range of 4 to 12 MHz. The power spectra measured from rat tumors are compared to theoretical power spectra derived from a 3D spatial autocorrelation function assuming a Gaussian distribution. Independent values of average scatterer diameter and acoustic concentration are obtained by approximating the measured power spectrum with a best-fit line. Enhanced B-mode images are made of the rat tumors and surrounding tissues with superimposed regions of interest quantified by estimated average scatterer sizes and acoustic concentrations. Scattering properties estimated inside the tumors and in surrounding tissues are shown to be distinct. Overall, estimates showed a 44.8% increase of average scatterer diameter inside the tumor as compared to tissues outside the tumor. With the exception of one rat, all estimates of the scatterers’ average acoustic concentration inside the tumor were less than outside the tumors.
Developing an anatomical model of the human laryngeal cartilages from magnetic resonance imaging
Authors: Selbie W. Scott , Gewalt Sally L. , Ludlow Christy L.
Published: September 2002

The purpose of this work was to construct a three-dimensional anatomical framework of the cartilages of the human larynx. The framework included representative surface models of the four laryngeal cartilages and estimated attachment points for the intrinsic laryngeal muscles. High-resolution magnetic resonance imaging (MRI) was used to scan one female and four male human cadaveric larynges. The cartilages were segmented manually from the MRI volume for analysis. Two of these larynges were subsequently dissected and the landmark distances on the cartilages measured for comparison with the MRI measures and previous studies. The MRI measures were 8% smaller than the anatomical measures and 12% smaller than data reported in the literature. A laryngeal coordinate system was defined using the plane of symmetry of the cricoid cartilage. Measures of cricoid cartilage symmetry had less than 3% difference between the two sides for a series of measures. An algorithm for registering larynges that minimized the root-mean-square distance between the surface of a reference cricoid cartilage and the surfaces of nonisotropically scaled candidate cricoid cartilages was evaluated. This study provided an anatomical framework for registering different larynges to the same coordinate space.
Temperature rise and safety considerations for radiation force ultrasound imaging
Authors: Herman Bruce A. , Harris Gerald R.
Published: September 2002

Current models for estimating temperature increase during ultrasound exposure calculate the steady-state rise, using time-averaged acoustic output, as the worst case for safety consideration. While valid for the typically very short (microsecond) pulses used by conventional diagnostic techniques, this analysis does not necessarily correspond to a worst case scenario for the longer pulses or pulse bursts used by a new method, radiation force imaging. Radiation force imaging, employing ultrasound pulse durations up to hundreds of milliseconds, produces and detects motion in solid tissue or acoustic streaming in fluids via a high intensity beam. Models that calculate the transient temperature rise from these pulses are developed for both the bone at focus and soft tissue cases. Based on accepted time–temperature dose criteria, it is shown that for pulse lengths and intensities utilized by this technique, temperature may increase to levels that raise safety concerns for bone at the focus of the ultrasound beam. Also, the impact on this modality of the current U.S. Food and Drug Administration output limits for diagnostic ultrasound devices is discussed.
Iron Emission Lines from Extended X-ray Jets in SS 433: Reheating of Atomic Nuclei
Authors: Migliari Simone , Fender Rob , Méndez Mariano
Published: September 2002

Powerful relativistic jets are among the most ubiquitous and energetic observational consequences of accretion around supermassive black holes in active galactic nuclei and neutron stars and stellar-mass black holes in x-ray binary (XRB) systems. But despite more than three decades of study, the structure and composition of these jets remain unknown. Here we present spatially resolved x-ray spectroscopy of arc second–scale x-ray jets from XRB SS 433 analyzed with the Chandra advanced charge-coupled device imaging spectrometer. These observations reveal evidence for a hot continuum and Doppler-shifted iron emission lines from spatially resolved regions. Apparently, in situ reheating of the baryonic component of the jets takes place in a flow that moves with relativistic bulk velocity even more than 100 days after launch from the binary core.
Lead Isotopic Ages of Chondrules and Calcium-Aluminum-Rich Inclusions
Authors: Amelin Yuri , Krot Alexander N. , Hutcheon Ian D. , Ulyanov Alexander A.
Published: September 2002

The lead-lead isochron age of chondrules in the CR chondrite Acfer 059 is 4564.7 ± 0.6 million years ago (Ma), whereas the lead isotopic age of calcium-aluminum–rich inclusions (CAIs) in the CV chondrite Efremovka is 4567.2 ± 0.6 Ma. This gives an interval of 2.5 ± 1.2 million years (My) between formation of the CV CAIs and the CR chondrules and indicates that CAI- and chondrule-forming events lasted for at least 1.3 My. This time interval is consistent with a 2- to 3-My age difference between CR CAIs and chondrules inferred from the differences in their initial
26
Al/
27
Al ratios and supports the chronological significance of the
26
Al-
26
Mg systematics.
Spatiotemporal Pattern of Neural Processing in the Human Auditory Cortex
Authors: Seifritz Erich , Esposito Fabrizio , Hennel Franciszek , Mustovic Henrietta , Neuhoff John G. , Bilecen Deniz , Tedeschi Gioacchino , Scheffler Klaus , Di Salle Francesco
Published: September 2002

The principles that the auditory cortex uses to decipher a stream of acoustic information have remained elusive. Neural responses in the animal auditory cortex can be broadly classified into transient and sustained activity. We examined the existence of similar principles in the human brain. Sound-evoked, blood oxygen level–dependent signal response was decomposed temporally into independent transient and sustained constituents, which predominated in different portions—core and belt—of the auditory cortex. Converging with unit recordings, our data suggest that this spatiotemporal pattern in the auditory cortex may represent a fundamental principle of analyzing sound information.
Cooperation of GGAs and AP-1 in Packaging MPRs at the Trans-Golgi Network
Authors: Doray Balraj , Ghosh Pradipta , Griffith Janice , Geuze Hans J. , Kornfeld Stuart
Published: September 2002

The Golgi-localized, γ-ear–containing, adenosine diphosphate ribosylation factor–binding proteins (GGAs) are multidomain proteins that bind mannose 6-phosphate receptors (MPRs) in the Golgi and have an essential role in lysosomal enzyme sorting. Here the GGAs and the coat protein adaptor protein–1 (AP-1) were shown to colocalize in clathrin-coated buds of the trans-Golgi networks of mouse L cells and human HeLa cells. Binding studies revealed a direct interaction between the hinge domains of the GGAs and the γ-ear domain of AP-1. Further, AP-1 contained bound casein kinase–2 that phosphorylated GGA1 and GGA3, thereby causing autoinhibition. This could induce the directed transfer of the MPRs from GGAs to AP-1. MPRs that are defective in binding to GGAs are poorly incorporated into AP-1–containing clathrin-coated vesicles. Thus, the GGAs and AP-1 interact to package MPRs into AP-1–containing coated vesicles.
Three Isoforms of Cyclophilin A Associated with Human Immunodeficiency Virus Type 1 Were Found by Proteomics by Using Two-Dimensional Gel Electrophoresis and Matrix-Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry
Authors: Misumi Shogo , Fuchigami Takashi , Takamune Nobutoki , Takahashi Ichiro , Takama Michiho , Shoji Shozo
Published: September 2002

Human immunodeficiency virus type 1 (HIV-1) strain LAV-1 (HIV-1
LAV-1
) particles were collected by ultracentrifugation, treated with subtilisin, and then purified by Sepharose CL-4B column chromatography to remove microvesicles. The lysate of the purified HIV-1
LAV-1
particles was subjected to two-dimensional (2D) gel electrophoresis and stained. The 2D gel electrophoresis image suggested that 24 proteins can be identified inside the virion. Furthermore, the stained protein spots were excised and digested with trypsin. The resulting peptide fragments were characterized by matrix-assisted laser desorption ionization-time of flight mass spectrometry. Peptide mass fingerprinting data suggested that two isoforms of cyclophilin A (CyPA), one with an isoelectric point (pI) of 6.40 and one with a pI of 6.53, are inside the viral membrane; that another isoform, with a pI of 6.88, is outside the viral membrane; and that the CyPA isoform with a pI of 6.53 is N acetylated. The mechanisms that permit the redistribution of CyPA on the viral surface have not yet been clarified, but it is surmised that the CyPA isoform with a pI of 6.88 may play a critical role in the attachment of virions to the surface of target cells and that both CyPA isoforms with pIs of 6.40 and 6.53 may regulate the conformation of the HIV-1 capsid protein.
Assembly and Translocation of Papillomavirus Capsid Proteins
Authors: Florin Luise , Sapp Cornelia , Streeck Rolf E. , Sapp Martin
Published: September 2002

The major and minor capsid proteins of polyomavirus are preassembled in the cytoplasm and translocated to the nucleus only as a VP1-VP2/VP3 complex. In this study, we describe independent nuclear translocation of the L1 major protein and the L2 minor capsid protein of human papillomavirus type 33 by several approaches. First, we observed that expression and nuclear translocation of L2 in natural lesions precede expression of L1. Second, using a cell culture system for coexpression, we found that accumulation of L2 in nuclear domain 10 (ND10) subnuclear structures precedes L1 by several hours. In contrast, complexes of L2 and mutants of L1 forced to assemble in the cytoplasm are translocated directly to ND10, like L2 expressed alone. Interestingly, accumulation of wild-type L1 is observed only after L2-induced release of the ND10-associated protein Sp100. Third, nuclear translocation of L2 but not of L1 was blocked by the proteasome inhibitor MG132. Our data suggest that L1 and L2 interaction occurs after L2-induced reorganization of ND10 subnuclear domains.
Crystal Structures of Zidovudine- or Lamivudine-Resistant Human Immunodeficiency Virus Type 1 Reverse Transcriptases Containing Mutations at Codons 41, 184, and 215
Authors: Chamberlain P. P. , Ren J. , Nichols C. E. , Douglas L. , Lennerstrand J. , Larder B. A. , Stuart D. I. , Stammers D. K.
Published: September 2002

Six structures of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) containing combinations of resistance mutations for zidovudine (AZT) (M41L and T215Y) or lamivudine (M184V) have been determined as inhibitor complexes. Minimal conformational changes in the polymerase or nonnucleoside RT inhibitor sites compared to the mutant RTMC (D67N, K70R, T215F, and K219N) are observed, indicating that such changes may occur only with certain combinations of mutations. Model building M41L and T215Y into HIV-1 RT-DNA and docking in ATP that is utilized in the pyrophosphorolysis reaction for AZT resistance indicates that some conformational rearrangement appears necessary in RT for ATP to interact simultaneously with the M41L and T215Y mutations.
Lack of Canonical E6 and E7 Open Reading Frames in Bird Papillomaviruses:
Fringilla coelebs
Papillomavirus and
Psittacus erithacus timneh
Papillomavirus
Authors: Terai Masanori , DeSalle Rob , Burk Robert D.
Published: September 2002

Determination and analyses of the complete sequence of
Fringilla coelebs
papillomavirus and
Psittacus erithacus timneh
papillomavirus indicate that they represent a distinct and distant lineage of papillomaviruses. The lack of canonical E6-E7 open reading frames suggests that they serve adaptive functions during papillomavirus evolution.