bluuebunny/crossref_metadata_2025 huggingface dataset:
An essential role for membrane rafts in the initiation of Fas/CD95‐triggered cell death in mouse thymocytes
Authors: Hueber Anne‐Odile , Bernard Anne‐Marie , Hérincs Zoltán , Couzinet Arnaud , He Hai‐Tao
Published: July 2002

Fas, a member of the tumor necrosis factor receptor family, can upon ligation by its ligand or agonistic antibodies trigger signaling cascades leading to cell death in lymphocytes and other cell types. Such signaling cascades are initiated through the formation of a membrane death‐inducing signaling complex (DISC) that includes Fas, the Fas‐associated death domain protein (FADD) and caspase‐8. We report here that a considerable fraction of Fas is constitutively partitioned into sphingolipid‐ and cholesterol‐rich membrane rafts in mouse thymocytes as well as the L12.10‐Fas T cells, and Fas ligation promotes a rapid and specific recruitment of FADD and caspase‐8 to the rafts. Raft disruption by cholesterol depletion abolishes Fas‐triggered recruitment of FADD and caspase‐8 to the membrane, DISC formation and cell death. Taken together, our results provide the first demonstration for an essential role of membrane rafts in the initiation of Fas‐mediated cell death signaling.
Improving the outcome of facial resurfacing—prevention of herpes simplex virus type 1 reactivation
Authors: Gilbert Stan
Published: July 2002

Facial resurfacing is becoming an increasingly popular method of cosmetic surgery for improving the appearance of the skin on the face and neck. However, since the majority of the population is infected with herpes simplex virus type 1 (HSV-1) by adulthood, complications such as widespread facial lesions and post-operative scarring arising from reactivation of the virus can threaten the success of the procedure. Although there are no prospective controlled trials, oral antiviral therapy has been shown to be effective in preventing post-operative reactivation of HSV-1 when administered from a minimum of 2 h before surgery and continued up to 10 days thereafter. Since such therapies have very acceptable clinical safety profiles, it has become common practice for all individuals undergoing facial resurfacing to be treated with oral antivirals effective against HSV-1, regardless of their HSV-1 history or baseline serology.
Verification of dynamic intensity‐modulated beam deliveries in canine subjects
Authors: Parsai Homayon , Phillips Mark H. , Cho Paul S. , Kippenes Hege , Gavin Patrick , Axen David
Published: July 2002

Our objective in this work was to assess the precision and degree of accuracy with which intensity modulated radiation therapy (IMRT) can deliver highly localized dose distributions to tumors near critical structures using the dynamic sliding window technique. Measurements of dose distribution were performed both in vivo and in vitro using a combination of dosimeters [thermoluminescent dosimeters (TLD's), films, and diodes]. In vivo measurements were performed in two groups of purpose‐bred dogs: one receiving four‐field three‐dimensional (3D) conformal treatment and the other receiving IMRT. The algorithms used in the inverse planning process included the Macro Pencil Beam (MPB) model and Projections onto Convex Sets (POCS). Single beam measurements were performed in phantoms to verify the accuracy of monitor unit settings required for delivering the desired doses. The composite doses from the delivery of the seven beam intensity modulated plans were measured in phantoms and cadavers. Biological end points (spinal cord toxicity and neurolgic deficits due to irradiation) were evaluated at the end of one year to determine the spatial accuracy of the IMRT treatments over a fractionated course in live subjects. Results in single beam measurements were used at first to improve the dose calculation and translation algorithms. Results of the measurements for the delivery of all seven beams in phantoms confirmed that the system was capable of accurate spatial and dosimetric IMRT delivery. The in vivo results showed dramatic differences between control and IMRT‐treated dogs, with the IMRT group showing no adverse effects and the control animals showing severe spinal cord injuries due to irradiation. The measurements presented in this paper have helped to verify the successful and accurate delivery of IMRT in a clinically related model using the University of Washington Medical Center (UWMC) system.
The effect of high-amplitude sound on the attenuation of perforated tube silencers
Authors: Dickey N. S. , Selamet A. , Novak J. M.
Published: July 2002

A time-domain computational approach is applied to investigate the behavior of perforated tube silencers at high sound levels. The one-dimensional computational technique employs a lumped parameter model for the perforate flows. The lumped parameter perforate model is based on time-invariant approximations for the equivalent length leq and resistance R, consistent with the use of a nonlinear perforate impedance. Empirical expressions for leq and R are developed experimentally using nondimensional scaling parameters. The model is applied to geometries representative of automotive resonators and multiple-duct mufflers. Conditions are simplified from those in an actual automotive system by considering single-frequency excitation and zero mean flow. Simulations with linear perforate behavior are compared to experimental data obtained with an extended impedance tube system. Simulations with nonlinear perforate behavior for one concentric tube resonator are compared to published experimental data.
Dispersion and characteristic surfaces of waves in laminated composite circular cylindrical shells
Authors: Xi Z. C. , Liu G. R. , Lam K. Y. , Shang H. M.
Published: July 2002

The dispersion behaviors and characteristic surfaces of waves in a laminated composite circular cylindrical shell are investigated using a semianalytical method based on the theory of three-dimensional elasticity. The radial displacement of the shell is modeled by finite elements, while the axial and circumferential displacements are expanded as the complex exponentials. The associated characteristic equation is developed by means of the Hamilton’s principle. The eigenvalues are established in terms of the Rayleigh quotient. Six characteristic wave surfaces, viz., the phase velocity, phase slowness, and phase wave surfaces, as well as the group velocity, group slowness, and group wave surfaces, are introduced to visualize the effects of anisotropy on wave propagation. Numerical examples demonstrate that the ratio of the inner radius to the thickness of the shell has a stronger influence on the frequency spectra in the circumferential wave than on that in the axial wave; that negative group velocity appears at a range of smaller wave numbers and the range varies as the wave normal and the ratio of the inner radius to the thickness of the shell; and that the characteristic wave surfaces vary with the propagation modes of waves, the ratio of the inner radius to the thickness of the shell, and the lay-ups of the laminated shells.
Reflectance properties of two-dimensional sonic band-gap crystals
Authors: Sanchis L. , Cervera F. , Sánchez-Dehesa J. , Sánchez-Pérez J. V. , Rubio C. , Martínez-Sala R.
Published: July 2002

An analysis of the reflectance of sonic band-gap crystals consisting of square arrays of rigid cylinders in air is presented. The standing wave formed in front of the structures is studied both experimentally and theoretically. Experiments have been performed with a mobile robotized microphone that obtains pressure maps on the plane perpendicular to the axes of the cylinders. Enhancements of the standing wave ratio (SWR) are observed in frequency regions where attenuation bands appear in zero-order transmission experiments. Also, the SWR presents oscillations that can be related to the finite dimension of the structure (Fabry–Perot effect). Both features are well described by calculations based on a double-scattering approach.
General scales of community reaction to noise (dissatisfaction and perceived affectedness) are more reliable than scales of annoyance
Authors: Job R. F. S. , Hatfield J. , Carter N. L. , Peploe P. , Taylor R. , Morrell S.
Published: July 2002

General measures of reaction to noise, which assess the respondent's perceived affectedness or dissatisfaction, appear to be more valid and internally consistent than more narrow measures, such as specific assessment of noise annoyance. However, the test–retest reliability of general and specific measures has yet to be compared. As a part of the large-scale Sydney Airport Health Study, 97 respondents participated in the same interview twice, several weeks apart. Test–retest reliabilities were found to be significant (p<0.001) for two general questions and three specific “annoyance” questions. The general measures were significantly more valid for four of the six correlations (with activity disturbance), and more stable than the annoyance scales for five of the six possible test–retest comparisons. Amongst 1015 respondents at Time 1, the questions regarding general reaction were more internally consistent than the questions regarding annoyance. Taken together, these data indicate that general measures of reaction to noise have superior psychometric properties (validity, internal consistency, and stability) compared with measures of specific reactions such as annoyance.
On the performance of acoustic crosstalk cancellation in a reverberant environment
Authors: Ward Darren B.
Published: July 2002

Acoustic crosstalk cancellation systems create a virtual audio environment by using loudspeakers to deliver appropriate binaural signals to the listener. Typically, the system is designed to equalize the direct-path transfer functions between the loudspeakers and the ears. In this paper statistical room acoustics is used to derive a closed-form expression that predicts the performance of such a system when used in a reverberant environment, and the expression is verified through simulations. The results of this paper enable designers to undertake a preliminary analysis of how well a given crosstalk cancellation system will perform in a reverberant environment, without resorting to time-consuming measurements or image-model simulations.
Development of an acoustic actuator for launch vehicle noise reduction
Authors: Henderson Benjamin K. , Lane Steven A. , Gussy Joel , Griffin Steve , Farinholt Kevin M.
Published: July 2002

In many active noise control applications, it is necessary that acoustic actuators be mounted in small enclosures due to volume constraints and in order to remain unobtrusive. However, the air spring of the enclosure is detrimental to the low-frequency performance of the actuator. For launch vehicle noise control applications, mass and volume constraints are very limiting, but the low-frequency performance of the actuator is critical. This work presents a novel approach that uses a nonlinear buckling suspension system and partial evacuation of the air within the enclosure to yield a compact, sealed acoustic driver that exhibits a very low natural frequency. Linear models of the device are presented and numerical simulations are given to illustrate the advantages of this design concept. An experimental prototype was built and measurements indicate that this design can significantly improve the low-frequency response of compact acoustic actuators.
Fresnel zones for modes
Authors: Virovlyansky Anatoly L. , Kurin Vasily V. , Pronchatov-Rubtsov Nikolay V. , Simdyankin Sergey I.
Published: July 2002

The notion of Fresnel zones for modes is introduced which is analogous to the usual Fresnel zones introduced for rays. It is shown that by using Fresnel zones for modes one can simplify the analysis of mode scattering at large-scale inhomogeneities in multimode waveguides. The mode amplitude variations due to scattering by an opaque screen and by refractive index inhomogeneities are considered. In the latter case the formulas obtained in the scope of this approach are statistical averaging suited and similar to those of geometrical optics and the Rytov method widely used to calculate fluctuations of ray complex amplitudes. The results of a tank experiment carried out to test the predictions concerning the mode scattering by an opaque screen are presented.
Amplitude modulation depth discrimination of a sinusoidal carrier: Effect of stimulus duration
Authors: Lee Jungmee , Bacon Sid P.
Published: July 2002

Discrimination of the change in depth of sinusoidal amplitude modulation (AM) was investigated as a function of stimulus duration. The carrier frequency was 4000 Hz, the standard modulation depth (m) was either 0.1, 0.18, or 0.3, and the modulation rate was either 10, 20, 40, or 80 Hz. For all standard depths and modulation rates, threshold (Δm) decreased by more than a factor of two as stimulus duration doubled from the shortest duration used up to a certain duration (critical duration), beyond which the threshold decreased only slightly or remained constant. The critical duration corresponded to about four cycles of modulation. Psychometric functions were measured for different stimulus durations to examine the extent to which a multiple-looks model could explain the present data. This model provided a reasonable prediction of the change in AM depth discrimination threshold as a function of stimulus duration.
Modulation detection interference with two-component masker modulators
Authors: Sheft Stanley , Yost William A.
Published: July 2002

Thresholds were measured for detecting amplitude modulation of a single tonal carrier in the presence of modulated maskers. The masker modulator contained either one or two sinusoidal components. As found in previous studies, there was a detrimental effect of masker modulation on the detection of probe modulation. Interference was obtained with a 4-Hz separation between the two components of the masker modulator with the probe modulated at the 4-Hz beat rate. The amount of interference obtained with the two-component masker modulator was greater than that produced by the individual components of the masker modulator. The amount of interference increased with the depth of the masker-modulator beating and the number of masker carriers. The interference due to beating of the masker-modulator components was reduced when the beat rate was increased from 4 to 10 Hz. Results obtained with two-component masker modulators indicate a masking effect not predicted by a spectral representation of the probe and masker envelopes.
Comparison of basin-scale acoustic transmissions with rays and further evidence for a structured thermal field in the northeast Pacific
Authors: Norris David E. , Spiesberger John L. , Merdes Daniel W.
Published: July 2002

From May to September of 1987, 250-Hz, 16-ms resolution acoustic signals were transmitted between four sources and nine receivers in the northeast Pacific. This paper examines the acoustic transmissions across nine of the sections within this group, with path lengths ranging from approximately 1700 to 3300 km. Acoustic multipaths are tracked in the data, and ray theory is successfully used to identify the multipaths, where the spring and summer Levitus’ climatological databases are used to determine the sound speeds. The observed multipaths arrive on the order of 1 s later than the predicted rays. Travel time differences greater than 0.15 s are due to temperature errors in Levitus’ climatology within the ocean’s upper 1 km. The resulting corrections to Levitus’ spring and summer oceans are −0.2 and −0.3 °C, respectively. The upper turning depths for all rays are found to vary by less than 50 m from spring to summer. Variations in the measured travel times over the four month period are about 0.5 s. Some sections warm between the spring and summer seasons, while other sections cool. This variability is inconsistent with a temperature field dominated by seasonal effects. The spatial and temporal scales of the heat content are qualitatively similar to those found from other basin-scale acoustic sections in the northeast Pacific [J. L. Spiesberger et al., J. Acoust. Soc. Am. 92, 384–396 (1992)].
Sound propagation in dilute suspensions of rigid particles
Authors: Temkin S.
Published: July 2002

This paper considers sound propagation in suspensions of rigid particles, when both heat and momentum are exchanged between the particles and the host fluid. A theory is developed for small-amplitude, single-frequency oscillatory motions, on the assumption that the temperature of each particle is uniform. This theory applies to dilute suspensions that have arbitrary particle and fluid material densities, and yields the attenuation and the speed of sound in the suspension in terms of the particles’ velocity and temperature fluctuations. These quantities are not specified by the theory, but are available for some situations of interest which cover a very wide frequency range. In the particular case when the particle force and the heat transfer rate are not affected by the compressibility of the fluid, the particle’s velocity and temperature are given by closed-form results that are used to obtain explicit formulas for the attenuation and sound speed. For this case, the present theory reproduces all fundamental predictions available in the literature, and yields new basic results where none seem to exist. Results are also shown for the important case when the particle force includes compressibility effects in the fluid. These provide a unified description for the attenuation and the dispersions which covers the viscous and the scattering regions, as well as the transition region between them.
The Wiener–Hopf technique and scattering of acoustic waves in ducts
Authors: Albertson Fredrik
Published: July 2002

The reactive silencer is the standard product for attenuating noise in ducts with flue gases. A model problem is solved for such a silencer by calculating the scattering of acoustic waves at sharp edges in a two-dimensional waveguide. In this waveguide the walls are considered acoustically hard and to ensure the existence of a unique solution an edge condition is applied. An exact analytical solution is found using the Wiener–Hopf technique, which relies heavily on the Fourier transform with assumptions on regularity of the solution. Control methods are employed to check the theory and the accuracy of the numerical results. One of the control methods is derived from the energy conservation principle. Symmetries, so-called reciprocity relations, are found for the reflection and transmission matrices and are first used to check the analytic calculation and later to reduce the numerical work. A quasistationary model is also used for control purposes. It is valid for low frequencies and checks the phase of the transmission and reflection coefficients, while the energy method only covers the corresponding absolute values. Physical results as the behavior of the reflection and transmission coefficients are also presented. These coefficients are analyzed as functions of both frequency and geometry.
The masking-level difference in low-noise noise
Authors: Hall Joseph W. , Grose John H. , Hartmann William Morris
Published: July 2002

In experiment 1 NoSo and NoSπ thresholds for a 500-Hz pure tone were obtained in a low-fluctuation masking noise and a high-fluctuation masking noise for six normal-hearing listeners. The noise bandwidth was 10 Hz. In agreement with previous investigations, the NoSo thresholds were lower in low-fluctuation noise than in high-fluctuation noise. For three listeners, NoSπ thresholds were similar for the two types of noise, while for the other three listeners, NoSπ thresholds were higher for low-fluctuation noise than for high-fluctuation noise. In experiment 2, the masker was created by amplitude modulating a 500-Hz pure tone by a 0–10-Hz low-pass noise. The degree of masker fluctuation was controlled by adjusting the average modulation depth (100%, 63%, 40%, and 25%). The signal was a 10-Hz-wide noise centered on 500 Hz. Results were similar to those of experiment 1: for the NoSo conditions, signal detection improved with decreasing degree of fluctuation, and for NoSπ conditions, the results were subject dependent. For three listeners, NoSπ thresholds were again similar in the two types of noise, while for the other three listeners, NoSπ thresholds were again higher in low-fluctuation noise than in high-fluctuation noise. The results showed that a high degree of masker fluctuation sometimes facilitates NoSπ detection. It is possible that the binaural detection mechanism utilizes the relatively good signal-to-noise ratios that occur in the low power or “dip” regions of fluctuating masker waveforms.
Masker fluctuation and the masking-level difference
Authors: Grose John H. , Hall Joseph W.
Published: July 2002

Previous work suggests that, for some listeners, masker fluctuation may be advantageous for NoSπ detection. This study tested the hypothesis that the benefit of masker fluctuation to binaural analysis is based on the ability to take advantage of epochs of low masker energy in the fluctuating masker where the cues underlying binaural signal detection are more salient. The hypothesis was evaluated using the time-domain version of COSS analysis derived by Buus et al. [J. Acoust. Soc. Am. 99, 2288–2297 (1996)] which measures the perceptual weight applied by a listener within a relatively brief time window as a function of the masker level during the window. The results indicated a dependency of signal detection on short-term masker level in the NoSπ condition but not in the NoSo condition. This finding supports a new perspective indicating that binaural signal detection depends upon the envelope of a masker in a way that is fundamentally different from that typically associated with monaural detection.
Acoustic characterization of contrast agents for medical ultrasound imaging
Authors: Hoff Lars , Sontum Per C.
Published: July 2002

Nycomed’s ultrasound contrast agent NC100100 has been investigated by in vitro acoustic measurements. Acoustic attenuation spectra were used to determine resonance frequencies of the particles. The spectra were correlated with size distributions, and it was found that the shell-encapsulated gas bubbles can be described as viscoelastic particles with bulk modulus 700 kPa. When exposed to hydrostatic overpressures mimicking those found in vivo during the systolic heart cycle, the resonance frequency increased, as expected by the particles’ increased stiffness. This effect was reversible: After the pressure was released, the particles went back to giving the original attenuation spectrum. This shows that the particles are not destroyed or otherwise changed by the pressure. Acoustic backscatter measured as a function of distance through a contrast agent was used to estimate the backscatter efficiency of the particles, that is, the ratio between scattered and absorbed ultrasound. Results from these measurements agree with theoretical estimates based on the attenuation spectra. Measurements on NC100100 were compared with earlier results from measurements on Albunex® and measurements on an experimental polymer-encapsulated contrast agent, showing how different shell materials cause differences in particle stability and stiffness.
Effects of spectral pattern on the perceptual salience of partials in harmonic and frequency-shifted complex tones: A performance measure
Authors: Roberts Brian
Published: July 2002

A single even harmonic added to an odd-harmonic complex is often judged to be more salient than its odd neighbors in a clarity rating task [Roberts and Bregman, J. Acoust. Soc. Am. 90, 3050–3060 (1991)]. This study used similar complexes in a two-interval forced-choice procedure. Each interval consisted of a complex tone followed by a pure tone, whose frequency matched that of a harmonic in one interval but was changed by ±0.5×fundamental frequency in the other. Subjects were asked to identify the matching interval. Since the pure tone followed the complex tone, it could not cue listening to a particular frequency region. The possibility of cross-interval cuing was reduced by changing the fundamental frequency between intervals (100–150 Hz range). The procedure was designed to maximize the effects on performance of differences in immediate perceptual salience between the partials. The added even harmonic was typically judged with greater accuracy than its odd neighbors (experiment 1), though this effect was greatly reduced for harmonics above 8 (experiment 2). The even–odd difference persisted when the original stimuli were made inharmonic by applying a frequency shift of 15%, but was abolished for stimuli consisting of successive partials (experiment 3).
An innovative design of a probe-tube attachment for a 12-in. microphone
Authors: Franzoni Linda P. , Elliott Christopher M.
Published: July 2002

Nonintrusive devices are needed to measure sound pressure levels in the mid- to high-frequency range. This need arises due to the small acoustic wavelengths which are present at these frequencies, and the interference caused by conventional microphones which are typically of relatively large diameter. Smaller microphones are less sensitive, and may not be small enough to be useful at very high frequencies or when physical size constraints are limiting. Simple probe attachments have been developed by others to address these problems; however, generally the transfer functions of these devices have possessed undesirable peaks due to the presence of standing waves within the transducers. In this paper, several possible options for making a microphone attachment that will convert a standard 12-in.-diam microphone into a probe-tube are discussed. Recommendations are made with regard to the particular use and ease of construction of the attachment. The new concepts eliminate standing waves, within certain frequency bands that are controlled by the geometry of the attachment, without the addition of damping material in the sound path.
Modeling temporal asymmetry in the auditory system
Authors: Patterson Roy D. , Irino Toshio
Published: July 2002

Sound sources in the environment produce waves that are almost invariably asymmetric in time, and human listeners are highly sensitive to temporal asymmetry. The spectral analysis and neural transduction processes in the cochlea enhance temporal asymmetry, as do time-domain models of cochlear processes, but it appears that the resulting asymmetry is not sufficient to explain the observed perceptual asymmetry. In the auditory image model (AIM) of hearing, the temporal asymmetry in the neural activity produced by the cochlea is further enhanced by the “strobed” temporal integration that converts the neural activity pattern into an auditory image, and the temporal asymmetry in the auditory image is sufficient to explain the perceptual asymmetry. Modern versions of the “duplex model” of pitch have time-domain cochlea simulations that produce neural activity with temporal asymmetry similar to that produced by AIM. In the final stage, however, they apply autocorrelation to the neural pattern and autocorrelation is a symmetric process in time. In this paper the effect of autocorrelation on temporal asymmetry is examined in a range of auditory models with varying forms of auditory filterbank, compression, and neural transduction. It is concluded that autocorrelation does not enhance temporal asymmetry and often reduces it, and that autocorrelogram models cannot explain the magnitude of the perceptual asymmetry in their current form. Then, the original version of strobed-temporal-integration is reviewed with regard to temporal asymmetry, and the delta-gamma theory of temporal asymmetry [Irino and Patterson, J. Acoust. Soc. Am. 99, 2316–2331 (1996)] is used to develop a new version of strobed-temporal-integration that is more robust and physiologically more plausible.
Time-reversing array retrofocusing in simple dynamic underwater environments
Authors: Khosla Sunny R. , Dowling David R.
Published: July 2002

A time-reversing array (TRA) has the ability to retrofocus acoustic energy, in both time and space, to the original sound-source location without any information about the acoustic environment in which it is deployed. This unique capability may be limited or lost when the acoustic medium or its boundaries are time dependent, or propagation losses are prevalent. In this paper, predictions are made for the size, field-amplitude decay rate (or time), and location of the retrofocus for a TRA deployed in the presence of three dynamic acoustic propagation complexities commonly present in shallow ocean waters: (i) volume scattering from a random superposition of linear internal waves convecting a gradient in the sound speed profile; (ii) reflection and volume scattering from a deterministic soliton internal wave traveling on the thermocline between two water masses with differing sound speed; and (iii) surface scattering from a wind-driven dynamic random rough ocean surface. Analytical propagation models for narrow-band signals are used to highlight separately the influence of each propagation complexity on TRA retrofocusing. As expected, internal wave time scales are long enough so that TRA retrofocusing should persist for several minutes for source-array ranges of several kilometers at frequencies approaching 1 kHz. However, the comparatively rapid motion of ocean surface waves should prevent TRA exploitation of acoustic scattering from a wind-driven ocean surface at ranges greater than a few hundred meters, independent of acoustic frequency. Interestingly, multiple time-invariant propagation paths are not found to consistently enhance retrofocusing unless the TRA has sufficient angular resolution to distinguish them.
Acceptable delays in hearing aids and implications for feedback cancellation
Authors: Laugesen S. , Hansen K. V. , Hellgren J.
Published: July 2002

The advent of digital hearing aids has made it possible to realize a vast range of advanced signal processing algorithms. Undoubtedly, some candidate algorithms will involve comprehensive throughput delays. This applies, for instance, to all algorithms that are based on the discrete Fourier transform, due to the inherent block processing. The results of a literature study on the potential audible effects of delays in hearing aids will be presented in an outline. The rather restrictive limitations on throughput delay that appear from this study have consequences for many attractive hearing aid applications of digital signal processing. As an example, digital feedback cancellation without additive probe noise is considered. Such a system is based on adaptive identification of the feedback path, found only by means of the excitation provided by the external input signal to the hearing aid. Since the external input signal appears both as reference and disturbance in the adaptive system identification, the estimate of the feedback path becomes erroneous when the external input signal contains significant amounts of autocorrelation. It is shown that the only effective remedy to this problem is to increase the throughput delay of the hearing aid.
Acoustics education in Ukraine
Authors: Mayevskyy Stanislav M. , Gelman Leonid M.
Published: July 2002

Acoustics education in Ukraine is considered. In more than 40 universities, students learn acoustics: in the acoustics department of the National Technical University in Ukraine (only one department in Ukraine) and many related departments such as Nondestructive Testing, Physics, Electrical Engineering, etc. Acoustical specializations of departments are presented. The most promising and developing acoustical specialization is biomedical acoustics.
Outer-flow effects on turbulent boundary layer wall pressure fluctuations
Authors: Brungart Timothy A. , Lauchle Gerald C. , Deutsch Steven , Riggs Eric T.
Published: July 2002

The outer-flow contribution to the pressure fluctuations occurring at the wall beneath a turbulent boundary layer was studied experimentally. A moving wall wind-tunnel facility was developed for the work. A flat test plate was suspended at various heights over the movable tunnel wall such that interacting and noninteracting turbulent boundary layers were developed in the resultant channel. Mean and fluctuating velocity components were measured for cases with and without wall motion. Pressure fluctuations were measured, with pinhole microphones on the surface of the test plate forming the upper-channel boundary, at corresponding test conditions. The data show that the wall-pressure fluctuations are relatively insensitive to the details of the outer flow, even over the range of frequencies dominated by outer-flow turbulence structures.
Measuring the threshold for speech reception by adaptive variation of the signal bandwidth. I. Normal-hearing listeners
Authors: Noordhoek Ingrid M. , Houtgast Tammo , Festen Joost M.
Published: July 2002

An adaptive test has been developed to determine the minimum bandwidth of speech that a listener needs to reach 50% intelligibility. Measuring this speech-reception bandwidth threshold (SRBT), in addition to the more common speech-reception threshold (SRT) in noise, may be useful in investigating the factors underlying impaired suprathreshold speech perception. Speech was bandpass filtered (center frequency: 1 kHz) and complementary bandstop filtered noise was added. To obtain reference values, the SRBT was measured in 12 normal-hearing listeners at four sound-pressure levels, in combination with three overall spectral tilts. Plotting SRBT as a function of sound-pressure level resulted in U-shaped curves. The most narrow SRBT (1.4 octave) was obtained at an A-weighted sound-pressure level of 55 dB. The required bandwidth increases with increasing level, probably due to upward spread of masking. At a lower level (40 dBA) listeners also need a broader band, because parts of the speech signal will be below threshold. The SII (Speech Intelligibility Index) model reasonably predicts the data, although it seems to underestimate upward spread of masking.
Anderson localization of vibration on a framed cylindrical shell
Authors: Photiadis Douglas M. , Houston Brian H.
Published: July 2002

Analysis of the measured response of a near-periodic framed shell to a point force reveals that the higher-order azimuthal modes (n>10) on the shell are significantly localized. A quantitative analysis of the data yielding the spatial attenuation rates, the measured group speeds, and the total measured damping factors for various azimuthal orders is presented. The two principal mechanisms which could account for the spatial attenuation rates, damping and Anderson localization, are investigated. Predictions based on these underlying phenomena are obtained and compared with the measurements. The spatial attenuation rates resulting from damping are typically a factor of 2.3 times too small to account for the measurements, while the spatial localization due to irregularity and the data are in reasonable agreement. This evidence, along with the strongly fluctuating nature of the response, indicates that Anderson localization is the dominant mechanism at work in this system.
The representation of pure tones and noise in a model of cochlear nucleus neurons
Authors: Eriksson Jan L. , Robert Arnaud
Published: July 2002

The limited dynamic range of the majority of auditory-nerve fibers represents a difficulty in accounting for normal hearing capabilities over the known psychoacoustic intensity range. The presence of noise is an additional complication because it will tend to saturate these fibers, thereby considerably reducing their dynamic range, i.e., the range of mean firing rates. In this study, simulations involving a model of auditory nerve and cochlear nucleus neurons were conducted using pure-tone stimuli in the presence of noise. The main focus is on the role of inhibition in regulating the activity of cells, improving their capability to represent signals in background noise. This concerns in particular those inhibitory neurons that receive input from a wide range of auditory-nerve fibers and respond with an onset chopper pattern. A detailed model of stellate cells is used. It allows several parameters such as the number, location, and strength of inputs to be manipulated. The first part of this paper presents the model and its responses to pure-tone and noise stimuli presented separately. The model’s capacity to generalize to tone/noise combinations is then tested. Responses to these stimuli are found to be qualitatively similar to neurophysiological findings. Model neurons exhibit appropriate shifts in their rate-level functions and their responses are inhibited or suppressed by tones outside their characteristic frequency. The model stellate cell is also found to display many of the temporal patterns reported in electrophysiological studies as a result of appropriate settings of certain parameters. Therefore, the model is sufficient to account for a large number of findings and should serve as a basis for predicting responses to novel stimuli, or as a building block for modeling larger networks.
Methods for estimating the sound pressure at the eardrum
Authors: Hudde H. , Engel A. , Lodwig A.
Published: July 2002

The problem of estimating the sound pressure generated at individual eardrums is systematically investigated. In audiometry, the reference to the pressure at the eardrum is usually realized by using a coupler such as the IEC 711 ear simulator, which is intended to approximate an average ear. The errors caused by individually shaped ear canals are calculated for a typical audiometric earphone (Beyer DT 48) in combination with the IEC 711 ear simulator and with an “ideal” coupler. These errors can reach 15 dB and are clearly more important than deviations of the ear simulator from an average ear. In order to obtain correct estimations, the chain matrices of individual ear canals have to be determined. Best estimates are obtained using the “reflectance phase method,” but the “pressure minima method” also provides surprisingly good results, except in narrow frequency ranges. The reflectance phase method is checked using a physical model of the ear canal and the middle ear. The resulting errors of estimation remain within a limit of 3 dB up to more than 10 kHz.
On the lingual organization of the German vowel system
Authors: Hoole Philip
Published: July 2002

A hybrid PARAFAC and principal-component model of tongue configuration in vowel production is presented, using a corpus of German vowels in multiple consonant contexts (fleshpoint data for seven speakers at two speech rates from electromagnetic articulography). The PARAFAC approach is attractive for explicitly separating speaker-independent and speaker-dependent effects within a parsimonious linear model. However, it proved impossible to derive a PARAFAC solution of the complete dataset (estimated to require three factors) due to complexities introduced by the consonant contexts. Accordingly, the final model was derived in two stages. First, a two-factor PARAFAC model was extracted. This succeeded; the result was treated as the basic vowel model. Second, the PARAFAC model error was subjected to a separate principal-component analysis for each subject. This revealed a further articulatory component mainly involving tongue-blade activity associated with the flanking consonants. However, the subject-specific details of the mapping from raw fleshpoint coordinates to this component were too complex to be consistent with the PARAFAC framework. The final model explained over 90% of the variance and gave a succinct and physiologically plausible articulatory representation of the German vowel space.
Transport parameters for an ultrasonic pulsed wave propagating in a multiple scattering medium
Authors: Tourin Arnaud , Derode Arnaud , Peyre Aymeric , Fink Mathias
Published: July 2002

A set of ultrasonic experimental methods was developed to characterize a multiple scattering medium in terms of ls, l*, la, respectively, the elastic, transport, and absorption mean free paths and D the diffusion constant. Actually, these quantities are the key parameters for a wave propagating in a disordered medium. Although they are widely used in optics, they are less common in acoustics. The underlying model is based on the expansion of the average solution for the heterogeneous Green’s function equation. To validate this theoretical approach, a sample made of randomly located steel rods was used as a prototype. Through time-resolved measurements of the transmitted amplitude, the difference between the ballistic and the coherent wave is highlighted. In varying the sample thickness, ls is determined, the coherent and diffusive regime are distinguished, and the transition from one to the other is followed. Furthermore, as a limit to a description of the average intensity based on the diffusion approximation, the existence of a coherent backscattering effect is shown. This latter gives a method to estimate D and l*. These quantities being determined, it becomes possible to infer la using average time-resolved intensity measurements. Finally, some applications to coarse-grain stainless steels are discussed.
Molecular Rheology of Coniferous Wood Tissues
Authors: Chow S.
Published: July 2002

The time-dependent molecular motions were observed by infrared polarization technique for wood components strained parallel to the fiber axis. A two-stage molecular motion involving three wood components, cellulose, hemicellulose, and lignin, is suggested as the course of wood molecular relaxation. The first stage begins at equilibrium, when a specimen is not stressed, and extends immediately to a minimum dichroic ratio (A⊥/A∥) of carbohydrate components represented by 1160 cm−1 (cellulose) and 1730 cm−1 (hemicellulose) bands, and the maximum dichroism of 1500 cm−1 (lignin). The second stage starts at the end of the first stage and extends to equilibrium recovery. Regardless of the form of external excitation (creep or stress relaxation), or the time of excitation (ramp- or step-loading), the basic two-stage molecular motion pattern was followed, while damping of the molecules accompanied the whole rheological process. The pattern of molecular motion for a wood component is a compensatory result of the interaction of all components. Removing one or more wood components changes the motion patterns of the remaining components. The response of cellulose in a specimen without the presence of lignin and hemicellulose is comparable to that of the other synthetic linear polymers.
Digital Narratives of Living With Lupus: Lived Experiences and Meanings for Latin American and Latino Patients and Their Families
Authors: Colmenares‐Roa Tirsa , Gastelum‐Strozzi Alfonso , Crosley Erica , Fuentes‐Silva Yurilis , Reategui‐Sokolova Cristina , Elera‐Fitzcarrald Claudia , Ibañez Soledad , Cairoli Ernesto , Pons‐Estel Bernardo A. , Drenkard Cristina , Peláez‐Ballestas Ingris
Published: February 2022

Objective

Systemic lupus erythematosus (SLE) disproportionately affects Latin American and Latino populations, with worse outcomes compared to nonminority populations. Understanding patients' views is critical to provide culturally competent care. The objective of this research is to analyze lived experiences with SLE from comments made by Latin American and Latino patients, and their relatives and friends, on the public Facebook group “Hablemos de Lupus” (in English: “Let's Talk about Lupus”).

Methods

Deidentified narratives posted as a reaction to the most popular resources shared by the page were extracted using the Facepager application. We conducted a thematic analysis under an interpretative medical anthropology framework.

Results

Five core themes were demonstrated by social media comments: lived experiences with lupus, religious/spiritual thoughts, metaphors, heredity, and experiences of family and friends. Being diagnosed with lupus is perceived as a life‐changing event. The fluctuating course of the disease causes uncertainty, and the perception of invisibility within the patient's social circle generates feelings of being misunderstood. Faith and spiritual thoughts are coping strategies. Patients use metaphors about the disease's meaning and their lived experiences (the purple butterfly, not belonging, bellicose metaphors) to communicate with others. Relatives and friends are impacted by their loved one's distress.

Conclusion

Patients perceive lupus as an unpredictable illness and use metaphors to foster empathy and communicate their experiences to others. Religion is as important as medical treatment to cope with the disease, and the experience of having lupus extends to family and friends. Findings can be used to improve physician–patient communication and lupus education campaigns in the Latin American and Latino population.
All‐Solid‐State Vertical Three‐Terminal N‐Type Organic Synaptic Devices for Neuromorphic Computing
Authors: Xie Zhichao , Zhuge Chenyu , Zhao Yanfei , Xiao Wei , Fu Yujun , Yang Dongliang , Zhang Shunpeng , Li Yingtao , Wang Qi , Wang Yazhou , Yue Wan , McCulloch Iain , He Deyan
Published: February 2022

Artificial synaptic devices are the basic composition units for neuromorphic computing processors that realize massive parallel computing. However, the n‐type organic transistors have failed to achieve good performance as an artificial synaptic device for neuromorphic computing until now. Here, a vertical three‐terminal n‐type organic artificial synapse (TNOAS) using a lithium ion‐based organic dielectric and the n‐type donor–acceptor (D–A) conjugated polymer‐naphthalene‐1,4,5,8‐tetracarboxylic‐diimide‐thiophene‐vinyl‐thiophene (NDI‐gTVT) as the channel is proposed. The TNOAS achieves nonvolatile conductance modulation with high current density operation (≈10 KA cm−2) at low voltage and mimics the basic functions of biological synapses, such as long‐term synaptic plasticity and paired‐pulse facilitation. The minimum energy consumption of a response event triggered by a single action potential is 6.16 pJ, which can be comparable with p‐type counterparts. Moreover, simulation using handwritten digital datasets exhibit a high recognition accuracy of 94%.
Kirigami Design and Modeling for Strong, Lightweight Metamaterials
Authors: Zhang Hongying , Paik Jamie
Published: February 2022

Kirigami is the art of paper cutting, and it is emerging as an elegant design and manufacturing solution in mechanical metamaterials. Currently, the majority of kirigami designs focus on shape‐morphing, but there is little attention on the remarkable mechanical properties they can produce: high strength to weight ratio where they can bear thousands of times of their own weight. This paper proposes a kirigami‐based, strong, yet lightweight metamaterial, which is created by folding pop‐up and pop‐down from a checkerboard pattern with blocks. To transform the kirigami metamaterial into arbitrary objects, the challenge lies in how to automatically design the kirigami folding to approximate the outline of the object. Herein, a computational model that is based on deploying discretized objects onto a planar sheet is proposed. Additionally, to achieve high strength, a glue‐free connector that can lock the collocated cuts in the folded configuration is designed. The standard compression tests show that the kirigami metamaterial, weighing 12.05 g, can carry 346.4 N payloads. Meanwhile, six examples of curved surfaces are prototyped to verify the shape transforming capability of the proposed kirigami metamaterial. This study paves the way towards using the kirigami technique for weight reduction in industrial applications.