bluuebunny/crossref_metadata_2025 huggingface dataset:
An approximation for propagating the fourth moment through a fluctuating ocean
Authors: Berman David H. , Dacol Dalcio K.
Published: October 2005

In this paper an approximation for fourth moment and second moment (two-frequency) path integrals is presented. The approximation is similar in spirit and form to an approximation recently developed by Uscinski et al. [B. J. Uscinski, C. Macaskill, and M. Spivak, J. Sound Vib. 106, 509–528 (1986)]. However, the present approximation has the advantage that, for the cross-frequency intensity, it factorizes to products of the cross-frequency coherence for long ranges when the latter is calculated in the same approximation. In addition, it is easily demonstrated that the present approximation is the second of a sequence of approximations that will converge to the exact path integral. The idea of the approximation is to replace paths appearing in phase structure functions by “classical” paths plus a number times the Green's function for the spreading or Jacobi equation. The calculation then reduces to a phase screen calculation, with the coefficient of the Green's function appearing as the position at which a ray crosses the screen.
Bistatic resonant scattering from elastic spheroidal shells and the resonance order
Authors: Werby Michael F. , Überall Herbert , Nagl Anton
Published: October 2005

Bistatic scattering at a resonance frequency can determine the order of the resonance, as demonstrated experimentally [G. Maze and J. Ripoche, J. Acoust. Soc. Am. 73, 41 (1983)] and theoretically [M. F. Werby and H. überall, J. Acoust. Soc. Am., in press] for elastic bodies of separable geometry (cylinders, spheres). For obstacles of more general shape, mode mixing takes place, but it was found (e.g., for solid prolate spheroids) [H. Überall, M. F. Werby, S. H. Brown, and J. W. Dickey, J. Acoust. Soc. Am. Suppl. 1 80, S128 (1986)] that, for moderate aspect ratios (up to 3:1), one mode remains dominant in the bistatic pattern, and may serve to characterize the resonance, even while a crossing of Rayleigh and Whispering Gallery resonances takes place. This method is applied to the resonances of spherical and spheroidal shells, characterized by low-frequency resonances related to the plate Lamb-wave modes. Our application of the bistatic method confirms these relations, showing again that mode-order assignments remain valid for moderate spheroids' eccentricities. [Work supported in part by the ONR.]
Computer-based piano performance reproduction system
Authors: Vincent Hal
Published: October 2005

This session will consist of a demonstration of the Bosendorfer 225SE computer-based piano performance reproduction system. The system incorporates an optical sensing mechanism to monitor and record individual key positions for subsequent exact reproduction of performance dynamics. The demonstration will take approximately 1 h, followed by a 1/2-h question and answer period. It will be repeated again from 3:30–5:00 p.m., and again on Wednesday from 10:00–11:30 a.m., and on Friday from 9:00–10:30 a.m. The instrument will also be available, by arrangement, for small group hands-on evaluations.
Effects of talker uncertainty II: Encoding speech into memory
Authors: Martin Christopher S. , Mullennix John W.
Published: October 2005

Individual talkers vary in a large number of articulatory and acoustic characteristics. Little research has been conducted concerning the effects of talker uncertainty on encoding speech into memory. In order to examine this problem, a serial-ordered recall experiment was conducted. The stimuli were CVC monosyllabic English words produced by different male and female talkers. Listeners were presented with lists of ten items produced by a singler talker or lists of ten items produced by multiple talkers, and were required to recall the items in the order presented. Percent correct recall in the primary region of the serial position curve was lower as the amount of talker variability within the lists increased. The result suggest that the encoding of speech into memory is affected by uncertainty from trial to trial due to talker variability. The hypothesis that perceptual processes involved in talker normalization are located at an auditory-to-phonetic level will be discussed. [Work supported by NIH.]
Evaluation of a speaker-dependent recognition metric as a substitute for human judgments of speech quality
Authors: Watson C. S. , Kewley-Port D. , Maki D. , Reed D.
Published: October 2005

The Indiana Speech Training Aid project (ISTRA) is evaluating the use of speaker-dependent speech recognition to provide speech-drill feed-back for deaf or misarticulating children. The ISTRA systems employ IBM PC's with Interstate Voice Products Vocalink SRB boards. The basic approach is to form templates from the child's best current productions. Feedback in drill sessions is then based on a goodness metric. That metric represents the “match” between 10-ms sampling of a new utterance and the corresponding information for the stored template. The goodness metric has been partially validated as a substitute for feedback judgments provided by a human teacher. In general, the method compares values of the goodness metric to actual ratings by a jury of listeners. For words spoken by either normal speakers who intentionally vary the quality of their pronounciations, or by hearing-impaired speakers, average inter-listener correlations for ratings of quality did not differ from the correlations between the goodness metric and the average listener's judgements. Test-retest reliability is, of course, much higher for computer than for the human listener. [Work supported by NSF.]
The feedback mechanism of supersonic edge and plate tones
Authors: Powell Alan
Published: October 2005

Intense tones are generated when supersonic (choked) “2-D” jets impinge on edges [Powell, Acoustica 3, 233–243 (1955)] or on normal flat plates [Krothapalli, AIAA J. 23, 1910–1915 (1985)] considered herein equivalent to a 180° edge. A feedback mechanism is now proposed: Puffing to alternating sides of the high-impedance midplane, the jet generates essentially monopole radiation into half-or quarter-space, respectively. The resultant sound pressure p′ at the nozzle changes the (quasistatic) efflux angle by p′/ρjcj (Mj2−1)1/2/Mj (Mj is the jet Math number), as for choked jet screech. The induced jet sinuosity is amplified by flow instability until interacting with edge or plate. The phase criterion of I yields the principal frequencies: f = c0h′ N + p(1 + M̄con−1), N= integer, where h′ is the nozzle to effective source distance, c0 is the ambient sound speed, M̄con is the averaged instability convection Math number, and p = 1/4. Limited experimental data yield p≅0.25, N≅7 for edge tones; for plate tones 2 < N < 5, and p = 0 (sometimes, but M̄con , values are uncertain!). Again following I, the gain criterion yields sound intensity and lateral jet displacements consistent with experiment.
Signal detection analyses of neonates' responsiveness to sound
Authors: Gray Lincoln
Published: October 2005

Receiver operating characteristics (ROC curves) were generated from momentary delays in the regular peeping of newborn chicks that occur in response to acoustic stimuli. Areas under these curves have been used to evaluate the effects of age, intensity, and habituation. In the present paper, such ROC curves are used to evaluate the effect of prestimulus behavioral state on poststimulus responsiveness. Neonates are known to cycle through periods of high and low activity, and undoubtedly through periods of increasing and decreasing attention to external stimuli. Signal-detection analyses can be used to break the circularity in the argument that “neonates are more responsive when alert,” and to help decrease the high variability in neonatal data. As expected, desirable prestimulus states are at moderate levels of activity; psychophysical performance is reduced during periods of high and low activity. Interestingly, the older subjects perform best when they are slightly more active than average, while the youngest subjects perform best when they are slightly less active than average. Similar analyses should be useful in other studies that depend on the changing rate of repetitive responses. [Work supported by NIH.]
Rapid computation of acoustic fields in three-dimensional ocean environments
Authors: Porter Michael B. , Kuperman W. A. , Ingenito F. , Piacsek Andrew A.
Published: October 2005

A wave-theory-based technique for the rapid computation of propagation loss over a wide geographical area with a complex three-dimensional environment has been developed. The method relies on an adiabatic normal mode approach that reduces the wave equation to a set of coupled equations in the depth variable z and the plan variables (x,y). The coupled equations are solved with a fast algorithm based on dividing the (x,y) domain into triangular patches. A unique feature of the technique, which greatly speeds the computation, is the precalculation of an impedance surface that replaces the oceanographically stable portion of the sound-speed profile and the geo-acoustic structure of the ocean bottom, both derived from archival information. Once the modes are calculated, new source/receiver configurations are easily treated since the modes do not need to be recalculated. Because of the precalculated nature of the algorithm, areas with complex topography or bottom structures require no additional running time over simpler environments. As an example, a deep water scenario containing both a seamount and an eddy is considered.
Influence of horizontal random bottom structure on acoustic intensity in a shallow ocean
Authors: Ashley C. E. , Jacobson M. J. , Siegmann W. L.
Published: October 2005

Effects of random bottom structure on acoustic intensity in isospeed shallow water are studied. The randomness is due to stochastic variations in the bottom density and sound speed in the horizontal direction beneath a plane water–bottom interface. Ray geometry, spreading loss, and bottom loss and phase shift are examined in order to derive formulas for mean intensity and the variance of intensity. The expressions obtained are sufficiently general to permit their use with different bottom-acoustic models of sound reflection. In this paper, for illustrative and comparative purposes, two such models, one developed by Mackenzie and the other by Rayleigh, are considered. The distinctive acoustic consequences of bottoms of different density mean, variance, and horizontal correlation are discussed, as are comparisons of results for the two bottom-reflection models. Intensity moments are obtained also for differing source–receiver range and water depth.
Late-onset auditory deprivation: Effects of monaural versus binaural hearing aids
Authors: Silman Shlomo , Gelfand Stanley A. , Silverman Carol Ann
Published: October 2005

Performance on tests of pure-tone thresholds, speech-recognition thresholds, and speech-recognition scores for the two ears of each subject were evaluated in two groups of adults with bilateral hearing losses. One group was composed of individuals fitted with binaural hearing aids, and the other group included persons with monaural hearing aids. Performance prior to the use of hearing aids was compared to performance after 4–5 years of hearing aid use in order to determine whether the unaided ear would show effects of auditory deprivation. There were no differences over time for pure-tone thresholds or speech-recognition thresholds for both ears of both groups. Nevertheless, the results revealed that the speech-recognition difference scores of the binaurally fitted subjects remained stable over time whereas they increased for the monaurally fitted subjects. The findings reveal an auditory deprivation effect for the unfitted ears of the subjects with monaural hearing aids.
Nonlinear phenomena as observed in the ear canal and at the auditory nerve
Authors: Fahey P. F. , Allen J. B.
Published: October 2005

We report here several measures of nonlinear effects in the mammalian ear made in the external auditory meatus and in single neurons of the auditory nerve. We have measured the 2f1−f2 and the f2−f1 distortion products and we have found that (a) the neural distortion product threshold curve for 2f1−f2 mirrors the low-frequency side of the frequency threshold curve, (b) when the neural distortion product threshold curve of 2f1−f2 is plotted versus log(f2/f1) its slope is about 50 dB/oct and its intercept is 10–20 dB above the frequency threshold at the characteristic frequency CF, (c) substantial 2f1−f2 distortion was seen in all animals studied while the f2−f1 distortion product was only rarely found at substantial levels, and (d) the distortion product pressure observed in the ear canal was at a level equal to that detected at threshold by the neural units under study. We have also made measurements of two-tone rate suppression thresholds using two new and consistent threshold paradigms. We find that (a) for high and intermediate characteristic frequency neural units the suppression threshold is independent of frequency and at a level of about 70 dB SPL, (b) the suppression above CF is much less than below CF, and (c) the tip of the frequency tuning curve can be suppressed by up to 40 dB by a low-frequency suppressor.
Spectral sharpness and vowel dissimilarity
Authors: van Veen T. M. , Houtgast T.
Published: October 2005

The effect of sharpening or smoothing the spectral envelopes of synthetic vowellike sounds on the dissimilarities perceived among these sounds was investigated by means of triadic comparisons. When a spectral envelope (dB on a log-frequency scale) is considered the sum of a series of sinusoidal spectral modulations (or ripples) of different densities (the ripple spectrum), spectral sharpening or smoothing can be described as an amplification or attenuation of a part of the original ripple spectrum. For a set of nine sounds comprising different degrees of spectral sharpening of a single vowel, the perceived dissimilarities were found to be dominated by a specific part of the ripple spectrum, i.e., by spectral modulations with a density of about 2 ripples/oct. The possible role of lateral suppression in relation to this dominant region is discussed. For a set of 18 sounds comprising six vowels, each in three different versions (sharpened, normal, or smoothed), the dissimilarities were found to be determined mainly by the global shape of the spectral envelopes, i.e., by spectral modulations up to about 1.5–2 ripples/oct. Details of the spectral envelope (including the region of 2 ripples/oct where lateral suppression is effective) appear to be of minor influence on vowel dissimilarities.
A fast field model for three-dimensional wave propagation in stratified environments based on the global matrix method
Authors: Schmidt H. , Glattetre J.
Published: October 2005

A three-dimensional fast field program (FFP) model based on the global matrix method will be presented. Compared to traditional propagator matrix methods, the global matrix method allows for a more efficient, and, furthermore, numerically stable computation. The three-dimensional expansion does not restrict sources to be on the center axis, but allows for an arbitrary source geometry—as opposed to earlier two-dimensional versions. As a consequence, the solution includes simultaneously both vertically and horizontally polarized shear waves. A mathematical description will be given and the numerical aspects will be discussed. Some of the features of the model will be illustrated in two test cases: free-space and shallow water with strongly reflecting bottom. The free-space case shows that the three-dimensional solution gives results identical to those obtained by the two-dimensional model except for ranges close to the axis r≡0 of a cylindrical coordinate system. For the shallow water case, the well-known energy transportation in discrete modes above critical wavenumber is first demonstrated. Then the model is used to analyze the field radiated by a long horizontal array, and it is shown that different modes will propagate in slightly different directions.
A temporal analysis of auditory-nerve fiber responses to spoken stop consonant–vowel syllables
Authors: Carney Laurel H. , Geisler C. Daniel
Published: October 2005

Auditory-nerve fiber spike trains were recorded in response to spoken English stop consonant–vowel syllables, both voiced (/b,d,g/) and unvoiced (/p,t,k/), in the initial position of syllables with the vowels /i,a,u/. Temporal properties of the neural responses and stimulus spectra are displayed in a spectrographic format. The responses were categorized in terms of the fibers’ characteristic frequencies (CF) and spontaneous rates (SR). High-CF, high-SR fibers generally synchronize to formants throughout the syllables. High-CF, low/medium-SR fibers may also synchronize to formants; however, during the voicing, there may be sufficient low-frequency energy present to suppress a fiber’s synchronized response to a formant near its CF. Low-CF fibers, from both SR groups, synchronize to energy associated with voicing. Several proposed acoustic correlates to perceptual features of stop consonant–vowel syllables, including the initial spectrum, formant transitions, and voice-onset time, are represented in the temporal properties of auditory-nerve fiber responses. Nonlinear suppression affects the temporal features of the responses, particularly those of low/medium-spontaneous-rate fibers.
Response to ‘‘Comments on ‘Sound diffraction for a spherical microphone’ ’’  [J. Acoust. Soc. Am. 7
8, 266–267(1985)]
Authors: Peterson Arnold P. G.
Published: October 2005

Dr. Cooper’s confirmation of essential features of Table II in ‘‘Sound diffraction for a spherical microphone’’ [A. P. G. Peterson, J. Acoust. Soc. Am. 78, 266–267 (1985)] is appreciated. [AIP]
Upslope sound propagation through the bottom of a wedge-shaped ocean beyond cutoff
Authors: Miller John F. , Nagl Anton , Überall Herbert
Published: October 2005

Previous studies of the propagation of sound through an ocean wedge with a penetrable bottom [beginning with F. B. Jensen and W. A. Kuperman, J. Acoust. Soc. Am. 67, 1564–1566 (1980)] have been restricted to the case of an isovelocity fluid wedge and bottom. Consequently, for upslope propagation through the wedge, where all modes successively cut off down to the last one, the sound energy refracts into the bottom at each mode cutoff point, travels downward, and gets lost in the depths. In contrast, it is shown here that if (as is often the case) the sediment possesses a positive sound-speed gradient, the sound refracted into the bottom beyond its mode cutoff in the water wedge may continue traveling upslope in the sediment below the water, hence carrying ocean-originated acoustic information closer to shore where it may be registered by bottom-mounted receivers.
Free vibration of axisymmetrical solid bodies with meridionally varying profile
Authors: Irie Toshihiro , Yamada Gen , Okada Ichiro
Published: October 2005

An analysis is presented for the three-dimensional vibration problem of determining the natural frequencies and the mode shapes of axisymmetrical solid bodies, with meridionally varying profiles, expressed as an arbitrary function. For this purpose, the body is transformed into a circular cylinder with unit axial length and unit radius, by a transformation of variables. With the displacements of the transformed cylinder assumed in the forms of algebraic polynomials, the dynamical energies of the cylinder are evaluated, and the frequency equation is derived by the Ritz method. This method is applied to barrel or hourglass-type bodies and frustums of cone, under two combinations of boundary conditions at the ends, and the natural frequencies and the mode shapes are calculated, numerically giving the results.
The effect of across-frequency differences in masking level on spectro–temporal pattern analysis
Authors: Hall Joseph W.
Published: October 2005

Masking noise well separated in frequency from the signal may improve the detectability of the signal if the masking noise is modulated. This effect is referred to as co-modulation masking release (CMR). The present experiments examine the effect of across-frequency differences in masking noise level on CMR. Three experiments were performed, each using a different method to create modulated noise stimuli having across-frequency differences in the spectrum level. All stimulation was monaural. Experiment I used a notched noise method (selectively reducing the level for the critical band centered on the signal). Experiment II used a method in which the level of a 100-Hz-wide masker centered on the signal was varied, and flanking noise bands were of constant level. Experiment III used a method in which flanking noise bands were varied in level, and the 100-Hz-wide masker centered on the signal was of constant level. The signal was a 1000-Hz, 300-ms pure tone. The CMR effect was negated by small spectral notches centered on the signal (experiment I). However, CMR proved to be relatively robust to across-frequency level differences in experiments II and III (a CMR effect occurred for across-frequency differences in spectrum level as great as 20 dB). Low CMR’s obtained in experiment I were probably due to relatively poor correlation of across-frequency modulation pattern which occurred with notched noise. The results of experiments II and III suggest that the fluctuation pattern is of primary importance in providing release from masking, and that information on absolute levels, coded across frequency, is of less importance.
Transverse vibrations of rectangular plates continuous in two directions
Authors: Laura P. A. A. , Ercoli L. , Cortinez V. H. , Padín de Iriso Z.
Published: October 2005

The present paper deals with the determination of the fundamental frequency of vibration of continuous plates by means of the Rayleigh–Schmidt technique. The use of simple polynomial coordinate functions allows for the determination of accurate engineering results. The entire algorithmic procedure can be handled very efficiently using a desk computer.
Acoustic mode propagation in a range-dependent ocean
Authors: Desaubies Yves , Chiu Ching-Sang , Miller James H.
Published: October 2005

Analytical approximate solutions to the Helmholtz’s equation are obtained for acoustic mode propagation in a slowly varying ocean waveguide. Specific calculations are displayed for the particular case of propagation through mesoscale eddies in the western North Atlantic. An asymptotic expansion of the solution to the coupled equations governing the range variations of the modal amplitudes gives explicit expressions for the correction terms to the adiabatic approximation, which is discussed in detail. The validity of the adiabatic and asymptotic approximations is found to depend strongly on acoustic frequency, mode number, and propagation range. It is also found to depend on the particular acoustic quantity considered, such as magnitude, phase, and travel time.
A special integral equation formulation for acoustic radiation and scattering for axisymmetric bodies and boundary conditions
Authors: Seybert A. F. , Soenarko B. , Rizzo F. J. , Shippy D. J.
Published: October 2005

This paper presents a simplified model of the Helmholtz integral equation for bodies with axisymmetric shape and boundary conditions. By taking advantage of a body’s axisymmetric properties, the surface integral is reduced to a line integral along the generator of the body and an integral over the angle of revolution. The integration over the angle is performed partly analytically in terms of elliptic integrals and partly numerically using a Gaussian quadrature formula. The analytical formulation leading to elliptic integrals deals directly with the singularities in the Green’s function and its normal derivative. Examples are shown for scattering from a single sphere and two spheres and radiation from a finite cylinder. The results are compared with analytical, approximate, and other accepted solutions.
Optimization of the Kohn–Kato enclosure theorem: Application to vibrations problems
Authors: Laura Patricio A. A. , Cortínez Victor H.
Published: October 2005

Finding close upper and lower bounds to eigenvalues in vibrations and elastic stability problems constitutes a highly desired situation for the applied mathematician or research engineer since their knowledge allows for a clear evaluation of the error involved when determining natural frequencies or buckling loads. Among the methods which allow for the determination of upper and lower bounds one must certainly cite the Kohn–Kato bounding technique. The present paper deals with a simple yet quite substantial optimization of the original approach by Kohn and Kato. It is shown that by inclusion of an exponential undetermined parameter in the coordinate function it is possible to minimize the upper bound and maximize the lower bound, improving considerably the ‘‘closeness’’ of the bounds, especially in the case of higher eigenvalues.
Angular dependence of ultrasonic wave propagation in a stressed, orthorhombic continuum: Theory and application to the measurement of stress and texture
Authors: Thompson R. Bruce , Lee S. S. , Smith J. F.
Published: October 2005

A theory for ultrasonic wave propagation in a symmetry plane of a biaxially stressed, orthorhombic continuum is presented. Since many of the material parameters which appear in the analysis are unknown, in particular the third-order elastic constants of polycrystalline metals, emphasis is placed on the angular dependence of the velocities. An expansion to first order in stress-induced anisotropy and to second order in textural anisotropy reveals terms with twofold, fourfold, and sixfold symmetry. Scenarios are proposed for using various properties of this symmetry to deduce the difference in magnitude and directions of the principal stresses independent of textural anisotropy and the textural anisotropy independent of the stresses. Experimental results are presented for the cases of aluminum, 304 stainless steel, and copper.
Spike-rate intensity functions of cat cortical neurons studied with combined tone-noise stimuli
Authors: Phillips D. P. , Hall S. E.
Published: October 2005

In the auditory cortex of anesthetized cats, single neurons were studied for their sensitivity to tones presented against backgrounds of continuous wide-spectrum noise. Tone pulses and noise stimuli were mixed acoustically and presented using calibrated, sealed stimulating systems. Data collected were spike-rate intensity functions for tones delivered alone and in the presence of noise. In most neurons, noise of any given intensity induced tone sensitivity shifts that were greatest for frequencies to which the neurons were most sensitive. When the sensitivity loss was in excess of about 15 dB, continuous noise usually caused a steepening of the slope of the tone intensity function. These data suggest that the excitatory response area of a cortical neuron is shaped by multiple, incompletely overlapping inputs of varying sensitivities. In the presence of a continuous noise mask, the disparate thresholds of these inputs may be brought into closer register, resulting in a steepened rate intensity function. These observations may be germane to the neural genesis of the ‘‘recruitment’’ seen in the loudness judgments of normal listeners for masked tones.
The decoupling of stepwise coupled modes
Authors: Evans Richard B.
Published: October 2005

A decoupling algorithm is applied to the calculation of stepwise coupled modes. The stepwise coupled mode method solves the reduced wave equation in a discretely range-dependent environment. The solution contains both forward and backscattered energy and hence involves waves that decay and grow with range. Numerical difficulties can arise in trying to resolve both rapidly growing and decaying waves over many wavelengths. The decoupling algorithm described here solves the numerical problem and extends the applicability of the stepwise coupled mode method.
Anomalous polarization of elastic waves in transversely isotropic media
Authors: Helbig Klaus , Schoenberg Michael
Published: October 2005

The orientation of the displacement vector U of a plane wave in a homogeneous anisotropic elastic medium is the polarization of that plane wave. For transversely isotropic media, U of the fastest plane wave propagating in a given direction need not be in or near the direction of propagation, i.e., the direction of the slowness vector s. Moreover, with the x3 axis the transverse axis of the medium, when c13+c44<0, there are directions of propagation for which U can be perpendicular to s which means that the first arrival in that direction is a purely transverse wave. The two plane waves whose displacement vectors lie in the plane of the direction of propagation and the x3 axis—the faster usually called ‘‘quasi-P’’ and the slower usually called ‘‘quasi-SV’’—have mutually orthogonal displacement vectors. The polarization of these waves as a function of propagation direction depends strongly on the sign of c13+c44 whereas the magnitudes of the slowness vectors, which give the shape of the slowness surface, do not. In the x3 direction and perpendicular to the x3 direction the waves are purely longitudinal and purely transverse. When c13+c44 is positive, which is the usual case, the particle displacement vectors rotate in the same sense as the slowness vector. When c13+c44 is negative, which is the ‘‘anomalous’’ case, the sense of rotation of the particle displacement vector is opposite to that of the slowness vector and there always exists a direction of propagation in the medium for which U of the fast (or inner or quasi-P) sheet of the slowness surface is perpendicular to that direction and U of the slow (or outer or quasi-SV) sheet is parallel to that direction. The stability conditions on the transversely isotropic moduli even admit media that are (almost) kinematically isotropic, i.e., characterized by spherical wave fronts emanating from point sources, but which are characterized by anomalous polarization.

A layered medium can be equivalent, in the long-wavelength limit, to an anomalous transversely isotropic medium. For a layered medium composed of two alternating constituent substrates, this can occur when the larger volume fraction constituent has a negative Poisson’s ratio, the smaller volume fraction constituent has a positive Poisson’s ratio, and the ratio of the shear modulus of the negative Poisson’s ratio constituent to the shear modulus of the positive Poisson’s ratio constituent is very large.
Difference limens for fundamental frequency contours in sentences
Authors: Harris M. S. , Umeda N.
Published: October 2005

Difference limens (DLs) for fundamental frequency (F0) of naturally spoken sentences were studied. The experiments can be classified into two major categories. In the first category the fundamental frequency of a portion of sentences of 2 to 3 s in duration was manipulated. The second set of experiments used very short sentences (‘‘The subject verb’’) in which the F0 of the entire sentence was manipulated. Across experiments, sentences of comparable length yielded similar DLs, except when the F0 was abruptly shifted within a continuous voicing period. However, the DLs did vary significantly as a function of stimulus complexity and speaker. The range of DLs obtained in this series of experiments was between 10 and 50 times greater than that found with sustained synthetic vowels.
Transient masking and the temporal course of simultaneous tone-on-tone masking
Authors: Bacon Sid P. , Moore Brian C. J.
Published: October 2005

Previous studies have shown that threshold for a signal in tone-on-tone simultaneous masking is sometimes lower when the masker is continuous than when it is gated. Threshold may also decline as signal onset is delayed relative to the onset of a longer duration masker, though it may increase again near masker offset. In the present study, the level of a 1250-Hz sinusoidal masker was found which would just mask a 20-ms, 1000-Hz sinusoid presented at 10-dB sensation level (SL). Masker duration was 20 or 400 ms; in the latter case, the signal was presented in one of three temporal positions within the masker. The level of the 1250-Hz masker necessary to mask the signal was reduced, sometimes by as much as 20–25 dB, by a 20-ms, 500-Hz sinusoid (transient masker) presented at the times when the signal might occur, but at a level 30 dB below that at which it would mask the 10-dB SL signal. This suggests that, in the earlier studies, at least some of the elevation in threshold in the presence of a short-duration masker or at the beginning (or end) of a longer duration masker may have been due to the transient responses to the masker affecting detection of the signal, but not necessarily masking the signal in terms of excitation in the signal ‘‘channel.’’
Serotype-Specific Detection of Dengue Viruses in a Fourplex Real-Time Reverse Transcriptase PCR Assay
Authors: Johnson Barbara W. , Russell Brandy J. , Lanciotti Robert S.
Published: October 2005

The dengue (DEN) viruses are positive-strand RNA viruses in the genus
Flavivirus
. Dengue fever and dengue hemorrhagic fever/dengue shock syndrome are important human arboviral diseases caused by infection with one of four closely related but serologically distinct DEN viruses, designated DEN-1, DEN-2, DEN-3, and DEN-4 viruses. All four DEN serotypes are currently cocirculating throughout the subtropics and tropics, and genotypic variation occurs among isolates within a serotype. A real-time quantitative nucleic acid amplification assay has been developed to detect viral RNA of a single DEN virus serotype. Each primer-probe set is DEN serotype specific, yet detects all genotypes in a panel of 7 to 10 representative isolates of a serotype. In single reactions and in fourplex reactions (containing four primer-probe sets in a single reaction mixture), standard dilutions of virus equivalent to 0.002 PFU of DEN-2, DEN-3, and DEN-4 viruses were detected; the limit of detection of DEN-1 virus was 0.5 equivalent PFU. Singleplex and fourplex reactions were evaluated in a panel of 40 viremic serum specimens with 10 specimens per serotype, containing 0.002 to 6,000 equivalent PFU/reaction (0.4 to 1.2 × 10
6
PFU/ml). Viral RNA was detected in all viremic serum specimens in singleplex and fourplex reactions. Thus, this serotype-specific, fourplex real-time reverse transcriptase PCR nucleic acid detection assay can be used as a method for differential diagnosis of a specific DEN serotype in viremic dengue patients and as a tool for rapid identification and serotyping of DEN virus isolates.
Variability of
Clostridium difficile
Surface Proteins and Specific Serum Antibody Response in Patients with
Clostridium difficile
-Associated Disease
Authors: Péchiné Séverine , Janoir Claire , Collignon Anne
Published: October 2005

Pathogen attachment is a crucial early step in mucosal infections. This step is mediated by important virulence factors, such as surface proteins.
Clostridium difficile
surface proteins have been identified as (i) adhesins (the flagellar cap protein FliD; the flagellin FliC; and the cell wall protein Cwp66 with a two domain-structure [Cw66 N-terminal and Cwp66 C-terminal domains]) and (ii) protease (the Cwp84 protein). To address the roles of these proteins in the pathogenesis of
Clostridium difficile
and to identify vaccine antigen candidates, we analyzed the variability of the proteins and their immunogenicities in 17 patients with
C. difficile
-associated disease. PCR-restriction fragment length polymorphism analysis of amplified gene products revealed interstrain homogeneity with
fliC
and
fliD
, in contrast to
cwp66
genes. Immunoblot analysis showed that FliC and FliD were detected in the majority of isolates. The N-terminal domain of Cwp66 and Cwp84 were present in all strains tested, in contrast to the Cwp66 C-terminal domain, the expression of which was heterogeneous. The 17 sera from the corresponding patients were analyzed by enzyme-linked immunosorbent assay to detect antibodies directed against these proteins. Many patients developed antibodies to FliC, FliD, Cwp84, and the Cwp66 C-terminal domain, but not to the Cwp66 N-terminal domain. In conclusion, this study confirms the expression of these surface proteins of
C. difficile
during the course of the disease. In addition, the FliC, FliD, and Cwp84 proteins appeared to be good potential vaccine candidates.
Polymorphism of Variable-Number Tandem Repeats at Multiple Loci inMycobacterium tuberculosis
Authors: Smittipat Nat , Billamas Pamaree , Palittapongarnpim Manee , Thong-On Arunee , Temu Mansuet M. , Thanakijcharoen Prateep , Karnkawinpong Opart , Palittapongarnpim Prasit
Published: October 2005

Genotyping based on variable-number tandem repeats (VNTR) is currently a very promising tool for studying the molecular epidemiology and phylogeny ofMycobacterium tuberculosis. Here we investigate the polymorphisms of 48 loci of direct or tandem repeats inM. tuberculosispreviously identified by our group. Thirty-nine loci, including nine novel ones, were polymorphic. Ten VNTR loci had high allelic diversity (Nei's diversity indices ≥ 0.6) and subsequently were used as the representative VNTR typing set for comparison to IS6110-based restriction fragment length polymorphism (RFLP) typing. The 10-locus VNTR set, potentially providing >2 × 109allele combinations, obviously showed discriminating capacity over the IS6110RFLP method forM. tuberculosisisolates with fewer than six IS6110-hybridized bands, whereas it had a slightly better resolution than IS6110RFLP for the isolates having more than five IS6110-hybridized bands. Allelic diversity of many VNTR loci varied in each IS6110RFLP type. Genetic relationships inferred from the 10-VNTR set supported the notion thatM. tuberculosismay have evolved from two different lineages (high and low IS6110copy number). In addition, we found that the lengths of many VNTR loci had statistically significant relationships to each other. These relationships could cause a restriction of the VNTR typing discriminating capability to some extent. Our results suggest that VNTR-PCR typing is practically useful for application to molecular epidemiological and phylogenetic studies ofM. tuberculosis. The discriminating power of the VNTR typing system can still be enhanced by the supplementation of more VNTR loci.
SHV-Type Extended-Spectrum Beta-Lactamase Production Is Associated with Reduced Cefepime Susceptibility in
Enterobacter cloacae
Authors: Szabó Dóra , Bonomo Robert A. , Silveira Fernanda , Pasculle A. William , Baxter Carla , Linden Peter K. , Hujer Andrea M. , Hujer Kristine M. , Deeley Kathleen , Paterson David L.
Published: October 2005

Cefepime is a potentially useful antibiotic for treatment of infections with
Enterobacter cloacae
. However, in our institution the MIC
90
for
E. cloacae
bloodstream isolates is 16 μg/ml. PCR amplification of
bla
genes revealed that one-third (15/45) of
E. cloacae
bloodstream isolates produced SHV-type extended-spectrum beta-lactamases (ESBLs) in addition to hyperproduction of AmpC-type beta-lactamases. The majority (11/15) of ESBL producers also produced the TEM-1 beta-lactamase. The SHV types included SHV-2, -5, -7, -12, -14, and -30. All but two of the ESBL-producing
E. cloacae
isolates, but none of the non-ESBL-producing strains, had MICs of cefepime of ≥2 μg/ml. The MIC
90
for cefepime for ESBL-producing strains was 64 μg/ml, while for non-ESBL producers it was 0.5 μg/ml. Using current Clinical and Laboratory Standards Institute breakpoints for cefepime, two thirds (10/15) of ESBL-producing isolates would have been regarded as susceptible to cefepime. Phenotypic ESBL detection methods were generally unreliable with these
E. cloacae
isolates. Based on these results, pharmacokinetic, pharmacodynamic, and clinical reevaluation of cefepime breakpoints for
E. cloacae
may be prudent.
Contemporary Methicillin-Resistant
Staphylococcus aureus
Clones in Hong Kong
Authors: Ip Margaret , Yung R. W. H. , Ng T. K. , Luk W. K. , Tse Cindy , Hung Philip , Enright Mark , Lyon Donald J.
Published: October 2005

Two hundred nonduplicate methicillin-resistant
Staphylococcus aureus
(MRSA) isolates causing bacteremia in patients in four major Hong Kong hospitals during the period 2000 to 2001 were characterized by antibiogram, pulsed-field gel electrophoresis (PFGE) using SmaI restriction enzymes, and determination of staphylococcal cassette chromosome
mec
(SCC
mec
) types. Nine PFGE types, A to I, were obtained. PFGE type A constituted 50% (99/200) of all isolates and was present in isolates from all four hospitals. PFGE types A to E, had previously been identified as the major types at one of the hospitals from 1988 to 2000. The majority had a resistance profile to tetracycline (T), erythromycin (E), clindamycin (D), gentamicin (G), tobramycin (To), and ciprofloxacin (Ci), and belonged to SCC
mec
type III; and representatives belonged to clonal complex 239 (CC239) (MRSA with SCC
mec
type III and sequence type 239, designated ST239-MRSA-III). PFGE types F to I were new patterns that had not been previously identified in isolates from Hong Kong. PFGE type F constituted 18% (35/200) of MRSAs, had resistance profile TEGToCi, and belonged to CC5 (ST5-MRSA-II). PFGE type G included 13% (26/200) of MRSAs, had resistance profile TECi, and belonged to CC45 with SCC
mec
type I or II. PFGE type H had characteristics similar to those of CC239, while PFGE type I included three isolates, two of which expressed resistance to oxacillin and fusidic acid only. Two of these strains had SCC
mec
IVa and carried sequence type 389, with a multilocus sequence typing allelic profile of 3-35-19-2-20-26-39. Contemporary MRSAs causing bacteremia in Hong Kong hospitals belong to three clonal complexes (CC5, CC45, and CC239). The most prevalent MRSA clone in Hong Kong belongs to CC239, with PFGE types A to E and H, SCC
mec
type III, ST239, and a resistance profile of TEDGToCi.
Characterization of Isolates of
Salmonella enterica
Serovar Typhimurium Displaying High-Level Fluoroquinolone Resistance in Japan
Authors: Izumiya Hidemasa , Mori Kadumi , Kurazono Takayuki , Yamaguchi Masanori , Higashide Masato , Konishi Noriko , Kai Akemi , Morita Koji , Terajima Jun , Watanabe Haruo
Published: October 2005

Strains of the multidrug-resistant (MDR)
Salmonella enterica
serovar Typhimurium isolated in Japan were examined for high-level fluoroquinolone resistance. Since the first isolation in 2000 (described in reference 13), we have identified 12 human and 5 nonhuman isolates with high-level fluoroquinolone-resistance (ciprofloxacin MIC of 24 μg/ml or more). Most of these isolates shared some features including definitive phage type (DT12/193), resistance type (ACSSuTNCp; resistant to ampicillin, chloramphenicol, streptomycin, sulfonamides, tetracycline, nalidixic acid, and ciprofloxacin), and genotype on pulsed-field gel electrophoresis that were different from those of the MDR
S. enterica
Typhimurium DT104. Mutations in quinolone resistance-determining regions of
gyrA
and
parC
were also conserved in almost all of the isolates despite the absence of any apparent epidemiological relationships among cases. This suggests that a specific clonal group of the serovar Typhimurium with high levels of fluoroquinolone resistance is disseminating among animals and humans in Japan.
Two-Year Evaluation of
Borrelia burgdorferi
Culture and Supplemental Tests for Definitive Diagnosis of Lyme Disease
Authors: Coulter Peggy , Lema Clara , Flayhart Diane , Linhardt Amy S. , Aucott John N. , Auwaerter Paul G. , Dumler J. Stephen
Published: October 2005

Lyme disease is usually diagnosed and treated based on clinical manifestations. However, laboratory testing is useful for patients with confusing presentations and for validation of disease in clinical studies. Although cultivation of
Borrelia burgdorferi
is definitive, prior investigations have shown that no single test is optimal for Lyme disease diagnosis. We applied high-volume blood culture, skin biopsy culture, PCR, and serodiagnosis to a cohort of patients with suspected Lyme disease acquired in Maryland and southern Pennsylvania. The study was performed to confirm the relative utility of culture and to identify laboratory testing algorithms that will supplement clinical diagnosis. Overall, 30 of 86 patients (35%) were culture positive, whereas an additional 15 of 84 (18%) were seropositive only (51% total sero- and culture positive), and PCR on skin biopsy identified 4 additional patients who were neither culture nor seropositive. Among 49 laboratory test-positive patients, the highest sensitivity (100%) for diagnosis was obtained when culture, skin PCR, and serologic tests were used, although serologic testing with skin PCR was almost as sensitive (92%). Plasma PCR was infrequently positive and provided no additional diagnostic value. Although culture is definitive and has a relatively high sensitivity, the results required a mean of 3.5 weeks to recovery. The combination of acute-phase serology and skin PCR was 75% sensitive, offering a practical and relatively rapid alternative for confirming clinical impression. The full battery of tests could be useful for patients with confusing clinical signs or for providing strong laboratory support for clinical studies of Lyme disease.
Delineation of
Campylobacter concisus
Genomospecies by Amplified Fragment Length Polymorphism Analysis and Correlation of Results with Clinical Data
Authors: Aabenhus Rune , On Stephen L. W. , Siemer Berit L. , Permin Henrik , Andersen Leif P.
Published: October 2005

Campylobacter concisus
has been as frequently isolated from human diarrhea as the important enteropathogen
Campylobacter jejuni
, but it also occurs in the feces of healthy individuals. The role of
C. concisus
in human disease has been difficult to determine, since the species comprises at least two phenotypically indistinguishable but genetically distinct taxa (i.e., genomospecies) that may vary in pathogenicity. We examined 62
C. concisus
strains by amplified fragment length polymorphism (AFLP) profiling and correlated the results with clinical data. All
C. concisus
strains gave unique AFLP profiles, and numerical analysis of these data distributed the strains among four clusters. The clustering was of taxonomic significance: two clusters contained, respectively, the type strain (of oral origin) and a reference strain (from diarrhea) of each of the known genomospecies. Genomospecies 2 strains were more frequently isolated from immunocompetent patients and/or patients without concomitant infections that presented with fever, chronic diarrhea, and gut inflammation than was genomospecies 1, clustering with the type strain of oral origin. Bloody diarrhea was recorded only with
C. concisus
genomospecies 2 infections. We identified two additional
C. concisus
genomospecies: genomospecies 3 comprised a single strain from an immunocompetent patient, and genomospecies 4 contained five isolates from severely immunodeficient patients, i.e., organ transplantation recipients or those with hematological malignancies. All genomospecies 4 strains were of the same protein profile group and failed to react with a
C. concisus
species-specific PCR assay based on 23S rRNA gene sequences: the taxonomic position of this group requires closer investigation.
Campylobacter concisus
is genetically and taxonomically diverse and contains at least four distinct genomospecies that may exhibit differences in their spectra of virulence potential.