bluuebunny/crossref_metadata_2025 huggingface dataset:
Threshold limit value for exposure of the hand to vibration
Authors: Braimmer A. J.
Published: October 2005

Habitual exposure of the hand to vibration frequently leads to tingling and numbness followed by episodes of finger blanching, with reduction in manual dexterity and tactile sensitivity, and damage to soft tissue and joints in severe cases. The dose-effect relations reported elsewhere for the development of vibration-induced white finger [A. J. Brammer, in Vibration Effects an the Hand and Arm in Industry, edited by A. J. Brammer and W. Taylor (Wiley, New York, 1982), pp. 283–290] have been extended to low vibration levels and prevalences of symptoms, in order to predict the acceleration at which the duration of exposure prior to the onset of finger blanching just exceeds a working lifetime. The vibration threshold so obtained is compared with those derived from other epidemiological studies of working populations, and laboratory measures of human response to vibration. The comparison suggests that the threshold limit value for exposure of the hand to vibration throughout the workday is in the range of 1 < ak < 2 m/s2, where ak is a frequency-weighted, rms, component acceleration specified according to ISO/DIS 5349, 1979.
Diffraction tomography
Authors: Mueller R. K. , Kaveh M.
Published: October 2005

Diffraction tomography is basically the inversion of an inhomogeneous Helmholtz equation, that is, the “reconstruction” of the inhomogeneity from observed field data. The underlying Helmholtz equation is an approximation (Born or Rytov's} to a general wave equation which describes sound propagation in viscoelastic media. The rather complex relationship of the inhomogeneity to the viscoelastic parameters of the object of interest is briefly described together with the nature of the approximation errors for Born and Rytov. The basic principles of data acquisition and image reconstruction as they apply to diffraction tomography are discussed for two cases of object insonification: plane wave and fan beam. Finally we examine the relative merits of frequency and spatial domain reconstructions with respect to computational efficiency and accuracy of interpolation. Several simulation and experimental examples are presented to show the effectiveness of this approach in practice. [Work supported by NSF Grant ECS-7926008.]
The analysis and testing of blade platform friction dampers used in the high pressure fuel turbopump [HPFTP] of the space shuttle main engine [SSME]
Authors: Dominic Robert J.
Published: October 2005

Premature cracking of the first stage turbine blades in the HPFTP of the SSME have caused greater than expected repair costs. It is expected that the operational life of these blades can be extended by redesigning the platform friction dampers that are used to reduce the vibration response of the blades. Vibratory excitation of the resonance modes of the blades is induced by their passage through the wakes of the front bearing support struts and the first stage nozzles of the turbopump. Analytical studies, by the lumped mass method, of friction damper effectiveness, and spin pit tests of a bladed disk have been performed. Test blades were instrumented with strain gauges and were excited magnetically. Methodologies used in the program are described. Preliminary results show that the effectiveness of the blade platform dampers can be increased if the frequency and amplitude of the most damping forcing functions (s) can be defined. [Work sponsored by Marshall Space Flight Center of NASA.]
The effect of absorptive side walls on the propagation from a line source inside a slot
Authors: Lee B. H. , Lim B. D.
Published: October 2005

The effect of absorptive side walls of a slotted geometry on the sound propagation from a line source inside the slot is investigated analytically. The problem is modeled as a rectangular waveguide with a reflective baffle whose side walls have finite acoustic impedances. The source is located along the axis of the waveguide. The acoustic field inside the waveguide is represented by a series of mode functions with unknown coefficients and the field outside the waveguide is represented by an inverse cosine transform of an unknown function. The unknown coefficients and unknown function are determined from the boundary conditions inside the waveguide, radiation condition and the continuity of both pressure and normal velocity on the aperture plane. An infinite system of linear equations is truncated by a finite one and its error is evaluated using the edge conditions. Also a closed form representation of the transform function is given in an asymptotic form of an infinite integral. Limiting cases are compared with the earlier results by Howard [J. Math. Phys. 13, 482–490 (1972)] who treated the same geometry with perfectly reflective and absorptive walls.
Detection of pure tones in bandlimited modulated and unmodulated noise
Authors: Hall Joseph W. , Fernandes Mariano A. , Haggard Mark
Published: October 2005

Detection of 400-ms pure tones was examined in masking noise. Either wideband unmodulated noise or wideband noise multiplied (modulated) by a low-pass noise from 0–50 Hz was used as a masker. The unmodulated and modulated noises were bandlimited and pure tone thresholds were determined as a function of the bandwidth of the noise which was centered on the signal frequency. In unmodulated noise, threshold increased as the bandwidth was widened, and continued to increase up to the critical bandwidth (CB). In modulated noise, threshold decreased as the noise bandwidth was widened. Furthermore, threshold was affected by noise well outside the CB of the signal. The modulated noise results are discussed in terms of cues, well outside the CB of the signal, which are important in detecting signals in modulated noise.
Auditory detection of broadband sonar echoes from a sphere in white noise
Authors: Martin Douglas W. , Au Whitlow W. L.
Published: October 2005

Psychometric functions were obtained for two observers detecting broadband sonar echoes from a 7.62-cm-diam stainless steel water-filled sphere in white noise. The results were compared with dolphin results obtained by Au and Penner [J. Acoust. Soc. Am. 70, 687–693 (1981)]. A broadband dolphin-like signal with a peak frequency of 120 kHz was used in obtaining the echoes. The analog signals were digitized and stored on magnetic tape. Using a PDP-11/40 digital computer, the echoes were presented to subjects at 32 pulses per second for three different stretch-time expansion factors of 75, 50, and 25, resulting in echoes with peak frequencies of 1.6, 2.4, and 4.8 kHz. For each trial, the subject's task was to indicate whether a stimulus contained a signal plus noise or noise only. The 75% correct response thresholds for observer A occurred at S/N's of 5.4, 8.0, and 11.4 dB for stretch factors of 75, 50, and 25, respectively. For observer B, the threshold occurred at S/N's of 6.4 and 9.1 dB for stretch factors of 50 and 25, respectively. Threshold was not obtained for observer B at a stretch factor of 75. The subjects performed better than the dolphins at stretch factors of 75 and 50, and were comparable to the dolphins at a stretch factor of 25. The performance difference as a function of the stretch factor may be due to the critical bandwidth increasing more rapidly than the signal bandwidth as the frequency is increased. The effects of signal duration at the different stretch factors were also considered.
Interrelations among combination tones, combination bands, and suppression
Authors: Norton Susan J. , Weber Daniel L.
Published: October 2005

When two stimuli, S1 and S2, are presented simultaneously, both suppression and combination tone generation may occur. Both processes are thought to reflect cochlear nonlinearity, possibly the same nonlinearity. We compared the effects of narrowband noise and sinusoids in the operation of these processes by estimating the threshold for a 20-ms sinusoid forward masked by a fixed S1 and a variable level S2. S1 was a 50-dB SPL, 2.0-kHz sinusoid. S2 was either a 2.4-kHz sinusoid or a 50-Hz-wide, narrowband noise geometrically centered at 2.4 kHz. We examined the suppression of S1 by S2 by measuring the threshold for a 2.0-kHz signal (S1 frequency) masked by S1 alone and S1 plus S2. The amplitude of cubic difference tones or bands produced by S1 and S2 was estimated from the threshold for a 1.6-kHz signal (2S1-S2). Our data on the amount of suppression and the combination tone level as a function of S2 level show good agreement with earlier studies. However, the narrowhand noise S2 was a less effective suppressor than the sinusoid, whereas there were no significant differences in the levels of the combination tones and bands produced by these stimuli. This differential effect on combination tone generation versus two tone suppression indicates at least a partial disassociation of the mechanisms responsible for the two phenomena. [Research supported by grants from NIH and NSF.]
Temporal range of backward recognition masking as measured by an “endpoint” psychophysical method
Authors: Foyle David C. , Watson Charles S.
Published: October 2005

The temporal range of backward recognition masking (BRM) has been estimated to extend about 250 ms, based on experiments in which brief signals are identified with chance accuracy when followed immediately by a masking sound, but with 90%–100% accuracy when the masker is delayed by 250 ms [e.g., D. W. Massaro, J. Acoust. Soc. Am. 58, 1059–1065 (1975)]. Three normal listeners were tested in two variants of a single-interval BRM task. In the first half of this study, subjects were to identify as “high” or “low” a 20-ms tone (780 or 820 Hz), which was followed by an 800-Hz, 100-ms masking tone (a frequency discrimination task with a Δf of 40 Hz). Six intertone gaps (Δt's of 0 to 320 ms) were used. Typical BRM effects were found in the early stages of practice, but after approximately four hours of training, performance was near perfect for all Δt's. In the second variant, a tracking procedure using six interleaved tracks lone for each Δt) varied the values of Δf. Thresholds (Δf for d′ = 1.0) were found to decrease exponentially from 18 Hz at 0 ms to 8 Hz at 320 ms, with a time constant of 33 ms. This masking decay rate is much more rapid than those estimated in the early stages of training. [Work supported by NIH/NINCDS.]
Interrupted noise as a tinnitus masker
Authors: Thompson Virginia , Letowski Tomasz
Published: October 2005

One aspect of tinnitus reasearch deals with tinnitus masking and the phenomenon of residual inhibition. This paper compares residual inhibition time produced by 60 s of interrupted or continuous white noise masking. Six tinnitus subjects participated in the first part of the study. The masking signal was presented at 10 dB SL. Results indicate no significant difference in residual inhibition time resulting from 2, 10, 40 PPS or continuous white noise. In the second part of the study, annoyance levels for interrupted white noise with 2, 4, 10, 20, and 40 PPS and continuous white noise presented 20, 40, and 60 dB SL were compared. The same tinnitus subjects and six normal hearing subjects participated. Subjects adjusted the interrupted noise to be equally annoying as the continuous noise. Results indicate that the interrupted noise was more annoying for both groups. Results also show significant differences in the equal annoyance levels as a function of interruption rate for both groups. In conclusion, interrupted noise as a tinnitus masker does not seem to be promising. [Work supported by NIHR.]
Increment detection, intensity discrimination, and tone decay at high frequencies
Authors: Viemeister Neal F. , Bacon Sid P.
Published: October 2005

Continuous high-frequency tones decay to inaudibility several seconds after onset. We have studied this phenomenon in “normal-hearing” subjects by measuring the just-detectable intensity increment in a continuous 16-kHz tone and the just-detectable intensity difference between two 16-kHz, 200-ms tone pulses. Over the wide range of intensities examined, the continuous tone became inaudible and the nominal task of increment detection become absolute detection. The continuous tone did, however, elevate the threshold: at 100 dB, for example, the continuous tone raised the “detection” threshold by approximately 50 dB. More generally, the results are similar to those observed at lower frequencies: the Weber fraction (ΔI/I) was slightly lower for increment detection than for intensity discrimination and, in both eases, decreased slightly with increasing intensity. These data suggest that high-frequency tone decay results from an attenuative, rather than a subtractive, process and, in this respect, difffers fundamentally from the adaptation of primary fibers. [Supported by NINCDS NS12125.]
Discrimination of changes in random auditory profiles: Effects of frequency irregularities
Authors: Kidd Gerald , Green David M. , Mason Christine R.
Published: October 2005

Listeners discriminated between two multitone complexes that differed only in the intensity of a single fixed-frequency component (948 Hz). A two-interval forced-choice procedure was used with the level of the complex chosen randomly over a range of 40 dB for each interval of every trial. The frequencies of the remaining components of the 11-component complexes were randomly drawn from a pool of 200 tones equally spaced in logrithmic frequency from 300 to 3000 Hz. For a set of 20 random samples the thresholds for detecting an intensity increment to the 948-Hz component varied over a range of about 15 dB. The difference in detectability observed between the samples remained approximately constant over 1800 trials with the thresholds improving an average of about 10 dB from the first 300 trials to the last 300 trials of the experiment. [This research was supported by NIH.]
Effective interfacial conditions for elastic wave propagation in media separated by thin rough layers
Authors: Nayfeh Adnan H.
Published: October 2005

Effective approximate interfacial continuity conditions are derived for the propagation of elastic waves in two media that arc separated by periodically rough-surfaced layer. The specific model considered is restricted to the situation where both surfaces of the layer have identical one-dimensional periodicity which are in phase. This is motivated by the desire to obtain results for two rough half-spaces in full contact (i.e., in the absence of the layer). For small layer thickness and roughness, superimposed effects in the forms of jumps in stresses and displacements across the layer's surfaces are obtained. When examined in conjunction with existing solutions for smooth interfaces these new conditions are found to predict and explain the various effects produced by roughness. These include the predictions of scattering directions, ranges (in frequency of angles of incidence) of surface wave excitations and mode conversions. Results are found to compare favorably with existing experimental data. [Research supported by NSF Grant CME 8021054 and AF Contract F33615-80-C-5015.]
Acoustic diffraction from joined plates
Authors: Hayek Sabih I. , Seren Cetin
Published: October 2005

The solution for the acoustic diffraction from the joint made by joined elastic plates is obtained analytically. One plate is infinite in extent and is in contact with an acoustic medium and the other plate is either finite or semi-infinite in extent. The two plates are joined at right angles, where the joint can be represented as a rigid or an elastic weld. An incident plane wave is diffracted by the joint and the diffracted acoustic waves are evaluated analytically through the use of integral transforms and asymptotic methods. The farfield kR≫1 and the quasi-nearfield kR ∼ 1 are obtained by different asymptotic methods. The analytic solutions are then compared to experiments made on joined steel plates in the frequency range 10–100 kHz. The steel plates were insonified by a plane cw wave pulse of 0.1–0.3 msec duration and the diffracted acoustic pressure was measured at a distance of 2 m from the joint. [Work supported by NAVSEA.]
Fast field program for a layered medium bounded by complex impedance surfaces
Authors: Rasper Richard , Lee S. W. , Gilbert R. , Bong N. , Richards R. F. , Kuester E. F. , Chang D. C.
Published: October 2005

The accurate prediction of sound levels propagating through a layered atmosphere is important in many diverse applications. A powerful prediction method is the Fast Field Program (FFP), in which the Green's function integral in the spectral domain is numerically evaluated by the Fast Fourier Transform. However, existing FFP's require the lowest layer to be semi-infinite liquid or solid, which does not accurately model the effect of the earth's surface on sound propagation. Chessel's [J. Acoust. Soc. Am. 62, 825–834 (1977)] empirical model of the ground surface as a complex impedance plane has produced good agreement between experiment and prediction for homogeneous atmospheres. In this paper, we generalize the FFP by incorporating Chessell's boundary conditions. Thus, our program is capable of calculating the sound attenuation of a point source in a layered medium bounded by a complex impedance surface. In a simple test case (both the source and microphone are above a complex impedance surface in a homogeneous atmosphere), our FFP solution is in excellent agreement with Donato's asymptotic solution [J. Acoust. Soc. Am. 60, 34–39 (1976)].
Interaction between a fluid and a compliant surface with an inhomogeneous transition layer at the interface
Authors: Pierucci Mauro
Published: October 2005

In most applications, the flow of energy from one medium to another occurs at the interface. The interface is assumed to be an infinitesimal line which separates the properties of the two media; it is a line of discontinuity across which particle velocities (or displacements) and stresses are conserved. In this paper, it is assumed that the interface is replaced by a continuously changing inhomogeneous layer. The properties of this transition layer vary smoothly from those of the compliant surface on one side to those of the fluid on the other. The effect of this transition layer upon the fluid coating interaction due to a plane acoustic wave is presented. [Work sponsored by ONR.]
Compressional wave velocity measurements in alternating fluid-solid layer systems
Authors: Plona T. J. , Winkler K. W. , Schoenberg Michael
Published: October 2005

Ultrasonic velocity measurements have been made in systems consisting of alternating layers of water and solid. The two systems studied were water/Plexiglas and water/aluminum; all layers were 0.79 mm thick. Velocity measurements were made in these anisotropic systems in the 200–500-kHz band. In agreement with theoretically derived low-frequency slowness surfaces and group velocity surfaces there was one arrival normal to the layers, and two arrivals parallel to the layers. The fast parallel arrival was faster than the long wavelength extensional plate wave speed of the solid. The slower arrival was slower than the fluid speed. At non-normal directions a stopband in horizontal slowness (which is proportional to angle of incidence) was observed for which essentially no wave was transmitted through the system. This corresponds to angles of incidence larger than the critical angle for the fast wave yet smaller than the minimum angle of incidence at which the slow wave appears. At these values of horizontal slowness only evanescent waves are possible.
Propagation through the convective boundary layer
Authors: Roth S. David
Published: October 2005

The convective boundary layer (CBL) has been studied for many years by meteorologists. The CBL is when the atmosphere has become unstable due to solar heating and convective turbulence is present. The dynamics and structure of the CBL have only recently been of concern to acousticians. The acoustics community has studied propagation through the CBL only in the most general terms. How mean wind velocity and temperture profiles affect propagation is fairly well understood from ray trace studies. The effect of scatter due to small scale turbulence on propagating signals is understood as well [E. H. Brown and S. F. Clifford, J. Acoust. Soc. Am. 60, 788–794 (1976)]. However, larger scale cellular eddies known as “thermals” have not been considered by the acoustics community. Thermals play an important role in outdoor sound propagation within the CBL. They can cause variation in signals propagating over a 100-m path by about 30 dB. Theoretical and experimental results are presented showing the effect of thermals on acoustic propagation. [Work supported by USDA Forest Service through the Consortium for Environmental Forestry Studies.]
Dispersive propagation of grazing coherently scattered sound at a rough surface
Authors: D'Spain Gerald L. , Childs Emily H. , Medwin Herman
Published: October 2005

Our purpose has been to learn about sound scatter from the ocean bottom by using laboratory models. Previously we have reported measurements of the amplitude of the grazing coherent sound scatter from slightly rough surfaces; we have verified that the cylindrically diverging scattered (boundary) wave amplitude can surpass the spherically diverging direct wave amplitude from a point source. This is true for both deterministically and randomly rough surfaces. Now we compare the dispersive propagation velocity v of these waves over surfaces constructed of rigid spherical and hemispherical bosses, and of rigid corrugations of half-cylinders and wedges, with the free field speed c over the smooth surface. From Tolstoy [J. Acoust. Soc. Am. 72, 960–972 (1979)] one expects the dispersion to be (c − v)/c = 12ε2k2 with maximum value 0.1% at kh = 1 for close-packed rigid hemispherical bosses. There are similar expressions for other roughness elements, where ε is the scattering parameter which depends on the shapes, sizes, and spacing h of the scattering elements; k is the wavenumber. In fact, we find that: the power law dependence on k is a function of range and frequency; the dispersion is significantly larger than predicted at frequencies below kh = 1; and the dispersion follows a k2 or higher power dependence to frequencies far beyond the expected cutoff at kh = 1. Values of dispersion from 0.1% to 10% have been measured. Dispersion measurements are a sensitive tool for the determination of the effective scattering parameter ε to which the boundary wave amplitude is proportional. [Research supported by the Office of Naval Research.]
Reflection losses of underwater sound from a rough sea surface
Authors: Roderick William I.
Published: October 2005

Low grazing angle acoustic reflection losses were measured from the sea surface over the frequency range 10–30 kHz. A parametric array projected a narrow beam of underwater acoustic energy at the sea surface and the reflected signals were received in the specular direction. Oceanographic data, in terms of the sea surface time-varying wave height, were measured simultaneously with the acoustic data. Physical optics methods, with the familar Kirchhoff boundary condition, Fresnel phase, and consistent slope approximations were used to model the reflection losses and power spectral (Doppler) characteristics. Ocean wave spectra wave-height statistics were computed from the measured time-varying wave height. Under the environmental conditions encountered in the experiment, the reflection losses were confined between 2 to 12 dB.
High-frequency bottom backscattering measurements
Authors: Crisp J. J. , Thomson P. A. G. , Baird A. M. , Jackson D. R.
Published: October 2005

Backscattering measurements at several shallow water ocean sites showed scattering strength to be approximately independent of frequency over the range 20–85 kHz. A grazing angle interval of 10° to 40° was covered at most sites, but the larger interval of 5° to 90° was covered at selected sites. At a grazing angle of 20°, sites with compositions ranging from sandy silt to coarse sand exhibited similar scattering strengths, in the range −25 to −30 dB. Gravel and rock bottoms had considerably higher scattering strengths. Data on sediment grain size and core sample acoustic properties have been provided for several sites by E. L. Hamilton of the Naval Ocean Systems Center, San Diego. Stereophotographic roughness data are available for sites near the United Kingdom, and small-scale roughness data and in-situ sediment acoustic data are available for some of the US sites [Y. Igarashi and R. L. Allman, J. Acoust. Soc. Am. Suppl. I 72, S36, S98 (1982)]. [D. R. Jackson's work supported by NAVSEA.]
A spheroidal coordinate description of acoustic scattering by elastic elongated bodies
Authors: Hackman Roger H. , Uzes C. A.
Published: October 2005

The spherical coordinate based T matrix has been successfully used to calculate the acoustic scattering from submerged, elastic bodies in the low kl/2 region for small aspect ratios (x⩽5). As the aspect ratio of the scatterer increases, however, the system of algebraic equations generated by this technique grows larger in number (roughly as x2) and tends to be numerically ill-conditioned. This limits the usefulness of the approach for large aspect ratios. To obviate this and related difficulties, we have developed a spheroidal coordinate based T-matrix formalism. This coordinate system provides a more natural basis for the description of elongated bodies. As a first application of the formalism, we calculate the back scattered farfield form function of a solid elastic prolate spheroid as a function of frequency for a variety of aspect ratios at end-on incidence.
Resonance scattering by an elastic cylinder in water—Theory and experiment
Authors: Brill D. , Gaunaurd G. C.
Published: October 2005

A landmark experiment recently performed at Le Havre, France has isolated the modal resonances contained within the backscattering cross-section of a submerged elastic cylinder. The isolation was accomplished via a background subtraction, experimentally achieved by a clever time-gating technique. In this paper we generate tailor-made calculations and graphs intended to closely examine the experiment in the light of the Resonance Scattering Theory (RST). Our predictions: (a) display the whispering gallery and Rayleigh-type poles in the complex frequency plane and show their connection with the target resonances they generate, which manifest themselves as circumferential waves around the cylinder, (b) quantitatively explain why some of the modal resonances were missed in the experiment, (c) establish comparisons between predicted and observed monostatic and bistatic form-functions in the direct scattering mode of operation of the RST, and (d) show ways to improve the observations, paving the way toward the solution of the inverse scattering situation. Within the limits of simple shapes and compositions, and within the controlled and relatively noise-free environment of the laboratory, these favorable comparisons have satisfactorily validated many of the RST predictions in the field of Acoustics.
Acoustic wave scattering from elliptical shells
Authors: Radlinski Ronald P. , Simon Murray M.
Published: October 2005

A T-matrix method for acoustic scattering has been derived from a modification of the extended boundary condition formulation developed for elastic wave scattering from infinite cylindrical shells of arbitrary shape [M. M. Simon and R. P. Radlinski, J. Acoust. Soc. Am. 71, 273–281; (1982)]. The boundary condition of no tangential component of surface traction at the fluid-shell interface allows a simplification of the thin shell equations assumed to describe the motion of the scatterer. Expansion of the normal and tangential displacements of the shell in Fourier series which are a function of arclength reduces the shell equations to algebraic form. For this presentation the geometry is specialized to elliptical shells. Results are presented for shells of different materials and eccentricities. Comparison are made between acoustic scattering and elastic p-p wave scattering.
Scattering from layered material immersed in a fluid
Authors: Hackman R. , Werby M. F. , Green L. H. , Flax L.
Published: October 2005

We employ the transition matrix formalism to derive expressions to describe acoustical scattering from elastic solids embedded in elastic materials submerged in a fluid. Calculations are then presented for several different materials and shapes for the solid embedded material. Both form function and backscattered monostatic patterns are presented to determine characteristic effects associated with both material and shape properties. Results will be presented for a k⋅L/2 (k = 2π/wavelength, L is a characteristic length) range from 4 to 12.
Transient response of an elastic shell to an acoustic impulse using Green's theorem
Authors: Turner Robert , Ginsberg Jerry H.
Published: October 2005

The transient response of a sphere subjected to an incident acoustic impulse is studied by the boundary integral method. The problem is reduced from three dimensions to one independent variable on the shell's surfaces by use of the free-space Green's function. Three different shell models are used: (1) a rigid shell, for which the normal derivative of the pressure at the surface is zero, (2) a single surface thin shell for which Green's theorem is applied only to the fluid pressure since the thin shell equations model the surface dynamics, and (3) a two surface thick shell for which Green's theorem must also be applied to the curl and the divergence of the solid displacement vector. The surface is discreetized and the problem is numerically integrated in time. The state variables are related by finite differences. The results are compared to those of previous studies. The rigid shell problem gives good agreement. Numerical instabilities in the elastic shell solutions are discussed.
Acoustic image reconstruction of elastic shells in water from ramp response signatures
Authors: Tsao S. J. , Varadan V. V. , Varadan V. K. , Young J. D.
Published: October 2005

A technique for generating a target image utilizing acoustic transient response signature data is explained and demonstrated for elastic shells in water. The technique combines features of physical optics inverse diffraction and feature-space target identification approaches. Complex harmonic backscattering spectrum in the low resonance range is used as input data for this approach. A periodic ramp in response waveform synthesized from these data is shown to be correlated to the cross-sectional area versus distance along the line-of-sight, or profile function, of the targets measured. Visual images simulating an isometric view of the target are constructed.
Application of time delay spectrometry to medical imaging
Authors: Rooney J. A. , Heyset R. C. , Hestenes J. D. , LeCroissette D. H.
Published: October 2005

A medical ultrasonic imaging system based upon reflective mode time delay spectrometry (TDS) is being developed at JPL. The frequency is linearly swept from 1 to 10 MHz in 20 ms. The signals from the targets of interest are received at the transducer with a time delay proportional to range. In the TDS processing system the received and transmitted signals are coherently mixed to produce a difference signal in a lower frequency range. After detection and low-pass filtering to remove unwanted higher frequency components, a fast Fourier transform (FFT) is used to convert the frequency components into a time display. The FFT processes the magnitude of the analytic signal to obtain an energy-time curve. This curve is always positive and displays the time dependence of the total energy response of the received signal. A two-dimensional image is constructed from a series of scan lines. Images produced using TDS have the higher range resolution and signal-to-noise ratios required for deep arterial imaging. [This work was sponsored in part by the National Heart, Lung and Blood Institute through an agreement with the National Aeronautics and Space Administration through Contract NAS7-918.]
Molecular Phylogeny of the
Pseudallescheria boydii
Species Complex: Proposal of Two New Species
Authors: Gilgado Felix , Cano Josep , Gené Josepa , Guarro Josep
Published: October 2005

Pseudallescheria boydii
(anamorph
Scedosporium apiospermum
) is the species responsible for human scedosporiosis, a fungal infection with a high mortality rate and which is difficult to treat. Recently, it has been demonstrated that high genetic variation exists within this species. We have performed a morphological and molecular study involving numerous strains of clinical or environmental origins and from different countries. The analysis of partial sequences of the β-tubulin (two loci) and calmodulin genes and the internal transcribed spacer region of the rRNA gene has demonstrated that
P. boydii
is a species complex. The combined analysis of the sequences of the four loci of 60 strains has showed the presence of 44 haplotypes in the ingroup. Three species morphologically related to
P. boydii
sensu stricto, i.e.,
Pseudallescheria angusta
,
Pseudallescheria ellipsoidea
, and
Pseudallescheria fusoidea
, which had previously been considered synonyms, could be differentiated genetically from
P. boydii
in our study. It is relevant that two of the three strains now included in
P. ellipsoidea
have caused invasive infections. The species
Pseudallescheria minutispora
and
Scedosporium aurantiacum
are clearly phylogenetically separated from the other species studied and are here proposed as new. Morphological features support this proposal. All the strains included in
S. aurantiacum
species have a clinical origin, while those included in
P. minutispora
are environmental. Further studies are needed to demonstrate whether all the species included in the
P. boydii
complex have different clinical spectra and antifungal susceptibility.
Variation of the
Mycobacterium tuberculosis
PE_PGRS33 Gene among Clinical Isolates
Authors: Talarico Sarah , Cave M. Donald , Marrs Carl F. , Foxman Betsy , Zhang Lixin , Yang Zhenhua
Published: October 2005

PE_PGRS33, one of about 60 PE_PGRS genes in the
Mycobacterium tuberculosis
genome, encodes a surface-expressed protein that may be involved in the antigenic variation of
M. tuberculosis
strains and evasion of the host immune system. While genetic differences between the PE_PGRS33 genes of H37Rv and CDC1551 have been noted, genetic variation in this gene among clinical isolates has not been evaluated. In order to gain a better understanding of the genetic basis for the role of PE_PGRS in antigenic variation and evasion of the host immune system, we investigated the genetic diversity of the PE_PGRS33 gene among 123 clinical
M. tuberculosis
isolates from a population-based study, using PCR and DNA sequencing. The 123 isolates belonged to principal genetic groups 1, 2, and 3 and had IS
6110
copy numbers ranging from 1 to 22. Eighty-four (68.3%) of the 123 isolates were found to have at least one sequence variation in the PE_PGRS33 gene, relative to that of H37Rv. Twenty-five different sequence variations were observed and included three insertions (ranging from 9 to 87 bp), nine deletions (ranging from 1 to 273 bp), one insertion-and-deletion event, and 12 single-nucleotide polymorphisms (six synonymous and six nonsynonymous). Analysis of the relationships among the different PE_PGRS33 gene sequence variations suggests that polymorphisms in the gene are shifting along evolutionary lineages. The observed genetic diversity of the PE_PGRS33 gene supports its role in antigenic variation and can serve as a basis for future investigations of the function of the PE_PGRS33 gene among clinical isolates.
Outbreak of Infection with a Multiresistant
Klebsiella pneumoniae
Strain Associated with Contaminated Roll Boards in Operating Rooms
Authors: van 't Veen Annemarie , van der Zee Anneke , Nelson Jolande , Speelberg Ben , Kluytmans Jan A. J. W. , Buiting Anton G. M.
Published: October 2005

An outbreak with a multiresistant
Klebsiella pneumoniae
(MRKP) strain among seven patients admitted to the adult intensive care unit (ICU) of a regional teaching hospital in The Netherlands was investigated. Epidemiologic investigations revealed a short delay between an operation and the acquisition of the MRKP strain. A case-control study comprising 7 cases and 14 controls was conducted to identify the risk factors associated with the acquisition of the MRKP strain. An operation at each of two operation rooms was strongly associated with the acquisition of the MRKP strain: odds ratio of 36 (95% confidence interval, 2.7 to 481.2;
P
= 0.003, Fisher exact two-tailed test). Cultures of environmental specimens of the operation rooms revealed contamination of the roll boards used to transport patients from the bed to the operation table with the MRKP strains. Molecular genotyping of the isolates revealed clonal similarity between the isolates of the seven cases, isolates from environmental specimen cultures, and in addition, an MRKP isolate from a repatriated ICU patient from earlier that year. The outbreak ended after cleaning and replacement of the roll boards in the operation rooms and implementation of additional barrier precautions for colonized or infected patients. It was concluded that two operation rooms played a significant role in the transmission of an MRKP strain between ICU patients during the presented outbreak.
Diagnosis of Invasive Pneumococcal Infection by Serotype-Specific Urinary Antigen Detection
Authors: Leeming John P. , Cartwright Keith , Morris Rhonwen , Martin Siobhan A. , Smith Michael D.
Published: October 2005

Widespread use of conjugate pneumococcal polysaccharide-protein vaccines may alter the spectrum of pneumococci producing invasive disease. Novel sensitive diagnostic methods would be valuable for monitoring the epidemiology of pneumococcal disease within populations and vaccine recipients. Ideally, these methods should allow determination of the serotype of the infecting clone. Serotype-specific enzyme-linked immunosorbent assays (ELISA) for 13 capsular polysaccharides (types 1, 3, 4, 5, 6A, 6B, 7A, 9V, 14, 18C, 19A, 19F, and 23F) were developed. Experiments with pure capsular polysaccharide demonstrated that the assays were sensitive (0.01 to 1.0 ng/ml) and specific. These assays were used to detect capsular polysaccharide in urine from 263 adult patients with proven (blood culture-positive) invasive pneumococcal disease and pneumonia of unknown etiology and from patients with positive blood cultures yielding bacteria other than pneumococci (control group). Among 76 patients with invasive pneumococcal disease from whom blood culture isolates had been serotyped, 62 (82%) had infections with pneumococci of serotypes represented in the ELISA panel. Capsular antigen matching the serotype of the blood culture isolate was detected in the urine of 52 of these patients, giving a sensitivity of 83.9% for the target serotypes. The tests were significantly more sensitive for urine from patients with pneumococcal pneumonia (89.8%) than for urine from patients with nonpneumonic invasive infection (61.5%;
P
< 0.05). Data from the control group indicated a specificity of 98.8%. These assays should prove valuable in epidemiological investigation of invasive pneumococcal infection in adults, particularly if combined with a sensitive C-polysaccharide detection assay to screen for positive samples.
Use of Real-Time PCR To Process the First Galactomannan-Positive Serum Sample in Diagnosing Invasive Aspergillosis
Authors: Millon Laurence , Piarroux Renaud , Deconinck Eric , Bulabois Claude-Eric , Grenouillet Frédéric , Rohrlich Pierre , Costa Jean-Marc , Bretagne Stéphane
Published: October 2005

Positive galactomannan (GM) antigenemias are included as a microbiological item in the diagnosis of probable or possible invasive aspergillosis (IA). Because false-positive GM results frequently occur, at least two positive results on two different samples are required. Waiting for clinical specimens can delay the initiation of treatment. As an alternative, we wondered whether detection of circulating
Aspergillus
DNA on the first positive GM serum sample could aid in diagnosing IA. Therefore, we retrospectively screened the first GM-positive serum samples from 29 patients from our hematology unit for
Aspergillus
DNA using real-time PCR. We compared the real-time PCR results with the final classification of proven, probable, and possible IA according to consensual criteria. No clear correlation between PCR results and the classification with the medical files could be shown. However, a positive PCR result was associated with a poor prognosis (Fisher's test;
P
= 0.01). Our preliminary data suggest that a positive PCR result could indicate a more advanced stage of the disease. Therefore, concomitant positive PCR and GM results may justify the initiation of antifungal therapy in neutropenic patients. In contrast, a negative PCR on the first positive GM sample may argue for postponing costly antifungal administration until additional arguments for the diagnosis of IA are presented.
Evaluation of Diagnostic Markers for Measles Virus Infection in the Context of an Outbreak in Spain
Authors: Mosquera María M. , de Ory Fernando , Gallardo Virtudes , Cuenca Loreto , Morales Mercedes , Sánchez-Yedra Waldo , Cabezas Teresa , Hernández Juan M. , Echevarría Juan E.
Published: October 2005

A measles outbreak occurred from January to July 2003 in Spain, despite the fact that the Plan of Eradication of Measles and its surveillance program had been set up in 2001. Different diagnostic markers for measles virus infection were compared for 246 patients in tests of serum, urine, and pharyngeal exudate specimens. Measles virus immunoglobulin M (IgM) and IgG and rubella virus and parvovirus IgM levels in serum were assayed. Multiplex PCR was done on urine, serum, and pharyngeal exudates, and isolation of measles virus in the B95a cell line from urine was attempted. At least one positive marker for measles virus was obtained from 165 patients (67.1%; total number of patients, 246). A total of 136 cases (82.4% of the patients showing positive markers) were diagnosed by PCR and/or isolation and IgM detection methods. The results for 27 patients (16.4%) were positive only by direct methods. The results for two patients (1.2%) were positive only by IgM detection. In the case of the first group (136 cases), the time elapsed from appearance of the rash was significantly longer than in the case of the group which was only positive by PCR. Besides, 8 out of 27 PCR-positive IgM-negative cases showed specific IgG results, suggesting either secondary vaccine failure or reinfection. Numbers resulting from PCR performed with pharyngeal exudates proved to be significantly higher than those obtained with other specimens. Phylogenetic analysis showed the presence of genotype B3. The results strongly back the World Health Organization recommendation that detection of IgM should be supplemented by PCR and isolation for the diagnosis of measles virus infection.
Molecular Epidemiology of
Neisseria meningitidis
Isolated in the African Meningitis Belt between 1988 and 2003 Shows Dominance of Sequence Type 5 (ST-5) and ST-11 Complexes
Authors: Nicolas Pierre , Norheim Gunnstein , Garnotel Eric , Djibo Saacou , Caugant Dominique A.
Published: October 2005

At the two World Health Organization Collaborating Centers for Reference and Research on Meningococci in Marseilles, France, and Oslo, Norway, the multilocus sequence typing technique was used for the characterization of a total of 357 strains of meningococci isolated from meningitis cases in 13 African countries of the meningitis belt between 1988 and 2003. Among these strains, 278 of 357 (77.9%) belonged to the sequence type 5 (ST-5) complex; 23.2% were ST-5 and 53.5% were ST-7. ST-5 was probably introduced in Africa in 1987 and was responsible for most of the meningitis cases between 1988 and 2001. ST-7 emerged in the mid-1990s and has totally replaced ST-5 since 2002. These two STs characterized serogroup A strains and have been responsible for hundreds of thousands of cases. Fifty-two strains (14.3%) belonged to the ST-11 complex. The ST-11 complex was characterized by serogroup W135, which has been responsible for an increasing number of sporadic cases since 2000 and the first W135 epidemic ever seen in Africa (in Burkina Faso in 2002). Identification of W135 ST-11 strains in many countries is a great concern for the region. Apart from these two major clonal complexes, a few other clones, such as ST-2881, ST-181, and ST-751, were sporadically detected. Careful surveys for these clones need to be conducted, but at present they play only a minor role in the overall epidemiology of meningococcal meningitis.
Development of PCR Assays Targeting the Genes Involved in Synthesis and Assembly of the New
Escherichia coli
O174 and O177 O Antigens
Authors: Beutin Lothar , Kong Qingke , Feng Lu , Wang Quan , Krause Gladys , Leomil Luciana , Jin Qi , Wang Lei
Published: October 2005

Escherichia coli
O174 and O177 are newly described O serogroups which were reported as human pathogens. Identification of these strains by serotyping has been restricted, as the required sera are not commercially available. In this study, a collection of 13
E. coli
O174 strains and 12
E. coli
O177 strains was studied on the O:H serotypes and virulence markers. The O-antigen gene clusters of
E. coli
O174 and O177 were sequenced, and associated genes were assigned functions on the basis of homology. Two genes, each specific for
E. coli
O174 and O177, were identified. PCR assays based on the O-antigen-specific genes were developed and tested on 25 clinical and environmental isolates of those two serogroups as well as 26 isolates of other O serogroups. As little as 1 pg per μl of chromosomal DNA and as few as 0.1 CFU per g of pork and water samples were detected for either strain. The PCR assays established in this study were shown to be highly sensitive and reliable and could be the method of choice for detection of these two human pathogens from clinical, food, and other environmental samples.
Use of a Three-Dimensional Microarray System for Detection of Levofloxacin Resistance and the
mecA
Gene in
Staphylococcus aureus
Authors: Nagaoka Tomonori , Horii Toshinobu , Satoh Takatomo , Ito Tomoko , Monji Akio , Takeshita Akihiro , Maekawa Masato
Published: October 2005

We evaluated a novel three-dimensional microarray (PamChip microarray) system to detect the presence of levofloxacin-related resistance mutations and the
mecA
gene. The results were compared to those obtained for 27
Staphylococcus aureus
isolates by conventional DNA sequencing or PCR methods. Hybridization and fluorescence detection were performed using an FD10 system designed for PamChip microarray under conditions optimized for each target/probe on the array. In dilution series analysis using multiplex PCR samples, the sensitivity of the microarray was about 10 times greater than that of conventional PCR methods. A high level of data reproducibility was also confirmed in those analyses. Various point mutations in quinolone resistance-determining regions detected by our system corresponded perfectly to the results obtained by conventional DNA sequencing. The results of the
mecA
gene detection using our system also corresponded to the PCR method; that is, signal/band was detected in all isolates of methicillin-resistant
S. aureus
, and no signal/band was detected in any isolate of methicillin-susceptible
S. aureus
. In conclusion, our novel three-dimensional microarray system provided rapid, specific, easy, and reproducible results for the simultaneous detection of levofloxacin resistance and the
mecA
gene in
S. aureus
.