bluuebunny/crossref_metadata_2025 huggingface dataset:
Rhodopsin kinase: Expression in mammalian cells and a two-step purification
Authors: Bruel Christophe , Cha Kiweon , Reeves Philip J. , Getmanova Elena , Khorana H. Gobind
Published: July 2002

A suitable system for expression of the rhodopsin kinase (RK) gene
and its mutants is needed for structure–function studies of RK.
Previously, investigation of the baculovirus system showed satisfactory
production of RK, but posttranslational isoprenylation was deficient.
We now report on a comparative study of expression of the RK gene in
yeast (
Pichia pastoris
), COS-1 cells and in an HEK293
stable cell line. Expression in COS-1 cells, by using pCMV5 vector, is
the most satisfactory. A two-step procedure for purification of the
expressed enzyme with an N-terminal histidine tag has been developed.
The purified enzyme has correct posttranslational modifications and
shows a somewhat broader pH vs. catalytic activity profile than the
wild-type enzyme.
Autoantibodies in alcoholic liver disease
Authors: McFarlane Ian G.
Published: July 2002

Despite many decades of research, the reasons why only a relatively small proportion of individuals who consume excessive quantities of alcohol develop clinically significant liver disease remain unknown. The association with features of autoimmune diseases, including hypergammaglobulinaemia, circulating autoantibodies, inheritance of certain immunogenetic (HLA) markers and response to corticosteroid therapy in some patients has led to a persistent impression that altered immune regulation with a relative loss of self‐tolerance underlies susceptibility to the development of the more severe forms of alcoholic liver disease (alcoholic hepatitis and/or cirrhosis). However, review of the data from the numerous studies that have been conducted over the past 30 years fails to reveal sufficiently convincing evidence that autoimmunity plays a primary role in alcohol‐related liver damage. In particular, most of the wide range of circulating autoantibodies that have been reported in patients are found mainly at low titres, are not confined to those with severe liver injury, and are probably more likely to be a response to the hepatic insult than causally related to liver damage. Additionally, an association with various HLA phenotypes has not been confirmed by meta‐analysis. Interpretation is complicated by evidence that alcohol may have direct effects on some components of the immune system but, if there is an immunogenetic basis for alcoholic liver disease, the present evidence suggests that this might be related more to cytokine gene polymorphisms than to a predisposition to autoimmunity per se.
Regulation of B Lymphocyte Development by the Truncated Immunoglobulin Heavy Chain Protein Dμ
Authors: Tornberg Ulla-Carin , Bergqvist Ingela , Haury Matthias , Holmberg Dan
Published: July 2002

The development of B lymphocytes from progenitor cells is dependent on the expression of a pre–B cell–specific receptor made up by a μ heavy chain associated with the surrogate light chains, immunoglobulin (Ig)α, and Igβ. A variant pre–B cell receptor can be formed in which the μ heavy chain is exchanged for a truncated μ chain denoted Dμ. To investigate the role of this receptor in the development of B cells, we have generated transgenic mice that express the Dμ protein in cells of the B lineage. Analysis of these mice reveal that Dμ expression leads to a partial block in B cell development at the early pre–B cell stage, probably by inhibiting VH to DHJH rearrangement. Furthermore, we provide evidence that Dμ induces VL to JL rearrangements.
Anomalous L-Type Calcium Channels of Rat Spinal Motoneurons
Authors: Hivert Bruno , Luvisetto Siro , Navangione Anacleto , Tottene Angelita , Pietrobon Daniela
Published: July 2002

Single channel patch-clamp recordings show that embryonic rat spinal motoneurons express anomalous L-type calcium channels, which reopen upon repolarization to resting potentials, displaying both short and long reopenings. The probability of reopening increases with increasing voltage of the preceding depolarization without any apparent correlation with inactivation during the depolarization. The probability of long with respect to short reopenings increases with increasing length of the depolarization, with little change in the total number of reopenings and in their delay. With less negative repolarization voltages, the delay increases, while the mean duration of both short and long reopenings decreases, remaining longer than that of the openings during the preceding depolarization. Open times decrease with increasing voltage in the range −60 to +40 mV. Closed times tend to increase at V > 20 mV. The open probability is low at all voltages and has an anomalous bell-shaped voltage dependence. We provide evidence that short and long reopenings of anomalous L-type channels correspond to two gating modes, whose relative probability depends on voltage. Positive voltages favor both the transition from a short-opening to a long-opening mode and the occupancy of a closed state outside the activation pathway within each mode from which the channel reopens upon repolarization. The voltage dependence of the probability of reopenings reflects the voltage dependence of the occupancy of these closed states, while the relative probability of long with respect to short reopenings reflects the voltage dependence of the equilibrium between modes. The anomalous gating persists after patch excision, and therefore our data rule out voltage-dependent block by diffusible ions as the basis for the anomalous gating and imply that a diffusible cytosolic factor is not necessary for voltage-dependent potentiation of anomalous L-type channels.
Orthotropic transform for planar anisotropic elasticity and reduced dependence of elastic constants
Authors: Yang Wei , Ma Chien-Ching
Published: July 2002

The resurgence in the literature on the reduced dependence of elastic constants for damaged materials and composites has been largely inspired by the exploration of the stress invariance under a modulus shift by Cherkeav and others in 1992 (henceforth referred to as the CLM shift) in planar elasticity. However, a CLM shift can at most reduce the dependence of two elastic constants. The present work devises an approach that combines the CLM shift and an orthotropic transform. As a result, the governing equation of a general planar anisotropic solid only contains a single dimensionless elastic constant (denoted by |
c
∗
2
| in this paper) in the transformed coordinates. The damage compliance of a solid with holes can be expressed explicitly through a function depending only on |
c
∗
2
|. If an elastic composite consists of a matrix and inclusions of aligned anisotropy, its overall compliance can be expressed through a function of three combinative parameters, namely |
c
∗
2
| and two Dundurs parameters. Furthermore, a configuration invariant transform is found for layered materials of aligned anisotropy. The stress analysis of such configurations only involves four elastic constants.
Empirical dosimetric characterization of model I125‐SL brachytherapy source in phantom
Authors: Wallace Robert E.
Published: July 2002

Low‐energy photon emitting radionuclides encapsulated for a permanent implant are routinely applied in prostate cancer brachytherapy. Before clinical use, a new source design requires full dosimetric analysis and calibration standardization. The results of one such experimental measurement and analysis are reported here for a new design of source, model I125‐SL. Dose measurements were made using standard methods employing thermoluminscent dosimeters in a water equivalent plastic phantom, in accord with the AAPM Task Group #43 recommendation of liquid water reference material. Precision machined bores in the phantom located dosimeters and source(s) in a reproducible fixed geometry providing for transverse‐axis and angular dose profiles over a range of distances from 0.17 to 10 cm. The data were analyzed in terms of parameters recommended by AAPM TG43. The dose‐rate constant, Λ, was evaluated by two methods, the first with reference to a standard, accounting for response variation with photon energy spectrum. Second, the dose‐rate constant was determined with reference to phantom measurements using NIST traceable calibrated model 6702 and 6711 sources. The radial dose function, the anisotropy function, the anisotropy factor, and the point‐source approximation anisotropy constant, were derived from one‐ and two‐dimensional dose distribution data measured in the phantom, accounting for finite dosimeter volume and with attention to interchip effects. The results are compared to TG43 and other existing data for sources. The new source is comparable to the model 6711 source design.
Optimizing beam weights and wedge filters with the concept of the super‐omni wedge
Authors: Dai Jianrong , Zhu Yunping , Ji Qing
Published: July 2002

This study introduces a new concept, the super‐omni wedge, and proposes an algorithm for optimizing beam weights, wedge angles, and wedge orientations on the basis of this new concept. The super‐omni wedge is a generalization of the omni wedge. Instead of combining one open beam and two orthogonal wedged beams, it uses two orthogonal pairs of nominal wedged beams to generate a wedged dose distribution with an arbitrary wedge angle and an arbitrary wedge orientation. The orientations of a pair of nominal wedges are opposite each other. In this way, the effective wedge orientation can vary from 0° to 360° rather than being restricted to one quadrant. When the concept of the super‐omni wedge is used, the optimization of beam weights, wedge angles, and wedge orientations for J beams is transformed into the optimization of beam weights for 4J beams. A quadratic dose‐based objective function is defined, and the method of sequential quadratic programming is used to find the 4J beam weights that minimize it. After the weights of the nominal wedged beams have been determined, the beams can be delivered in one of four methods: Directly, by using the omni wedge technique, by using the universal wedge technique, and by using the virtual wedge technique. When tested with two clinical cases, the algorithm achieved homogeneous dose distributions in target volumes while meeting the constraints to the organs at risk. A prominent feature of the algorithm is that there is no need to manually preselect the orientations of nominal wedges.
A method for physically based radiotherapy optimization with intelligent tissue weight determination
Authors: Jones Lois , Hoban Peter
Published: July 2002

An important aspect of the intensity modulated radiotherapy (IMRT) process is that of optimizing the beam intensity profiles. Most such methods use a comparison between the defined dose distribution (including prescription dose and dose limits for critical structures) and the current distribution. The comparison may involve dose differences or dose ratios. This paper investigates four different ratio‐based methods, with a hypothetical U‐shaped target and cylindrical phantom as the test case. All methods are shown to give satisfactory results. There are differences in the dose distributions produced and these can be related to the formulation of the respective fluence‐update methods. In common with other IMRT beam optimization methods the techniques used here include tissue‐weighting factors which express the relative importance of achieving the goal dose level or limit. Altering the values of these weights can improve the ability of the optimization algorithm to adhere to the goal dose levels. Typically the weights are adjusted on a “trial and error” basis until the planner is satisfied with the results. In this paper a technique for automatic updating of the weights according to the optimization results is applied to each of the four fluence update methods. With this technique the difference between the current dose level in each tissue and the specified dose constant for that tissue is used to increase the weight should the constraint not be met. It is found that the four methods yield similar results if the weights are updated in this way.
Monte Carlo calculations of dosimetry parameters of the Urocor Prostaseed source
Authors: Li Zuofeng
Published: July 2002

This report presents the results of Monte Carlo calculations of the dosimetric parameters of the Urocor ProstaSeed seed source. This source contains five spherical silver markers, of 0.5 mm diameter, with deposited on the spheres through ion exchange. The silver spheres are then encapsulated within a 0.8 mm in diameter and 4.5 mm long cylindrical shell of titanium, as is common to this type of sources. Physical dimensions of the source are confirmed by measurement. Four (4) geometric models of the source, based on different assumptions on the locations of the silver spheres within the seed, were used in dose rate calculations. Monte Carlo photon transport simulation was used to calculate the dosimetric parameters of dose rate constant, radial dose function, and anisotropy function using these geometric models of the source. The Monte Carlo calculated dose rate constant of the ProstaSeed source was found equal to 0.925 cGy/U h with approximate uncertainties of 5%. Radial dose function values and anisotropy function values were derived from the relative dose distribution around the source calculated by the Monte Carlo code. The calculated values of these dosimetric parameters agree with previously published thermoluminescence‐dosimeter‐measured values for this source after consideration of measurement and calculation uncertainties.
Off‐axis primary‐dose measurements using a mini‐phantom
Authors: Johnsson Stefan A. , Ceberg Crister P.
Published: July 2002

The characterization of the incident photon beam is usually divided into its dependence on collimator setting (head‐scatter factor) and off‐axis position (primary off‐axis ratio). These parameters are normally measured “in air” with a build‐up cap thick enough to generate full dose build‐up at the depth of dose maximum. In order to prevent any influence from contaminating electrons, it has been recommended that head‐scatter measurements are carried out using a mini‐phantom rather than a conventional build‐up cap. Due to the volume of the mini‐phantom, the effects from attenuation and scatter are not negligible. In relative head‐scatter measurements these effects cancel and the head scatter is thus a good representation of the variation of the incident photon beam with collimator setting. However, in off‐axis measurements, attenuation and scatter conditions vary due to beam softening and do not cancel in the calculation of the primary off‐axis ratio. The purpose of the present work was to estimate the effects from attenuation and phantom scatter in order to determine their influence on primary off‐axis ratio measurements. We have characterized the off‐axis beam‐softening effect by means of narrow‐beam transmission measurements to obtain the effective attenuation coefficient as a function of off‐axis position. We then used a semi‐analytical expression for the phantom‐scatter calculation that depends solely on this attenuation coefficient. The derived formalism for relative “in air” measurements using a mini‐phantom is clear and consistent, which enables the user to separately calculate the effects from scatter and attenuation. For the investigated beam qualities, 6 and 18 MV, our results indicate that the effects from attenuation and scatter in the mini‐phantom nearly cancel (the combined effect is less than 1%) within 12.5 cm from the central beam axis. Thus, no correction is needed when the primary off‐axis ratio is measured with a mini‐phantom.
System considerations in CCD‐based x‐ray imaging for digital chest radiography and digital mammography
Authors: Hejazi Shahram , Trauernicht David P.
Published: July 2002

System modeling is used to investigate the effect of various system parameters on the image quality in CCD‐based x‐ray imaging systems. The systems considered consist of a typical phosphor‐based scintillating screen coupled to a CCD through lens or fiberoptic taper. Two applications, chest radiography and mammography, are analyzed. For each application typical system characteristics and operating conditions are used to determine the detective quantum efficiency (DQE) as a function of spatial frequency, optical collection efficiency, optical demagnification factor, and electronic noise. The DQE is modeled by extending the analysis for storage phosphor systems. The calculations are done for typical exposure conditions (0.25 mR for chest and 10.0 mR for mammography); however, the exposure effects are also discussed. It was found that a reasonable DQE can be obtained for both applications through each coupling approach; however, the demagnification requirements and electronic noise limitations are more stringent for the digital mammography application.
A comprehensive physical image quality evaluation of a selenium based digital x‐ray imaging system for thorax radiography
Authors: Launders J. H. , Kengyelics S. M. , Cowen A. R.
Published: July 2002

A selenium based digital x‐ray system dedicated to chest radiography has been installed by the UK Department of Health's Medical Devices Agency at Leeds General Infirmary, UK, to undergo a comprehensive evaluation, including the physical image quality. The underlying characteristics which define the overall image quality of a system are the following: sensitometric response, modulation transfer function, and noise power spectrum. These have been measured objectively on preprocessed digital data acquired under relevant radiographic conditions. The image data is further processed prior to hard copy display. The displayed image quality may only be measured subjectively; threshold contrast detail detectability is such a measure which can be related to the objective measures of image quality. The objective imaging characteristics suggest that Thoravision has a significant advantage over conventional radiography imaging systems. However, subjective measures have demonstrated that the image processing can have a significant effect on the perceived image quality. Thoravision has the potential to deliver a significantly improved image quality to clinicians with no increase in radiation exposure to the patient, or image quality may be maintained with a reduction in radiation exposure. Digital image processing is central to the efficiency with which it achieves this.
CT image reconstruction from fan‐parallel data
Authors: Besson Guy
Published: July 2002

Third generation fan‐beam computerized tomography (CT) scanners acquire data one entire projection at a time. The associated filtered‐backprojection algorithm requires a computationally expensive pixel‐dependent weight factor in the backprojector. Methods of simplifying the reconstruction include rebinning the fan‐beam data to parallel projections. The rebinning can be separated into two steps: azimuthal interpolation, leading to the fan‐parallel geometry, where data are unevenly spaced on radial lines through the origin of Radon space, and a subsequent axial interpolation to parallel data. Under appropriate view and projection sampling conditions, the azimuthal interpolation can be replaced by either data resorting or projection channel‐dependent delays. This article investigates an arcsin algorithm to reconstruct an image directly from the fan‐parallel data. Although it is shown that the algorithm cannot be exact, a natural approximation is described. The pre‐ and postconvolution weights, and the reconstruction filter, are derived analytically. Imaging results demonstrate that arcsin image quality matches that of parallel reconstruction. The fan‐parallel reconstruction method eliminates the resolution‐compromising axial interpolation and the costly pixel‐dependent backprojection weight. Further, an arcsin detector design is proposed for direct parallel reconstruction from fan‐beam data.
Extrapolated surface dose measurements with radiochromic film
Authors: Butson Martin J. , Yu Peter K. N. , Metcalfe Peter E.
Published: July 2002

A radiochromic film extrapolation method is described for the measurement of surface dose from high energy photon beams. Extrapolated central axis entrance surface dose using Gafchromic film for a field size is and of for 6 and 10 MV x rays, respectively. Extrapolated surface dose for a field with a 10 mm perspex block tray is and of for 6 and 10 MV beams, respectively. All results agree with uncorrected Attix parallel plate ionization chamber surface ionization within 4% for the same beam energies and configurations.
Study on dosimetry for therapeutic carbon beams (in Japanese)
Authors: Fukumura Akifumi
Published: July 2002

The main objective of this study is to establish reliable dosimetry for high‐energy carbon beams used for cancer treatment. The thesis describes and compares the absolute dosimetry using an ionization chamber, a calorimeter, and a fluence detector. The doses obtained with the three methods were in agreement within experimental errors. The discrepancy between the ionization chamber and calorimeter methods was less than 1%, making the ionization chamber method appropriate for carbon beam dosimetry. Good agreement, within 0.5%, was obtained in a dosimetry intercomparison between two different carbon beam facilities, NIRS and GSI‐DKFZ in Germany. Miniature p‐type silicon diodes were investigated as relative dosimeters. They were used in a head phantom for the verification of the treatment planning. A simple method using visible light emitted from a bare plastic scintillator allowed real‐time range measurements with spatial resolution better than 0.5 mm. Fragmentation of carbon nuclei in an energy absorber may possibly change the fluence of carbon beams to be used for patient irradiation. Survival of primary carbon beams after passing through an absorber was measured with ΔE plastic scinitillator. The results showed that polyethylene and PMMA were water equivalent in terms of the nuclear reactions and appropriate as energy absorbers to shift the range of the primary beams. The total charge‐changing cross sections of several materials for carbon beams were deduced from the slope of the attenuation. Dosimetry is essential to compare and/or to discuss biological effects and clinical results. This study contributed significantly to the NIRS carbon beam therapy trials.
Perceived continuity and pitch perception
Authors: Plack Christopher J. , White Louise J.
Published: July 2002

Three experiments investigated the importance of perceived stimulus continuity for the perception of the fundamental frequency (F0) of an unresolved complex tone. The F0 of the complex was 250 Hz and the harmonics were bandpass filtered between 5500 and 7500 Hz. In the first experiment, F0 discrimination was measured for single-burst tones with durations of 20, 40, and 80 ms, and for stimuli containing two 20- or 40-ms tone bursts separated by an 8- or 16-ms gap. For the single-burst conditions, there was a large decrease in threshold as the duration was increased from 20 to 40 ms. However, performance in the gapped conditions was much worse than that for the single-burst condition with the same cumulative duration (e.g., two 20-ms bursts separated by 8 ms produced higher thresholds than one 40-ms burst). Adding a bandpass noise (with the same spectral envelope as the tone) in the gap between the two tone bursts improved performance to the level of the single-burst condition. When the noise was added, the two discrete tone bursts were perceived as one single tone burst interrupted by the noise, and this seemed to facilitate discrimination. In a second experiment, the effects on pitch of an envelope delay (phase shift) of 0.75 periods between two tone bursts separated by an 8-ms gap were investigated. If the gap was silent, the pitch of the pair was unaffected by the phase shift. However, if the gap contained the bandpass noise, the phase shift between the bursts did produce a significant downward shift in the pitch of the pair. Finally, the third experiment showed that presenting a noise before a single 20-ms burst may improve discrimination performance in some listeners, but not sufficiently to account for the results of the first experiment purely in terms of an improvement in the discriminability of the second tone burst in the pair. The experiments suggest that a level decrease between two tone bursts may disrupt or reset a long integration mechanism, decreasing performance. When there is no level decrease between the bursts, the auditory system may assume that the two bursts belong to the same single tone and analyze them together in order to derive F0.
An optimization approach to multi-dimensional time domain acoustic inverse problems
Authors: Gustafsson Mats , He Sailing
Published: July 2002

An optimization approach to a multi-dimensional acoustic inverse problem in the time domain is considered. The density and/or the sound speed are reconstructed by minimizing an objective functional. By introducing dual functions and using the Gauss divergence theorem, the gradient of the objective functional is found as an explicit expression. The parameters are then reconstructed by an iterative algorithm (the conjugate gradient method). The reconstruction algorithm is tested with noisy data, and these tests indicate that the algorithm is stable and robust. The computation time for the reconstruction is greatly improved when the analytic gradient is used.
Time-domain analyses of acoustics–structure interactions for piezoelectric transducers
Authors: Yi Sung , Ling Shih Fu , Ying Ming
Published: July 2002

Piezoelectric transducers coupled with a surrounding medium are analyzed in time domain using the coupled finite element and boundary element method. Three-dimensional solid elements are employed to model the piezoelectric transducer, while the surrounding medium is described by the boundary integral equation and the boundary of the medium is modeled by two-dimensional spatial elements. Verification studies were conducted to evaluate the accuracy and convergence of the present numerical algorithm and they show that the present numerical solutions agree well with the analytical ones. The influence of the surrounding medium on the acoustic field is studied. The interaction between the structure and surrounding medium affects the structure dynamic performances and acoustic pressure distributions significantly. However, in the present study we show that the radiation directivity is insignificantly influenced by the surrounding medium.
A method for measuring the diaphragm tension of condenser microphones using electric admittance
Authors: Yan Xinche , Crocker Malcolm J.
Published: July 2002

This paper presents a method to measure the diaphragm tension of a condenser microphone where the fundamental frequency of the diaphragm is found from the input conductance of the microphone as a function of frequency. In this contact-free, purely electrical approach only the diaphragm and the backplate of the microphone are used as the main system for exciting and detecting the diaphragm vibration.
Noise-evoked otoacoustic emissions in humans
Authors: Maat Bert , Wit Hero P. , van Dijk Pim
Published: July 2002

Click-evoked otoacoustic emissions (CEOAEs) and acoustical responses evoked by bandlimited Gaussian noise (noise-evoked otoacoustic emissions; NEOAEs) were measured in three normal-hearing subjects. For the NEOAEs the first- and second-order Wiener kernel and polynomial correlation functions up to the sixth order were calculated by cross correlating the noise stimulus and the emission response. Emission components were only found in the first-order Wiener kernel. These kernels were dependent on the stimulus level, indicative of the nonlinear response of the cochlea. For each subject the frequency contents of the CEOAE and the first-order Wiener kernel were nearly identical. In the second-order Wiener kernels and higher-order polynomial correlation functions no significant contributions were identified. Apparently, odd and even order nonlinearities cannot be detected by Wiener kernel analysis.
Transient response of quasi-isotropic fiber composite laminates to internal line sources
Authors: Green E. Rhian , Green W. A.
Published: July 2002

This article considers the propagation of elastic waves in an eight-ply quasi-isotropic laminate arising from line sources of dislocation located at each of the seven interfaces in turn. The laminate is composed of identical layers of a fiber composite material which is modeled as a homogeneous transversely isotropic elastic continuum with the axis of transverse isotropy along the fiber direction. The line source sets up a straight crested wave traveling along the laminate in the direction normal to the load line and the elastodynamic equations within each layer are solved by taking the Laplace transform with respect to time and the Fourier transform with respect to the spatial coordinate in the direction of propagation. The resulting system of six first-order differential equations in each layer is solved to obtain the transforms of the displacement and stress components throughout the laminate. The time history of any displacement or stress component at any location may then be recovered by numerical inversion of the double transform. The graphs presented show the time history of the normal displacement of the top surface of the laminate at distances of 1 and 20 plate thicknesses from the plane of action of the sources. These graphs are for four different orientations of the line of action of the sources, namely, at angles 0, 30, 60, and 90 degrees to the fiber direction in the surface layer. The numerical inversion involves a summation over different modes of Rayleigh–Lamb waves in the laminate and results are also presented showing the contributions to the overall response from some of the individual modes.
Seismic-like scaling regime in impulse reflection from underwater sediment
Authors: Smith Eric
Published: July 2002

A universal scaling law is known empirically to characterize the high-frequency decay of bandpassed seismic coda. An explanation advanced for this universality, based on multiple-Rayleigh scatter of nonuniform strength, is generic enough to suggest that similar scaling may apply to decay of the impulse response in other random media. A submerged sand layer is probed experimentally as a candidate for such a medium, and its incoherent acoustic impulse reflection is found to have an exponential decay regime similar to that in seismology.
Specificity of perceptual learning in a frequency discrimination task
Authors: Irvine Dexter R. F. , Martin Russell L. , Klimkeit Ester , Smith Rachel
Published: July 2002

On a variety of visual tasks, improvement in perceptual discrimination with practice (perceptual learning) has been found to be specific to features of the training stimulus, including retinal location. This specificity has been interpreted as evidence that the learning reflects changes in neuronal tuning at relatively early processing stages. The aim of the present study was to examine the frequency specificity of human auditory perceptual learning in a frequency discrimination task. Difference limens for frequency (DLFs) were determined at 5 and 8 kHz, using a three-alternative forced choice method, for two groups of eight subjects before and after extensive training at one or the other frequency. Both groups showed substantial improvement at the training frequency, and much of this improvement generalized to the nontrained frequency. However, a small but statistically significant component of the improvement was specific to the training frequency. Whether this specificity reflects changes in neural frequency tuning or attentional changes remains unclear.
Structure-borne noise reduction for an infinite, elastic cylindrical shell
Authors: Ko Sung-Hwan , Seong Woojae , Pyo Sangwoo
Published: July 2002

A theoretical model was developed to evaluate the reduction of structure-borne noise generated by an axially symmetric ring force which is applied on the interior of the cylindrical shell. The vibrating cylindrical shell is coated with a microvoided elastomer that is acoustically soft material designed for the reduction of the generated noise. The analytical model is a two-layer shell structure comprised of a cylindrical shell and an outer layer (coating) that is perfectly bonded to the cylindrical shell. The outer and inner surfaces of the coated shell are in contact with water and air, respectively. The analysis for this problem is based on the theory of elasticity, acoustic wave equations, and pertinent boundary conditions. Effects of various parameters such as coating thickness and material properties on the noise reductions are presented.
Wave transmission through structural inserts
Authors: Mace B. R. , Jones R. W. , Harland N. R.
Published: July 2002

The transmission of waves through two discontinuities in a one-dimensional waveguide system is considered. Attention is focused on transmission through a structural insert, which is defined here to be a waveguide segment which is inserted into an otherwise continuous structural member with different properties. A general expression for the net transmission through the insert is found. It has bandpass/stop characteristics and its frequency average is somewhat greater than that normally assumed due to the coherent interaction of the waves in the insert. The particular case is then considered where the insert comprises a three-layer composite beam inserted in a thin beam which vibrates in bending. The composite beam comprises two elastic faceplates and a core filled with a tunable electro- or magneto-rheological fluid. The net transmission and the stop bands depend on the properties of the insert. Since these properties are tunable by adjusting the field to which the tunable fluid is exposed, then so too are the transmission characteristics of the insert.
The speed of pitch resolution in a musical context
Authors: Ranvaud R. , Thompson W. F. , Silveira-Moriyama L. , Balkwill L.-L.
Published: July 2002

In five experiments, we investigated the speed of pitch resolution in a musical context. In experiments 1–3, listeners were presented an incomplete scale (doh, re, mi, fa, sol, la, ti) and then a probe tone. Listeners were instructed to make a rapid key-press response to probe tones that were relatively proximal in pitch to the last note of the scale (valid trials), and to ignore other probe tones (invalid trials). Reaction times were slower if the pitch of the probe tone was dissonant with the expected pitch (i.e., the completion of the scale, or doh) or if the probe tone was nondiatonic to the key implied by the scale. In experiments 4 and 5, listeners were presented a two-octave incomplete arpeggio, and then a probe tone. In this case, listeners were asked to make a rapid key-press response to probe tones that were relatively distant in pitch from the last note of the arpeggio. Under these conditions, registral direction and pitch proximity were the dominant influences on reaction time. Results are discussed in view of research on auditory attention and models of musical pitch.
A multifrequency scintillation method for ocean flow measurement
Authors: Fuks I. , Charnotskii M. , Naugolnykh K.
Published: July 2002

The transverse flow of inhomogeneous fluid produces fluctuation of the acoustic signal passing through it. The coherence of frequency-spaced signal fluctuation is related to the advection of the inhomogeneous medium through the sound path, thus providing a basis for the current velocity measurement. This method can be considered to be the “frequency-domain” version of the conventional scintillation approach to the current velocity registration based on the measurement of the signal correlation transmitted from the source to the two separated in space receivers (space-domain scintillation) [S. Clifford and D. Farmer, J. Acoust. Soc. Am. 74, 1826–1832 (1983)]. The sensitivity of the method depends on the features of the ocean fine structure, which is determined mainly by the internal waves and turbulence. To estimate the sensitivity of the multifrequency method of transverse current probing, the coherence function of two signals propagating through a frozen and moving internal wave field and through the turbulence is considered. The application of the multifrequency signal allows estimation of the fine-structure parameters as well as the current velocity.
Exact solutions for free vibration of shear-type structures with arbitrary distribution of mass or stiffness
Authors: Li Q. S.
Published: July 2002

In this paper, shear-type structures such as frame buildings, etc., are treated as nonuniform shear beams (one-dimensional systems) in free-vibration analysis. The expression for describing the distribution of shear stiffness of a shear beam is arbitrary, and the distribution of mass is expressed as a functional relation with the distribution of shear stiffness, and vice versa. Using appropriate functional transformation, the governing differential equations for free vibration of nonuniform shear beams are reduced to Bessel’s equations or ordinary differential equations with constant coefficients for several functional relations. Thus, classes of exact solutions for free vibrations of the shear beam with arbitrary distribution of stiffness or mass are obtained. The effect of taper on natural frequencies of nonuniform beams is investigated. Numerical examples show that the calculated natural frequencies and mode shapes of shear-type structures are in good agreement with the field measured data and those determined by the finite-element method and Ritz method.
Numerical simulation of optimal deconvolution in a shallow-water environment
Authors: Cazzolato Ben S. , Nelson Philip , Joseph Phillip , Brind Richard J.
Published: July 2002

A fast technique for deconvolving signals in a dispersive multipath shallow-water environment using inverse filters is compared with the more commonly used deconvolution technique of time reversal (also known as phase conjugation). The objective of such techniques is to improve the accuracy of sound transmission from a source array to some receiving space. Time reversal provides benefits in this regard but here the additional performance that can be gained from inverse filters is examined. Several strategies for obtaining a set of inverse filters are discussed, each aimed at improving the accuracy of the reconstruction of the desired time signals through inverse techniques. It will be shown that an “optimal” inversion (in the sense of achieving a flat system response in the frequency domain) does not necessarily achieve a realizable time domain filter. A fast field model (using OASES) of the Giglio Basin shallow-water test facility is used as the basis for evaluating the various focusing strategies for single receiver locations. It will be seen that inverse filter arrays provide enhanced temporal and spatial focusing when compared to time reversal arrays. In addition, inverse filtering allows multiple receivers to be used, thereby increasing bandwidth or improving redundancy.
Reply to “Comment on ‘Free vibration analysis of laminated piezoceramic hollow spheres [J. Acoust. Soc. Am. 109, 41 (2001)]’ ”
Authors: Chen W. Q.
Published: July 2002

We reply to the preceding Comment.
The behavior of evoked otoacoustic emissions during and after postural changes
Authors: de Kleine Emile , Wit Hero P. , Avan Paul , van Dijk Pim
Published: July 2002

Click-evoked and stimulus frequency otoacoustic emissions (CEOAEs and SFOAEs, respectively) were studied in humans during and after postural changes. The subjects were tilted from upright to a recumbent position (head down 30 deg) and upright again. Due to the downward posture change, CEOAEs showed a phase increase (80 deg at 1 kHz) and a level decrease (0.5 at 1 kHz), especially for frequency components below 2 kHz. For SFOAEs, the typical ripple pattern showed a positive shift along the frequency axis, which can be interpreted as a phase shift of the inner-ear component of the microphone signal (90 deg at 1 kHz). This also occurred mainly for frequencies below 2 kHz. The altered posture is thought to cause an increase of the intracranial pressure, and consequently of the intracochlear fluid pressure, which results in an increased stiffness of the stapes system. The observed emission changes are in agreement with predictions from a model in which the stiffness of the cochlear windows was altered. For CEOAEs, the time to regain stability after a downward turn was of the order of 30 s, while this took about 20 s after an upward turn. For SFOAEs, this asymmetry was not found to be present (about 11 s, both for up- and downward turns).
A probabilistic union model with automatic order selection for noisy speech recognition
Authors: Jančovič Peter , Ming Ji
Published: July 2002

A critical issue in exploiting the potential of the sub-band-based approach to robust speech recognition is the method of combining the sub-band observations, for selecting the bands unaffected by noise. A new method for this purpose, i.e., the probabilistic union model, was recently introduced. This model has been shown to be capable of dealing with band-limited corruption, requiring no knowledge about the band position and statistical distribution of the noise. A parameter within the model, which we call its order, gives the best results when it equals the number of noisy bands. Since this information may not be available in practice, in this paper we introduce an automatic algorithm for selecting the order, based on the state duration pattern generated by the hidden Markov model (HMM). The algorithm has been tested on the TIDIGITS database corrupted by various types of additive band-limited noise with unknown noisy bands. The results have shown that the union model equipped with the new algorithm can achieve a recognition performance similar to that achieved when the number of noisy bands is known. The results show a very significant improvement over the traditional full-band model, without requiring prior information on either the position or the number of noisy bands. The principle of the algorithm for selecting the order based on state duration may also be applied to other sub-band combination methods.
Vibratory characteristics of multistep nonuniform orthotropic shear plates with line spring supports and line masses
Authors: Li Q. S.
Published: July 2002

A new exact approach for free-vibration analysis of multistep nonuniform orthotropic shear plates with line spring supports and line masses is presented. The governing differential equation for free vibrations of an orthotropic shear plate with variably distributed mass and stiffness is established. It is proved that it is possible to separate a shear plate as two independent shear beams for free-vibration analysis. The jkth natural frequency of a shear plate is equal to the square root of the square sum of the jth natural frequency of a shear beam and the kth natural frequency of another shear beam. The jkth mode shape of the shear plate is the product of the jth mode shape of a shear beam and the kth mode shape of another shear beam. In this paper, the function for describing the distribution of mass of each step plate can be selected as an arbitrary one, and the distribution of shear stiffness is expressed as a functional relation with the mass distribution, and vice versa. The exact solutions of one-step shear plates with varying cross section are obtained first for eight cases. Then, the derived exact solutions are used to establish the frequency equation of a multistep nonuniform orthotropic shear plate with spring supports and line masses using the transfer matrix method and the recurrence method developed in this paper. The numerical example shows that the calculated results are in good agreement with the experimental data, and the proposed procedure is an exact and efficient method.
Validation of sonic boom propagation codes using SR-71 flight test data
Authors: Ivanteyeva Lyudmila G. , Kovalenko Victor V. , Pavlyukov Evgeny V. , Teperin Leonid L. , Rackl Robert G.
Published: July 2002

The results of two sonic boom propagation codes, ZEPHYRUS (NASA) and BOOM (TsAGI), are compared with SR-71 flight test data from 1995. Options available in the computational codes are described briefly. Special processing methods are described which were applied to the experimental data. A method to transform experimental data at close ranges to the supersonic aircraft into initial data required by the codes was developed; it is applicable at any flight regime. Data are compared in near-, mid-, and far fields. The far-field observation aircraft recorded both direct and reflected waves. Comparison of computed and measured results shows good agreement with peak pressure, duration, and wave shape for direct waves, thus validating the computational codes.
The Monte Carlo method to determine the error in calculation of objective acoustic parameters within the ray-tracing technique
Authors: Giner Javier , Militello Carmelo , Garcı́a Amando
Published: July 2002

This article is an extension of the procedure to estimate errors in ray-tracing calculations of room response proposed by Giner et al. [J. Acoust. Soc. Am. 106, 816–823 (1999)]. The previous article presented an expression to estimate the error in computing the energy reaching a receptor during a small time interval. This expression was obtained assuming that a pure ray-tracing program is used and a Monte Carlo Technique is applied. In the present work these ideas are extended in order to compute the objective acoustic parameters of a room. The corresponding equations are presented in closed form. Our results show that the number of rays involved in the analysis depends on the nature of the parameters to be evaluated. Some examples are shown in order to validate our conclusions.
Inaccuracies in sound pressure level determination from room impulse response
Authors: Ćirić Dejan G. , Milošević Miroslava A.
Published: July 2002

The integration over discrete squared room impulse response (RIR) leads to the sound pressure level (SPL). However, certain inaccuracies in SPL determination appear as a consequence of influences of finite integration upper limit (UL) and noise. Due to that, these influences are investigated using two types of RIRs: those generated by simulation and those measured in the room. The investigations show that for RIRs with sufficiently small noise floors (below −20 or −15 dB) acceptably small inaccuracies are obtained if the integration UL is placed at T/3 (alternatively at T/4). A more general solution is to set UL at the knee representing the point where main decay intersects noise floor. For even smaller inaccuracies, it would be better to set UL at the point somewhat before the knee called optimal UL. The influences of finite integration UL and noise can also be reduced by implementation of finite UL compensation and noise subtraction.