bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of clean GaAs(100) studied by synchrotron radiation photoemission
Authors: Liu Zhi , Sun Yun , Machuca Francisco , Pianetta Piero , Spicer William E. , Pease R. F. W.
Published: January 2003

Chemical cleaning of the GaAs(100) surface has been studied with high-resolution photoemission spectroscopy using synchrotron radiation (in the range of 30–1300 eV) at the Stanford Synchrotron Radiation Laboratory. The high surface sensitivity of the technique has allowed us to identify the chemical state of the surface species after both the chemical cleaning and final vacuum processing steps. In order to eliminate contamination from the surroundings, all chemical cleaning steps were performed in an Ar purged glovebox attached to the load lock allowing samples to be transferred into the system without being exposed to air. Samples were etched in H2SO4:H2O2:H2O solution and then heat cleaned in vacuum at 500 °C. After chemical etching in the solution, elemental As (∼2 ML), arsenic oxides (<0.2 ML), gallium oxides (<0.2 ML), and C (0.5∼1 ML) are found on the surface. Subsequent annealing at <500 °C in ultrahigh vacuum produces a stoichiometric, oxide-free surface as determined by valence-band and core-level photoemission. In addition, C has been reduced to less than 0.1 ML. We believe that the C can be removed by heating because the elemental As from the earlier cleaning step tends to protect the GaAs surface. The chemical reactions and species at different cleaning stages are discussed.
Preparation of clean InP(100) surfaces studied by synchrotron radiation photoemission
Authors: Sun Yun , Liu Zhi , Machuca Francisco , Pianetta Piero , Spicer William E.
Published: January 2003

The chemical cleaning of indium phosphide (InP),(100) surfaces is studied systematically by using photoemission electron spectroscopy. In order to achieve the necessary surface sensitivity and spectral resolution, synchrotron radiation with photon energies ranging from 60 to 600 eV are used to study the indium 4d, phosphorus 2p, carbon 1s, and oxygen 1s core levels, and the valence band. Typical H2SO4:H2O2:H2O solutions used to etch GaAs(100) surfaces are applied to InP(100) surfaces. It is found that the resulting surface species are significantly different from those found on GaAs(100) surfaces and that a second chemical cleaning step using a strong acid is required to remove residual surface oxide. This two-step cleaning process leaves the surface oxide free and with approximately 0.4 ML of elemental phosphorus, which is removed by vacuum annealing. The carbon coverage is also reduced dramatically from approximately 1 to about 0.05 ML. The chemical reactions are investigated, the resulting InP surface species at different cleaning stages are determined, and the optimum cleaning procedure is presented.
Deposition of Bi4−xLaxTi3O12 films by direct liquid injection-metalorganic chemical vapor deposition
Authors: Kang Sang-Woo , Rhee Shi-Woo
Published: January 2003

Deposition of Bi4−xLaxTi3O12 (BLT) films with direct liquid injection-metal organic chemical vapor deposition using a single-mixed solution of Bi(Ph)3, Ti(dmae)4, and La(tmhd)3- pentamethyldiethylenetriamine was studied. On Pt surface, the deposition rate of the BLT film was almost independent of the deposition temperature. Above 425 °C, it appears that precursors were dissociated in the gas phase and the deposition rate was decreased. The film composition could be controlled by adjusting the concentration of Bi and La precursors in the solution through the competitive substitution of Bi and La element in the Bi site of Bi-layer perovskite structure (Bi4 Ti3 O12). Fatigue-free and highly c-axis oriented BLT thin films were grown on Pt/TiO2/SiO2/Si at the deposition temperature of 400 °C. For the film annealed at 650 °C, the remanent polarization (2Pr) and coercive field (Ec) were 12 μC/cm2 and 56 kV/cm, respectively. The BLT capacitors did not show any significant fatigue up to 4×1010 cycles at a frequency of 1 MHz.
Information depth and the mean escape depth in Auger electron spectroscopy and x-ray photoelectron spectroscopy
Authors: Jablonski A. , Powell C. J.
Published: January 2003

The information depth (ID) is a measure of the sampling depth for the detected signal in Auger-electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) while the mean escape depth (MED) is a measure of surface sensitivity. We report ID and MED calculations for Si 2s, Si 2p3/2, Cu 2s, Cu 2p3/2, Au 4s, and Au 4f7/2 photoelectrons excited by Mg Kα x rays. These calculations were made for various electron emission angles and for a common XPS configuration. Similar calculations were made for Si L3VV, Si KL23L23, Cu M3VV, Cu L3VV, Au N7VV, and Au M5N67N67 Auger transitions. The IDs and MEDs were derived from an analytical expression for the signal-electron depth distribution function obtained from a solution of the kinetic Boltzmann equation within the transport approximation. The ratios of the IDs and the MEDs to the corresponding values found if elastic-electron scattering were assumed to be negligible, RID and RMED, were less than unity and varied slowly with electron emission angle α for emission angles less than 50°. For larger emission angles, these ratios increased rapidly with α. For α⩽50°, average values of RID and RMED varied linearly with the single-scattering albedo, ω, a simple function of the electron inelastic mean-free path and transport mean-free path. For α=70° and α=80°, RID also varied linearly with ω but RMED showed a quadratic variation. The albedo is thus a useful measure of the magnitude of elastic-scattering effects on the ratios RID and RMED. As a result of the elastic scattering of the signal electrons, AES and XPS measurements at α=80° are less surface sensitive than would be expected if elastic scattering had been neglected. Conversely, AES and XPS measurements made for α⩽50° are more surface sensitive as a result of elastic-scattering effects.
Spectral and modal formulations for the Doppler-shifted field scattered by an object moving in a stratified medium
Authors: Lai Yi-san , Makris Nicholas C.
Published: January 2003

Spectral and normal mode formulations for the three-dimensional field scattered by an object moving in a stratified medium are derived using full-field wave theory. The derivations are based on Green’s theorem for the time-domain scalar wave equation and account for Doppler effects induced by target motion as well as source and receiver motion. The formulations are valid when multiple scattering between the object and waveguide boundaries can be neglected, and the scattered field can be expressed as a linear function of the object’s plane wave scattering function. The advantage of the spectral formulation is that it incorporates the entire wave number spectrum, including evanescent waves, and therefore can potentially be used at much closer ranges to the target than the modal formulation. The normal mode formulation is more computationally efficient but is limited to longer ranges. For a monochromatic source that excites N incident modes in the waveguide, there will be roughly N2 distinct harmonic components in the scattered field. The Doppler shifts in the scattered field are highly dependent upon the waveguide environment, target shape, and measurement geometry. The Doppler effects are illustrated through a number of canonical examples.
Echolocation signals of wild Atlantic spotted dolphin (Stenella frontalis)
Authors: Au Whitlow W. L. , Herzing Denise L.
Published: January 2003

An array of four hydrophones arranged in a symmetrical star configuration was used to measure the echolocation signals of the Atlantic spotted dolphin (Stenella frontalis) in the Bahamas. The spacing between the center hydrophone and the other hydrophones was 45.7 cm. A video camera was attached to the array and a video tape recorder was time synchronized with the computer used to digitize the acoustic signals. The echolocation signals had bi-modal frequency spectra with a low-frequency peak between 40 and 50 kHz and a high-frequency peak between 110 and 130 kHz. The low-frequency peak was dominant when the signal the source level was low and the high-frequency peak dominated when the source level was high. Peak-to-peak source levels as high as 210 dB re 1 μPa were measured. The source level varied in amplitude approximately as a function of the one-way transmission loss for signals traveling from the animals to the array. The characteristics of the signals were similar to those of captive Tursiops truncatus, Delphinapterus leucas and Pseudorca crassidens measured in open waters under controlled conditions.
An auditory-periphery model of the effects of acoustic trauma on auditory nerve responses
Authors: Bruce Ian C. , Sachs Murray B. , Young Eric D.
Published: January 2003

Acoustic trauma degrades the auditory nerve’s tonotopic representation of acoustic stimuli. Recent physiological studies have quantified the degradation in responses to the vowel /ɛ/ and have investigated amplification schemes designed to restore a more correct tonotopic representation than is achieved with conventional hearing aids. However, it is difficult from the data to quantify how much different aspects of the cochlear pathology contribute to the impaired responses. Furthermore, extensive experimental testing of potential hearing aids is infeasible. Here, both of these concerns are addressed by developing models of the normal and impaired auditory peripheries that are tested against a wide range of physiological data. The effects of both outer and inner hair cell status on model predictions of the vowel data were investigated. The modeling results indicate that impairment of both outer and inner hair cells contribute to degradation in the tonotopic representation of the formant frequencies in the auditory nerve. Additionally, the model is able to predict the effects of frequency-shaping amplification on auditory nerve responses, indicating the model’s potential suitability for more rapid development and testing of hearing aid schemes.
A method of images for a penetrable acoustic waveguide
Authors: Fawcett John A.
Published: January 2003

In this paper the complex-image approximation to the reflection coefficient for water over a seabed half-space is used to generate an image representation for a bounded acoustic waveguide with an underlying layered seabed. The images are true point sources; they have constant amplitudes which are raypath independent and, in the case of a Pekeris waveguide, frequency-independent. This image representation is ideal for constructing the Green’s function kernel of the boundary integral equation method for target scattering in a waveguide. The singular behavior of the Green’s function for an infinitesimal source/receiver separation, possibly with the target adjacent to one of the interfaces, is modeled correctly and the image expansion has a simple analytic form which can be analytically differentiated. The method is also accurate for significant source/receiver separations, which means that it can be used in the modeling of scattering from large-sized objects and can also be used as an efficient and accurate short-range propagation model for harmonic and broadband propagation in a penetrable waveguide.
Laboratory measurements of sound scattering from a buried sphere above and below the critical angle (L)
Authors: Simpson Harry J. , Houston Brian H. , Lin Raymond
Published: January 2003

Laboratory measurements of low frequency (1–10 kHz) evanescent wave field scattering from a sphere buried in water-saturated sand was examined. A 60 cm stainless steel sphere was buried just below a sand–water interface and the acoustic backscattering cross section was measured for above and below critical angle geometries. The below critical angle insonification results clearly show significant levels of backscatter from the buried sphere due to evanescent wave insonification at the lower end of the spectrum (1–3.5 kHz). These measurements compare favorably with first principle estimates of the backscattered target strength and with a T-matrix-based numerical model.
Objective estimates of cochlear tuning by otoacoustic emission analysis
Authors: Moleti Arturo , Sisto Renata
Published: January 2003

A new method is presented for estimating cochlear tuning starting from measurements of either the transient evoked otoacoustic emission latency or the spontaneous otoacoustic emission minimal spacing. This method could be useful in obtaining indirect information about the tuning curve, particularly for subjects that, like neonates, cannot be studied with psycho-acoustical techniques. Theoretical models of the acoustic transmission along the cochlea based on the transmission line formalism predict a relation between the otoacoustic emission latency and the frequency. This relation depends on the tuning curve, i.e., the frequency dependence of the quality factor of the cochlear resonances. On the other hand, models for the generation of spontaneous emissions based on the concept of coherent scattering from cochlear random inhomogeneities imply an independent relation between the tuning curve and the minimal frequency spacing between spontaneous emissions. In this study, experimental measurements of the otoacoustic emission latency and of the minimal spacing between spontaneous emissions are presented. Theoretical relations are derived, which connect these two measured quantities and the tuning curve. The typically longer latency of neonates implies a higher degree of tuning at high levels of stimulation.
Physiopathological significance of distortion-product otoacoustic emissions at 2 f1–f2 produced by high- versus low-level stimuli
Authors: Avan Paul , Bonfils Pierre , Gilain Laurent , Mom Thierry
Published: January 2003

Distortion product otoacoustic emissions emitted by the cochlea at 2 f1–f2 in response to pairs of pure tones at f1 and f2 (DPOAE) form a class of otoacoustic emissions and as such, are viewed as a reliable tool for screening outer hair cell (OHC) dysfunctions on a pass/fail basis. However, the persistence of residual DPOAEs from impaired cochleae at high stimulus levels has suggested that above 60–70 dB SPL, instead of reflecting “active” cochlear motion, DPOAEs might represent another “passive” modality: they would thus become unsuitable for analyzing cochlear function. The present work reports the consequences on high- vs low-level DPOAEs of three types of cochlear impairments involving OHCs: progressive OHC degeneration of genetic origin in CD1 mice, complete cochlear ischemia in gerbils, and furosemide injection vs ischemia–reperfusion in gerbils. An alternative to the “active–passive” model was used wherein regardless of stimulus level, cubic DPOAEs are produced by N (probably OHC-borne) nonlinear elements driven by input I and modulated by a function F3 of their operating point o; thus, DPOAE∝NI3F3(o). When OHCs degenerated, thereby implying a decrease of N, DPOAE levels also decreased regardless of the stimulus level up to 80 dB SPL, in line with the previous formula but at variance with the prediction of the active–passive concept. Instead of affecting N, the other two experiments impaired the efficiency of the cochlear feedback loop as a result of its electrical drive being decreased by strial dysfunction. As it is well accepted that the impaired basilar-membrane motion, although greatly reduced at low levels, tends to catch up with a normal one at higher levels, it was assumed the same was true with I so that DPOAE levels had to be, and indeed were little affected at high levels while plummeting at low levels, without any need for invoking two modalities for DPOAE generation. Finally, comparisons of furosemide vs ischemia effects revealed additional influences on DPOAEs, possibly accounted for by function F3(o). These results lead to the proposal that although high-level DPOAEs are expected to be poor audiometric indicators, they seem well adapted to assessing the functional integrity of nonlinear elements in OHCs, i.e., presumably their mechanoelectrical transduction channels.
Unfolding of phonetic information over time: A database of Dutch diphone perception
Authors: Smits Roel , Warner Natasha , McQueen James M. , Cutler Anne
Published: January 2003

We present the results of a large-scale study on speech perception, assessing the number and type of perceptual hypotheses which listeners entertain about possible phoneme sequences in their language. Dutch listeners were asked to identify gated fragments of all 1179 diphones of Dutch, providing a total of 488 520 phoneme categorizations. The results manifest orderly uptake of acoustic information in the signal. Differences across phonemes in the rate at which fully correct recognition was achieved arose as a result of whether or not potential confusions could occur with other phonemes of the language (long with short vowels, affricates with their initial components, etc.). These data can be used to improve models of how acoustic-phonetic information is mapped onto the mental lexicon during speech comprehension.
Circumferential resonance modes of solid elastic cylinders excited by obliquely incident acoustic waves
Authors: Fan Ying , Honarvar Farhang , Sinclair Anthony N. , Jafari Mohammad-Reza
Published: January 2003

When an immersed solid elastic cylinder is insonified by an obliquely incident plane acoustic wave, some of the resonance modes of the cylinder are excited. These modes are directly related to the incidence angle of the insonifying wave. In this paper, the circumferential resonance modes of such immersed elastic cylinders are studied over a large range of incidence angles and frequencies and physical explanations are presented for singular features of the frequency-incidence angle plots. These features include the pairing of one axially guided mode with each transverse whispering gallery mode, the appearance of an anomalous pseudo-Rayleigh in the cylinder at incidence angles greater than the Rayleigh angle, and distortional effects of the longitudinal whispering gallery modes on the entire resonance spectrum of the cylinder. The physical explanations are derived from Resonance Scattering Theory (RST), which is employed to determine the interior displacement field of the cylinder and its dependence on insonification angle.
Reynolds number effects on flow/acoustic mechanisms in spherical windscreens
Authors: Zheng Z. Charlie , Tan Bee K.
Published: January 2003

There is a practical need to fully understand the mechanisms involved in the flow/pressure fluctuations around a screened microphone. A stream of uniform flow with low-frequency turbulence encountering a rigid, impermeable spherical windscreen is considered in this study. Pressure distributions on the surface of the sphere are determined by the flow structure. Pressure fluctuations at the center of the sphere are then calculated based on the integration of surface pressure distributions. Because of the low-frequency assumption, results from steady-state laminar flows can be used to investigate the Reynolds number effects on wind noise reduction. Three types of flow have been studied in this paper: an inviscid case, a low-Reynolds-number Stokes flow, and intermediate- and high-Reynolds-number flows. A Reynolds-number/wind-noise-reduction correlation shows that the wind noise reduction increases with decreasing Reynolds number.
Derivation of an optimal directivity pattern for sweet spot widening in stereo sound reproduction
Authors: Ródenas Josep A. , Aarts Ronald M. , Janssen A. J. E. M.
Published: January 2003

In this paper the correction of the degradation of the stereophonic illusion during sound reproduction due to off-center listening is investigated. The main idea is that the directivity pattern of a loudspeaker array should have a well-defined shape such that a good stereo reproduction is achieved in a large listening area. Therefore, a mathematical description to derive an optimal directivity pattern lopt that achieves sweet spot widening in a large listening area for stereophonic sound applications is described. This optimal directivity pattern is based on parametrized time/intensity trading data coming from psycho-acoustic experiments within a wide listening area. After the study, the required digital FIR filters are determined by means of a least-squares optimization method for a given stereo base setup (two pair of drivers for the loudspeaker arrays and 2.5-m distance between loudspeakers), which radiate sound in a broad range of listening positions in accordance with the derived lopt. Informal listening tests have shown that the lopt worked as predicted by the theoretical simulations. They also demonstrated the correct central sound localization for speech and music for a number of listening positions. This application is referred to as “Position-Independent (PI) stereo.”
Electromechanical coupling factor of capacitive micromachined ultrasonic transducers
Authors: Caronti Alessandro , Carotenuto Riccardo , Pappalardo Massimo
Published: January 2003

Recently, a linear, analytical distributed model for capacitive micromachined ultrasonic transducers (CMUTs) was presented, and an electromechanical equivalent circuit based on the theory reported was used to describe the behavior of the transducer [IEEE Trans. Ultrason. Ferroelectr. Freq. Control 49, 159–168 (2002)]. The distributed model is applied here to calculate the dynamic coupling factor kw of a lossless CMUT, based on a definition that involves the energies stored in a dynamic vibration cycle, and the results are compared with those obtained with a lumped model. A strong discrepancy is found between the two models as the bias voltage increases. The lumped model predicts an increasing dynamic k factor up to unity, whereas the distributed model predicts a more realistic saturation of this parameter to values substantially lower. It is demonstrated that the maximum value of kw, corresponding to an operating point close to the diaphragm collapse, is 0.4 for a CMUT single cell with a circular membrane diaphragm and no parasitic capacitance (0.36 for a cell with a circular plate diaphragm). This means that the dynamic coupling factor of a CMUT is comparable to that of a piezoceramic plate oscillating in the thickness mode. Parasitic capacitance decreases the value of kw, because it does not contribute to the energy conversion. The effective coupling factor keff is also investigated, showing that this parameter coincides with kw within the lumped model approximation, but a quite different result is obtained if a computation is made with the more accurate distributed model. As a consequence, keff, which can be measured from the transducer electrical impedance, does not give a reliable value of the actual dynamic coupling factor.
Central locus for nonspeech context effects on phonetic identification (L)
Authors: Lotto Andrew J. , Sullivan Sarah C. , Holt Lori L.
Published: January 2003

Recently, Holt and Lotto [Hear. Res. 167, 156–169 (2002)] reported that preceding speech sounds can influence phonetic identification of a target syllable even when the context sounds are presented to the opposite ear or when there is a long intervening silence. These results led them to conclude that phonetic context effects are mostly due to nonperipheral auditory interactions. In the present paper, similar presentation manipulations were made with nonspeech context sounds. The results agree qualitatively with the results for speech contexts. Taken together, these findings suggest that the same nonperipheral mechanisms may be responsible for effects of both speech and nonspeech context on phonetic identification.
Microparticle column geometry in acoustic stationary fields
Authors: Hancock Andrew , Insana Michael F. , Allen John S.
Published: January 2003

Particles suspended in a fluid will experience forces from stationary acoustic fields. The magnitude of the force depends on the time-averaged energy density of the field and the material properties of the particles and fluid. Forces acting on known particles smaller than 20 μm were studied. Within a 500 kHz acoustic beam generated by a plane-piston circular source, observations were made of the geometry of the particle column that is formed. Varying the acoustic energy altered the column width in a manner predicted by equations for the primary acoustic radiation force from scattering of particles in the long-wavelength limit. The minimum pressures required to trap gas, solid, and liquid particles in a water medium at room temperature were also estimated to within 12%. These results highlight the ability of stationary acoustic fields from a plane-piston radiator to impose nano-Newton-scale forces onto fluid particles with properties similar to biological cells, and suggest that it is possible to accurately quantify these forces.
Motion compensation for adaptive horizontal line array processing
Authors: Yang T. C.
Published: January 2003

Large aperture horizontal line arrays have small resolution cells and can be used to separate a target signal from an interference signal by array beamforming. High-resolution adaptive array processing can be used to place a null at the interference signal so that the array gain can be much higher than that of conventional beamforming. But these nice features are significantly degraded by the source motion, which reduces the time period under which the environment can be considered stationary from the array processing point of view. For adaptive array processing, a large number of data samples are generally required to minimize the variance of the cross-spectral density, or the covariance matrix, between the array elements. For a moving source and interference, the penalty of integrating over a large number of samples is the spread of signal and interference energy to more than one or two eigenvalues. The signal and interference are no longer clearly identified by the eigenvectors and, consequently, the ability to suppress the interference suffers. We show in this paper that the effect of source motion can be compensated for the (signal) beam covariance matrix, thus allowing integration over a large number of data samples without loss in the signal beam power. We employ an equivalent of a rotating coordinate frame to track the signal bearing change and use the waveguide invariant theory to compensate the signal range change by frequency shifting.
Sounds produced by individual white whales, Delphinapterus leucas, from Svalbard during capture (L)
Authors: Van Parijs Sofie M. , Lydersen Christian , Kovacs Kit M.
Published: January 2003

Recordings were made of the sounds produced by white whales during capture events in Storfjorden, Svalbard, in the late autumn. Only four of eight captured individuals produced sounds. Four subadults, one female and three males, between 330 and 375 cm long, did not produce sounds during handling. The four animals that produced sounds were as follows: a female subadult of 280 cm produced repetitive broadband clicks; a solitary calf produced harmonic sounds, which we suggest may serve as mother–calf “contact calls,” and a mother–calf pair were the two animals that produced the most sounds in the study. The mother produced “crooning” broadband clicks and frequently moved her head toward her calf while producing underwater sounds. The calf produced three types of frequency-modulated sounds interspersed within broadband click trains. No sounds were heard from any of the animals once they were free-swimming, or during ad lib recording sessions in the study area, even though groups of white whales were sighted on several occasions away from the capture net.
Narrow band laser-generated surface acoustic waves using a formed source in the ablative regime
Authors: Kenderian Shant , Djordjevic B. Boro , Green Robert E.
Published: January 2003

A narrow band laser-generated acoustic signal was created using a 4-element lenticular array. This arrangement of the array produces an acoustical signal with frequency content that is compatible with the response of a noncontact and remote broadband receiver, such as a capacitive air-coupled transducer. To support the experimental observations, a simplified concept is presented to explain the effect of a line array source on the frequency content of a surface acoustic wave. The analytical model solution for the wave front shape is derived from the point load solution of Lamb’s problem that represents the displacement of a surface acoustic wave generated by an ablative line array. The distribution function, which was used for the model to represent the laser light energy, was tailored to depict the actual energy distribution that illuminates the lenticular array. Filtering functions are applied to the resultant surface displacement function to retain frequencies similar to those detected by the broadband 50 kHz–2.25 MHz receiver. The theoretical model showed good agreement with experimental results.
Lattice form adaptive infinite impulse response filtering algorithm for active noise control
Authors: Lu Jing , Shen Chunhua , Qiu Xiaojun , Xu Boling
Published: January 2003

In some situations of active noise control, infinite impulse response (IIR) filters are more suitable than finite impulse response (FIR) filters owing to the poles in the transfer function. A number of algorithms have been derived for applying IIR filters in active noise control; however, most of them use the direct form IIR filter structure, which faces the difficulties of checking stability and relatively slow convergence speed for noise composed of narrow-band components with large power disparity. To overcome these difficulties along with using the direct form IIR filters, a new adaptive algorithm is proposed in this paper, which uses and updates the lattice form adaptive IIR filter in an active noise control system. Full mathematical derivations of the proposed algorithm are presented, and the comparison between the proposed algorithm and the commonly used filtered-u LMS and filtered-v LMS algorithms shows the superiority of the proposed algorithm.
Sound source reconstruction using inverse boundary element calculations
Authors: Schuhmacher Andreas , Hald Jørgen , Rasmussen Karsten Bo , Hansen Per Christian
Published: January 2003

Whereas standard boundary element calculations focus on the forward problem of computing the radiated acoustic field from a vibrating structure, the aim in this work is to reverse the process, i.e., to determine vibration from acoustic field data. This inverse problem is brought on a form suited for solution by means of an inverse boundary element method. Since the numerical treatment of the inverse source reconstruction results in a discrete ill-posed problem, regularization is imposed to avoid unstable solutions dominated by errors. In the present work the emphasis is on Tikhonov regularization and parameter-choice methods not requiring an error-norm estimate for choosing the right amount of regularization. Several parameter-choice strategies have been presented lately, but it still remains to be seen how well these can handle industrial applications with real measurement data. In the present work it is demonstrated that the L-curve criterion is robust with respect to the errors in a real measurement situation. In particular, it is shown that the L-curve criterion is superior to the more conventional generalized cross-validation (GCV) approach for the present tire noise studies.
Learning to produce speech with an altered vocal tract: The role of auditory feedback
Authors: Jones Jeffery A. , Munhall K. G.
Published: January 2003

Modifying the vocal tract alters a speaker’s previously learned acoustic–articulatory relationship. This study investigated the contribution of auditory feedback to the process of adapting to vocal-tract modifications. Subjects said the word /t𝕒s/ while wearing a dental prosthesis that extended the length of their maxillary incisor teeth. The prosthesis affected /s/ productions and the subjects were asked to learn to produce “normal” /s/’s. They alternately received normal auditory feedback and noise that masked their natural feedback during productions. Acoustic analysis of the speakers’ /s/ productions showed that the distribution of energy across the spectra moved toward that of normal, unperturbed production with increased experience with the prosthesis. However, the acoustic analysis did not show any significant differences in learning dependent on auditory feedback. By contrast, when naive listeners were asked to rate the quality of the speakers’ utterances, productions made when auditory feedback was available were evaluated to be closer to the subjects’ normal productions than when feedback was masked. The perceptual analysis showed that speakers were able to use auditory information to partially compensate for the vocal-tract modification. Furthermore, utterances produced during the masked conditions also improved over a session, demonstrating that the compensatory articulations were learned and available after auditory feedback was removed.
Controlled ultrasonic tissue erosion
Authors: Cain Charles
Published: January 2003

Controlled ultrasonic tissue erosion has many clinical applications, including the placement of very precise sharply defined perforations in biological interfaces and membranes with focused ultrasound. With carefully chosen acoustic parameters, tissue can be rapidly eroded away at a constant etching rate. The maximum erosion rate for minimal propagated energy is obtained by using very short high intensity pulses. The etching rate is higher with shorter pulse durations. For short pulses less than 10 cycles of the drive frequency, an optimum pulse repetition rate exists which maximizes the etching rate. Higher gas saturation in the surrounding medium reduces the etching rate and reduces the spatial sharpness of the holes produced. Most of the erosion appears to be produced in the first several cycles of the therapy pulse. For example, a series of short (about 3 cycles) focused pulses of 2100 W/cm2 (Isppa) at 788 kHz can erode a very well defined 2 mm diameter hole in a 1 mm thick sample of fresh pork atrial posterior wall in about 1 min at the optimum pulse repetition rate (about 18 kHz). Controlled ultrasonic tissue erosion may provide an effective image guided noninvasive tool in treatment of neonatal patients with hypoplastic left heart syndrome. Without the mixing of oxygenated blood across perforations placed in the atrial septum, these infants do not survive.
Neurobehavioral Changes Resulting from Recombinase Activation Gene 1 Deletion
Authors: Cushman Jesse , Lo Jeannette , Huang Zhi , Wasserfall Clive , Petitto John M.
Published: January 2003

Recombinase activation gene 1 (RAG-1) function is essential for V(D)J recombination in T-cell-receptor and immunoglobulin rearrangements whereby the immune system may encode memories of a vast array of antigens. The RAG-1 gene is also localized to neurons in the hippocampal formation and related limbic regions that are involved in spatial learning and memory as well as other parameters of neurobehavioral performance. Since the unique ability to encode memory is shared by the immune system and the brain, we tested the hypothesis that loss of the RAG-1 gene in the brain would influence learning and memory performance and examined several different domains of behavior in RAG-1-knockout and control mice. Compared to control mice, RAG-1-knockout mice exhibited increased locomotor activity in an open field under both dim and bright lighting conditions and decreased habituation (reduction in the expected decline in locomotor activity with increasing familiarity with the novel environment in a 1-h test session) in bright lighting. RAG-1-knockout mice also showed reduced levels of fearfulness for some measures of fear-motivated behavior in both the open-field behavior test and elevated-plus maze test. Contrary to our hypothesis, no differences in spatial learning and memory were found between the groups, although modest differences were observed visible-platform testing in the Morris water maze. Neither prepulse inhibition, a measure of sensorimotor gating, nor reflexive acoustic startle responses differed between the RAG-1-knockout and control mice. It remains to be determined if these changes are due to the loss of RAG-1 gene expression in the brain, are due to the absence of the gene in the immune system (e.g., the loss of cytokines with neuromodulatory activities), or are due to some combination of both effects. Study of the neurobiological actions of RAG-1 in the brain may provide new insights into important processes involved in normal brain function and disease.
Simultaneous Detection of 15 Human Cytokines in a Single Sample of Stimulated Peripheral Blood Mononuclear Cells
Authors: de Jager Wilco , te Velthuis Henk , Prakken Berent J. , Kuis Wietse , Rijkers Ger T.
Published: January 2003

Cytokines secreted by cells of the immune system can alter the behavior and properties of immune or other cells. At a site of inflammation, sets of cytokines interact with immune cells, and their combined effect is often more important than the function of one isolated component. Conventional techniques, such as enzyme-linked immunosorbent assays, generally require large quantities of cells to characterize a complete cytokine profile of activated lymphocytes. The Bio-Plex system from Bio-Rad Laboratories combines the principle of a sandwich immunoassay with the Luminex fluorescent-bead-based technology. We developed a multiplex cytokine assay to detect different cytokines simultaneously in culture supernatant of human peripheral blood mononuclear cells stimulated with antigen and with mitogen. Fifteen human cytokines (interleukin 1α [IL-1α], IL-1β, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-12p70, IL-13, IL-15, IL-17, IL-18, gamma interferon, and tumor necrosis factor alpha) were validated with a panel of healthy individuals, rheumatoid arthritis patients, and juvenile idiopathic arthritis patients. Comparing the multiplex assay with a regular enzyme-linked immunosorbent assay technique with this donor panel resulted in correlation coefficients for all cytokines ranging from 0.75 to 0.99. Intra-assay variance proved to be less then 10%, whereas interassay variability ranged between 10 and 22%. This multiplex system proved to be a powerful tool in the quantitation of cytokines. It will provide a more complete picture in differences between activated lymphocyte cytokine profiles from healthy individuals and those from patients with chronic inflammatory diseases.
Functional and Morphological Development of Lymphoid Tissues and Immune Regulatory and Effector Function in Rhesus Monkeys: Cytokine-Secreting Cells, Immunoglobulin-Secreting Cells, and CD5+B-1 Cells Appear Early in Fetal Development
Authors: Makori Norbert , Tarantal Alice F. , Lü Fabien X. , Rourke Tracy , Marthas Marta L. , McChesney Michael B. , Hendrickx Andrew G. , Miller Christopher J.
Published: January 2003

Little is known regarding the timing of immune ontogeny and effector function in fetal humans and nonhuman primates. We studied the organization of lymphocyte and antigen-presenting cell populations in developing lymphoid tissues of rhesus monkey fetuses during the second and third trimesters (65 to 145 days of gestation; term = 165 days). Immunoglobulin-secreting and cytokine-secreting cells were detected at day 80. The thymus, spleen, lymph nodes, and intestinal mucosa were examined for cells expressing CD3, CD5, CD20, CD68, p55, and HLA-DR. In the spleens of 65-day-old fetuses (early second trimester), the overwhelming majority of total lymphocytes were CD5+CD20+B-1 cells. The remaining lymphocytes were CD3+T cells. By day 80, splenic B and T cells were equal in number. Intraepithelial CD3+CD5−T cells and lamina propria CD20+CD5+B cells were present in the intestines of 65-day-old fetuses. By day 80, numerous CD20+CD5+B cells were present in the jejunums and colons and early lymphocyte aggregate formation was evident. The spleens of 80- to 145-day-old fetuses contained immunoglobulin M (IgM)-secreting cells, while IgA-, IgG-, interleukin-6-, and gamma interferon-secreting cells were numerous in the spleens and colons. Thus, by the second trimester, the lymphoid tissues of the rhesus monkey fetus have a complete repertoire of properly organized antigen-presenting cells, T cells, and B cells.
Keratinocyte Expression of Human β Defensin 2 following Bacterial Infection: Role in Cutaneous Host Defense
Authors: Dinulos James G. H. , Mentele Laurel , Fredericks L. Page , Dale Beverly A. , Darmstadt Gary L.
Published: January 2003

Human β defensin 2 (hβD-2) is thought to play an important role in cutaneous immune defense. We hypothesized that (i) keratinocyte expression of hβD-2, measured by reverse transcription-PCR, would be upregulated in response to challenge with pathogenic bacteria, particularly highly adherent strains of
Streptococcus pyogenes
and
Staphylococcus aureus
, and (ii) hβD-2 would have potent antimicrobial activity against pathogenic but not commensal organisms. Expression of hβD-2 was induced consistently by
S
.
aureus
,
Staphylococcus epidermidis
,
Escherichia coli
, and
Pseudomonas aeruginosa
, whereas strains of
S
.
pyogenes
were poor and variable inducers of hβD-2. No correlation was found between levels of bacterial adherence and keratinocyte expression of hβD-2.
S
.
pyogenes
was significantly more sensitive to killing by hβD-2 than
S
.
epidermidis
. We conclude that the ability to induce hβD-2 expression in combination with sensitivity to its antimicrobial effects may contribute to the rarity of skin infections with the gram-negative bacterial organisms, whereas lack of stimulation of hβD-2 expression by
S
.
pyogenes
may be important in its ability to evade innate defenses and cause skin disease. Induction of expression of hβD-2 but relative tolerance to it may enable
S
.
epidermidis
to survive on the skin surface and modulate hβD-2 expression when the stratum corneum barrier is disrupted.
Immunoglobulin G Antibodies against the Endosymbionts of Filarial Nematodes (
Wolbachia
) in Patients with Pulmonary Dirofilariasis
Authors: Simón F. , Prieto G. , Morchón R. , Bazzocchi C. , Bandi C. , Genchi C.
Published: January 2003

The dog parasite
Dirofilaria immitis
can infect humans. Patients with pulmonary dirofilariasis were tested for immunoglobulin G (IgG) antibodies against the surface protein of
Wolbachia
, the bacterial endosymbiont of
D
.
immitis
. These patients showed significantly higher IgG titers than healthy individuals from areas in which
D
.
immitis
was endemic as well as areas in which it was not endemic. Titration of anti-
Wolbachia
surface protein IgG could become useful for diagnostic applications.
Effect of Multiple Freeze-Thaw Cycles on Detection of Measles, Mumps, and Rubella Virus Antibodies
Authors: Pinsky Norman A. , Huddleston Jeanne M. , Jacobson Robert M. , Wollan Peter C. , Poland Gregory A.
Published: January 2003

We investigated the effect of multiple freeze-thaw cycles on mumps, measles, and rubella virus serum antibody levels with whole-virus immunoglobulin G enzyme-linked immunoassays. Fresh serum samples from nine healthy adult volunteers were divided into six sets of five aliquots each. Samples were taken through a total of 10 freeze-thaw cycles and stored at 4°C until assayed. Each assay measurement was done in replicates of five, and the mean value was reported. After completing 10 freeze-thaw cycles, we found no clinically or statistically significant effect on measured antibody levels and found no discernible detrimental effect on the ability to measure these antibodies by enzyme-linked immunoassays.
Systemic Immunoresponses in Mice after Repeated Exposure of Lungs to Spores of
Streptomyces californicus
Authors: Jussila J. , Pelkonen J. , Kosma V.-M. , Mäki-Paakkanen J. , Komulainen H. , Hirvonen M.-R.
Published: January 2003

Microbial growth in moisture-damaged buildings is associated with respiratory and other symptoms in the occupants.
Streptomyces
spp. are frequently isolated from such buildings. In the present study, we evaluated the responses of mice after repeated exposure to spores of
Streptomyces californicus
. Mice were exposed via intratracheal instillation to six doses (at 7-day intervals) of the spores of
S. californicus
, originally isolated from the indoor air of a moisture-damaged building, at three dose levels (2 × 10
3
, 2 × 10
5
, and 2 × 10
7
spores). Inflammation and toxicity, including changes in cell populations in the lungs, lymph nodes, and spleen, were evaluated 24 h after the last dosage. The exposure provoked a dose-dependent inflammatory cell response, as detected by the intense recruitment of neutrophils, but the numbers of macrophages and lymphocytes in the airways also increased. The cellular responses corresponded to the dose-dependent increases in inflammation- and cytotoxicity-associated biochemical markers (i.e., levels of albumin, total protein, and lactate dehydrogenase) in bronchoalveolar lavage fluid. The spore exposure increased the number of both activated and nonactivated T lymphocytes. Also, the amounts of CD3
−
CD4
−
and unconventional CD3
−
CD4
+
lymphocytes in the lung tissue were augmented. Interestingly, the spore exposure decreased cells in the spleen. This effect was strongest at the dose of 2 × 10
5
spores. These results indicate that the spores of
S. californicus
are capable of provoking both immunostimulation in lungs (inflammation) and systemic immunotoxicity, especially in the spleen. The immunotoxic effect resembled that caused by chemotherapeutic agents, originally isolated from
Streptomyces
spp. Thus,
S. californicus
must be considered a microbial species with potential to cause systemic adverse health effects in occupants of moisture-damaged buildings.
Destructive Arthritis in Vaccinated Interferon Gamma-Deficient Mice Challenged withBorrelia burgdorferi: Modulation by Tumor Necrosis Factor Alpha
Authors: Christopherson John A. , Munson Erik L. , England Douglas M. , Croke Cindy L. , Remington Monica C. , Molitor Melanie L. , DeCoster David J. , Callister Steven M. , Schell Ronald F.
Published: January 2003

We found thatBorrelia burgdorferi-vaccinated gamma interferon-deficient (IFN-γ0) mice challenged withB.burgdorferideveloped prominent chronic destructive osteoarthropathy. When these mice were treated with anti-tumor necrosis factor alpha (TNF-α) antibody, the severity of the destructive osteoarthritis was enhanced and affected the mobility of the animals. In addition, extensive swelling of the hind paws occurred. In contrast, treatment ofB.burgdorferi-vaccinated, challenged IFN-γ0mice with recombinant TNF-α (rTNF-α) inhibited the development of arthritis, including swelling of the hind paws. Moreover, treatment of vaccinated, challenged IFN-γ0mice with anti-TNF-α inhibited fourfold the production of an antibody that killsB.burgdorferi, while treatment of vaccinated, challenged IFN-γ0mice with rTNF-α slightly elevated the level of the borreliacidal antibody. These results suggest that the level of TNF-α directly or indirectly regulates the production of borreliacidal antibody and the development of vaccine-induced destructive Lyme osteoarthritis. Studies are in progress to determine the mechanism by which TNF-α-dependent cytokines generate the destructive arthritis.