bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical properties of acoustic emission signals from metal cutting processes
Authors: Farrelly F. A. , Petri A. , Pitolli L. , Pontuale G. , Tagliani A. , Novi Inverardi P. L.
Published: August 2004

Acoustic emission (AE) data from single point turning machining are analyzed in this paper in order to gain a greater insight of the signal statistical properties for tool condition monitoring applications. A statistical analysis of the time series data amplitude and root mean square (rms) value at various tool wear levels are performed, finding that aging features can be revealed in all cases from the observed experimental histograms. In particular, AE data amplitudes are shown to be distributed with a power-law behavior above a crossover value. An analytic model for the rms values probability density function is obtained resorting to the Jaynes’ maximum entropy principle; novel technique of constraining the modeling function under few fractional moments, instead of a greater amount of ordinary moments, leads to well-tailored functions for experimental histograms.
Perceptuomotor bias in the imitation of steady-state vowels
Authors: Vallabha Gautam K. , Tuller Betty
Published: August 2004

Previous studies suggest that speakers are systematically inaccurate, or biased, when imitating self-produced vowels. The direction of these biases in formant space and their variation may offer clues about the organization of the vowel perceptual space. To examine these patterns, three male speakers were asked to imitate 45 self-produced vowels that were systematically distributed in F1/F2 space. All three speakers showed imitation bias, and the bias magnitudes were significantly larger than those predicted by a model of articulatory noise. Each speaker showed a different pattern of bias directions, but the pattern was unrelated to the locations of prototypical vowels produced by that speaker. However, there were substantial quantitative regularities: (1) The distribution of imitation variability and bias magnitudes were similar for all speakers, (2) the imitation variability was independent of the bias magnitudes, and (3) the imitation variability (a production measure) was commensurate with the formant discrimination limen (a perceptual measure). These results indicate that there is additive Gaussian noise in the imitation process that independently affects each formant and that there are speaker-dependent and potentially nonlinguistic biases in vowel perception and production.
Frequent word section extraction in a presentation speech by an effective dynamic programming algorithm
Authors: Itoh Yoshiaki , Tanaka Kazuyo
Published: August 2004

Word frequency in a document has often been utilized in text searching and summarization. Similarly, identifying frequent words or phrases in a speech data set for searching and summarization would also be meaningful. However, obtaining word frequency in a speech data set is difficult, because frequent words are often special terms in the speech and cannot be recognized by a general speech recognizer. This paper proposes another approach that is effective for automatic extraction of such frequent word sections in a speech data set. The proposed method is applicable to any domain of monologue speech, because no language models or specific terms are required in advance. The extracted sections can be regarded as speech labels of some kind or a digest of the speech presentation. The frequent word sections are determined by detecting similar sections, which are sections of audio data that represent the same word or phrase. The similar sections are detected by an efficient algorithm, called Shift Continuous Dynamic Programming (Shift CDP), which realizes fast matching between arbitrary sections in the reference speech pattern and those in the input speech, and enables frame-synchronous extraction of similar sections. In experiments, the algorithm is applied to extract the repeated sections in oral presentation speeches recorded in academic conferences in Japan. The results show that Shift CDP successfully detects similar sections and identifies the frequent word sections in individual presentation speeches, without prior domain knowledge, such as language models and terms.
Age effects on discrimination of timing in auditory sequences
Authors: Fitzgibbons Peter J. , Gordon-Salant Sandra
Published: August 2004

The experiments examined age-related changes in temporal sensitivity to increments in the interonset intervals (IOI) of components in tonal sequences. Discrimination was examined using reference sequences consisting of five 50-ms tones separated by silent intervals; tone frequencies were either fixed at 4 kHz or varied within a 2–4-kHz range to produce spectrally complex patterns. The tonal IOIs within the reference sequences were either equal (200 or 600 ms) or varied individually with an average value of 200 or 600 ms to produce temporally complex patterns. The difference limen (DL) for increments of IOI was measured. Comparison sequences featured either equal increments in all tonal IOIs or increments in a single target IOI, with the sequential location of the target changing randomly across trials. Four groups of younger and older adults with and without sensorineural hearing loss participated. Results indicated that DLs for uniform changes of sequence rate were smaller than DLs for single target intervals, with the largest DLs observed for single targets embedded within temporally complex sequences. Older listeners performed more poorly than younger listeners in all conditions, but the largest age-related differences were observed for temporally complex stimulus conditions. No systematic effects of hearing loss were observed.
Environmentally adaptive reverberation nulling using a time reversal mirror
Authors: Song H. C. , Kim S. , Hodgkiss W. S. , Kuperman W. A.
Published: August 2004

Backscattering from the rough water-bottom interface can serve as a surrogate probe source in time reversal. A time-gated portion of the reverberation then is refocused to the bottom interface at the corresponding range [Lingevitch et al., J. Acoust. Soc. Am. 111, 2609–2614 (2002)]. In this paper, reverberation nulling is investigated to enhance active target detection without a priori knowledge of the environment. The basic idea is to minimize the acoustic energy incident on the corresponding scattering interface by applying an excitation weight vector on the time reversal mirror which is in the complementary subspace orthogonal to the focusing vector. Numerical simulations illustrate the potential of reverberation nulling using a time reversal mirror.
A linear least-squares version of the algorithm of mode isolation for identifying modal properties. Part II: Application and assessment
Authors: Allen Matt , Ginsberg Jerry H.
Published: August 2004

The latest modifications of the algorithm of mode isolation (AMI) for identification of modal properties from frequency response data are tested with synthetic data derived from an analytical model of an elastic frame in which flexure and torsion are coupled. The parameters of this model are selected to cause the occurrence of localized modal patterns in two modes having close natural frequencies. The response data is contaminated with white noise at a level sufficient to almost mask the two close modes. Results for the real and imaginary part of the eigenvalues are tabulated. The analytical modal patterns of displacement and torsional rotation are depicted graphically, accompanied by the discrete values obtained from AMI. Excellent agreement is found to occur for each mode, other than one of the pair of close modes. The poorer quality of that mode’s identified properties is shown to be a consequence of its localized modal pattern. Results for the eigenvalues obtained by the rational fraction polynomial algorithm, which is an alternative modal identification technique, are found to be substantially less accurate as a consequence of difficulty in the presence of noise.
Effect of polymer surface activity on cavitation nuclei stability against dissolution
Authors: Porter Tyrone M. , Crum Lawrence A. , Stayton Patrick S. , Hoffman Allan S.
Published: August 2004

The persistence of acoustic cavitation in a pulsed wave ultrasound regime depends upon the ability of cavitation nuclei, i.e., bubbles, to survive the off time between pulses. Due to the dependence of bubble dissolution on surface tension, surface-active agents may affect the stability of bubbles against dissolution. In this study, measurements of bubble dissolution rates in solutions of the surface-active polymer poly(propyl acrylic acid) (PPAA) were conducted to test this premise. The surface activity of PPAA varies with solution pH and concentration of dissolved polymer molecules. The surface tension of PPAA solutions (55–72 dynes/cm) that associated with the polymer surface activity was measured using the Wilhelmy plate technique. Samples of these polymer solutions then were exposed to 1.1 MHz high intensity focused ultrasound, and the dissolution of bubbles created by inertial cavitation was monitored using an active cavitation detection scheme. Analysis of the pulse echo data demonstrated that bubble dissolution time was inversely proportional to the surface tension of the solution. Finally, comparison of the experimental results with dissolution times computed from the Epstein–Plesset equation suggests that the radii of residual bubbles from inertial cavitation increase as the surface tension decreases.
Categorization and discrimination of nonspeech sounds: Differences between steady-state and rapidly-changing acoustic cues
Authors: Mirman Daniel , Holt Lori L. , McClelland James L.
Published: August 2004

Different patterns of performance across vowels and consonants in tests of categorization and discrimination indicate that vowels tend to be perceived more continuously, or less categorically, than consonants. The present experiments examined whether analogous differences in perception would arise in nonspeech sounds that share critical transient acoustic cues of consonants and steady-state spectral cues of simplified synthetic vowels. Listeners were trained to categorize novel nonspeech sounds varying along a continuum defined by a steady-state cue, a rapidly-changing cue, or both cues. Listeners’ categorization of stimuli varying on the rapidly changing cue showed a sharp category boundary and posttraining discrimination was well predicted from the assumption of categorical perception. Listeners more accurately discriminated but less accurately categorized steady-state nonspeech stimuli. When listeners categorized stimuli defined by both rapidly-changing and steady-state cues, discrimination performance was accurate and the categorization function exhibited a sharp boundary. These data are similar to those found in experiments with dynamic vowels, which are defined by both steady-state and rapidly-changing acoustic cues. A general account for the speech and nonspeech patterns is proposed based on the supposition that the perceptual trace of rapidly-changing sounds decays faster than the trace of steady-state sounds.
Local/global homogenization of fluid-loaded periodic structures
Authors: Danilov Pavel , Bliss Donald
Published: August 2004

A novel homogenization method for periodic structures that utilizes a local/global separation of the high and low wavenumber spectrum is presented. The low-wavenumber global problem has an infinite-order operator. The global problem is self-contained; local solutions can be reconstructed after the fact if desired. Global problems are constructed for a membrane and a plate in vacuo, each with periodic impedance discontinuities. A fluid-loading approximation is introduced in order to homogenize problems of interaction between fluid and structure. Radiating acoustic modes are contained in the smooth global problem, and the global structural operator accounts for an influence of evanescent acoustic modes. As an example, oblique sound reflection from a flexible barrier with impedance discontinuities is analyzed. Accurate results are obtained from the method.
Response of multiple rigid porous layers to high levels of continuous acoustic excitation
Authors: Umnova Olga , Attenborough Keith , Shin Ho-Chul , Cummings Alan
Published: August 2004

A model has been developed for the response of a rigid-porous hard-backed medium containing an arbitrary number of layers to high amplitude sound. Nonlinearity is introduced by means of a velocity-dependent flow resistivity in Johnson’s equivalent fluid model for the complex tortuosity of each layer. Numerical solution of the resulting system of algebraic equations allows prediction of the dependence of surface impedance and reflection coefficient on the incident pressure amplitude. Measurements have been made of the surface impedance of various triple layers, made from different diameters of spherical lead shot and double layers consisting of gravel with different mean particle size, subject to high-intensity continuous sound. Good agreement between the model predictions and data for these multiple-granular layers is demonstrated. Moreover it is shown both theoretically and experimentally that the layer configuration giving optimum performance at low sound intensities may not continue to do so as the incident sound level is increased and the response becomes increasingly nonlinear. It is shown also that the nonlinear behavior depends strongly on layering and that, in some cases, the behavior is changed simply by changing the top layer thickness.
Quantifying the auditory saltation illusion: An objective psychophysical methodology
Authors: Kidd Joanna C. , Hogben John H.
Published: August 2004

Under conditions of rapid presentation, brief acoustic stimuli repeatedly delivered first at one location, then at another, are systematically mislocalized, with stimuli perceived as traveling smoothly between the two locations. This robust illusory motion percept is termed “auditory saltation.” Currently, the characteristics and mechanisms of auditory saltation are not well understood. The lack of objective methods capable of quantifying the illusion on an individual basis seems a limiting factor for this area of research. In this study, we outline an objective psychophysical task that estimates the interstimulus interval at which the saltation illusion is reliably distinguishable from simulated motion. Experiment 1 examined the psychophysical function relating task performance to ISI and addressed the suitability of the task for use with adaptive psychophysical procedures. Experiment 2 directly compared performance on the task with that of another quantification method. The results suggested that this objective approach to the study of auditory saltation overcomes difficulties associated with more subjective methods, and provides a reliable paradigm within which to quantify the temporal parameters of saltation on an individual basis.
Power spectrum of shear waves in finite one-dimensional granular medium
Authors: de Billy M.
Published: August 2004

In this paper, we consider the propagation of shear acoustic waves in a single spherical bead and in linear one-dimensional periodic chains of identical spheres. In both cases, normal force of interaction compresses the sphere(s) and obeys the nonlinear Hertz’ law. In the low-frequency domain, the spectroscopy of the transmitted impulses gives rise to peaks the existence and the origin of which are discussed.
Theoretical study in applications of doublet mechanics to detect tissue pathological changes in elastic properties using high frequency ultrasound
Authors: Layman Christopher , Wu Junru
Published: August 2004

The mathematical framework of a new elastic theory—doublet mechanics (DM)—was reviewed. The fundamental difference between DM and classical continuum mechanics (CCM) is that the former has taken the discrete nature of tissue on the cellular level into account and the latter assumes tissue is uniform and continuous. Theoretical calculations based on DM were performed for reflection coefficients of a substrate–tissue layer–substrate assembly. Results of computer simulations have shown that ultrasound reflection coefficients in the range of 15–30 MHz are sensitive to changes in cell size and elastic moduli of tissue according to DM but not to CCM. Potential experimental applications of this technique to tissue characterization are discussed.
Manipulation of sound intensity within a selected region using multiple sources
Authors: Choi Joung-Woo , Kim Yang-Hann
Published: August 2004

In this paper, the authors propose a method of enhancing sound in a selected region by controlling multiple sources. The physical variables of enhancing sound have not been well defined, but we may consider basic acoustic variables such as acoustic potential energy, sound power or intensity. A method of maximizing sound potential energy was found to be very straightforward [J.-W. Choi and Y.-H. Kim, J. Acoust. Soc. Am. 111, 1695 (2002)]. In this paper, the authors attempt to control the sound power or intensity of a zone in a desired direction. It is noteworthy that control of the direction and magnitude is needed to enhance the sound intensity. This control requires a new definition of the direction and magnitude of spatially distributed intensity. For this purpose, the authors introduce two different kinds of cost functions, and the theoretical formulation based on the new definitions show the possibility of maximizing the sound intensity of a selected zone in a desired direction.
Virtual sensing for broadband noise control in a lightly damped enclosure
Authors: Yuan Jing
Published: August 2004

Available virtual sensing schemes either depend on assumptions that are valid for isolated frequencies, or require heavy online adaptations. A simple method is proposed here to predict the virtual signal exactly for broadband noise control in a lightly damped enclosure. The proposed method requires two physical sensors installed judiciously in a sound field to predict a virtual signal. The method is based on an exact mathematical relation between the virtual and physical sensors, which is valid for the entire frequency of interest. It is possible to use multiple sensor-pairs to reduce the sensitivity of the proposed method with respect to acoustic parameters, such as speed of sound or sensor mismatching. Experimental results are presented to verify the analytical results.
Vowel formant discrimination for high-fidelity speech
Authors: Liu Chang , Kewley-Port Diane
Published: August 2004

The goal of this study was to establish the ability of normal-hearing listeners to discriminate formant frequency in vowels in everyday speech. Vowel formant discrimination in syllables, phrases, and sentences was measured for high-fidelity (nearly natural) speech synthesized by STRAIGHT [Kawahara et al., Speech Commun. 27, 187–207 (1999)]. Thresholds were measured for changes in F1 and F2 for the vowels /ɪ, ɛ, æ, Λ/ in /bVd/ syllables. Experimental factors manipulated included phonetic context (syllables, phrases, and sentences), sentence discrimination with the addition of an identification task, and word position. Results showed that neither longer phonetic context nor the addition of the identification task significantly affected thresholds, while thresholds for word final position showed significantly better performance than for either initial or middle position in sentences. Results suggest that an average of 0.37 barks is required for normal-hearing listeners to discriminate vowel formants in modest length sentences, elevated by 84% compared to isolated vowels. Vowel formant discrimination in several phonetic contexts was slightly elevated for STRAIGHT-synthesized speech compared to formant-synthesized speech stimuli reported in the study by Kewley-Port and Zheng [J. Acoust. Soc. Am. 106, 2945–2958 (1999)]. These elevated thresholds appeared related to greater spectral-temporal variability for high-fidelity speech produced by STRAIGHT than for formant-synthesized speech.
The across frequency independence of equalization of interaural time delay in the equalization-cancellation model of binaural unmasking
Authors: Akeroyd Michael A.
Published: August 2004

The equalization stage in the equalization-cancellation model of binaural unmasking compensates for the interaural time delay (ITD) of a masking noise by introducing an opposite, internal delay [N. I. Durlach, in Foundations of Modern Auditory Theory, Vol. II., edited by J. V. Tobias (Academic, New York, 1972)]. Culling and Summerfield [J. Acoust. Soc. Am. 98, 785–797 (1995)] developed a multi-channel version of this model in which equalization was “free” to use the optimal delay in each channel. Two experiments were conducted to test if equalization was indeed free or if it was “restricted” to the same delay in all channels. One experiment measured binaural detection thresholds, using an adaptive procedure, for 1-, 5-, or 17-component tones against a broadband masking noise, in three binaural configurations (N0S180, N180S0, and N90S270). The thresholds for the 1-component stimuli were used to normalize the levels of each of the 5- and 17-component stimuli so that they were equally detectable. If equalization was restricted, then, for the 5- and 17-component stimuli, the N90S270 and N180S0 configurations would yield a greater threshold than the N0S180 configurations. No such difference was found. A subsequent experiment measured binaural detection thresholds, via psychometric functions, for a 2-component complex tone in the same three binaural configurations. Again, no differential effect of configuration was observed. An analytic model of the detection of a complex tone showed that the results were more consistent with free equalization than restricted equalization, although the size of the differences was found to depend on the shape of the psychometric function for detection.
Mathematical modeling of the radial profile of basilar membrane vibrations in the inner ear
Authors: Homer Martin , Champneys Alan , Hunt Giles , Cooper Nigel
Published: August 2004

Motivated by recent experimental results, an explanation is sought for the asymmetry in the radial profile of basilar membrane vibrations in the inner ear. A sequence of one-dimensional beam models is studied which take into account variations in the bending stiffness of the basilar membrane as well as the potential presence of structural hinges. The results suggest that the main cause of asymmetry is likely to be differences between the boundary conditions at the two extremes of the basilar membrane’s width. This has fundamental implications for more detailed numerical simulations of the entire cochlea.
Modal theory applied to the acoustic scattering by elastic cylinders of arbitrary cross section
Authors: Léon Fernand , Chati Farid , Conoir Jean-Marc
Published: August 2004

A modal theory is developed for investigating the acoustic scattering by elastic cylinders of arbitrary cross section immersed in a fluid. Numerical results are presented for a plane wave incidence normal to the axis of an elliptical cylinder but arbitrary with respect to the noncircular cross section. Experimental results are obtained for an aluminum elliptical cylinder with the use of an impulse method. Comparisons between theoretical and experimental data are performed in the broad frequency range 8.5⩽ka⩽30 (k is the wave number in the fluid and a the major axis radius of the elliptic cylinder). The experimental observations are in good agreement with the theoretical predictions.
The field of sound of a circular membrane
Authors: Zeitler Berndt , Zeitler Elmar
Published: August 2004

In this note we give a simple straightforward method for obtaining, in closed form, the expansion coefficients in the solution of a basic acoustic problem with symmetry, the baffled vibrating membrane.
Adapting the Lagrangian speckle model estimator for endovascular elastography: Theory and validation with simulated radio-frequency data
Authors: Maurice Roch L. , Ohayon Jacques , Finet Gérard , Cloutier Guy
Published: August 2004

Intravascular ultrasound (IVUS) is known to be the reference tool for preoperative vessel lesion assessments and for endovascular therapy planning. Nevertheless, IVUS echograms only provide subjective information about vessel wall lesions. Since changes in the vascular tissue stiffness are characteristic of vessel pathologies, catheter-based endovascular ultrasound elastography (EVE) has been proposed in the literature as a method for outlining the elastic properties of vessel walls. In this paper, the Lagrangian Speckle Model Estimator (LSME) is formulated for investigations in EVE, i.e., using a polar coordinate system. The method was implemented through an adapted version of the Levenberg-Marquardt minimization algorithm, using the optical flow equations to compute the Jacobbian matrix. The theoretical framework was validated with simulated ultrasound rf data of mechanically complex vessel wall pathologies. The results, corroborated with Ansys finite element software, demonstrated the potential of EVE to provide useful information about the heterogeneous nature of atherosclerotic plaques.
Wideband micromachined capacitive microphones with radio frequency detection
Authors: Hansen Sean T. , Ergun A. Sanli , Liou William , Auld Bertram A. , Khuri-Yakub Butrus T.
Published: August 2004

Silicon microphones based on capacitive micromachined ultrasonic transducer membranes and radio frequency detection overcome many of the limitations in bandwidth, uniformity of response, and durability associated with micromachined condenser microphones. These membranes are vacuum-sealed to withstand submersion in water and have a flat mechanical response from dc up to ultrasonic frequencies. However, a sensitive radio frequency detection scheme is necessary to detect the small changes in membrane displacement that result from utilizing small membranes. In this paper we develop a mathematical model for calculating the expected output signal and noise level and verifies the model with measurements on a fabricated microphone. Measurements on a sensor with 1.3 mm2 area demonstrate less than 0.5 dB variation in the output response between 0.1 Hz to 100 kHz under electrostatic actuation and an A-weighted equivalent noise level of 63.6 dB(A) SPL in the audio band. Because the vacuum-sealed membrane structure has a low mechanical noise floor, there is the potential for improved sensitivity using higher carrier frequencies and more sophisticated detection circuitry.
Space–time variations of the acoustic field scattered from a penetrable isovelocity wedge
Authors: Feuillade C. , Chu D. , Clay C. S.
Published: August 2004

The formalism of D. Chu [J. Acoust. Soc. Am. 86, 1883–1896 (1989)] is used to detail the spatial and time domain variations of the scattered field of a penetrable isovelocity wedge. The direct, reflected, and diffracted field components, and their relationships, are investigated. Since diffractions often dominate rough surface scattering, these waves are carefully studied, with particular emphasis on the wave phenomena and transition behavior around the forward scattering shadow boundary, where the causal relationship between the direct and diffracted fields is specifically examined. The wave processes here, and above and below the geometrical shadow zone, lead to complicated temporal and azimuthal variations of the field. The phenomenon of diffractions associated with specular reflections of the source in the wedge faces is also studied. Among the conclusions reached are (i) direct/reflected impulses arrive first, followed by and separated from their associated diffractions; (ii) the direct/reflected impulse is a delta function, with arrival predicted by the source-receiver raypath travel time, and amplitude determined by spherical spreading and reflection/transmission coefficients at the wedge faces; and (iii) diffractions are causally associated with direct/reflected impulses interacting with the wedge apex, and their amplitude depends on the degree of acoustic shadowing at the apex.
The role of head-induced interaural time and level differences in the speech reception threshold for multiple interfering sound sources
Authors: Culling John F. , Hawley Monica L. , Litovsky Ruth Y.
Published: August 2004

Three experiments investigated the roles of interaural time differences (ITDs) and level differences (ILDs) in spatial unmasking in multi-source environments. In experiment 1, speech reception thresholds (SRTs) were measured in virtual-acoustic simulations of an anechoic environment with three interfering sound sources of either speech or noise. The target source lay directly ahead, while three interfering sources were (1) all at the target’s location (0°,0°,0°), (2) at locations distributed across both hemifields (−30°,60°,90°), (3) at locations in the same hemifield (30°,60°,90°), or (4) co-located in one hemifield (90°,90°,90°). Sounds were convolved with head-related impulse responses (HRIRs) that were manipulated to remove individual binaural cues. Three conditions used HRIRs with (1) both ILDs and ITDs, (2) only ILDs, and (3) only ITDs. The ITD-only condition produced the same pattern of results across spatial configurations as the combined cues, but with smaller differences between spatial configurations. The ILD-only condition yielded similar SRTs for the (−30°,60°,90°) and (0°,0°,0°) configurations, as expected for best-ear listening. In experiment 2, pure-tone BMLDs were measured at third-octave frequencies against the ITD-only, speech-shaped noise interferers of experiment 1. These BMLDs were 4–8 dB at low frequencies for all spatial configurations. In experiment 3, SRTs were measured for speech in diotic, speech-shaped noise. Noises were filtered to reduce the spectrum level at each frequency according to the BMLDs measured in experiment 2. SRTs were as low or lower than those of the corresponding ITD-only conditions from experiment 1. Thus, an explanation of speech understanding in complex listening environments based on the combination of best-ear listening and binaural unmasking (without involving sound-localization) cannot be excluded.
Coding of vowellike signals in cochlear implant listeners
Authors: Laback Bernhard , Deutsch Werner A. , Baumgartner Wolf-Dieter
Published: August 2004

Neural-population interactions resulting from excitation overlap in multi-channel cochlear implants (CI) may cause blurring of the “internal” auditory representation of complex sounds such as vowels. In experiment I, confusion matrices for eight German steady-state vowellike signals were obtained from seven CI listeners. Identification performance ranged between 42% and 74% correct. On the basis of an information transmission analysis across all vowels, pairs of most and least frequently confused vowels were selected for each subject. In experiment II, vowel masking patterns (VMPs) were obtained using the previously selected vowels as maskers. The VMPs were found to resemble the “electrical” vowel spectra to a large extent, indicating a relatively weak effect of neural-population interactions. Correlation between vowel identification data and VMP spectral similarity, measured by means of several spectral distance metrics, showed that the CI listeners identified the vowels based on differences in the between-peak spectral information as well as the location of spectral peaks. The effect of nonlinear amplitude mapping of acoustic into “electrical” vowels, as performed in the implant processors, was evaluated separately and compared to the effect of neural-population interactions. Amplitude mapping was found to cause more blurring than neural-population interactions. Subjects exhibiting strong blurring effects yielded lower overall vowel identification scores.
Cochlear implant speech recognition with speech maskers
Authors: Stickney Ginger S. , Zeng Fan-Gang , Litovsky Ruth , Assmann Peter
Published: August 2004

Speech recognition performance was measured in normal-hearing and cochlear-implant listeners with maskers consisting of either steady-state speech-spectrum-shaped noise or a competing sentence. Target sentences from a male talker were presented in the presence of one of three competing talkers (same male, different male, or female) or speech-spectrum-shaped noise generated from this talker at several target-to-masker ratios. For the normal-hearing listeners, target-masker combinations were processed through a noise-excited vocoder designed to simulate a cochlear implant. With unprocessed stimuli, a normal-hearing control group maintained high levels of intelligibility down to target-to-masker ratios as low as 0 dB and showed a release from masking, producing better performance with single-talker maskers than with steady-state noise. In contrast, no masking release was observed in either implant or normal-hearing subjects listening through an implant simulation. The performance of the simulation and implant groups did not improve when the single-talker masker was a different talker compared to the same talker as the target speech, as was found in the normal-hearing control. These results are interpreted as evidence for a significant role of informational masking and modulation interference in cochlear implant speech recognition with fluctuating maskers. This informational masking may originate from increased target-masker similarity when spectral resolution is reduced.
KIF1A Alternately Uses Two Loops to Bind Microtubules
Authors: Nitta Ryo , Kikkawa Masahide , Okada Yasushi , Hirokawa Nobutaka
Published: July 2004

The motor protein kinesin moves along microtubules, driven by adenosine triphosphate (ATP) hydrolysis. However, it remains unclear how kinesin converts the chemical energy into mechanical movement. We report crystal structures ofmonomeric kinesin KIF1A with three transition-state analogs: adenylyl imidodiphosphate (AMP-PNP), adenosine diphosphate (ADP)–vanadate, and ADP-AlFx (aluminofluoride complexes). These structures, together with known structures of the ADP-bound state and the adenylyl-(β,γ-methylene) diphosphate (AMP-PCP)–bound state, show that kinesin uses two microtubule-binding loops in an alternating manner to change its interaction with microtubules during the ATP hydrolysis cycle; loop L11 is extended in the AMP-PNP structure, whereas loop L12 is extended in the ADP structure. ADP-vanadate displays an intermediate structure in which a conformational change in two switch regions causes both loops to be raised from the microtubule, thus actively detaching kinesin.
Osedax
: Bone-Eating Marine Worms with Dwarf Males
Authors: Rouse G. W. , Goffredi S. K. , Vrijenhoek R. C.
Published: July 2004

We describe a new genus,
Osedax
, and two new species of annelids with females that consume the bones of dead whales via ramifying roots. Molecular and morphological evidence revealed that
Osedax
belongs to the Siboglinidae, which includes pogonophoran and vestimentiferan worms from deep-sea vents, seeps, and anoxic basins.
Osedax
has skewed sex ratios with numerous dwarf (paedomorphic) males that live in the tubes of females. DNA sequences reveal that the two
Osedax
species diverged about 42 million years ago and currently maintain large populations ranging from 10
5
to 10
6
adult females.
Grain Boundary-Mediated Plasticity in Nanocrystalline Nickel
Authors: Shan Zhiwei , Stach E. A. , Wiezorek J. M. K. , Knapp J. A. , Follstaedt D. M. , Mao S. X.
Published: July 2004

The plastic behavior of crystalline materials is mainly controlled by the nucleation and motion of lattice dislocations. We report in situ dynamic transmission electron microscope observations of nanocrystalline nickel films with an average grain size of about 10 nanometers, which show that grain boundary–mediated processes have become a prominent deformation mode. Additionally, trapped lattice dislocations are observed in individual grains following deformation. This change in the deformation mode arises from the grain size–dependent competition between the deformation controlled by nucleation and motion of dislocations and the deformation controlled by diffusion-assisted grain boundary processes.
Engineered Interface of Magnetic Oxides
Authors: Yamada Hiroyuki , Ogawa Yoshihiro , Ishii Yuji , Sato Hiroshi , Kawasaki Masashi , Akoh Hiroshi , Tokura Yoshinori
Published: July 2004

Interface-selective probing of magnetism is a key issue for the design and realization of spin-electronic junction devices. Here, magnetization-induced second-harmonic generation was used to probe the local magnetic properties at the interface of the perovskite ferromagnet La
0.6
Sr
0.4
MnO
3
with nonmagnetic insulating layers, as used in spin-tunnel junctions. We show that by grading the doping profile on an atomic scale at the interface, robust ferromagnetism can be realized around room temperature. The results should lead to improvements in the performance of spin-tunnel junctions.
Herbivores Promote Habitat Specialization by Trees in Amazonian Forests
Authors: Fine Paul V. A. , Mesones Italo , Coley Phyllis D.
Published: July 2004

In an edaphically heterogeneous area in the Peruvian Amazon, clay soils and nutrient-poor white sands each harbor distinctive plant communities. To determine whether a trade-off between growth and antiherbivore defense enforces habitat specialization on these two soil types, we conducted a reciprocal transplant study of seedlings of 20 species from sixgenera of phylogenetically independent pairs of edaphic specialist trees and manipulated the presence of herbivores. Clay specialist species grew significantly faster than white-sand specialists in both soil types when protected from herbivores. However, when unprotected, white-sand specialists dominated in white-sand forests and clay specialists dominated in clay forests. Therefore, habitat specialization in this system results from an interaction of herbivore pressure with soil type.
Foundering Lithosphere Imaged Beneath the Southern Sierra Nevada, California, USA
Authors: Boyd Oliver S. , Jones Craig H. , Sheehan Anne F.
Published: July 2004

Seismic tomography reveals garnet-rich crust and mantle lithosphere descending into the upper mantle beneath the southeastern Sierra Nevada. The descending lithosphere consists of two layers: an iron-rich eclogite above a magnesium-rich garnet peridotite. These results place descending eclogite above and east of high
P
wave speed material previously imaged beneath the southern Great Valley, suggesting a previously unsuspected coherence in the lithospheric removal process.
The Pathophysiology of Mitochondrial Cell Death
Authors: Green Douglas R. , Kroemer Guido
Published: July 2004

In the mitochondrial pathway of apoptosis, caspase activation is closely linked to mitochondrial outer membrane permeabilization (MOMP). Numerous pro-apoptotic signal-transducing molecules and pathological stimuli converge on mitochondria to induce MOMP. The local regulation and execution of MOMP involve proteins from the Bcl-2 family, mitochondrial lipids, proteins that regulate bioenergetic metabolite flux, and putative components of the permeability transition pore. MOMP is lethal because it results in the release of caspase-activating molecules and caspase-independent death effectors, metabolic failure in the mitochondria, or both. Drugs designed to suppress excessive MOMP may avoid pathological cell death, and the therapeutic induction of MOMP may restore apoptosis in cancer cells in which it is disabled. The general rules governing the pathophysiology of MOMP and controversial issues regarding its regulation are discussed.
Pinpointing the Source of a Lunar Meteorite: Implications for the Evolution of the Moon
Authors: Gnos Edwin , Hofmann Beda A. , Al-Kathiri Ali , Lorenzetti Silvio , Eugster Otto , Whitehouse Martin J. , Villa Igor M. , Jull A. J. Timothy , Eikenberg Jost , Spettel Bernhard , Krähenbühl Urs , Franchi Ian A. , Greenwood Richard C.
Published: July 2004

The lunar meteorite Sayh al Uhaymir 169 consists of an impact melt breccia extremely enriched with potassium, rare earth elements, and phosphorus [thorium, 32.7 parts per million (ppm); uranium, 8.6 ppm; potassium oxide, 0.54 weight percent], and adherent regolith. The isotope systematics of the meteorite record four lunar impact events at 3909 ± 13 million years ago (Ma), ∼2800 Ma, ∼200 Ma, and <0.34 Ma, and collision with Earth sometime after 9.7 ± 1.3 thousand years ago. With these data, we can link the impact-melt breccia to Imbrium and pinpoint the source region of the meteorite to the Lalande impact crater.
Synthetic Mammalian Prions
Authors: Legname Giuseppe , Baskakov Ilia V. , Nguyen Hoang-Oanh B. , Riesner Detlev , Cohen Fred E. , DeArmond Stephen J. , Prusiner Stanley B.
Published: July 2004

Recombinant mouse prion protein (recMoPrP) produced in
Escherichia coli
was polymerized into amyloid fibrils that represent a subset of β sheet–rich structures. Fibrils consisting of recMoPrP(89–230) were inoculated intracerebrally into transgenic (Tg) mice expressing MoPrP(89–231). The mice developed neurologic dysfunction between 380 and 660 days after inoculation. Brain extracts showed protease-resistant PrP by Western blotting; these extracts transmitted disease to wild-type FVB mice and Tg mice overexpressing PrP, with incubation times of 150 and 90 days, respectively. Neuropathological findings suggest that a novel prion strain was created. Our results provide compelling evidence that prions are infectious proteins.
The Complete Genome Sequence of
Propionibacterium Acnes
, a Commensal of Human Skin
Authors: Brüggemann Holger , Henne Anke , Hoster Frank , Liesegang Heiko , Wiezer Arnim , Strittmatter Axel , Hujer Sandra , Dürre Peter , Gottschalk Gerhard
Published: July 2004

Propionibacterium acnes
is a major inhabitant of adult human skin, where it resides within sebaceous follicles, usually as a harmless commensal although it has been implicated in acne vulgaris formation. The entire genome sequence of this Gram-positive bacterium encodes 2333 putative genes and revealed numerous gene products involved in degrading host molecules, including sialidases, neuraminidases, endoglycoceramidases, lipases, and pore-forming factors. Surface-associated and other immunogenic factors have been identified, which might be involved in triggering acne inflammation and other
P. acnes
–associated diseases.
APOBEC-Mediated Editing of Viral RNA
Authors: Bishop Kate N. , Holmes Rebecca K. , Sheehy Ann M. , Malim Michael H.
Published: July 2004

Retroviral DNA can be subjected to cytosine-to-uracil editing through the action of members of the APOBEC family of cytidine deaminases. Here we demonstrate that APOBEC-mediated cytidine deamination of human immunodeficiency virus (HIV) virion RNA can also occur. We speculate that the natural substrates of the APOBEC enzymes may extend to RNA viruses that do not replicate through DNA intermediates. Thus, cytosine-to-uracil editing may contribute to the sequence diversification of many viruses.
Hunting for Origins
Authors: Cameron R. Andrew
Published: July 2004

On the Origin of Phyla
. by James W. Valentine. University of Chicago Press, Chicago, 2004. 638 pp. $55, £38.50. ISBN 0-226-84548-6.

The authors provide a thorough and critical review and synthesis of recent research on the origin of species, covering both plants and animals.
How Species Arise
Authors: Blackman Benjamin K. , Rieseberg Loren H.
Published: July 2004

Speciation
. by Jerry A. Coyne and H. Allen Orr. Sinauer, Sunderland, MA, 2004. 557 pp. $89.95. ISBN 0-87893-091-4. Paper, $54.95, £34.99. ISBN 0-87893-089-2.

The authors provide a thorough and critical review and synthesis of recent research on the origin of species, covering both plants and animals
Mating Type Sequences in Asexually Reproducing
Fusarium
Species
Authors: Kerényi Zoltán , Moretti Antonio , Waalwijk Cees , Oláh Brigitta , Hornok László
Published: August 2004

To assess the potential for mating in several
Fusarium
species with no known sexual stage, we developed degenerate and semidegenerate oligonucleotide primers to identify conserved mating type (
MAT
) sequences in these fungi. The putative α and high-mobility-group (HMG) box sequences from
Fusarium avenaceum
,
F. culmorum
,
F. poae
, and
F. semitectum
were compared to similar sequences that were described previously for other members of the genus. The DNA sequences of the regions flanking the amplified
MAT
regions were obtained by inverse PCR. These data were used to develop diagnostic primers suitable for the clear amplification of conserved mating type sequences from any member of the genus
Fusarium
. By using these diagnostic primers, we identified mating types of 122 strains belonging to 22 species of
Fusarium
. The α box and the HMG box from the mating type genes are transcribed in
F. avenaceum
,
F. culmorum
,
F. poae
, and
F. semitectum
. The novelty of the PCR-based mating type identification system that we developed is that this method can be used on a wide range of
Fusarium
species, which have proven or expected teleomorphs in different ascomycetous genera, including
Calonectria
,
Gibberella
, and
Nectria
.
Polyhydroxyalkanoate (PHA) Accumulation in Sulfate-Reducing Bacteria and Identification of a Class III PHA Synthase (PhaEC) in
Desulfococcus multivorans
Authors: Hai Tran , Lange Daniela , Rabus Ralf , Steinbüchel Alexander
Published: August 2004

Seven strains of sulfate-reducing bacteria (SRB) were tested for the accumulation of polyhydroxyalkanoates (PHAs). During growth with benzoate
Desulfonema magnum
accumulated large amounts of poly(3-hydroxybutyrate) [poly(3HB)].
Desulfosarcina variabilis
(during growth with benzoate),
Desulfobotulus sapovorans
(during growth with caproate), and
Desulfobacterium autotrophicum
(during growth with caproate) accumulated poly(3HB) that accounted for 20 to 43% of cell dry matter.
Desulfobotulus sapovorans
and
Desulfobacterium autotrophicum
also synthesized copolyesters consisting of 3-hydroxybutyrate and 3-hydroxyvalerate when valerate was used as the growth substrate.
Desulfovibrio vulgaris
and
Desulfotalea psychrophila
were the only SRB tested in which PHAs were not detected. When total DNA isolated from
Desulfococcus multivorans
and specific primers deduced from highly conserved regions of known PHA synthases (PhaC) were used, a PCR product homologous to the central region of class III PHA synthases was obtained. The complete
pha
locus of
Desulfococcus multivorans
was subsequently obtained by inverse PCR, and it contained adjacent

phaE
Dm

and

phaC
Dm

genes. PhaC

Dm

and PhaE

Dm

were composed of 371 and 306 amino acid residues and showed up to 49 or 23% amino acid identity to the corresponding subunits of other class III PHA synthases. Constructs of

phaC
Dm

alone (pBBRMCS-2::

phaC
Dm

) and of

phaE
Dm
C
Dm

(pBBRMCS-2::

phaE
Dm
C
Dm

) in various vectors were obtained and transferred to several strains of
Escherichia coli
, as well as to the PHA-negative mutants PHB
−
4 and GPp104 of
Ralstonia eutropha
and
Pseudomonas putida
, respectively. In cells of the recombinant strains harboring

phaE
Dm
C
Dm

small but significant amounts (up to 1.7% of cell dry matter) of poly(3HB) and of PHA synthase activity (up to 1.5 U/mg protein) were detected. This indicated that the cloned genes encode functionally active proteins. Hybrid synthases consisting of PhaC

Dm

and PhaE of
Thiococcus pfennigii
or
Synechocystis
sp. strain PCC 6308 were also constructed and were shown to be functionally active.