bluuebunny/crossref_metadata_2025 huggingface dataset:
Acoustic modes in a thin rigid cylinder with periodic gaps
Authors: Chang S. K.
Published: January 2006

Axisymmetric acoustic modes in a thin rigid cylinder with periodic gaps immersed in a fluid are studied. The gaps are circular slots on the circumference of the cylinder. The displacement potential in the fluid is expressed in terms of the Floquet waves in the cylindrical geometry. A Galerkin's method is applied to formulate the linear equations in relation to the boundary conditions on the cylinder and in the gaps. The modal wavenumbers are the location of the zeroes of the determinant of the matrix in the complex wavenumber plane. The zeroes are found by a Newton-Raphson iterative method. For an axisymmetric acoustic field, the modes are leaky waves. It was found that these leaky waves are fast waves that have a phase velocity faster than the sound waves in the ambient fluid medium. Since energy can leak out of the structure, these leaky waves are all attenuative in the axial direction. Longer gaps increases the modal attenuation since it is more difficult to trap the waves in the structure.
Temporal-neural-response correlates of pitch-intensity effects and diplacusis
Authors: Jones K. , Tubis A. , Burns E. M.
Published: January 2006

Pure-tone pitch anomalies such as pitch-intensity effects and diplacusis have been traditionally considered as evidence against temporal theories of pitch. These phenomena, however, may at least in part, be correlated with stochastic model calculations of VIIIth nerve firing probabilities. These calculations predict shifts in the peaks of the ISI histogram as a function of the intensity of acoustic stimulation which are consistent with average human pitch-intensity data. The same models suggest a temporal basis for some features of central-processor-type algorithms in complex-tone pitch perception. They also account qualitatively for the frequency-dependent deviation from unity of the ratio of the first ISI histogram peak to the stimulus period, as seen in ISI measurements. Physiological and psychophysical measurements, and detailed neural model studies which are designed to check the validity of these preliminary results, will be described. [Work supported by NIH Grant NS 15405 and NSF Grant BNS 8021529.]
Problems with duration models: Evidence from Chinese
Authors: Hongmo Ren
Published: January 2006

Durations of (1) closure, (2) frication noise, (3) aspiration, and (4) voice in Chinese sounds under different linguistic conditions were measured on oscillomink displays of waveforms. A set of rules of percentage duration variation were formulated to reflect the effects of each of several linguistic factors such as distinctive features, syllable structures, word lengths, tone and stress patterns, etc. The notion of “incompressibility” [I. Lehiste, J. Acoust. Soc. Am. 51, 2018–2024 (1972); D. H. Klatt, J. Acoust. Soc. Am. 54, 1102–1104 (1973)], i.e., that durations resist being shortened under combined shortening rules, is discussed. Like English, Chinese vowel durations are incompressible under several shortening rules; unlike English, Chinese consonant durations do not show clear incompressibility. Two problems were found in applying the formula Dj = K*(Di − Dmin) + Dmin [D. H. Klatt, J. Acoust. Soc. Am. 59, 1208–1221 (1976)] in Chinese, one is that Chinese data show two values of “minimum duration” (one duration symptomatic of word length effects, and a shorter duration under neutral tone); another problem is that different combinations of shortening rules may result in different powers of incompressibility in duration.
Noise segment and vocalic cues of French fricatives
Authors: McCasland George P.
Published: January 2006

A fricative identification test was administered to native French speakers. Test stimuli had been edited from naturally spoken fricative-vowel utterances: /s,∫,f,θ/ − /i,α,u/. See [J. Acoust. Soc. Am. Suppl. 1 70, S33 (1981); and 73, S30 (1983)] for prior use with English and Spanish speakers. The results indicated that both noise segment intensity and spectrum were major acoustic cues for the French fricatives. These cues were redundant for the /f/, either low intensity noise or nonsibilant spectrum sufficed. A much weaker cue due to the original fricative, sibilant or nonsibilant, of the vocalic portion of the edited syllables must be taken into account. By comparison, Delattre had concluded using synthetic speech stimuli [Phonetica 18, 198–230 (1968)] that noise spectrum was necessary and noise intensity was redundant as cues for all French fricatives. Results implicate the specific language experience of the subjects, e.g., French lacks /θ/; the impact of natural or synthetic speech as sources of stimulus materials; and phonetic perception. Haskins Laboratories on NICHD Contract NIH-71-2420 was helpful in the preparation of stimulus materials.
Transmission, reflection, and absorption of structureborne noise by discontinuities on a fluid-loaded plate
Authors: Feit D. , Caspar J.
Published: January 2006

The propagation of structureborne noise over a fluid-loaded structure with a number of discrete structural discontinuities is modeled. An analysis is presented for an elastic plate excited by a uniform time harmonic line force; the structural discontinuities are each modeled as a translational (zero moment impedance) single degree of freedom (SDOF) vibrational system (mass-spring-dashpot) attached to the plate. Wave energy incident on the discontinuities are either reflected, transmitted absorbed by the acoustic medium in the form of radiated sound waves, or absorbed by the dashpot of the attached vibrational system. The reflection, transmission, and absorption coefficients are presented as a function of frequency for a finite number of periodically spaced discontinuities. The frequency dependence of these coefficients are affected by the resonance frequency of the SDOF as well as resonance frequencies associated with the spacing of the discontinuities.
Assessment of the performance of hearing protectors for hearing conservation purposes
Authors: Berger Elliott H.
Published: January 2006

Rating hearing protector performance for hearing conservation purposes can be most accurately accomplished when not only laboratory, but also field performance data are taken into consideration. Although standardized laboratory test data have been commonly available since the 1950's (ANSI Z24.22-1957; ANSI S3.19-1974), it is only since the mid 1970's that significant work has been conducted in the area of field performance evaluation of hearing protectors. Currently, a number of field techniques are available, including: real-ear attenuation at threshold and/or mid-line lateralization tests using actual noise exposed employees as subjects, either at their workplaces or at special test clinics; dosimetry studies via miniature microphones; and temporary threshold shift evaluations of hearing protection users in noisy industries. These real world methods will be reviewed and contrasted to the laboratory techniques, and key points illustrated with representative data.
Long-range Pacific acoustic multipath identification
Authors: Northrop John , Shockley Richard C.
Published: January 2006

Acoustic signals from three long-range (500–700 km) transmission paths in the Northeast Pacific were examined for multipath structure. Sound propagation along each path encountered both different sound-speed provinces and unique bathymetry which, together with the range differences, caused characteristic pulse arrival patterns at each hydrophone site. The receivers were all on a sloping bottom at depths between 1200 and 1400 m and the source depth was at 450 m in deep water. Raypath arrivals were modeled using IMPULSE, a new ray-theoretical impulse response code written by one of us (RCS). This code uses piecewise continuous cubic polynomials to fit the sound-speed profile and bathymetric profile, and Runge-Kutta methods to solve the ray equation of motion. It allows arbitrary ray density in launch angle, and identifies eigenrays by searching for rays whose depths bracket the receiver and which were adjacent at the source. Using this procedure, we were able to identify most of the major pulse arrivals observed at each of the recording sites.
Acoustic propagation of AFAR: Theory and experiment
Authors: Reynolds Stephen A. , Flatté Stanley M. , Dashen Roger , Buehler Barry , Maciejewski Pat
Published: January 2006

We examine the statistics of the second and fourth moments of the acoustic field measured at the Azores Fixed Acoustic Range (AFAR). The results are from pulse transmissions during 1973 and 1975 of several acoustic frequencies over two volume-refracted paths in different scattering regimes: a 2.9-km geometric and a 35-km partially saturated path. The Garrett-Munk internal wave model is used to specify the index-of-refraction fluctuations; model parameters are entirely determined by environmental observations. Predictions based upon the path-integral formulation [Sound Transmission through a Fluctuating Ocean, edited by S. M. Flatté(1979)] compare favorably with the acoustic observations. The arrival time (phase) fluctuations are predominantly geometric. However at 35 km, microray effects in the phase can be identified. The 2.9-km amplitude behavior appears geometric although comparison is hampered by a short time series. At 35 km, log-amplitude and intensity fluctuations are due largely to microray effects; the power spectra of log-amplitude are described by a single parameter model where the parameter is related to the intensity decorrelation caused by the microrays. [Work supported by ONR, Code 425UA.]
A wide bandwidth constant beamwidth end-fire array
Authors: Ugrinovich Beatriz , Hixson Elmer L.
Published: January 2006

An end-fire array using five electret microphones and “bucket-brigade” analog delay lines are used to produce the desired beamwidth at 353 Hz. A half-scale model is implemented by adding two more microphones and using three redundant microphones to give the same beamwidth at 707 Hz. High-pass and low-pass filters are used in the respective array outputs which are summed to produce a constant beamwidth over the octave. The design process is repeated to produce a constant beamwidth 3-octave array. Predicted and measured characteristics will be presented.
Perceived speech rate: The effects of articulation rate and speaking style in spontaneous speech
Authors: Koreman Jacques
Published: January 2006

In this study, the effect of articulation rate and speaking style on the perceived speech rate is investigated. The articulation rate is measured both in terms of the intended phones, i.e., phones present in the assumed canonical form, and as the number of actual, realized phones per second. The combination of these measures reflects the deletion of phones, which is related to speaking style. The effect of the two rate measures on the perceived speech rate is compared in two listening experiments on the basis of a set of intonation phrases with carefully balanced intended and realized phone rates, selected from a German database of spontaneous speech. Because the balance between input-oriented (effort) and output-oriented (communicative) constraints may be different at fast versus slow speech rates, the effect of articulation rate is compared both for fast and for slow phrases from the database. The effect of the listeners’ own speaking habits is also investigated to evaluate if listeners’ perception is based on a projection of their own behavior as a speaker. It is shown that listener judgments reflect both the intended and realized phone rates, and that their judgments are independent of the constraint balance and their own speaking habits.
Signal-to-noise ratio and frequency analysis of continuous loop averaging deconvolution (CLAD) of overlapping evoked potentials
Authors: Özdamar Özcan , Bohórquez Jorge
Published: January 2006

In this study, a frequency domain formulation of continuous loop averaging deconvolution (CLAD) of overlapping evoked potentials is developed and applied for the extraction of transient responses from recordings obtained at high stimulation rates. This formulation allows for a faster execution of CLAD by using fast Fourier transform algorithms. The frequency characteristics of the deconvolution filter depends exclusively on the stimulus sequence and determines whether the noncoherent noise is amplified or attenuated in different frequencies. A formula for calculating the signal-to-noise ratio (SNR) achieved by the deconvolution process is developed. The newly developed theory and the methodology is applied to the extraction of the auditory brainstem and middle latency responses using various sequences. The effects of the sequence used and the number of sweeps averaged in ongoing acquisition on SNR are examined by using single sweep recordings. The results verify the deconvolution theory and the methodology and show its limitations. Depending on the frequency characteristics of the sequence, the deconvolution process can amplify or attenuate the EEG noise. Proper selection of the stimulus sequence can increase the SNR enhancement obtained with conventional averaging.
A large ultrasonic bounded acoustic pulse transducer for acoustic transmission goniometry: Modeling and calibration
Authors: Bouzidi Youcef , Schmitt Douglas R.
Published: January 2006

A large, flat ultrasonic transmitter and a small receiver are developed for studies of material properties in acoustic transmission goniometry. While the character of the wave field produced by the transmitter can be considered as a plane wave as observed by the receiver, diffraction effects are noticeable near critical angles and result in the appearance of weak but detectable arrivals. Transmitted ultrasonic waveforms are acquired in one elastic silicate glass and two visco-elastic acrylic glass sample plates as a function of the angle of incidence. Phase velocities are determined from modeling of the shape of curves of the observed arrival times versus angle of incidence. The waveform observations are modeled using a phase propagation technique that incorporates full wave behavior including attenuation. Subtle diffraction effects are captured in addition to the main bounded pulse propagation. The full propagation modeling allows for various arrivals to be unambiguously interpreted. The results of the plane wave solution are close to the full wave propagation modeling without any corrections to the observed wave field. This is an advantage as it places confidence that later analyses can use simpler plane wave solutions without the need for additional diffraction corrections. A further advantage is that the uniform bounded acoustic pulse allows for the detection of weak arrivals such as a low energy edge diffraction observed in our experiments.
Automated categorization of bioacoustic signals: Avoiding perceptual pitfalls
Authors: Deecke Volker B. , Janik Vincent M.
Published: January 2006

Dividing the acoustic repertoires of animals into biologically relevant categories presents a widespread problem in the study of animal sound communication, essential to any comparison of repertoires between contexts, individuals, populations, or species. Automated procedures allow rapid, repeatable, and objective categorization, but often perform poorly at detecting biologically meaningful sound classes. Arguably this is because many automated methods fail to address the nonlinearities of animal sound perception. We present a new method of categorization that incorporates dynamic time-warping and an adaptive resonance theory (ART) neural network. This method was tested on 104 randomly chosen whistle contours from four captive bottlenose dolphins (Tursiops truncatus), as well as 50 frequency contours extracted from calls of transient killer whales (Orcinus orca). The dolphin data included known biologically meaningful categories in the form of 42 stereotyped whistles produced when each individual was isolated from its group. The automated procedure correctly grouped all but two stereotyped whistles into separate categories, thus performing as well as human observers. The categorization of killer whale calls largely corresponded to visual and aural categorizations by other researchers. These results suggest that this methodology provides a repeatable and objective means of dividing bioacoustic signals into biologically meaningful categories.
Frequency discrimination of complex tones; assessing the role of component resolvability and temporal fine structure
Authors: Moore Brian C. J. , Glasberg Brian R. , Flanagan Helen J. , Adams Joe
Published: January 2006

Thresholds for discriminating the fundamental frequency (F0) of a complex tone, F0DLs, are small when low harmonics are present, but increase when the number of the lowest harmonic, N, is above eight. To assess whether the relatively small F0DLs for N in the range 8–10 are based on (partly) resolved harmonics or on temporal fine structure information, F0DLs were measured as a function of N for tones with three successive harmonics which were added either in cosine or alternating phase. The center frequency was 2000Hz, and N was varied by changing the mean F0. A background noise was used to mask combination tones. The value of F0 was roved across trials to force subjects to make within-trial comparisons. N was roved by ±1 for every stimulus, to prevent subjects from using excitation pattern cues. F0DLs were not influenced by component phase for N=6 or 7, but were smaller for cosine than for alternating phase once N exceeded 7, suggesting that temporal fine structure plays a role in this range. When the center frequency was increased to 5000Hz, performance was much worse for low N, suggesting that phase locking is important for obtaining low F0DLs with resolved harmonics.
Alternate proof of the optical theorem for impenetrable targets
Authors: Kriegsmann G. A.
Published: January 2006

The optical theorem is proven for impenetrable targets without using the method of stationary phase. The proof depends upon the divergence theorem, the Helmholtz representation of the scattered field, and the law of cosines.
Auditory filter nonlinearity across frequency using simultaneous notched-noise masking
Authors: Baker Richard J. , Rosen Stuart
Published: January 2006

Psychoacoustic masking experiments have been widely used to investigate cochlear function in human listeners. Here we use simultaneous notched-noise masking experiments in normal hearing listeners to characterize the changes in auditory filter shape with stimulus level over the frequency range 0.25–6kHz. At each frequency a range of fixed signal levels (30–70dB SPL) and fixed masker levels (20–50dB SPL spectrum level) are used in order to obtain accurate descriptions of the filter shapes in individual listeners. The notched-noise data for individual listeners are fitted with two filter shape models: a rounded exponential (roex) shape in which the filter skirt changes as a linear function of probe-tone level and the other, in which the gain of the tip filter relative to the filter tail changes as a function of signal level [Glasberg and Moore, J. Acoust. Soc. Am. 108, 2318–2328 (2000)]. The parameters for these fitted models are then described with a simple set of equations that quantify the changes in auditory filter shape across level and frequency. Both these models fitted the data equally well and both demonstrated increasing tip-tail gain as frequency increased.
Decentralized harmonic active vibration control of a flexible plate using piezoelectric actuator-sensor pairs
Authors: Baudry Matthieu , Micheau Philippe , Berry Alain
Published: January 2006

We have investigated decentralized active control of periodic panel vibration using multiple pairs combining PZT actuators and PVDF sensors distributed on the panel. By contrast with centralized MIMO controllers used to actively control the vibrations or the sound radiation of extended structures, decentralized control using independent local control loops only requires identification of the diagonal terms in the plant matrix. However, it is difficult to a priori predict the global stability of such decentralized control. In this study, the general situation of noncollocated actuator-sensor pairs was considered. Frequency domain gradient and Newton-Raphson adaptation of decentralized control were analyzed, both in terms of performance and stability conditions. The stability conditions are especially derived in terms of the adaptation coefficient and a control effort weighting coefficient. Simulations and experimental results are presented in the case of a simply supported panel with four PZT-PVDF pairs distributed on it. Decentralized vibration control is shown to be highly dependent on the frequency, but can be as effective as a fully centralized control even when the plant matrix is not diagonal-dominant or is not strictly positive real (not dissipative).
Data error covariance in matched-field geoacoustic inversion
Authors: Dosso Stan E. , Nielsen Peter L. , Wilmut Michael J.
Published: January 2006

Many approaches to geoacoustic inversion are based implicitly on the assumptions that data errors are Gaussian-distributed and spatially uncorrelated (i.e., have a diagonal covariance matrix). However, the latter assumption is often not valid due to theory errors, and can lead to reduced accuracy for geoacoustic parameter estimates and underestimation of parameter uncertainties. This paper examines the effects of data error (residual) covariance in matched-field geoacoustic inversion. An inversion approach is developed based on a nonparametric method of estimating the full covariance matrix (including off-diagonal terms) from the data residuals and explicitly including this covariance in the misfit function. Qualitative and quantitative statistical tests for Gaussianity and for correlations in complex residuals are considered to validate the inversion results. The approach is illustrated for Bayesian geoacoustic inversion of broadband, vertical-array acoustic data measured in the Mediterranean Sea.
High frequency formulation for the acoustic power spectrum due to cascade-turbulence interaction
Authors: Cheong Cheolung , Joseph Phillip , Lee Soogab
Published: January 2006

This paper investigates the noise radiated by a cascade of flat-plate airfoils interacting with homogeneous, isotropic turbulence. An analytic formulation for the spectrum of acoustic power of a two-dimensional flat-plate is derived. The main finding of this paper is that the acoustic power spectrum from the cascade of flat airfoils may be split into two distinct frequency regions of low frequency and high frequency, separated by a critical frequency. Below this frequency, cascade effects due to the interaction between neighboring airfoils are shown to be important. At frequencies above the critical frequency, cascade effects are shown to be relatively weak. In this frequency range, acoustic power is shown to be approximately proportional to the number of blades. Based on this finding at high frequencies, an approximate expression is derived for the power spectrum that is valid above the critical frequency and which is in excellent agreement with the exact expression for the broadband power spectrum. The formulation is used to perform a parametric study on the effects on the power spectrum of the blade number, stagger angle, gap-chord ratio, and Mach number. The theory is also shown to provide a close fit to the measured spectrum of rotor-stator interaction.
Perception of amplitude modulation by hearing-impaired listeners: The audibility of component modulation and detection of phase change in three-component modulators
Authors: Sek Aleksander , Moore Brian C. J.
Published: January 2006

Two experiments were conducted to assess whether hearing-impaired listeners have a reduced ability to process suprathreshold complex patterns of modulation applied to a 4-kHz sinusoidal carrier. Experiment 1 examined the ability to “hear out” the modulation frequency of the central component of a three-component modulator, using the method described by Sek and Moore [J. Acoust. Soc. Am. 113, 2801–2811 (2003)]. Scores were around 70–80% correct when the components in the three-component modulator were widely spaced and when the frequencies of the target and comparison different sufficiently, but decreased when the components in the modulator were closely spaced. Experiment 2 examined the ability to hear a change in the relative phase of the components in a three-component modulator with harmonically spaced components. The frequency of the central component, fc, was either 50 or 100Hz. Scores were about 70% correct when the component spacing was ⩽0.5fc, but decreased markedly for greater spacings. Performance was only slightly impaired by randomizing the overall modulation depth from one stimulus to the next. For both experiments, performance was only slightly worse than for normally hearing listeners, indicating that cochlear hearing loss does not markedly affect the ability to process suprathreshold complex patterns of modulation.
Horizontal localization with bilateral hearing aids: Without is better than with
Authors: Van den Bogaert Tim , Klasen Thomas J. , Moonen Marc , Van Deun Lieselot , Wouters Jan
Published: January 2006

This paper studies the effect of bilateral hearing aids on directional hearing in the frontal horizontal plane. Localization tests evaluated bilateral hearing aid users using different stimuli and different noise scenarios. Normal hearing subjects were used as a reference. The main research questions raised in this paper are: (i) How do bilateral hearing aid users perform on a localization task, relative to normal hearing subjects? (ii) Do bilateral hearing aids preserve localization cues, and (iii) Is there an influence of state of the art noise reduction algorithms, more in particular an adaptive directional microphone configuration, on localization performance? The hearing aid users were tested without and with their hearing aids, using both a standard omnidirectional microphone configuration and an adaptive directional microphone configuration. The following main conclusions are drawn. (i) Bilateral hearing aid users perform worse than normal hearing subjects in a localization task, although more than one-half of the subjects reach normal hearing performance when tested unaided. For both groups, localization performance drops significantly when acoustical scenarios become more complex. (ii) Bilateral, i.e., independently operating hearing aids do not preserve localization cues. (iii) Overall, adaptive directional noise reduction can have an additional and significant negative impact on localization performance.
Sounds from an oil production island in the Beaufort Sea in summer: Characteristics and contribution of vessels
Authors: Blackwell Susanna B. , Greene Charles R.
Published: January 2006

The objective of this study was to determine the levels, characteristics, and range dependence of underwater and in-air sounds produced during the open-water seasons of 2000–2003 by the Northstar oil development, located in nearshore waters of the Alaskan Beaufort Sea. Specifically, sounds originating at the island itself (from construction, drilling, and oil production activities) were compared with sounds produced by vessels performing island support. Sounds were obtained with boat-based recordings (at distances up to 37km from Northstar), a cabled hydrophone (distance ∼450m), and with autonomous seafloor recorders (distance ∼22km). Vessels (crew boat, tugs, self-propelled barges) were the main contributors to the underwater sound field and were often detectable underwater as much as ∼30km offshore. Without vessels, broadband island sounds reached background values at 2–4km. Island sound levels showed more variation (lower min, higher max) during construction than during drilling and production. In-air broadband measurements were not affected by the presence of vessels and reached background values 1–4km from Northstar. However, one airborne tone (81Hz) believed to originate at Northstar was still detectable in the spectrum 37km away.
A reflected energy prediction model for long-range hydroacoustic reflection in the oceans
Authors: Upton Zachary M. , Pulli Jay J. , Myhre Brian , Blau David
Published: January 2006

Acoustic energy from underwater earthquakes and explosions can propagate over long distances with very little attenuation in the deep ocean. When this sound encounters a seamount, island, or continental margin, it can scatter and again propagate over long distances. Hydrophones in the deep sound channel can detect these reflections tens of minutes or hours after arrivals from the direct source-to-receiver path. This paper presents the Reflected Energy Prediction (REP) model, a model for predicting these reflected arrivals. For a given source and receiver, the REP model uses a detailed knowledge of the underwater environment and components of the Hydroacoustic Coverage Assessment Model, HydroCAM, to predict the impulse response of the ocean. When this impulse response is convolved with a source function, a waveform envelope prediction is made that can be compared with recorded data. In this paper we present the model and a few applications of the model using data recorded from earthquakes and explosions in the Atlantic and Indian Oceans. These examples illustrate the use of the model and initial steps toward model calibration.
A hydromechanical biomimetic cochlea: Experiments and models
Authors: Chen Fangyi , Cohen Howard I. , Bifano Thomas G. , Castle Jason , Fortin Jeffrey , Kapusta Christopher , Mountain David C. , Zosuls Aleks , Hubbard Allyn E.
Published: January 2006

The construction, measurement, and modeling of an artificial cochlea (ACochlea) are presented in this paper. An artificial basilar membrane (ABM) was made by depositing discrete Cu beams on a piezomembrane substrate. Rather than two fluid channels, as in the mammalian cochlea, a single fluid channel was implemented on one side of the ABM, facilitating the use of a laser to detect the ABM vibration on the other side. Measurements were performed on both the ABM and the ACochlea. The measurement results on the ABM show that the longitudinal coupling on the ABM is very strong. Reduced longitudinal coupling was achieved by cutting the membrane between adjacent beams using a laser. The measured results from the ACochlea with a laser-cut ABM demonstrate cochlear-like features, including traveling waves, sharp high-frequency rolloffs, and place-specific frequency selectivity. Companion computational models of the mechanical devices were formulated and implemented using a circuit simulator. Experimental data were compared with simulation results. The simulation results from the computational models of the ABM and the ACochlea are similar to their experimental counterparts.
Level dependence of auditory filters in nonsimultaneous masking as a function of frequency
Authors: Oxenham Andrew J. , Simonson Andrea M.
Published: January 2006

Auditory filter bandwidths were measured using nonsimultaneous masking, as a function of signal level between 10 and 35dB SL for signal frequencies of 1, 2, 4, and 6kHz. The brief sinusoidal signal was presented in a temporal gap within a spectrally notched noise. Two groups of normal-hearing subjects were tested, one using a fixed masker level and adaptively varying signal level, the other using a fixed signal level and adaptively varying masker level. In both cases, auditory filters were derived by assuming a constant filter shape for a given signal level. The filter parameters derived from the two paradigms were not significantly different. At 1kHz, the equivalent rectangular bandwidth (ERB) decreased as the signal level increased from 10to20dB SL, after which it remained roughly constant. In contrast, at 6kHz, the ERB increased consistently with signal levels from 10to35dB SL. The results at 2 and 4kHz were intermediate, showing no consistent change in ERB with signal level. Overall, the results suggest changes in the level dependence of the auditory filters at frequencies above 1kHz that are not currently incorporated in models of human auditory filter tuning.
Cytokinin Signaling and Its Inhibitor AHP6 Regulate Cell Fate During Vascular Development
Authors: Mähönen Ari Pekka , Bishopp Anthony , Higuchi Masayuki , Nieminen Kaisa M. , Kinoshita Kaori , Törmäkangas Kirsi , Ikeda Yoshihisa , Oka Atsuhiro , Kakimoto Tatsuo , Helariutta Ykä
Published: January 2006

The cell lineages that form the transporting tissues (xylem and phloem) and the intervening pluripotent procambial tissue originate from stem cells near the root tip. We demonstrate that in Arabidopsis, cytokinin phytohormones negatively regulate protoxylem specification. AHP6, an inhibitory pseudophosphotransfer protein, counteracts cytokinin signaling, allowing protoxylem formation. Conversely, cytokinin signaling negatively regulates the spatial domain of AHP6 expression. Thus, by controlling the identity of cell lineages, the reciprocal interaction of cytokinin signaling and its spatially specific modulator regulates proliferation and differentiation of cell lineages during vascular development, demonstrating a previously unrecognized regulatory circuit underlying meristem organization.
Variability in Nocturnal Nitrogen Oxide Processing and Its Role in Regional Air Quality
Authors: Brown S. S. , Ryerson T. B. , Wollny A. G. , Brock C. A. , Peltier R. , Sullivan A. P. , Weber R. J. , Dubé W. P. , Trainer M. , Meagher J. F. , Fehsenfeld F. C. , Ravishankara A. R.
Published: January 2006

Nitrogen oxides in the lower troposphere catalyze the photochemical production of ozone (O
3
) pollution during the day but react to form nitric acid, oxidize hydrocarbons, and remove O
3
at night. A key nocturnal reaction is the heterogeneous hydrolysis of dinitrogen pentoxide, N
2
O
5
. We report aircraft measurements of NO
3
and N
2
O
5
, which show that the N
2
O
5
uptake coefficient, g(N
2
O
5
), on aerosol particles is highly variable and depends strongly on aerosol composition, particularly sulfate content. The results have implications for the quantification of regional-scale O
3
production and suggest a stronger interaction between anthropogenic sulfur and nitrogen oxide emissions than previously recognized.
Quantum Dynamics of a d-Wave Josephson Junction
Authors: Bauch Thilo , Lindström Tobias , Tafuri Francesco , Rotoli Giacomo , Delsing Per , Claeson Tord , Lombardi Floriana
Published: January 2006

Here we present the direct observation of macroscopic quantum properties in an all high-critical-temperature superconductor d-wave Josephson junction. Although dissipation caused by low-energy excitations is expected to strongly suppress macroscopic quantum effects, we demonstrate energy level quantization in our d-wave Josephson junction. The result indicates that the role of dissipation mechanisms in high-temperature superconductors has to be revised, and it may also have consequences for the class of solid-state “quiet” quantum bits with superior coherence time.
Ethnic variations in the management of patients with acute stroke
Authors: Bourke J , Sylvester R , Sharma P
Published: January 2006

Background

There is increasing interest in the management of stroke in ethnic minorities but few studies have considered this issue. This study investigated if differences in acute stroke management exist between a white European and Bangladeshi populations living in London, England.

Methods

All stroke surviving patients discharged over a five year period in a major London teaching hospital based in an ethnically diverse area of inner city London were recruited. Cerebrovascular risk factors, their management, and investigation for acute stroke syndromes were recorded and comparison between white and Bangladeshi cohorts was made. Categorical data were analysed using Fisher's exact test.

Results

Measurement of cholesterol concentrations are undertaken less often in those from a Bangladeshi background (25%) compared with white Europeans (76%) (p<0.0001). Statin therapy tends to be given less often to Bangladeshis. However, neuroimaging (p<0.05) and echocardiography (p<0.0001) is performed more often in Bangladeshis compared with white Europeans.

Conclusion

There are variations in the management of acute stroke because of ethnicity and these variations could have substantial consequences on secondary rates of cerebrovascular and cardiovascular disease. Whether the reasons for this disparity are attributable to inequity or iniquity of care need to be further investigated perhaps along with the development of ethnicity specific protocols. Overall the management of stroke and its risk factors in either racial group remains lamentable.
Acquired haemophilia heralded by bleeding into the oral mucosa in a patient with bullous pemphigoid, rheumatoid arthritis, and vitiligo
Authors: Patel R S , Harman K E , Nichols C , Burd R M , Pavord S
Published: January 2006

Acquired haemophilia is rare and potentially fatal, with a mortality of 20% if left untreated. There is a strong association with other autoimmune diseases. This report describes a patient with rheumatoid arthritis, vitiligo, and bullous pemphigoid where the diagnosis of acquired haemophilia was made after an extensive bleed into a bullous lesion in the buccal mucosa. This case highlights some of the potential complications of acquired haemophilia and its treatment.
Application of Gleason analogous grading system and flow cytometry DNA analysis in a novel knock-in mouse prostate cancer model
Authors: Wu G , Yu Lei , Wang L , Wang H , Xuan J W
Published: January 2006

Objective

A new knock-in mouse adenocarcinoma prostate model (KIMAP) was established, which showed a close to human kinetics of tumour development. This study used a new mouse histological grading system similar to the human Gleason grading system and flow cytometry DNA analysis to measure and compare the new KIMAP model with human CaP and transgenic mouse adenocarcinoma prostate (TGMAP) model.

Methods

According to heterogeneity of the clinical standard for prostate cancer diagnosis, a close to human mouse standard for histological grading and scoring system, Gleason analogous grading system, was established in this study. Sixty KIMAP and 48 TGMAP prostate cancer samples were measured and compared with human CaP. Flow cytometry DNA analysis was performed on malignant prostate tissues obtained from both TGMAP and KIMAP models.

Results

Mice with CaP from KIMAP (n = 60) and TGMAP (n = 48) models showed a different distribution of histological scores (p = 0.000). KIMAP mice showed higher percentage (53.3%) of compound histological score rate than TGMAP (25%), but closer to the human clinical average (50%), which showed significant correlation with age (p = 0.001), while TGMAP mice showed unbalanced and random score distribution in all age groups. Flow cytometry analyses showed that most tumour tissues in KIMAP were diploid, analogous to the human condition, while all the TGMAP mice showed aneuploid tumours.

Conclusions

Results of this study further show that KIMAP, a new generation of murine prostate cancer model, could be used as a supplementary model in addition to the currently widely used transgenic models.
Amiodarone toxicity presenting as pulmonary mass and peripheral neuropathy: the continuing diagnostic challenge
Authors: Azzam I , Tov N , Elias N , Naschitz J E
Published: January 2006

A 64 year old man receiving long term amiodarone treatment presented with dyspnea, cough, and weight loss. Radiographs and computed tomography showed a lung mass with associated multiple pulmonary nodules. Biopsies of the pulmonary mass showed foamy histiocytes without malignant cells. However, findings on FDG-PET scan were consistent with a malignant tumour. These findings on computed tomography and PET scan and the unusually late resolution of the pulmonary lesions after withdrawal of amiodarone treatment posed a challenging diagnostic problem.
RESTRICTING COHOMOLOGICAL REPRESENTATIONS OF SO0(n,1) AND SU(n,1)
Authors: VALETTE ALAIN
Published: January 2006

Let G denote either SO 0(n,1) or SU (n,1). We study restrictions of cohomological representations of G to subgroups H isomorphic to SO 0(m,1) or SU (m,1). We prove that such a restriction contains, as a subrepresentation, some cohomological representation of H. When G = SU(n,1), we extend a result of Delorme by showing that cohomological representations are non-spherical in a strong sense: if H is isomorphic to SU (m,1) (with 1 ≤ m ≤ n), then the restriction of a cohomological representation to H is non-spherical.
EQUIVARIANT COHOMOLOGICAL CHERN CHARACTERS
Authors: LÜCK WOLFGANG
Published: January 2006

We construct for an equivariant cohomology theory for proper equivariant CW-complexes an equivariant Chern character, provided that certain conditions about the coefficients are satisfied. These conditions are fulfilled if the coefficients of the equivariant cohomology theory possess a Mackey structure. Such a structure is present in many interesting examples.
ON ARITHMETIC OPERATIONS OF INTERVAL NUMBERS
Authors: GANESAN K. , VEERAMANI P.
Published: January 2006

In this paper, by using Sengupta and Pal's method of comparison of interval numbers and a new set of arithmetic operations for interval numbers, we propose a theory for the study of arithmetic operations on interval numbers.
FUZZY RULE EXTRACTION FROM A FEED FORWARD NEURAL NETWORK BY TRAINING A REPRESENTATIVE FUZZY NEURAL NETWORK USING GRADIENT DESCENT
Authors: BROUWER ROELOF K.
Published: January 2006

Neural networks are good at representing functions or data transformations. However just as in the case of the biological brain the mathematical description of the data transformation is hidden. In the case of the human brain the transformation, in terms of rules, may be extracted by interviewing the person, In the case of the artificial neural network other approaches have to be utilized.

In the case described here a second neural network that represents the transformation in terms of fuzzy rules is trained using gradient descent. The parameters that are learned are the parameters of the fuzzy sets and also the connection weights in [0,1] between the outputs of the membership function units and the final output units. There is an output unit for each rule and consequent membership function. The fuzzy output set with the highest membership value is taken to be the output fuzzy set. The extracted rules are of the form if x 0 is Small or x 0 is Medium and x 1 is Large or x 1 is Medium then y is Large. x 0 and x 1 are inputs and y is the output.

The cost measure consists of several terms indicating how close the actual output is to a target output, how close the weights are to 0 and 1, and how close the output of membership values is to a 1 of n vector. The cost measure is a linear combination of these individual terms. By changing the constant multipliers the relative importance of the cost measures can be changed and studied.

The method has been tried on randomly generated feedforward neural networks and also on data produced by functions with specific properties. The fizzy network is trained using data produced by the feedforward neural network or the known function. This method can also be used in extracting rules such as control rules implicitly used by a human if input and output data is gathered from the human.
SIMPLIFYING BOOLEAN NETWORKS
Authors: RICHARDSON KURT A.
Published: January 2006

This paper explores the compressibility of complex systems by considering the simplification of Boolean networks. A method, which is similar to that reported by Bastolla and Parisi,4,5is considered that is based on the removal of frozen nodes, or stable variables, and network "leaves," i.e. those nodes with outdegree = 0. The method uses a random sampling approach to identify the minimum set of frozen nodes. This set contains the nodes that are frozen in all attractor schemes. Although the method can over-estimate the size of the minimum set of frozen nodes, it is found that the chances of finding this minimum set are considerably greater than finding the full attractor set using the same sampling rate. Given that the number of attractors not found for a particular Boolean network increases with the network size, for any given sampling rate, such a method provides an opportunity to either fully enumerate the attractor set for a particular network, or improve the accuracy of the random sampling approach. Indeed, the paper also shows that when it comes to the counting of attractors in an ensemble of Boolean networks, enhancing the random sample method with the simplification method presented results in a significant improvement in accuracy.
ORGANIZATIONAL STRATEGIC ADAPTATION IN THE PRESENCE OF INERTIA
Authors: BRABAZON ANTHONY , SILVA ARLINDO , DE SOUSA TIAGO FERRA , O'NEILL MICHAEL , MATTHEWS ROBIN , COSTA ERNESTO
Published: January 2006

This paper extends the particle swarm metaphor into the domain of organization science. A simulator (OrgSwarm) which can be used to model the adaptation of a population of organizations on a strategic landscape is introduced. The simulator embeds a number of features of the process of organizational adaptation, including the resistance of organizations to change (strategic inertia), errorful assessments of the payoffs to proposed strategies, and market competition. These features allow the examination of a wide range of real-life scenarios in organizational adaptation. The paper reports the results of a number of simulation experiments and these suggest that agent (management) uncertainty as to the payoffs to potential strategies has the effect of lowering the average payoffs obtained by a population of organizations. The results also suggest that a degree of strategic inertia can assist rather than hamper adaptive efforts at a populational level.
ON ASYNCHRONOUS CELLULAR AUTOMATA
Authors: HANSSON A. Å. , MORTVEIT H. S. , REIDYS C. M.
Published: January 2006

We study asynchronous cellular automata (ACA) induced by symmetric Boolean functions [1]. These systems can be considered as sequential dynamical systems (SDS) over words, a class of dynamical systems that consists of (a) a finite, labeled graph Y with vertex set {v1,…,vn} and where each vertex vi has a state xvi in a finite field K, (b) a sequence of functions (Fvi,Y)i, and (c) a word w = (w1,…,wk), where each wi is a vertex in Y. The function Fvi,Y updates the state of vertex vi as a function of the state of vi and its Y-neighbors and maps all other vertex states identically. The SDS is the composed map [Formula: see text]. In the particular case of ACA, the graph is the circle graph on n vertices (Y = Circ n), and all the maps Fvi are induced by a common Boolean function. Our main result is the identification of all w-independent ACA, that is, all ACA with periodic points that are independent of the word (update schedule) w. In general, for each w-independent SDS, there is a finite group whose structure contains information about for example SDS with specific phase space properties. We classify and enumerate the set of periodic points for all w-independent ACA, and we also compute their associated groups in the case of Y = Circ 4. Finally, we analyze invertible ACA and offer an interpretation of S35 as the group of an SDS over the three-dimensional cube with local functions induced by nor3 + nand3.