bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanisms proposed for spectrogram correlation and transformation deconvolution in FM bat sonar
Authors: Simmons James A.
Published: October 2013

Big brown bats use time/frequency distributions to represent FM biosonar pulses and echoes as a consequence of reception through frequency tuned channels of the inner ear and subsequent processing by similarly tuned neural channels in the auditory pathway. Integration time is 350 μs, yet delay resolution is 2−10 μs, which must be based on detecting changes in the echo spectrum caused by interference between overlapping reflections inside the integration time. However, bats perceive not merely the echo interference spectrum but the numerical value of the delay separation from the spectrum, which requires deconvolution. Because spectrograms are the initial representation, this process is spectrogram correlation and transformation (SCAT). Proposed SCAT deconvolution mechanisms include extraction of echo envelope ripples for time-domain spectrometry, cepstral analysis of echoes, use of coherent or noncoherent reconstruction with basis functions, segmentation of onsets of overlapping replicas at moderate to long time separations, and localization of the occurrence of spectral interference ripples at specific times within dechirped spectrograms. Physiological evidence from single-unit recordings reveals a cepstral-like time–frequency process based on freqlets, both single-unit and multiunit responses reveal which may prove to be time-domain basis functions, and multiunit responses exhibit modulations by onset and envelope ripple. [Work supported by NIH and ONR.]
Using music structure to improve beat tracking
Authors: Dannenberg Roger B.
Published: October 2013

Beats are an important feature of most music. Beats are used in music information retrieval systems for genre classification, similarity search, and segmentation. However, beats can be difficult to identify, especially in music audio. Traditional beat trackers attempt to (1) match predicted beats to observations of likely beats, and (2) maintain a fairly steady tempo. A third criterion can be added: when repetitions of musical passages occur, the beats in the first repetition should align with the beats in all other repetitions. This third criterion improves beat tracking performance significantly. Repetitions of musical passages are discovered in audio data by searching for similar sequences of chroma vectors. Beats are ‘‘tracked’’ by first locating a sequence of likely beats in the music audio using high frequency energy as an indicator of beat likelihood. This beat sequence is then extended by searching forward and backward for more matching beats, allowing slight variations in tempo, and using a relaxation algorithm to optimize the proposed beat locations with respect to the three criteria. Other high-level music features may offer further improvements in beat identification.
Representation and alignment of sung queries for music information retrieval
Authors: Adams Norman H. , Wakefield Gregory H.
Published: October 2013

The pursuit of robust and rapid query-by-humming systems, which search melodic databases using sung queries, is a common theme in music information retrieval. The retrieval aspect of this database problem has received considerable attention, whereas the front-end processing of sung queries and the data structure to represent melodies has been based on musical intuition and historical momentum. The present work explores three time series representations for sung queries: a sequence of notes, a ‘‘smooth’’ pitch contour, and a sequence of pitch histograms. The performance of the three representations is compared using a collection of naturally sung queries. It is found that the most robust performance is achieved by the representation with highest dimension, the smooth pitch contour, but that this representation presents a formidable computational burden. For all three representations, it is necessary to align the query and target in order to achieve robust performance. The computational cost of the alignment is quadratic, hence it is necessary to keep the dimension small for rapid retrieval. Accordingly, iterative deepening is employed to achieve both robust performance and rapid retrieval. Finally, the conventional iterative framework is expanded to adapt the alignment constraints based on previous iterations, further expediting retrieval without degrading performance.
Automatic detection of the dominant melody in acoustic musical signals
Authors: Klapuri Anssi P.
Published: October 2013

An auditory-model based method is described for estimating the fundamental frequency contour of the dominant melody in complex music signals. The core method consists of a conventional cochlear model followed by a novel periodicity analysis mechanism within the subbands. As the output, the method computes the salience (i.e., strength) of different fundamental frequency candidates in successive time frames. The maximum value of this vector in each frame can be used to indicate the dominant fundamental frequency directly. In addition, however, it was noted that the first-order time differential of the salience vector leads to an efficient use of temporal features which improve the performance in the presence of a large number of concurrent sounds. These temporal features include particularly the common amplitude or frequency modulation of the partials of the sound that is used to communicate the melody. A noise-suppression mechanism is described which improves the robustness of estimation in the presence of drums and percussive instruments. In evaluations, a database of complex music signals was used where the melody was manually annotated. Use of the method for music information retrieval and music summarization is discussed.
Using string alignment in a query-by-humming system for real world applications
Authors: Sailer Christian
Published: October 2013

Though query by humming (i.e., retrieving music or information about music by singing a characteristic melody) has been a popular research topic during the past decade, few approaches have reached a level of usefulness beyond mere scientific interest. One of the main problems is the inherent contradiction between error tolerance and dicriminative power in conventional melody matching algorithms that rely on a melody contour approach to handle intonation or transcription errors. Adopting the string matching/alignment techniques from bioinformatics to melody sequences allows to directly assess the similarity between two melodies. This method takes an MPEG-7 compliant melody sequence (i.e., a list of note intervals and length ratios) as query and evaluates the steps necessary to transform it into the reference sequence. By introducing a musically founded cost-of-replace function and an adequate post processing, this method yields a measure for melodic similarity. Thus it is possible to construct a query by humming system that can properly discriminate between thousands of melodies and still be sufficiently error tolerant to be used by untrained singers. The robustness has been verified in extensive tests and real world applications.
Discrimination of phoneme length differences in word and sentence contexts
Authors: Kawai Norimune , Carrell Thomas
Published: October 2013

The ability of listeners to discriminate phoneme duration differences within word and sentence contexts was measured. This investigation was part of a series of studies examining the audibility and perceptual importance of speech modifications produced by stuttering intervention techniques. Just noticeable differences (jnd’s) of phoneme lengths were measured via the parameter estimation by sequential testing (PEST) task, an adaptive tracking procedure. The target phonemes were digitally manipulated to vary from normal (130 m) to prolonged (210 m) duration in 2-m increments. In the first condition the phonemes were embedded in words. In the second condition the phonemes were embedded within words, which were further embedded in sentences. A four-interval forced-choice (4IAX) task was employed on each trial, and the PEST procedure determined the duration at which each listener correctly detected a difference between the normal duration and the test duration 71% of the time. The results revealed that listeners were able to reliably discriminate approximately 15-m differences in word context and 10-m differences in sentence context. An independent t-test showed a difference in discriminability between word and sentence contexts to be significant. These results indicate that duration differences were better perceived within a sentence context.
Turn exchange rhythm in English dialogues
Authors: Fon Janice
Published: October 2013

This study looked at the relationship between rhythm and exchange type in British English, a stress-timed language, and Singaporean English, a syllable-timed language, using a spontaneous speech corpus. Exchange intervals (EIs), or the time difference between the end of one speaker and the beginning of another, were measured and exchanges of different types were labeled. Results showed that, in a dialogue, EIs were generally limited to a narrow range. However, within this range, EIs had at least four functions. First, EIs were reflective of the cognitive load and functioned as a way to differentiate various exchange types. Those requiring more cognitive resources, such as question-and-answer pairs, generally needed longer EIs than those not as cognitively loaded, such as backchanneling pairs. Second, EIs were indicative of linguistic rhythm. Singaporean English tended to have shorter EIs than British English. Third, EIs were reflective of politeness. The degree of politeness correlated negatively with EI. Shorter EIs showed a higher degree of respect. Finally, EIs were also indicative of the level of insecurity of a speaker, which was best reflected by gender differences. Females in general had longer EIs than males.
Spectral correlates lexical prosody
Authors: Okobi Anthony
Published: October 2013

The purpose of this study is to derive a quantitative acoustic model of lexical-prosodic characteristics of stressed vowels by looking at several spectral properties associated with the articulatory mechanisms used in speech production. Native speakers of American English were asked to name disyllabic visualizable nouns. Words containing liquids or glides were not used in this study because of their effect on the spectra of adjacent vowels. Subjects uttered short phrases in which the target word was pitch accent half of the time and unaccented the other half. Results show that within the category of full vowels, unstressed and stressed vowels can be distinguished by syllable/vowel durations and spectral tilt. Spectral tilt (SpT) is an acoustic measure related to the degree of glottal spreading. Stressed full vowels had longer duration and less SpT. Distinction between unaccented and accented stressed vowels can be made by amplitude of voicing (AV), F0 (pitch), and intensity contour differences. Accented stressed vowels have higher pitch, and greater AV and intensity. These results suggest that there are acoustic correlates to lexical stress that can be used to determine the stressed syllable of a word, regardless of whether or not it is pitch accented. [Work supported by NIH T32-DC00038.]
The time course of speaking rate specificity effects in spoken word recognition
Authors: McLennan Conor T. , Luce Paul A.
Published: October 2013

Specificity effects in spoken word recognition were previously examined by examining the circumstances under which variability in speaking rate affects participants perception of spoken words. The word recognition and memory literatures are now replete with demonstrations that variability has representational and processing consequences. The research focuses on one of the conditions expected to influence the extent to which variability plays a role in spoken word recognition, namely time course of processing. Based on previous work, it was hypothesized that speaking rate variability would only affect later stages of spoken word recognition. The results confirmed this hypothesis: Specificity effects were only obtained when processing was relatively slow. However, previous stimuli not only differed in speaking rate, but also in articulation style (i.e., casual and careful). Therefore, in the current set of experiments, it was sought to determine whether the same pattern of results would be obtained with stimuli that only differed in speaking rate (i.e., in the absence of articulation style differences). Moreover, to further generalize time course findings, the stimuli were produced by a different speaker than the speaker in the earlier study. The results add to the knowledge of the circumstances under which variability affects the perception of spoken words.
A coupled oscillator model of intergestural timing within syllables
Authors: Nam Hosung , Goldstein Louis , Saltzman Elliot
Published: October 2013

A computational model has been developed that plans the relative timing of speech gestures within a syllable. Planning oscillators are associated with each of the gestures in a given utterance. These oscillators are phased to one another by being coupled in a pairwise, bidirectional manner according to the structure of a coupling graph that is part of the lexical specification of a word. A set of motion equations for the coupled oscillator system is implemented using the task-dynamical model of relative phase control [E. Saltzman and D. Byrd, Human Movement Sci. 19, 499–526 (2000)] extended to allow multiple, potentially competitive, couplings. In the model, consonant gestures in a syllable onset are all coupled synchronously with the vowel (and in some cases sequentially with each other), while coda consonant gestures are coupled sequentially with the vowel. The steady-state output of the coupled oscillator system is a set of limit-cycle oscillations with stabilized relative phases, from which the activation trajectories of gestural scores are derived. The gestural scores are used to generate coordinated articulatory movements and constriction trajectories via the task dynamics model, and acoustic output via a vocal-tract model and HLsyn. [Work supported by NIH.]
Perceptual learning of a talker resolves lexical ambiguity
Authors: Piorkowski Rebecca L. , Badecker William
Published: October 2013

Recent evidence [Allen and Miller, J. Acoust. Soc. Am. 115, 3171 (2004)] suggests that listeners are sensitive to talker-specific acoustic-phonetic properties. The present study examines whether experience with a particular talker’s realization of place of articulation can eliminate the ambiguity that arises when a word like ‘‘hen’’ assimilates in place of articulation to ‘‘hem’’ in a labial context (hen best). Using a cross-modal priming paradigm, the priming effect of words that assimilate to other words was measured in two conditions. In the first condition, listeners heard examples of the talker’s assimilation style in the form of words that assimilate to nonwords in a labial context (green beer) before the critical trials were heard. In the second condition, listeners did not hear any examples of the talker’s assimilation style before the critical trials were heard. Evidence will be presented showing that, without previous experience with the talker’s assimilation style, words that assimilate to other words create a lexical ambiguity for the listener. Additionally, evidence will be presented showing that experience with the talker’s assimilation style eliminates this lexical ambiguity and allows the listener to perceive the talker’s intended lexical form.
Lexical frequency effects and phonetic duration of English homophones: An acoustic study
Authors: Cohn Abigail C. , Brugman Johanna , Crawford Clifford , Joseph Andrew
Published: October 2013

Some current views of phonology assume a single abstract representation for each lexical item, while others assume extensive encoding of fine-grained detail. Some proponents of the latter view have claimed that differences in lexical (token) frequency are manifested as differences in phonetic duration. This claim was investigated in three experiments measuring the phonetic durations of heterographic pairs of homophonous English nouns differing in token frequency. Homophonous pairs were grouped according to magnitude of frequency difference within pairs: large difference (time ∼ thyme), medium difference (pain ∼ pane), and no difference (son ∼ sun). Four participants read (a) words in a list in a frame sentence; (b) target items in composed sentences; and (c) pairs in contrast. No systematic differences of ratio of duration (more frequent/less frequent) were found for individual speakers or across speakers in (a) or (b). Preliminary results for (c) show differences in duration correlated with contrastive focus and final lengthening, but not lexical frequency. The lack of positive correlation between duration and frequency calls into question the hypothesis that greater frequency leads to shorter duration, and underlines the need for a better understanding of the locus of frequency effects in the lexicon and speech production.
Rules for pluralization in African American English: Evidence from 4-, 5-, and 6-year-olds
Authors: Trent-Brown Sonja A.
Published: October 2013

This study investigated the African American English (AAE) forms produced by 4-, 5-, and 6-year-old children when pluralizing words ending in final consonant clusters. Participants were 105 child and 45 adult speakers of AAE. Speakers provided verbal responses to pictures of cartoon-like creatures with nonsense word names. Responses were recorded and presented to experienced listeners for language set and singular versus plural judgments. An acoustical analysis was conducted for comparison to the perceptual findings. Results suggest that although [s] inflection is nonobligatory in AAE, there are many instances in which it does occur. Variation in plural forms across final consonant clusters is discussed as well as other markers for pluralization in the absence of the [s] morpheme.
Estimation of acoustic vector sensor correlations in arbitrary noise field for optimal array processing
Authors: Minniti Robert J.
Published: October 2013

Optimal array processing relies heavily upon estimates of the noise field cross-correlation at the sensor locations to define sensor weights and establish an image of the field. For vector sensor arrays, the estimation process is complicated by the need to establish the correlations between the four sensors measuring the scalar pressure and three components of the acoustic particle velocity for a single location sensor and spatially displaced sensor pairs. Estimation of the noise-field correlation is typically based upon direct measurements at the sensor locations. However, it is often the case in practice that accurate direct estimation is not possible due to the limited availability of data at the analysis frequency of interest. In this paper, the author will obtain closed-form expressions for auto- and cross correlations between the components of acoustic vector sensors for within-sensor and displaced-sensor pairs in a wideband noise field of arbitrary spatial distribution. These results can be used to estimate the covariance matrix of an arbitrarily shaped array for use in a variety of optimal array processing methods. A numerical simulation applying the estimation process in a recursive implementation of minimum variance distortionless response (MVDR) will be provided as an example.
Acoustic vector fields in underwater waveguides
Authors: Rapids Brian
Published: October 2013

The ability to compute the sound pressure level as well as the vectors associated with the acoustic particle motion has existed for some time. However, propagation studies and ambient noise investigations have typically focused only upon the sound pressure levels that would be observed by an omnidirectional hydrophone or array of hydrophones. Recent interest in geophones and accelerometers for use as vector and dyadic sensors should encourage the investigation and analysis of the underlying vector fields contributing to the acoustic intensity and energy density fields. The frequency domain properties of the acoustic vector field generated by monopole sources having frequencies <1kHz in a simple iso-velocity waveguide are presented in order to build a fundamental understanding of the related quantities. Subsequently, similar field quantities computed for more realistic environments such as downward refracting profiles and deep-water profiles supporting convergence zone propagation will be discussed. Regions and phenomena associated with perturbations in the energy flux density will be highlighted.
Resolution issues of time-reversal operator decomposition (DORT) in beam space
Authors: Fromm David M. , Gaumond Charles F.
Published: October 2013

DORT has been previously demonstrated to work using beam-space source excitations and beam-space receiver using a vertical line array in shallow water. The backpropagation images of those results are shown to display effects that arise from incomplete ensonifications of the echo repeater, which was at relatively close range of approximately 20 water depths. The small improvement of the backpropagation images from the use of different receiver beam spaces is shown. Greater improvements are shown when more appropriate source beams are also used. These beam spaces include narrower ranges of beams as well as combinations of plane-wave beams. These results are shown to be consistent with the theoretical space of beams related to the detection volume. [Work supported by the ONR.]
Nonlinear parameter estimation in water-saturated sandy and muddy sediments
Authors: Kim Byoung-Nam , Lee Kang Il , Liu Jiehui , Yoon Suk Wang
Published: October 2013

Nonlinear acoustic responses of water-saturated sediments are very important to understand nonlinear phenomena of gassy ocean sediments. Especially, the second harmonic, the sum, and the difference frequency acoustic waves in water-saturated sediments can provide practical criteria to estimate the nonlinear parameters of gassy sediments. In this paper, the difference frequency acoustic waves in water-saturated sandy and muddy sediments were observed in a water tank experiment using a pulse transmission technique. Their pressure levels were 10 dB higher than the background noise level at a maximum driving pressure of source acoustic transducer. The experimental results were compared with theoretical estimations of the parametric acoustic array. The nonlinear parameters of water-saturated sandy and muddy sediments were estimated as a few tens in their comparison. The nonlinear parameters were also compared with those obtained with the second harmonic acoustic wave. [Work supported by MOCIE (Ministry of Commerce, Industry and Energy).]
Wideband multichannel time-reversal communications in a tunnel-like structure
Authors: Candy James , Robbins Christopher , Guidry Brian , Chambers David , Poggio Andrew , Dowla Farid
Published: October 2013

The development of multichannel time-reversal (T/R) processing continues to progress rapidly, especially when the need to communicate in a highly reverberant environment is critical. One such environment is a tunnel or cave, or even a pipe with many obstructions, multipath returns, severe background noise, disturbances, path disruptions (bends) as well as a long propagation path (∼120 ft.). For this environment, multichannel T/R receiver designs have been extended to include a wideband processor and modulation scheme along with designs to communicate in the highly reverberative tunnel-like environment that includes high background noise levels and disturbances. The acoustic information signals are transmitted by an 8-element host or base station array and received some distance away with a significant loss in transmitted signal levels. In this paper the results of the new wideband processor and modulation scheme coupled with the underlying T/R theory are discussed to demonstrate the overall performance for both high and low bit-level designs in the tunnel.
Experimental demonstration of time-reversed reverberation focusing in a rough waveguide. Application to target detection
Authors: Sabra Karim G. , Roux Philippe , Song Hee-Chun , Hodgkiss William , Kuperman William A. , Akal Tuncay , Stevenson Mark R.
Published: October 2013

For most shallow-water waveguides, the backscattered energy measured in a monostatic configuration is dominated by ocean bottom reverberation. A selected time-gated portion of the measured reverberation signals is used to provide a transfer function between a time-reversing array and a corresponding range interval on the bottom. Ultrasonic and at-sea experiments demonstrate focusing capabilities along the rough bottom interface of a time-reversing array using these reverberation signals only. The iterative time-reversal technique facilitates robust focusing along the ocean bottom, with little signal-processing effort involved and a priori information on the environment, and the enhancement of detection and localization of proud or buried targets in complex shallow-water environments. A passive implementation of the iterative time-reversal processing is used to construct reflectivity maps, similar to a sonar map, but with an enhanced contrast for the strongest reflectors (or scatterers), at the water–bottom interface. Ultrasonic and at-sea experiments show that targets lying on the seafloor located up to 400 wavelengths from the time-reversing array were detected over the bottom reverberation.
Second law performance of thermoacoustic systems
Authors: Paek Insu , Braun James E. , Mongeau Luc
Published: October 2013

Thermoacoustic cooler prototypes developed so far can be divided into three categories based on their cold-side operating temperatures: cryogenic, refrigeration, and the third is the air-conditioning. For most prototypes developed so far, the coefficient of performance (COP), defined as the cooling power divided by the acoustic power, was well above unity. The thermodynamic second law efficiency, defined as the COP to the reversible COP, however, varied between 0.03 and 0.22 for different prototypes. The objective of this work was to evaluate the best application area for thermoacoustic cooling from the point of view of the thermodynamic second law efficiency. Model predictions in conjunction with empirical heat transfer correlation models for thermoacoustic environments were used. The results suggest that refrigeration applications are better suited for thermoacoustic cooling than cryogenics or air-conditioning.
Sound quality parameters of an axial fan
Authors: Trautman Mark A. , Beltman Willem M.
Published: October 2013

In addition to meeting sound level criteria, an increasing emphasis is placed on the sound quality of systems and fans. In previous studies, numerical techniques were developed to predict noise from small cooling fans and a specialized experimental setup was presented for flow visualization. This paper outlines the next step: an experimental setup to quantify the sensitivity of several sound quality metrics to fan design parameters. The key metrics included in this study were sound pressure, loudness, tonality, sharpness, and roughness. In addition, the spatial variation of these metrics was characterized and empirical correlations between metrics were extracted. As an example, the experimental setup was used to characterize the design parameters that affect the sound quality of a small axial fan.
Investigation of two-dimensional numerical shock propagation using a weighted essentially non-oscillatory scheme
Authors: Wochner Mark S. , Atchley Anthony A.
Published: October 2013

This work is focused on the computational simulation of realistic jet noise propagation in air. Consequently, in addition to accurate absorption, dispersion, wave steepening, etc., propagation of multidimensional shocks is necessary. Time-domain propagation of shocks requires some special technique to ensure stability and this is usually accomplished using artificial viscosity. In this investigation, instead of using artificial viscosity, a weighted essentially non-oscillatory (WENO) scheme is used. The WENO scheme is unique in that it uses a combination of multiple stencils to calculate derivatives. Shock propagation is achieved in this method through its use of smoothness indicators, which work to leave out any candidate stencils that contain a discontinuity in the calculation of derivatives. Its ability to handle a wide variety of acoustical conditions and the future potential of such a model is shown. [Work supported by ONR and the Pennsylvania State University Applied Research Laboratory Exploratory and Foundational Program.]
Nonlinearity in outdoor propagation of high-power jet noise: measurement results
Authors: James Michael M. , Downing J. Micah , Hobbs Christopher M. , Gee Kent L. , Downing J. Micah , McInerny Sally A. , Sparrow Victor W.
Published: October 2013

Static run-up and flyover measurements of a high-performance military aircraft were conducted at Edwards Air Force Base, CA, as part of a joint program among Wyle Laboratories, The Pennsylvania State University, and The University of Alabama to develop better noise models for military aircraft. This paper describes the measurement program and the resulting acoustic data. These measurements clearly demonstrate nonlinear source and propagation effects from military jet aircraft. Moreover, these results serve as a comparative data set for the evaluation of propagation models. [Work is supported by the Strategic Environmental Research and Develop Program.]
Demonstrations of simple and complex auditory psychophysics for multiple platforms and environments
Authors: Horowitz Seth S. , Simmons Andrea M. , Blue China
Published: October 2013

Sound is arguably the most widely perceived and pervasive form of energy in our world, and among the least understood, in part due to the complexity of its underlying principles. A series of interactive displays has been developed which demonstrates that the nature of sound involves the propagation of energy through space, and illustrates the definition of psychoacoustics, which is how listeners map the physical aspects of sound and vibration onto their brains. These displays use auditory illusions and commonly experienced music and sound in novel presentations (using interactive computer algorithms) to show that what you hear is not always what you get. The areas covered in these demonstrations range from simple and complex auditory localization, which illustrate why humans are bad at echolocation but excellent at determining the contents of auditory space, to auditory illusions that manipulate fine phase information and make the listener think their head is changing size. Another demonstration shows how auditory and visual localization coincide and sound can be used to change visual tracking. These demonstrations are designed to run on a wide variety of student accessible platforms including web pages, stand-alone presentations, or even hardware-based systems for museum displays.
Vibration analysis of beams treated with passive constrained layer damping using spectral element method
Authors: Song J.-H. , Hong S.-Y.
Published: October 2013

This paper introduces a spectrally formulated finite element method (SFEM) for the beams treated with passive constrained layer damping (PCLD). The viscoelastic core of the beams has a complex modulus that varies with frequency. The SFEM is formulated in the frequency domain using dynamic shape functions based on the exact displacement solutions from progressive wave methods, which implicitly account for the frequency-dependent complex modulus of the viscoelastic core. The dynamic responses obtained by the spectral element method and the conventional finite element method (CFEM) are compared to evaluate the validity and accuracy of the present spectral PCLD beam element model. The spectral PCLD beam element model is found to provide very reliable results when compared with the conventional finite element model.
Preliminary investigation of acoustic bar codes for short-range underwater communications
Authors: Jones Dennis F.
Published: October 2013

In March 2005, underwater acoustic communications experiments were carried out from the DRDC Atlantic research vessel CFAV QUEST. A battery-operated BATS20 transmitter and a broadband barrel-stave flextensional transducer were used to broadcast noise containing acoustic bar code (ABC) information. The ABCs are silent frequency bands of fixed duration that resemble retail bar codes when viewed in a spectrogram. Two sites were selected for the experiments. The first was a shallow-water area west of the Berry Islands in the Bahamas, and the second was a deep-water site south of the Western Bank on the Scotian Shelf. Two receiver systems were deployed; autonomous, variable-buoyancy Stealth Buoys resting on the bottom at the shallow site, and drifting AN/SSQ-53F sonobuoys fitted with GPS at the deep site. Results from these experiments will be presented and future work will be discussed.
Signal processing to enhance ultrasonic tissue characterization in diagnostic medical imaging
Authors: Miller James G. , Wallace Kirk D. , Holland Mark R.
Published: October 2013

The goal of this presentation is to lay the background for identifying potential new contributions to medical diagnosis with ultrasonic imaging that might be provided by advanced signal-processing techniques. The focus of this talk is on ultrasonic tissue characterization, an approach that complements and extends presently available high-resolution imaging. Regional estimates of intrinsic material properties of normal and pathologically altered tissue are obtained from local measurements of attenuation and backscatter derived from the same signals that are used to form the ultrasonic images. Examples are drawn primarily from echocardiography, in part because imaging and characterizing the beating heart present significant challenges. Current echocardiographic images, frequently acquired with harmonic mode (nonlinear) imaging, exhibit substantial resolution of anatomical detail. Nevertheless, the estimates provided by tissue characterization of alterations in tissue properties arising from specific pathologies offer the promise of elevating echocardiographic imaging to a new plane. Among the challenges to be met in order to accomplish this goal are properly accounting for the intrinsic anisotropy of the heart and overcoming limitations that arise as a result of phase and amplitude aberrations associated with propagation through an intrinsically inhomogeneous medium. [Work supported by NIH R37HL40302 and R01 HL72761.]
Probability density function predictions of acoustic uncertainty in an underwater sound channel
Authors: James Kevin R. , Dowling David R.
Published: October 2013

The utility of forward acoustic propagation models is often limited by incomplete knowledge of environmental parameters. For this reason, information about the resulting uncertainty of acoustic field calculations is a valuable addition to the solutions generated by current propagation routines. However, extensive Monte Carlo simulations are presently the only means for quantifying this uncertainty. This presentation explores alternative methods for obtaining a complete description of the uncertainty of a time-harmonic acoustic field solution in the form of a probability density function (PDF). The isobaric contours of the field solution, including the uncertain parameters as independent variables, produce the relationship between acoustic pressure and the uncertain variables. In an ocean waveguide, the isobaric contours can be obtained approximately from a modal sum Green’s function using techniques similar to those that yield the waveguide invariant. Thus, information from a single field calculation can be used to transform PDFs for the uncertain environmental parameters into an uncertainty distribution for the calculated field solution. Results are shown for an ideal underwater sound channel and compared to results from Monte Carlo simulations. [Work sponsored by the ONR, Code 321.]
Stress field formation for multifrequency vibro-acoustography: A simulation study
Authors: Urban Matthew , Fatemi Mostafa , Greenleaf James
Published: October 2013

Vibro-acoustography is a method that uses the dynamic radiation force (stress) of ultrasound to locally excite an object at low frequency [Fatemi and Greenleaf, Science 280, 82]. A multifrequency vibro-acoustography method is proposed that uses a multifrequency radiation stress produced by an array transducer driven with N ultrasound frequencies. A multifrequency image at the different N(N−1)/2 frequencies is produced with one scan of the region of interest, increasing the information yield by a factor of N(N−1)/2. Image formation theory is presented for multifrequency vibro-acoustography using an annular array transducer. Simulations of the stress field were performed for a 20-element, 3.5-MHz annular array transducer. Four ultrasound frequencies produce six unique low-frequency components in the point spread function. Computer phantoms with small spheres are used to demonstrate the usefulness of multifrequency vibro-acoustography for microcalcification detection in breast imaging. The lateral and axial width of the main lobe at −6 dB is 0.68 and 6.47 mm, respectively. The lateral and axial sidelobe levels are −27.8 and −16.8 dB, respectively. The proposed method holds the potential for large gains of information with good spatial resolution and no increase in scanning time. [Work supported by Grant EB00535-03 from NIH.]
Ultrasound sensing of ground displacement in the presence of surface roughness for landmine detection
Authors: Ratilal Purnima , Donabed Ninos , Andrews Mark , Rappaport Carey , Fenneman Douglas
Published: October 2013

The presence of surface roughness often degrades the performance of the ultrasound sensor. Here, Green’s theorem is applied to analytically model the field reflected off the vibrating ground in the presence of surface roughness for a pair of ultrasound transducers. In the presence of surface roughness, the total field measured by the sensor is the sum of the reflected wave from the vibrating ground and that scattered off the roughness elements. The scattered field from the rough surface randomizes the phase of the received field. The performance of the sensor is examined as a function of the area of ground insonified, angle of incidence and frequency of the transducer, measurement time, correlation lengths, and amplitude of surface roughness.
Radiation and Atomic Literacy for Nonscientists
Authors: Johnson Andy
Published: October 2013

Inquiry into Radioactivity, an IBI prize-winning module, enables students to develop meaningful understandings of ionizing radiation through guided experimentation.
Mass-Independent Oxygen Isotopic Partitioning During Gas-Phase SiO
2
Formation
Authors: Chakraborty Subrata , Yanchulova Petia , Thiemens Mark H.
Published: October 2013

Explaining Anomalous Early Isotopes

Meteorites contain some of the oldest materials formed in the solar system, including silicate minerals similar in composition to those on Earth. These meteorites, however, often differ in their oxygen isotopic composition, implying that their formation involved a different chemical mechanism than younger solar-system materials.

Chakraborty
et al.

(p.
463
) performed a series of experiments and found that mixing of SiO gas and OH leads to a mass-independent isotope fractionation in SiO
2
solid products similar to those observed in the oldest meteorites. This oxidation reaction may thus have served as the first source for silicates with anomalous oxygen isotopic compositions in the solar nebula.
Natural Selection and Pain Meet at a Sodium Channel
Authors: Lewin Gary R.
Published: October 2013

Grasshopper mice can feed on toxic bark scorpions because they have evolved resistance to the pain normally caused by the toxin in the scorpion sting.

[Also see Research Article by

Rowe
et al.

]
Atomic Ironies
Life Atomic
A History of Radioisotopes in Science and Medicine

by Angela N. H. Creager

University of Chicago Press, Chicago, 2013. 505 pp. $45, £31.50. ISBN 9780226017808. Synthesis.
Authors: Radin Joanna
Published: October 2013

Creager documents how radioisotopes were used in and altered medicine and science in postwar United States.
36 Responses on Invasive Species
Invasive Species
What Everyone Needs to Know

by Daniel Simberloff

Oxford University Press, New York, 2013. 345 pp. $74, £47.99. ISBN 9780199922017. Paper, $16.95., £10.99. ISBN 9780199922031.
Authors: Vilà Montserrat
Published: October 2013

Drawing on a wide range of case studies, Simberloff offers nonspecialists a comprehensive survey of the biology and impact of invasive species.
Women, Fertility, and the Rise of Modern Capitalism
Authors: Alesina Alberto
Published: October 2013

How did the Black Plague change work and family opportunities for women?
Bricks and MOOCs
Authors: McNutt Marcia
Published: October 2013

Parents everywhere know that a college education for their children is key to a prosperous future. At a recent Summit on Higher Education,
*
journalist Fareed Zakaria, the keynote speaker, recalled a conversation with the prime minister of a large developing nation who stated (only half in jest) that his strategy for accessible higher education was to provide broadband wireless network capability to every corner of his country and tell students to take advantage of free online offerings from U.S. universities—the massive open online courses (MOOCs). Mitch Daniels, president of Purdue University, responded to the topic of online learning with the question: “How can universities articulate the value proposition that will motivate students to move in for four years?” In his words, how can universities pass the “pajama test”? Will MOOCs exist as a parallel track alongside residential university experiences, creating new opportunities and new markets? Or are they a disruptive technology that will replace conventional universities, sending them the way of the record player or typewriter?
Earliest Known Galaxy Formed Stars at a Breakneck Pace
Authors: Bhattacharjee Yudhijit
Published: October 2013

Astronomers using the Hubble Space Telescope have imaged the earliest galaxy yet, dating from just 700 million years after the big bang, and conclude that it was forming stars at a furious rate 100 times that of the modern Milky Way.
Immune Suppressant Unexpectedly Boosts Flu Vaccine
Authors: Cohen Jon
Published: October 2013

A drug used to suppress the immune system unexpectedly helped a flu vaccine defeat more strains of that virus.
Varmus's Second Act
Authors: Kaiser Jocelyn
Published: October 2013

Years after steering the National Institutes of Health into a 5-year budget doubling, the Nobel Prize–winning virologist is now helping the cancer institute deal with the aftermath.
High Nasal Burden of Methicillin-Resistant Staphylococcus aureus Increases Risk of Invasive Disease
Authors: Datta Rupak , Shah Atia , Huang Susan S. , Cui Eric , Nguyen Vinh , Welbourne Susan J. , Quan Kathleen A. , Thrupp Lauri
Published: October 2013

In a retrospective cohort study of 1,140 patients harboring methicillin-resistant
Staphylococcus aureus
, the nasal burden was low in 31%, category 1+ to 2+ in 54%, and category 3+ to 4+ in 15%. There was a significant trend in infection risk with increasing nasal burden (
P
= 0.007). In multivariate models, high nasal burden remained significantly associated with invasive infection.
Optimal Culture Incubation Time in Orthopedic Device-Associated Infections: a Retrospective Analysis of Prolonged 14-Day Incubation
Authors: Schwotzer Nora , Wahl Peter , Fracheboud Dominique , Gautier Emanuel , Chuard Christian
Published: October 2013

Accurate diagnosis of orthopedic device-associated infections can be challenging. Culture of tissue biopsy specimens is often considered the gold standard; however, there is currently no consensus on the ideal incubation time for specimens. The aim of our study was to assess the yield of a 14-day incubation protocol for tissue biopsy specimens from revision surgery (joint replacements and internal fixation devices) in a general orthopedic and trauma surgery setting. Medical records were reviewed retrospectively in order to identify cases of infection according to predefined diagnostic criteria. From August 2009 to March 2012, 499 tissue biopsy specimens were sampled from 117 cases. In 70 cases (59.8%), at least one sample showed microbiological growth. Among them, 58 cases (82.9%) were considered infections and 12 cases (17.1%) were classified as contaminations. The median time to positivity in the cases of infection was 1 day (range, 1 to 10 days), compared to 6 days (range, 1 to 11 days) in the cases of contamination (
P
< 0.001). Fifty-six (96.6%) of the infection cases were diagnosed within 7 days of incubation. In conclusion, the results of our study show that the incubation of tissue biopsy specimens beyond 7 days is not productive in a general orthopedic and trauma surgery setting. Prolonged 14-day incubation might be of interest in particular situations, however, in which the prevalence of slow-growing microorganisms and anaerobes is higher.
Utility of a Commercial PCR Assay and a Clinical Prediction Rule for Detection of Toxigenic Clostridium difficile in Asymptomatic Carriers
Authors: Donskey Curtis J. , Sunkesula Venkata C. K. , Jencson Annette L. , Stone Nimalie D. , Gould Carolyn V. , McDonald L. Clifford , Samore Matthew , Mayer Jeanmarie , Pacheco Susan , Sambol Susan , Petrella Laurica , Terry Deborah , Gerding Dale N.
Published: October 2013

A commercial PCR assay of perirectal swab specimens detected 17 (68%) of 25 asymptomatic carriers of toxigenic
Clostridium difficile
, including 93% with skin and/or environmental contamination. A clinical prediction rule, followed by PCR screening, could be used to identify carriers at high risk of
C. difficile
shedding.
HIV Diversity as a Biomarker for HIV Incidence Estimation: Including a High-Resolution Melting Diversity Assay in a Multiassay Algorithm
Authors: Cousins Matthew M. , Konikoff Jacob , Laeyendecker Oliver , Celum Connie , Buchbinder Susan P. , Seage George R. , Kirk Gregory D. , Moore Richard D. , Mehta Shruti H. , Margolick Joseph B. , Brown Joelle , Mayer Kenneth H. , Koblin Beryl A. , Wheeler Darrell , Justman Jessica E. , Hodder Sally L. , Quinn Thomas C. , Brookmeyer Ron , Eshleman Susan H.
Published: October 2013

Multiassay algorithms (MAAs) can be used to estimate cross-sectional HIV incidence. We previously identified a robust MAA that includes the BED capture enzyme immunoassay (BED-CEIA), the Bio-Rad Avidity assay, viral load, and CD4 cell count. In this report, we evaluated MAAs that include a high-resolution melting (HRM) diversity assay that does not require sequencing. HRM scores were determined for eight regions of the HIV genome (2 in
gag
, 1 in
pol
, and 5 in
env
). The MAAs that were evaluated included the BED-CEIA, the Bio-Rad Avidity assay, viral load, and the HRM diversity assay, using HRM scores from different regions and a range of region-specific HRM diversity assay cutoffs. The performance characteristics based on the proportion of samples that were classified as MAA positive by duration of infection were determined for each MAA, including the mean window period. The cross-sectional incidence estimates obtained using optimized MAAs were compared to longitudinal incidence estimates for three cohorts in the United States. The performance of the HRM-based MAA was nearly identical to that of the MAA that included CD4 cell count. The HRM-based MAA had a mean window period of 154 days and provided cross-sectional incidence estimates that were similar to those based on cohort follow-up. HIV diversity is a useful biomarker for estimating HIV incidence. MAAs that include the HRM diversity assay can provide accurate HIV incidence estimates using stored blood plasma or serum samples without a requirement for CD4 cell count data.