bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolving while invading: rapid adaptive evolution in juvenile development time for a biological control organism colonizing a high‐elevation environment
Authors: McEvoy Peter B. , Higgs Kimberley M. , Coombs Eric M. , Karaçetin Evrim , Ann Starcevich Leigh
Published: June 2012

We report evidence of adaptive evolution in juvenile development time on a decadal timescale for the cinnabar moth
Tyria jacobaeae (Lepidoptera: Arctiidae) colonizing new habitats and hosts from the Willamette Valley to the Coast Range and Cascades Mountains in Oregon. Four lines of evidence reveal shorter egg to pupa juvenile development times evolved in the mountains, where cooler temperatures shorten the growing season: (i) field observations showed that the mountain populations have shorter phenological development; (ii) a common garden experiment revealed genetic determination of phenotypic differences in juvenile development time between Willamette Valley and mountain populations correlated with the growing season; (iii) a laboratory experiment rearing offspring from parental crosses within and between Willamette Valley and Cascades populations demonstrated polygenic inheritance, high heritability, and genetic determination of phenotypic differences in development times; and (iv) statistical tests that exclude random processes (founder effect, genetic drift) in favor of natural selection as explanations for observed differences in phenology. These results support the hypothesis that rapid adaptation to the cooler mountain climate occurred in populations established from populations in the warmer valley climate. Our findings should motivate regulators to require evaluation of evolutionary potential of candidate biological control organisms prior to release.
Understanding admixture patterns in supplemented populations: a case study combining molecular analyses and temporally explicit simulations in Atlantic salmon
Authors: Perrier Charles , Baglinière Jean‐Luc , Evanno Guillaume
Published: June 2012

Genetic admixture between wild and introduced populations is a rising concern for the management of endangered species. Here, we use a dual approach based on molecular analyses of samples collected before and after hatchery fish introduction in combination with a simulation study to obtain insight into the mechanisms of admixture in wild populations. Using 17 microsatellites, we genotyped pre‐ and post‐stocking samples from four Atlantic salmon populations supplemented with non‐native fish to estimate genetic admixture. We also used individual‐based temporally explicit simulations based on realistic demographic and stocking data to predict the extent of admixture. We found a low admixture by hatchery stocks within prestocking samples but moderate to high values in post‐stocking samples (from 12% to 60%). The simulation scenarios best fitting the real data suggested a 10–25 times lower survival of stocked fish relative to wild individuals. Simulations also suggested relatively high dispersal rates of stocked and wild fish, which may explain some high levels of admixture in weakly stocked populations and the persistence of indigenous genotypes in heavily stocked populations. This study overall demonstrates that combining genetic analyses with simulations can significantly improve the understanding of admixture mechanisms in wild populations.
Evolutionary divergence of the APETALA1 and CAULIFLOWER proteins
Authors: WANG Bin , ZHANG Ning , GUO Chun‐Ce , XU Gui‐Xia , KONG Hong‐Zhi , SHAN Hong‐Yan
Published: June 2012

Abstract  APETALA1 (AP1) and CAULIFLOWER (CAL) are a pair of paralogous genes that were generated through the pre‐Brassicaceae whole‐genome duplication event. AP1 and CAL have both partially redundant and unique functions. Previous studies have shown that the K and C regions of their proteins are essential for the functional divergence. However, which differences in these regions are the major contributors and how the differences were accumulated remain unknown. In the present study, we compared the sequences of the two proteins and identified five gaps and 55 amino acid replacements between them. Investigation of genomic sequences further indicated that the differences in the proteins were caused by non‐synonymous substitutions and changes in exon–intron structures. Reconstruction of three‐dimensional structures revealed that the sequence divergence of AP1 and CAL has resulted in differences between the two in terms of the number, length, position and orientation of α‐helices, especially in the K and C regions. Comparisons of sequences and three‐dimensional structures of ancestral proteins with AP1 and CAL suggest that the ancestral AP1 protein experienced fewer changes, whereas the ancestral CAL protein accumulated more changes shortly after gene duplication, relative to their common ancestor. Thereafter, AP1‐like proteins experienced few mutations, whereas CAL‐like proteins were not conserved until the diversification of the Brassicaceae lineage I. This indicates that AP1‐ and CAL‐like proteins evolved asymmetrically after gene duplication. These findings provide new insights into the functional divergence of AP1 and CAL genes.
Carbon isotopic fractionation in Fischer‐Tropsch‐type reactions and relevance to meteorite organics
Authors: JOHNSON Natasha M. , ELSILA Jamie E. , KOPSTEIN Mickey , NUTH Joseph A.
Published: June 2012

Abstract— Fischer‐Tropsch‐type (FTT) reactions have been hypothesized to contribute to the formation of organic compounds in the early solar system, but it has been difficult to identify a signature of such reactions in meteoritic organics. The work reported here examined whether temperature‐dependent carbon isotopic fractionation of FTT reactions might provide such a signature. Analyses of bulk organic deposits resulting from FTT experiments show a slight trend toward lighter carbon isotopic ratios with increasing temperature. It is unlikely, however, that these carbon isotopic signatures could provide definitive provenance for organic compounds in solar system materials produced through FTT reactions, because of the small scale of the observed fractionations and the possibility that signatures from many different temperatures may be present in any specific grain.
Chondrule cooling rates inferred from diffusive profiles in metal lumps from the Acfer 097 CR2 chondrite
Authors: HUMAYUN Munir
Published: June 2012

Abstract— CR chondrites contain metal lumps (>300 μm) either attached to chondrule silicates or apparently isolated in the matrix. Here, laser ablation microanalysis of six metal lumps from a polished thin section of the Acfer 097 CR2 chondrite at 15 μm spatial resolution revealed zoning profiles for the volatile elements Cu and Ga. The mutual diffusivities of Cu and Ga were used to infer T ∼ 1473 ± 100 K from the correlation of Cu versus Ga. The cooling rates of the metal lumps were calculated to be 0.5–50 K h−1 for Tp ∼ 1473 ± 100 K, with a maximum possible range of 0.1–400 K h−1 for Tp ∼ 1200–1800 K, overlapping the range of cooling rates inferred from petrological studies of type I chondrules (10–1000 K h−1). Chondrule textures were established near the peak heating temperatures of chondrules (approximately 1900–2000 K), while the Cu and Ga diffusive profiles were established after solidification (T ∼ 1500 K), consistent with nonlinear cooling. Furthermore, one chondrule (N2) has a more complex zoning profile that is modeled as a three‐stage cooling history involving initial cooling at approximately 1 K h−1, followed by mild re‐heating (T ∼ 1700 K) that re‐evaporated Cu and Ga from the outer approximately 100 μm of the metal lump and then cooled again at approximately 5 K h−1. The thermal effects of parent body and other preaccretionary heating events on the Cu and Ga zoning profiles are examined. Although CR parent bodies have experienced aqueous alteration, the thermal effects of this process can neither produce nor erase the Cu and Ga diffusive profiles. Thus, metal lumps in CR chondrites record the solid‐state thermal history of chondrules as they travelled away from the chondrule‐forming region.
Fractionated matrix composition in CV3 Vigarano and alteration processes on the CV parent asteroid
Authors: HURT Sean M. , RUBIN Alan E. , WASSON John T.
Published: June 2012

Abstract— Although CV3 Vigarano is one of the most primitive CV chondrites, it has lost most of the S from the matrix; matrix Na is also depleted relative to the concentration in bulk CV chondrites. We used a matrix‐grid technique to study thirteen 50 × 50 μm regions in Vigarano; in each area, we used an electron microprobe to gather data with an electron beam 3 μm in width. We found two end‐member types of matrix textures. One is coarse and porous, has lower Fe contents and lower analytical totals; it appears to be contaminated with comminuted chondrule debris. The other is finer grained and appears smooth; its mean composition has higher Fe, but lower S and Al contents, than the coarse matrix areas. Our tentative interpretation is that the larger grain size of the coarse areas resulted from the admixing of comminuted chondrule materials, and thus that the initial fraction of nebular fines was higher in the fine matrix regions. Aside from volatiles, the overall composition of Vigarano matrix is similar to that observed in matrix‐grid studies of other carbonaceous chondrites: Al, Si, Fe, and Mn have high whole‐chondrite‐normalized abundance ratios; Ca concentrations are low and highly variable. Because asteroidal alteration effects are present in our sample, it is difficult to resolve nebular signatures in the compositions of the grid areas.
What is the current practice of medicines reconciliation in children nationally in the UK?
Authors: Huynh Chi , Jani Yogini , Wong Ian Chi Kei , Dewchand Bhavika , Tomlin Stephen
Published: June 2012

Introduction

The National Institute for Health and Clinical Excellence/National Patient Safety Agency (NICE/NPSA) guidelines for medicines reconciliation (MR) on admission to hospital in adult inpatients were introduced in 2007, but they excluded children less than 16 years of age.

Method

We conducted a survey of 98 paediatric pharmacists (each from a different hospital) to find out what the current practice of MR in children is in the UK.

Key findings

Responses showed that 67% (43/64) of pharmacists surveyed carried out MR in all children at admission and only a third 34% (22/64) had policies for MR in children. Of the respondents who did not carry out MR in all children, 80% (4/5) responded that they did so in selected children. Pharmacists considered themselves the most appropriate profession for carrying out MR. When asked whether the NICE guidance should be expanded to include children, 98% (54/55) of the respondents answered ‘yes’.

Conclusion

In conclusion, the findings suggest that MR is being conducted inconsistently in children and most paediatric pharmacists would like national guidance to be expanded to include children.
The influence of evidence-based medicine training on decision-making in relation to over-the-counter medicines: a qualitative study
Authors: Hanna Lezley-Anne , Hughes Carmel
Published: June 2012

Objectives

To explore the role of evidence of effectiveness when making decisions about over-the-counter (OTC) medication and to ascertain whether evidence-based medicine training raised awareness in decision-making. Additionally, this work aimed to complement the findings of a previous study because all participants in this current study had received training in evidence-based medicine (unlike the previous participants).

Methods

Following ethical approval and an e-mailed invitation, face-to-face, semi-structured interviews were conducted with newly registered pharmacists (who had received training in evidence-based medicine as part of their MPharm degree) to discuss the role of evidence of effectiveness with OTC medicines. Interviews were recorded and transcribed verbatim. Following transcription, all data were entered into the NVivo software package (version 8). Data were coded and analysed using a constant comparison approach.

Key findings

Twenty-five pharmacists (7 males and 18 females; registered for less than 4 months) were recruited and all participated in the study. Their primary focus with OTC medicines was safety; sales of products (including those that lack evidence of effectiveness) were justified provided they did no harm. Meeting patient expectation was also an important consideration and often superseded evidence. Despite knowledge of the concept, and an awareness of ethical requirements, an evidence-based approach was not routinely implemented by these pharmacists. Pharmacists did not routinely utilize evidence-based resources when making decisions about OTC medicines and some felt uncomfortable discussing the evidence-base for OTC products with patients.

Conclusions

The evidence-based medicine training that these pharmacists received appeared to have limited influence on OTC decision-making. More work could be conducted to ensure that an evidence-based approach is routinely implemented in practice.
Characterizing Dynamic Transitions Associated With Snap-Through: A Discrete System
Authors: Wiebe R. , Virgin L. N. , Stanciulescu I. , Spottswood S. M. , Eason T. G.
Published: June 2012

Geometrically nonlinear structures often possess multiple equilibrium configurations. Under extreme conditions of excitation, it is possible for these structures to exhibit oscillations about and between these co-existing configurations. This behavior may have serious implications for fatigue in the context of aircraft surface panels. Snap-through is a name often given to sudden changes in dynamic behavior associated with mechanical instability (buckling). This is an often encountered problem in hypersonic vehicles in which severe thermal loading and acoustic excitation conspire to create an especially hostile environment for structural elements. In this paper, a simple link model is used, experimentally and numerically, to investigate the mechanisms of snap-through buckling from a phenomenological standpoint.
Swing-Up Control of a Three-Link Underactuated Manipulator by High-Frequency Horizontal Excitation
Authors: Endo Kazuya , Yabuno Hiroshi
Published: June 2012

In the present paper, we consider a three-link underactuated manipulator, the first joint of which is active and the second and third joints of which exhibit passive motion, on a plane inclined at slight angle from horizontal the plane. We analytically investigate changes in the stability of equilibrium points of the free links connected to the passive joints using high-frequency horizontal excitation of the first link. We derive autonomous averaged equations from the dimensionless equations of motion using the method of multiple scales. We clarify that the two free links can be swung up through pitchfork bifurcations and stabilized at some configurations by producing nontrivial and stable equilibrium points due to the high-frequency excitation. Furthermore, it is experimentally verified that increasing the excitation frequency multiplies stable and nontrivial equilibrium points.
Adaptive Control for a Class of Hysteretic Systems
Authors: Hossein Mousavi Seyyed , Khayatian Alireza
Published: June 2012

In this paper, the generalized Prandtl-Ishlinskii model is used to design an adaptive controller for a class of nonlinear systems which contain hysteresis phenomenon within their dynamic equation as a function of state variables. The controller design is carried out through adaptive backstepping approach and the stability proof is given based on Lyapunov stability theory. In contrast to the systems in which hysteresis appear in their input, the inverse based methods cannot be applied to systems with hysteresis in their states. The proposed controller is able to cope with different kinds of hysteresis nonlinearity (saturated and unsaturated). Finally, to show the effectiveness of the proposed method, simulations are carried out for a second order “mass–nonlinear spring–damper” system.
Nonlinear Bifurcation Analysis of a Single-DoF Model of a Robotic Arm Subject to Digital Position Control
Authors: Habib Giuseppe , Rega Giuseppe , Stepan Gabor
Published: June 2012

Precision and stability in position control of robots are critical parameters in many industrial applications where high accuracy is needed. It is well known that digital effect is destabilizing and can cause instabilities. In this paper, we analyze a single DoF model of a robotic arm and we present the stability limits in the parameter space of the control gains. Furthermore we introduce a nonlinearity relative to the saturation of the control force in the model, reduce the dynamics of the nonlinear map to its local center manifold, study the bifurcation along the stability border and identify conditions under which a supercritical or subcritical bifurcation occurs. The obtained results explain some of the typical instabilities occurring in industrial applications. We verify the obtained results through numerical simulations.
Autoparametric Resonances of Elastic Structures Coupled With Two Sloshing Modes in a Square Liquid Tank
Authors: Ikeda Takashi , Takashima Masaki , Harata Yuji
Published: June 2012

Nonlinear vibrations of an elastic structure coupled with liquid sloshing in a square tank subjected to vertical sinusoidal excitation are investigated. In the theoretical analysis, the ratios of the natural frequencies of the structure and two sloshing modes satisfy 2:1:1. The equations of motion for the structure and seven sloshing modes are derived using Galerkin’s method while considering the nonlinearity of sloshing. The linear damping terms are then incorporated into the modal equations to consider the damping effect of sloshing. The frequency response curves are determined using van der Pol’s method. The influences of the liquid level, the aspect ratio of the tank cross-section, the deviation of the tuning condition, and the excitation amplitude are investigated. When the liquid level is high, and depending on the excitation frequency, there are three patterns of sloshing: (i) both (1,0) and (0,1) sloshing modes appear at identical amplitudes; (ii) these two modes appear at different amplitudes; and (iii) either (1,0) or (0,1) mode appears. Small deviations of the tuning condition may cause Hopf bifurcations to occur followed by amplitude modulated motion including chaotic vibrations. Bifurcation sets are also calculated to illustrate the influence of the system parameters on the response of the system. It is found that for low liquid levels, square tuned liquid dampers (TLDs) work more effectively than rectangular TLDs. Experiments were also conducted in order to confirm the validity of the theoretical results and were in good agreement with the experimental data.
Low-Velocity Impact Response of Structures With Local Plastic Deformation: Characterization and Scaling
Authors: Christoforou Andreas P. , Yigit Ahmet S. , Majeed Majed
Published: June 2012

This paper presents a methodology for the characterization and scaling of the response of structures having different shapes, sizes, and boundary conditions that are under impact by spherical objects. The objectives are to demonstrate the accuracy of a new bilinear contact law that accounts for permanent indentation in the contact zone, and to show the efficacy of a characterization diagram in the analysis and design of structures subject to impact. The characterization diagram shows the normalized functional relationship between the maximum impact force and three nondimensional parameters that cover the complete dynamic spectrum for low-velocity impact. The validity of using the bilinear elastoplastic contact law is demonstrated by both finite element (FE) and Rayleigh-Ritz discretization procedures for simply-supported plates. The efficacy of the characterization diagram, which was developed using simple structural models, is demonstrated by the FE simulations of more complicated and realistic structures and boundary conditions (clamped, stiffened plates, and cylindrical panels). All of the necessary parameters needed for the characterization are ‘measured’ using the FE models simulating real-world experiments. Impact parameters are varied to cover the complete dynamic spectrum with excellent results.
Impact of Cofiring Ceria in Ni/YSZ SOFC Anodes for Operation With Syngas and n-Butane
Authors: Patel Siddharth , Jawlik Paul F. , Wang Lei , Jackson Gregory S. , Almansoori Ali
Published: June 2012

This study explores cofiring ceria (CeO2) with NiO and 8 mol% yttria-stabilized zirconia (YSZ) to form Ni-based cermet anodes for high-temperature solid oxide fuel cells (SOFCs) operating on syngas and n-butane/steam fuel feeds. Particular attention is paid to the suppression of carbon deposit growth in Ni-based anodes with carbonaceous fuel feeds. CeO2 was cofired with NiO and YSZ to form a porous Ni cermet anode support layer after reduction in H2 at 800°C. The porous anode support layer (1 mm thick) was combined with a Ni/YSZ functional layer (∼25 μm thick), a dense YSZ electrolyte (10–20 μm thick), and porous La0.8Sr0.2MnO3−x (LSM)/YSZ cathodes (∼50 μm thick) to form anode-supported button cells for electrochemical characterization. The button cells were tested from 700 °C to 800 °C on various fuels including syngas and n-butane/H2O mixtures at steam-to-carbon (S/C) ratios of 1.0 and 1.5. Electrochemical testing revealed that CeO2 addition provided stable performance at 800 °C without compromising power densities—up to 0.6 W/cm2 on syngas and 0.35 W/cm2 on direct butane feeds. Furthermore, the addition of CeO2 suppressed significant carbon deposition as observed for Ni/YSZ anode support layers without CeO2. Testing with syngas at different H2 and CO partial pressures indicated that high power densities can be maintained along an anode channel for up to 50% fuel conversion. The results indicate that cofiring CeO2 in Ni/YSZ anode support layers presents a viable option for stable SOFC operation on either prereformed or internally reformed light-hydrocarbon fuel feeds.
Proton irradiation energy dependence of dc and rf characteristics on InAlN/GaN high electron mobility transistors
Authors: Lo Chien-Fong , Liu Lu , Ren Fan , Pearton Stephen J. , Gila Brent P. , Kim Hong-Yeol , Kim Jihyun , Laboutin Oleg , Cao Yu , Johnson Jerry W. , Kravchenko Ivan I.
Published: June 2012

The effects of proton irradiation energy on dc and rf characteristics of InAlN/GaN high electron mobility transistors (HEMTs) were investigated. A fixed proton dose of 5 × 1015 cm−2 with 5, 10, and 15 MeV irradiation energies was used in this study. For the dc characteristics, degradation was observed for sheet resistance, transfer resistance, contact resistivity, saturation drain current, maximum transconductance, reverse-bias gate leakage current, and sub-threshold drain leakage current for all the irradiated HEMTs; however, the degree of the degradation was decreased as the irradiation energy increased. Similar trends were obtained for the rf performance of the devices, with ∼10% degradation of the unity gain cut-off frequency (fT) and maximum oscillation frequency ( fmax) for the HEMTs irradiated with 15 MeV protons but 30% for 5 MeV proton irradiation. The carrier removal rate was in the range 0.66–1.24 cm−1 over the range of proton energies investigated.
Very low angle annular dark field imaging in the scanning transmission electron microscope: A versatile tool for micro- and nano-characterization
Authors: Baumann Frieder H.
Published: June 2012

The author shows how very low angle annular dark field (VLAADF) imaging in the scanning transmission electron microscope (STEM) is used to delineate regions of different orientation or structural phase in the same material. First, the author describes the settings used to obtain images in which only very low indexed beams contribute to the image formation. These settings can be implemented easily on any commercial STEM/TEM by choosing the appropriate camera length and objective aperture. The author then demonstrates how VLAADF was used to perform detailed grain size studies in Cu interconnects, and show how the technique can be used to outline the amorphous region within the crystalline matrix in a phase change memory device. The author finishes by addressing and discussing the dependence of the “orientation contrast” on the main imaging parameters.
Orientation dependence of broadband acoustic backscattering from live squid
Authors: Lee Wu-Jung , Lavery Andone C. , Stanton Timothy K.
Published: June 2012

A controlled laboratory experiment of broadband acoustic backscattering from live squid (Loligo pealeii) was conducted using linear chirp signals (60–103 kHz) with data collected over the full 360° of orientation in the lateral plane, in <1° increments. The acoustic measurements were compared with an analytical prolate spheroid model and a three-dimensional numerical model with randomized squid shape, both based on the distorted-wave Born approximation formulation. The data were consistent with the hypothesized fluid-like scattering properties of squid. The contributions from the front and back interfaces of the squid were found to dominate the scattering at normal incidence, while the arms had a significant effect at other angles. The three-dimensional numerical model predictions out-performed the prolate spheroid model over a wide range of orientations. The predictions were found to be sensitive to the shape parameters, including the arms and the fins. Accurate predictions require setting these shape parameters to best describe the most probable squid shape for different applications. The understanding developed here serves as a basis for the accurate interpretation of in situ acoustic scattering measurements of squid.
The effects of sound level and vibration magnitude on the relative discomfort of noise and vibration
Authors: Huang Yu , Griffin Michael J.
Published: June 2012

The relative discomfort caused by noise and vibration, how this depends on the level of noise and the magnitude of vibration, and whether the noise and vibration are presented simultaneously or sequentially has been investigated in a laboratory study with 20 subjects. Noise and vertical vibration were reproduced with all 49 combinations of 7 levels of noise and 7 magnitudes of vibration to allow the discomfort caused by one of the stimuli to be judged relative to the other stimulus using magnitude estimation. In four sessions, subjects judged noise relative to vibration and vibration relative to noise, with both simultaneous and sequential presentations of the stimuli. The equivalence of noise and vibration was not greatly dependent on whether the stimuli were simultaneous or sequential, but highly dependent on whether noise was judged relative to vibration or vibration was judged relative to noise. When judging noise, higher magnitude vibrations appeared to mask the discomfort caused by low levels of noise. When judging vibration, higher level noises appeared to mask the discomfort caused by low magnitudes of vibration. The judgment of vibration discomfort was more influenced by noise than the judgment of noise discomfort was influenced by vibration.
Acoustic classification of multiple simultaneous bird species: A multi-instance multi-label approach
Authors: Briggs Forrest , Lakshminarayanan Balaji , Neal Lawrence , Fern Xiaoli Z. , Raich Raviv , Hadley Sarah J. K. , Hadley Adam S. , Betts Matthew G.
Published: June 2012

Although field-collected recordings typically contain multiple simultaneously vocalizing birds of different species, acoustic species classification in this setting has received little study so far. This work formulates the problem of classifying the set of species present in an audio recording using the multi-instance multi-label (MIML) framework for machine learning, and proposes a MIML bag generator for audio, i.e., an algorithm which transforms an input audio signal into a bag-of-instances representation suitable for use with MIML classifiers. The proposed representation uses a 2D time-frequency segmentation of the audio signal, which can separate bird sounds that overlap in time. Experiments using audio data containing 13 species collected with unattended omnidirectional microphones in the H. J. Andrews Experimental Forest demonstrate that the proposed methods achieve high accuracy (96.1% true positives/negatives). Automated detection of bird species occurrence using MIML has many potential applications, particularly in long-term monitoring of remote sites, species distribution modeling, and conservation planning.
Steady inter and intra-annual decrease in the vocalization frequency of Antarctic blue whales
Authors: Gavrilov Alexander N. , McCauley Robert D. , Gedamke Jason
Published: June 2012

Time averaged narrow-band noise near 27 Hz produced by vocalizations of many distant Antarctic blue whales intensifies seasonally from early February to late October in the ocean off Australia’s South West. Spectral characteristics of long term patterns in this noise band were analyzed using ambient noise data collected at the Comprehensive Nuclear-Test-Ban Treaty hydroacoustic station off Cape Leeuwin, Western Australia over 2002–2010. Within 7 day averaged noise spectra derived from 4096-point FFT (∼0.06 Hz frequency resolution), the −3-dB width of the spectral peak from the upper tone of Antarctic blue whale vocalization was about 0.5 Hz. The spectral frequency peak of this tonal call was regularly but not gradually decreasing over the 9 years of observation from ∼27.7 Hz in 2002 to ∼26.6 Hz in 2010. The average frequency peak steadily decreased at a greater rate within a season at 0.4–0.5 Hz/season but then in the next year recovered to approximately the mean value of the previous season. A regression analysis showed that the interannual decrease rate of the peak frequency of the upper tonal call was 0.135 ± 0.003 Hz/year over 2002–2010 (R2 ≈ 0.99). Possible causes of such a decline in the whale vocalization frequency are considered.
Modal analysis of the range evolution of broadband wavefields in the North Pacific Ocean: Low mode numbers
Authors: Udovydchenkov Ilya A. , Brown Michael G. , Duda Timothy F. , Mercer James A. , Andrew Rex K. , Worcester Peter F. , Dzieciuch Matthew A. , Howe Bruce M. , Colosi John A.
Published: June 2012

The results of mode-processing measurements of broadband acoustic wavefields made in the fall of 2004 as part of the Long-Range Ocean Acoustic Propagation Experiment (LOAPEX) in the eastern North Pacific Ocean are reported here. Transient wavefields in the 50–90 Hz band that were recorded on a 1400 -m long 40 element vertical array centered near the sound channel axis are analyzed. This array was designed to resolve low-order modes. The wavefields were excited by a ship-suspended source at seven ranges, between approximately 50 and 3200 km, from the receiving array. The range evolution of broadband modal arrival patterns corresponding to fixed mode numbers (“modal group arrivals”) is analyzed with an emphasis on the second (variance) and third (skewness) moments. A theory of modal group time spreads is described, emphasizing complexities associated with energy scattering among low-order modes. The temporal structure of measured modal group arrivals is compared to theoretical predictions and numerical simulations. Theory, simulations, and observations generally agree. In cases where disagreement is observed, the reasons for the disagreement are discussed in terms of the underlying physical processes and data limitations.
Far-field approximation for a point-excited anisotropic plate
Authors: Magliula Elizabeth A. , McDaniel J. Gregory , Pierce Allan D.
Published: June 2012

An analytic approximation is derived for the far-field response of a generally anisotropic plate to a time-harmonic point force acting normal to the plate. This approximation quantifies the directivity of the flexural wave field that propagates away from the force, which is expected to be useful in the design and testing of anisotropic plates. Derivation of the approximation begins with a two-dimensional Fourier transform of the flexural equation of motion. Inversion to the spatial domain is accomplished by contour integration over the radial component of wave number followed by an application of the method of stationary phase to integration over the circumferential component of wave number. The resulting approximation resembles that of an isotropic plate but involves wave numbers, wave amplitudes, and phases that depend on propagation angle. Numerical results for a plate comprised of bonded layers of a graphite-epoxy material illustrate the accuracy of the method compared to a numerical simulation based on discrete Fourier analysis. Three configurations are analyzed in which the relative angles of the layers are varied. In all cases, the agreement is quite good when the distance between force and observation point is greater than a few wavelengths.
Dispersion properties of helical waves in radially inhomogeneous elastic media
Authors: Syresin D. E. , Zharnikov T. V. , Tyutekin V. V.
Published: June 2012

In this paper, a method describing dispersion curve calculation for waves propagating in radially layered, inhomogeneous isotropic elastic waveguides is developed. Particular emphasis is placed on the helical waves with noninteger azimuthal wavenumbers, which can be potentially applied in such fields as nondestructive evaluation, acoustic tomography, etc., stipulating their practical importance. To solve the problem under consideration, the matrix Riccati equation is formulated for an impedance matrix. The use of the latter yields a simple form of the dispersion equation. Numerical computation of dispersion curves can encounter difficulties, which are due to potential singularities of the impedance matrix and the necessity to separate roots of the dispersion equation. These difficulties are overcome by employing the Cayley transform and invoking the parametric continuation method. The method developed by the authors is demonstrated by calculating dispersion diagrams in support of helical waves for several models of practical interest. Such computations for an inhomogeneous layer and its approximation by a set of homogeneous layers using a transfer matrix and Riccati equation methods revealed higher computational accuracy of the latter. Dispersion curves calculated for layers with different types of inhomogeneity demonstrated significant discrepancies at low frequencies.
Acoustic fields in binary gas mixtures: Mutual diffusion effects throughout and beyond the boundary layers
Authors: Guianvarc’h Cécile , Bruneau Michel
Published: June 2012

The acoustic behavior in thermo-viscous gas mixtures, both in proximity of walls and far from them (outside the boundary layers), involves deviations from the adiabatic and laminar movements in pure gases, which result from the influence of several diffusive fields, namely, shear, entropic, and concentration variation fields (their energy being provided by the acoustic field itself). Owing to the boundary conditions, that are slip condition, isothermal condition and concentration flux vanishing on the walls, a strong coupling between these fields occurs inside the boundary layers while their effects appear to be simple additive processes in the bulk of the medium. Although recent literature on this subject leads to interesting results, opening the way to several new issues [R. Raspet et al., J. Acoust. Soc. Am. 105, 65–73 (1999); R. Raspet et al., J. Acoust. Soc. Am. 112, 1414–1422 (2002); G. W. Swift and P. S. Spoor, J. Acoust. Soc. Am. 106, 1794–1800 (1999); D. A. Geller and G. W. Swift, J. Acoust. Soc. Am. 111, 1675–1684 (2002)], the results available still have limitations because they do not provide complete solutions for the propagative and diffusive fields throughout and beyond the boundary layers. The present work aims at providing these solutions in the whole domains considered. The results allow interpreting analytically the behavior of the fields above mentioned in closed cavities and ducts, and particularly in spherical cavities which are best suited to develop metrological applications.
A neurally inspired musical instrument classification system based upon the sound onset
Authors: Newton Michael J. , Smith Leslie S.
Published: June 2012

Physiological evidence suggests that sound onset detection in the auditory system may be performed by specialized neurons as early as the cochlear nucleus. Psychoacoustic evidence shows that the sound onset can be important for the recognition of musical sounds. Here the sound onset is used in isolation to form tone descriptors for a musical instrument classification task. The task involves 2085 isolated musical tones from the McGill dataset across five instrument categories. A neurally inspired tone descriptor is created using a model of the auditory system’s response to sound onset. A gammatone filterbank and spiking onset detectors, built from dynamic synapses and leaky integrate-and-fire neurons, create parallel spike trains that emphasize the sound onset. These are coded as a descriptor called the onset fingerprint. Classification uses a time-domain neural network, the echo state network. Reference strategies, based upon mel-frequency cepstral coefficients, evaluated either over the whole tone or only during the sound onset, provide context to the method. Classification success rates for the neurally-inspired method are around 75%. The cepstral methods perform between 73% and 76%. Further testing with tones from the Iowa MIS collection shows that the neurally inspired method is considerably more robust when tested with data from an unrelated dataset.
Asymptotic expansions for the coupled wavenumbers in an infinite orthotropic flexible fluid-filled cylindrical shell
Authors: Kunte M. V. , Sarkar Abhijit , Sonti Venkata R.
Published: June 2012

Analytical expressions are found for the coupled wavenumbers in flexible, fluid-filled, circular cylindrical orthotropic shells using the asymptotic methods. These expressions are valid for arbitrary circumferential orders. The Donnell–Mushtari shell theory is used to model the shell and the effect of the fluid is introduced through the fluid-loading parameter μ. The orthotropic problem is posed as a perturbation on the corresponding isotropic problem by defining a suitable orthotropy parameter ε, which is a measure of the degree of orthotropy. For the first study, an isotropic shell is considered (by setting ε = 0) and expansions are found for the coupled wavenumbers using a regular perturbation approach. In the second study, asymptotic expansions are found for the coupled wavenumbers in the limit of small orthotropy (ε≪1). For each study, isotropy and orthotropy, expansions are found for small and large values of the fluid-loading parameter μ. All the asymptotic solutions are compared with numerical solutions to the coupled dispersion relation and the match is seen to be good. The differences between the isotropic and orthotropic solutions are discussed. The main contribution of this work lies in extending the existing literature beyond in vacuo studies to the case of fluid-filled shells (isotropic and orthotropic).
Feasibility of using Nakagami distribution in evaluating the formation of ultrasound-induced thermal lesions
Authors: Zhang Siyuan , Zhou Fanyu , Wan Mingxi , Wei Min , Fu Quanyou , Wang Xing , Wang Supin
Published: June 2012

The acoustic posterior shadowing effects of bubbles influence the accuracy for defining the location and range of ablated thermal lesions during focused ultrasound surgery when using ultrasonic monitoring imaging. This paper explored the feasibility of using Nakagami distribution to evaluate the ablated region induced by focused ultrasound exposures at different acoustic power levels in transparent tissue-mimicking phantoms. The mean value of the Nakagami parameter m was about 0.5 in the cavitation region and increased to around 1 in the ablated region. Nakagami images were not subject to significant shadowing effects of bubbles. Ultrasound-induced thermal lesions observed in the photos and Nakagami images were overshadowed by bubbles in the B-mode images. The lesion size predicted in the Nakagami images was smaller than that predicted in the photos due to the sub resolvable effect of Nakagami imaging at the interface. This preliminary study on tissue-mimicking phantom suggested that the Nakagami parameter m may have the potential use in evaluating the formation of ultrasound-induced thermal lesion when the shadowing effect of bubbles is strong while the thermal lesion was small. Further studies in vivo and in vitro will be needed to evaluate the potential application.
Quantitative estimation of ultrasound beam intensities using infrared thermography—Experimental validation
Authors: Giridhar Dushyanth , Robinson Ronald A. , Liu Yunbo , Sliwa Jack , Zderic Vesna , Myers Matthew R.
Published: June 2012

Infrared (IR) thermography is a technique that has the potential to rapidly and noninvasively determine the intensity fields of ultrasound transducers. In the work described here, IR temperature measurements were made in a tissue phantom sonicated with a high-intensity focused ultrasound (HIFU) transducer, and the intensity fields were determined using a previously published mathematical formulation relating intensity to temperature rise at a tissue/air interface. Intensity fields determined from the IR technique were compared with those derived from hydrophone measurements. Focal intensities and beam widths determined via the IR approach agreed with values derived from hydrophone measurements to within a relative difference of less than 10%, for a transducer with a gain of 30, and about 13% for a transducer with a gain of 60. At axial locations roughly 1 cm in front (pre-focal) and behind (post-focal) the focus, the agreement with hydrophones for the lower-gain transducer remained comparable to that in the focal plane. For the higher-gain transducer, the agreement with hydrophones at the pre-focal and post-focal locations was around 40%.
Long-range multi-carrier acoustic communication in deep water using a towed horizontal array
Authors: Kang Taehyuk , Song H. C. , Hodgkiss W. S.
Published: June 2012

During a recent long-range acoustic communication experiment carried out in deep water, multi-carrier Orthogonal Frequency Division Multiplexing (OFDM) communication signals were transmitted with a 50 Hz bandwidth (225–275 Hz) at various source-receiver ranges from 100 to 700 km. The experiment consisted of two mobile components: (1) a source towed slowly at a speed of 2–3 knots at ∼75 m depth and (2) a horizontal line array towed at 3.5 knots at a depth of ∼200 m. In addition to beamforming, an interleaver gain is exploited to compensate for low signal-to-noise ratio at the expense of data rate while providing diversity in the frequency domain. Error-free performance is shown at effective data rates of 15 and 7.5 bits/s at ranges of 550 km and 700 km, respectively, by combining interleaved repetitions with low-density parity-check coding after beamforming, demonstrating the feasibility of multi-carrier OFDM communications in deep water using a towed horizontal array.
Modeling incoherent reflections from rough room surfaces with image sources
Authors: Siltanen Samu , Lokki Tapio , Tervo Sakari , Savioja Lauri
Published: June 2012

Reflections at rough surfaces change the temporal structure of the reflected signal. This paper shows how to incorporate this temporal behavior in geometric room acoustics modeling. Specifically, a beam tracer is used for calculating the image sources and reflection paths. The roughness of the surfaces is taken into account in post-processing. A single reflection is assumed to distribute the energy according to an exponential function in time based on Biot’s rough surface modeling theory. Multiple reflections are modeled with convolutions of exponential functions which are approximated as gamma functions.
Modeling nonlinear ultrasound propagation in heterogeneous media with power law absorption using a k-space pseudospectral method
Authors: Treeby Bradley E. , Jaros Jiri , Rendell Alistair P. , Cox B. T.
Published: June 2012

The simulation of nonlinear ultrasound propagation through tissue realistic media has a wide range of practical applications. However, this is a computationally difficult problem due to the large size of the computational domain compared to the acoustic wavelength. Here, the k-space pseudospectral method is used to reduce the number of grid points required per wavelength for accurate simulations. The model is based on coupled first-order acoustic equations valid for nonlinear wave propagation in heterogeneous media with power law absorption. These are derived from the equations of fluid mechanics and include a pressure-density relation that incorporates the effects of nonlinearity, power law absorption, and medium heterogeneities. The additional terms accounting for convective nonlinearity and power law absorption are expressed as spatial gradients making them efficient to numerically encode. The governing equations are then discretized using a k-space pseudospectral technique in which the spatial gradients are computed using the Fourier-collocation method. This increases the accuracy of the gradient calculation and thus relaxes the requirement for dense computational grids compared to conventional finite difference methods. The accuracy and utility of the developed model is demonstrated via several numerical experiments, including the 3D simulation of the beam pattern from a clinical ultrasound probe.
An experimental evaluation of two effective medium theories for ultrasonic wave propagation in concrete
Authors: Chaix Jean-François , Rossat Mathieu , Garnier Vincent , Corneloup Gilles
Published: June 2012

This study compares ultrasonic wave propagation modeling and experimental data in concrete. As a consequence of its composition and manufacturing process, this material has a high elastic scattering (sand and aggregates) and air (microcracks and porosities) content. The behavior of the “Waterman-Truell” and “Generalized Self Consistent Method” dynamic homogenization models are analyzed in the context of an application for strong heterogeneous solid materials, in which the scatterers are of various concentrations and types. The experimental validations of results predicted by the models are carried out by making use of the phase velocity and the attenuation of longitudinal waves, as measured by an immersed transmission setup. The test specimen material has a cement-like matrix containing spherical inclusions of air or glass, with radius close to the ultrasonic wavelength. The models are adapted to the case of materials presenting several types of scattering particle, and allow the propagation of longitudinal waves to be described at the scale of materials such as concrete. The validity limits for frequency and for particle volume ratio can be approached through a comparison with experimental data. The potential of these homogenization models for the prediction of phase velocity and attenuation in strongly heterogeneous solids is demonstrated.
Characterizing fundamental frequency in Mandarin: A functional principal component approach utilizing mixed effect models
Authors: Hadjipantelis Pantelis Z. , Aston John A. D. , Evans Jonathan P.
Published: June 2012

A model for fundamental frequency (F0, or commonly pitch) employing a functional principal component (FPC) analysis framework is presented. The model is applied to Mandarin Chinese; this Sino-Tibetan language is rich in pitch-related information as the relative pitch curve is specified for most syllables in the lexicon. The approach yields a quantification of the influence carried by each identified component in relation to original tonal content, without formulating any assumptions on the shape of the tonal components. The original five speaker corpus is preprocessed using a locally weighted least squares smoother to produce F0 curves. These smoothed curves are then utilized as input for the computation of FPC scores and their corresponding eigenfunctions. These scores are analyzed in a series of penalized mixed effect models, through which meaningful categorical prototypes are built. The prototypes appear to confirm known tonal characteristics of the language, as well as suggest the presence of a sinusoid tonal component that is previously undocumented.