bluuebunny/crossref_metadata_2025 huggingface dataset:
A Hamiltonian method for finding broadband modal eigenvalues
Authors: Wang Haozhong , Wang Ning , Gao Dazhi
Published: February 2012

For shallow water waveguides over a layered elastic bottom, modal eigenvalues can be determined by searching the locations in the complex plane of the horizontal wave number at which the complex phase function is a multiple of π [C. T. Tindle and N. R. Chapman, J. Acoust. Soc. Am. 96, 1777–1782 (1994)]. In this paper, a Hamiltonian method is introduced for tracing the path in the complex plane along which the phase function keeps real. The Hamiltonian method can also be extended to compute the broadband modal eigenvalues or the modal dispersion curves in the Pekeris waveguide with fluid/elastic bottoms. For each proper or leaky normal mode, a different Hamiltonian is constructed in the complex plane and used to trace automatically the complex dispersion curve with the eigenvalue in a reference frequency as the initial value. In contrast to the usual methods, the dispersion curve for each mode is determined individually. The Hamiltonian method shows good performance by comparing with kraken.
Resolving meso-scale seabed variability using reflection measurements from an autonomous underwater vehicle
Authors: Holland Charles W. , Nielsen Peter L. , Dettmer Jan , Dosso Stan
Published: February 2012

Seabed geoacoustic variability is driven by geological processes that occur over a wide spectrum of space-time scales. While the acoustics community has some understanding of horizontal fine-scale geoacoustic variability, less than O(100) m, and large-scale variability, greater than O(103) m, there is a paucity of data resolving the geoacoustic meso-scale O(100–103) m. Measurements of the meso-scale along an ostensibly “benign” portion of the outer shelf reveal three classes of variability. The first class was expected and is due to horizontal variability of layer thicknesses: this was the only class that could be directly tied to seismic reflection data. The second class is due to rapid changes in layer properties and/or boundaries, occurring over scales of meters to hundreds of meters. The third class was observed as rapid variations of the angle/frequency dependent reflection coefficient within a single observation and is suggestive of variability at scales of meter or less. Though generally assumed to be negligible in acoustic modeling, the second and third classes are indicative of strong horizontal geoacoustic variability within a given layer. The observations give early insight into possible effects of horizontal geoacoustic variability on long-range acoustic propagation and reverberation.
Acoustic hole filling for sparse enrollment data using a cohort universal corpus for speaker recognition
Authors: Suh Jun-Won , Hansen John H. L.
Published: February 2012

In this study, the problem of sparse enrollment data for in-set versus out-of-set speaker recognition is addressed. The challenge here is that both the training speaker data (5 s) and test material (2 ∼ 6 s) is of limited test duration. The limited enrollment data result in a sparse acoustic model space for the desired speaker model. The focus of this study is on filling these acoustic holes by harvesting neighbor speaker information to leverage overall system performance. Acoustically similar speakers are selected from a separate available corpus via three different methods for speaker similarity measurement. The selected data from these similar acoustic speakers are exploited to fill the lack of phone coverage caused by the original sparse enrollment data. The proposed speaker modeling process mimics the naturally distributed acoustic space for conversational speech. The Gaussian mixture model (GMM) tagging process allows simulated natural conversation speech to be included for in-set speaker modeling, which maintains the original system requirement of text independent speaker recognition. A human listener evaluation is also performed to compare machine versus human speaker recognition performance, with machine performance of 95% compared to 72.2% accuracy for human in-set/out-of-set performance. Results show that for extreme sparse train/reference audio streams, human speaker recognition is not nearly as reliable as machine based speaker recognition. The proposed acoustic hole filling solution (MRNC) produces an averaging 7.42% relative improvement over a GMM-Cohort UBM baseline and a 19% relative improvement over the Eigenvoice baseline using the FISHER corpus.
Pitch contour identification with combined place and temporal cues using cochlear implants
Authors: Luo Xin , Padilla Monica , Landsberger David M.
Published: February 2012

This study investigated the integration of place- and temporal-pitch cues in pitch contour identification (PCI), in which cochlear implant (CI) users were asked to judge the overall pitch-change direction of stimuli. Falling and rising pitch contours were created either by continuously steering current between adjacent electrodes (place pitch), by continuously changing amplitude modulation (AM) frequency (temporal pitch), or both. The percentage of rising responses was recorded as a function of current steering or AM frequency change, with single or combined pitch cues. A significant correlation was found between subjects’ sensitivity to current steering and AM frequency change. The integration of place- and temporal-pitch cues was most effective when the two cues were similarly discriminable in isolation. Adding the other (place or temporal) pitch cues shifted the temporal- or place-pitch psychometric functions horizontally without changing the slopes. PCI was significantly better with consistent place- and temporal-pitch cues than with inconsistent cues. PCI with single cues and integration of pitch cues were similar on different electrodes. The results suggest that CI users effectively integrate place- and temporal-pitch cues in relative pitch perception tasks. Current steering and AM frequency change should be coordinated to better transmit dynamic pitch information to CI users.
Sparsity driven ultrasound imaging
Authors: Tuysuzoglu Ahmet , Kracht Jonathan M. , Cleveland Robin O. , C¸etin Müjdat , Karl W. Clem
Published: February 2012

An image formation framework for ultrasound imaging from synthetic transducer arrays based on sparsity-driven regularization functionals using single-frequency Fourier domain data is proposed. The framework involves the use of a physics-based forward model of the ultrasound observation process, the formulation of image formation as the solution of an associated optimization problem, and the solution of that problem through efficient numerical algorithms. The sparsity-driven, model-based approach estimates a complex-valued reflectivity field and preserves physical features in the scene while suppressing spurious artifacts. It also provides robust reconstructions in the case of sparse and reduced observation apertures. The effectiveness of the proposed imaging strategy is demonstrated using experimental data.
A comparative evaluation of three hydrophones and a numerical model in high intensity focused ultrasound fields
Authors: Haller Julian , Jenderka Klaus-Vitold , Durando Gianni , Shaw Adam
Published: February 2012

The pressure fields of two different high intensity focused ultrasound (HIFU) transducers operated in burst mode were measured at acoustical power levels of 25 and 50 W (continuous wave equivalent) with three different hydrophones: A fiber-optic displacement sensor, a commercial HIFU needle hydrophone, and a prototype of a membrane hydrophone with a protective coating against cavitation effects. Additionally, the fields were modeled using a freely available simulations software package. The measured waveforms, the peak pressure profiles, as well as the spatial-peak temporal-average intensities from the different devices and from the modeling are compared and possible reasons for differences are discussed. The results clearly show that reliable pressure measurements in HIFU fields remain a difficult task concerning both the reliability of the measured values and the robustness of the sensors used: Only the fiber-optic hydrophone survived all four exposure regimes and the measured spatial-peak temporal-average intensities varied by a factor of up to 1.5 between the measurements and the modeling and between the measurements among themselves.
Sonar-induced pressure fields in a post-mortem common dolphin
Authors: Foote Kenneth G. , Hastings Mardi C. , Ketten Darlene R. , Lin Ying-Tsong , Reidenberg Joy S. , Rye Kent
Published: February 2012

Potential physical effects of sonar transmissions on marine mammals were investigated by measuring pressure fields induced in a 119-kg, 211-cm-long, young adult male common dolphin (Delphinus delphis) cadaver. The specimen was instrumented with tourmaline acoustic pressure gauges used as receiving sensors. Gauge implantation near critical tissues was guided by intraoperative, high-resolution, computerized tomography (CT) scanning. Instrumented structures included the melon, nares, ear, thoracic wall, lungs, epaxial muscle, and lower abdomen. The specimen was suspended from a frame equipped with a standard 50.8-mm-diameter spherical transducer used as the acoustic source and additional receiving sensors to monitor the transmitted and external, scattered field. Following immersion, the transducer transmitted pulsed sinusoidal signals at 5, 7, and 10 kHz. Quantitative internal pressure fields are reported for all cases except those in which the gauge failed or no received signal was detected. A full necropsy was performed immediately after the experiment to examine instrumented areas and all major organs. No lesions attributable to acoustic transmissions were found, consistent with the low source level and source-receiver distances.
Tracking of Pacific walruses in the Chukchi Sea using a single hydrophone
Authors: Mouy Xavier , Hannay David , Zykov Mikhail , Martin Bruce
Published: February 2012

The vocal repertoire of Pacific walruses includes underwater sound pulses referred to as knocks and bell-like calls. An extended acoustic monitoring program was performed in summer 2007 over a large region of the eastern Chukchi Sea using autonomous seabed-mounted acoustic recorders. Walrus knocks were identified in many of the recordings and most of these sounds included multiple bottom and surface reflected signals. This paper investigates the use of a localization technique based on relative multipath arrival times (RMATs) for potential behavior studies. First, knocks are detected using a semi-automated kurtosis-based algorithm. Then RMATs are matched to values predicted by a ray-tracing model. Walrus tracks with vertical and horizontal movements were obtained. The tracks included repeated dives between 4.0 m and 15.5 m depth and a deep dive to the sea bottom (53 m). Depths at which bell-like sounds are produced, average knock production rate and source levels estimates of the knocks were determined. Bell sounds were produced at all depths throughout the dives. Average knock production rates varied from 59 to 75 knocks/min. Average source level of the knocks was estimated to 177.6 ± 7.5 dB re 1 μPa peak @ 1 m.
Single-scattering parabolic equation solutions for elastic media propagation, including Rayleigh waves
Authors: Metzler Adam M. , Siegmann William L. , Collins Michael D.
Published: February 2012

The parabolic equation method with a single-scattering correction allows for accurate modeling of range-dependent environments in elastic layered media. For problems with large contrasts, accuracy and efficiency are gained by subdividing vertical interfaces into a series of two or more single-scattering problems. This approach generates several computational parameters, such as the number of interface slices, an iteration convergence parameter τ, and the number of iterations n for convergence. Using a narrow-angle approximation, the choices of n = 1 and τ = 2 give accurate solutions. Analogous results from the narrow-angle approximation extend to environments with larger variations when slices are used as needed at vertical interfaces. The approach is applied to a generic ocean waveguide that includes the generation of a Rayleigh interface wave. Results are presented in both frequency and time domains.
Tuning the Nigerian slit gong
Authors: Cannaday Ashley E. , August Brandon C. , Moore Thomas R.
Published: February 2012

An experimental and theoretical investigation of the Nigerian slit gong is reported. It is shown that in tuning the gong the artisan ensures that the frequencies of the two lowest mechanical resonances are nearly coincident with the frequencies of two of the acoustic resonances of the internal cavity. Four possible tuning parameters are identified and the effects of changing these parameters are discussed.
Influence of a wearer’s voice on noise dosimeter measurements
Authors: Ryherd Steven , Kleiner Mendel , Waye Kerstin Persson , Ryherd Erica E.
Published: February 2012

In recent years, interest in personal noise exposure has expanded beyond a workplace safety measure to become an effective means of investigating physiological effects of the acoustic environment on an individual. This work investigates the effects of the wearer’s voice as a possible dominant sound source on body-mounted noise dosimeters and develops methods to improve the application of dosimeter measurements in medium-level noise environments. Subjects experienced a controlled set of acoustic conditions while wearing a dosimeter. In each condition, sound pressure levels were recorded with and without the subject speaking controlled phrases. Three experimental variables were considered—room type, noise type, and noise level. All three variables had a statistically significant effect upon the contribution of speech to a dosimeter measurement; for example, noise level was shown to cause a change in speech contribution by as much as 5.5 dB between sequential levels. Based upon the analysis, a method of predicting the decibel contribution of a wearer’s voice was developed. The results of this study can be used to estimate the effect of a wearer’s voice on dosimeter measurements in medium-level noise environments.
A wave field synthesis approach to reproduction of spatially correlated sound fields
Authors: Berry Alain , Dia Rokhiya , Robin Olivier
Published: February 2012

This article discusses an open-loop wave field synthesis (WFS) approach for the reproduction of spatially correlated sound fields. The main application concerns laboratory reproduction of turbulent boundary layer wall pressure on aircraft fuselages and measurement of their sound transmission loss. The problem configuration involves reconstruction of random sound pressure distributions on a planar reproduction surface using a planar array of reproduction monopoles parallel to the reproduction plane. In this paper, the WFS formulation is extended to sound fields with imposed time and spatial correlation properties (or equivalently imposed cross-spectral density in the frequency and wave number domains). Numerical examples are presented for the reproduction of a propagating plane wave, diffuse acoustic field and wall pressure in subsonic or supersonic turbulent boundary layers. The reproduction accuracy is examined in terms of the size of the source plane and reproduction plane, their separation, and the number of reproduction sources required per acoustic wavelength. While the reproduction approach cannot reconstruct sub-wavelength correlation scales of subsonic turbulent boundary layers, it effectively reconstructs correlation scales larger than the acoustic wavelength, making it appropriate for diffuse acoustic field and supersonic turbulent layers.
Behavior of captive herring exposed to naval sonar transmissions (1.0–1.6 kHz) throughout a yearly cycle
Authors: Doksæter Lise , Handegard Nils Olav , Godø Olav Rune , Kvadsheim Petter H. , Nordlund Nina
Published: February 2012

Atlantic herring, Clupea harengus, is a hearing specialist, and several studies have demonstrated strong responses to man-made noise, for example, from an approaching vessel. To avoid negative impacts from naval sonar operations, a set of studies of reaction patters of herring to low-frequency (1.0–1.5 kHz) naval sonar signals has been undertaken. This paper presents herring reactions to sonar signals and other stimuli when kept in captivity under detailed acoustic and video monitoring. Throughout the experiment, spanning three seasons of a year, the fish did not react significantly to sonar signals from a passing frigate, at received root-mean-square sound-pressure level (SPL) up to 168 dB re 1μPa. In contrast, the fish did exhibit a significant diving reaction when exposed to other sounds, with a much lower SPL, e.g., from a two-stroke engine. This shows that the experimental setup is sensitive to herring reactions when occurring. The lack of herring reaction to sonar signals is consistent with earlier in situ behavioral studies. The complexity of the behavioral reactions in captivity underline the need for better understanding of the causal relationship between stimuli and reaction patterns of fish.
Auditory perception of material is fragile while action is strikingly robust
Authors: Lemaitre Guillaume , Heller Laurie M.
Published: February 2012

While many psychoacoustic studies have found that listeners can recover some causal properties of sound-generating objects (such as the material), comparatively little is known about the causal properties of the sound-generating actions and how they are perceived. This article reports on a study comparing the performance of listeners required to identify either the actions or the materials used to generate sound stimuli. Stimuli were recordings of a set of cylinders of two sizes and four materials (wood, plastic, glass, metal) undergoing four different actions (scraping, rolling, hitting, bouncing). Experiment 1 tested how well each sound conveyed that it was generated with a different action or material. Experiment 2 measured both accuracy and reaction times for the identification of actions and materials. Listeners were faster and more accurate at identifying the action than the material. Even for the subset of sounds for which actions and materials were equivalently well identified, listeners were faster at identifying the action than the material. These results suggest that the auditory system is well-suited to extract information about sound-generating actions.
The effect of entrance radii on intraglottal pressure distributions in the divergent glottis
Authors: Li Sheng , Scherer Ronald C. , Wan MingXi , Wang SuPin
Published: February 2012

Modeling laryngeal aerodynamics requires specification of the glottal geometry. Changing the glottal exit radius alters the intraglottal pressure distributions in the converging glottis [Scherer et al., J. Acoust. Soc. Am. 110, 2267–2269 (2001)]. This study examined the effects of the glottal entrance radius on the intraglottal pressure distributions for divergent angles of 5°, 10°, 20°, 30°, and 40°. Glottal airflow and minimal glottal diameter were held constant at 73.2 cm3/s and 0.02 cm, respectively. The computational code FLUENT was used to obtain the pressure distributions. Results suggest that a smaller glottal entrance radius tends to (1) lower the transglottal pressure (reduce glottal flow resistance), although this is angle dependent, (2) make the pressure dip near the glottal entrance more negative in value, (3) increase the slope of the pressure distribution just upstream of the glottal entrance, and (4) make the initial pressure recovery (rise) in the glottis steeper. A general empirical equation for transglottal pressure as a function of radius, angle, and separation point location is offered. These results suggest that glottal entrance curvature for the divergent glottis significantly affects the driving pressures on the vocal folds, and needs to be well specified when building computational and physical models.
Effects of age and hearing loss on the recognition of interrupted words in isolation and in sentences
Authors: Kidd Gary R. , Humes Larry E.
Published: February 2012

The ability to recognize spoken words interrupted by silence was investigated with young normal-hearing listeners and older listeners with and without hearing impairment. Target words from the revised SPIN test by Bilger et al. [J. Speech Hear. Res. 27(1), 32–48 (1984)] were presented in isolation and in the original sentence context using a range of interruption patterns in which portions of speech were replaced with silence. The number of auditory “glimpses” of speech and the glimpse proportion (total duration glimpsed/word duration) were varied using a subset of the SPIN target words that ranged in duration from 300 to 600 ms. The words were presented in isolation, in the context of low-predictability (LP) sentences, and in high-predictability (HP) sentences. The glimpse proportion was found to have a strong influence on word recognition, with relatively little influence of the number of glimpses, glimpse duration, or glimpse rate. Although older listeners tended to recognize fewer interrupted words, there was considerable overlap in recognition scores across listener groups in all conditions, and all groups were affected by interruption parameters and context in much the same way.
The effects of cross-generational and cross-dialectal variation on vowel identification and classification
Authors: Jacewicz Ewa , Fox Robert Allen
Published: February 2012

Cross-generational and cross-dialectal variation in vowels among speakers of American English was examined in terms of vowel identification by listeners and vowel classification using pattern recognition. Listeners from Western North Carolina and Southeastern Wisconsin identified 12 vowel categories produced by 120 speakers stratified by age (old adults, young adults, and children), gender, and dialect. The vowels /ɝ, o, ʊ, u/ were well identified by both groups of listeners. The majority of confusions were for the front /i, ɪ, e, ɛ, æ/, the low back /ɑ, ɔ/ and the monophthongal North Carolina /aɪ/. For selected vowels, generational differences in acoustic vowel characteristics were perceptually salient, suggesting listeners’ responsiveness to sound change. Female exemplars and native-dialect variants produced higher identification rates. Linear discriminant analyses which examined dialect and generational classification accuracy showed that sampling the formant pattern at vowel midpoint only is insufficient to separate the vowels. Two sample points near onset and offset provided enough information for successful classification. The models trained on one dialect classified the vowels from the other dialect with much lower accuracy. The results strongly support the importance of dynamic information in accurate classification of cross-generational and cross-dialectal variations.
Effects of seeing the interlocutor on the production of prosodic contrasts (L)
Authors: Cvejic Erin , Kim Jeesun , Davis Chris
Published: February 2012

This study investigated whether the production of prosodic focus and phrasing contrasts was modified when interlocutors could only hear each other [auditory only (AO)], compared to when they could hear and see each other [face to face (FTF)]. The prosodic characteristics of utterances produced by six talkers were examined using both acoustic and perceptual measures (ratings of the degree of focus or clarity of the statement-question contrast). The acoustic measures showed a range of differences between narrow focus and between phrasing contrasts and some of these differences were greater in the AO setting than the FTF one. The listener’s ratings of focus and phrasing showed a clear difference between the AO and FTF conditions, with perceptual attributes of both narrow focus and echoic question phrasing being rated as clearer in the AO condition. To explain these results it is proposed that talkers compensate for the lack of visual prosodic cues in the AO condition by taking extra care (relative to FTF conditions) to ensure the effective transmission of prosodic cues.
The role of vowel and consonant fundamental frequency, envelope, and temporal fine structure cues to the intelligibility of words and sentences
Authors: Fogerty Daniel , Humes Larry E.
Published: February 2012

The speech signal contains many acoustic properties that may contribute differently to spoken word recognition. Previous studies have demonstrated that the importance of properties present during consonants or vowels is dependent upon the linguistic context (i.e., words versus sentences). The current study investigated three potentially informative acoustic properties that are present during consonants and vowels for monosyllabic words and sentences. Natural variations in fundamental frequency were either flattened or removed. The speech envelope and temporal fine structure were also investigated by limiting the availability of these cues via noisy signal extraction. Thus, this study investigated the contribution of these acoustic properties, present during either consonants or vowels, to overall word and sentence intelligibility. Results demonstrated that all processing conditions displayed better performance for vowel-only sentences. Greater performance with vowel-only sentences remained, despite removing dynamic cues of the fundamental frequency. Word and sentence comparisons suggest that the speech envelope may be at least partially responsible for additional vowel contributions in sentences. Results suggest that speech information transmitted by the envelope is responsible, in part, for greater vowel contributions in sentences, but is not predictive for isolated words.
Effects of sound source location and direction on acoustic parameters in Japanese churches
Authors: Soeta Yoshiharu , Ito Ken , Shimokura Ryota , Sato Shin-ichi , Ohsawa Tomohiro , Ando Yoichi
Published: February 2012

In 1965, the Catholic Church liturgy changed to allow priests to face the congregation. Whereas Church tradition, teaching, and participation have been much discussed with respect to priest orientation at Mass, the acoustical changes in this regard have not yet been examined scientifically. To discuss acoustic desired within churches, it is necessary to know the acoustical characteristics appropriate for each phase of the liturgy. In this study, acoustic measurements were taken at various source locations and directions using both old and new liturgies performed in Japanese churches. A directional loudspeaker was used as the source to provide vocal and organ acoustic fields, and impulse responses were measured. Various acoustical parameters such as reverberation time and early decay time were analyzed. The speech transmission index was higher for the new Catholic liturgy, suggesting that the change in liturgy has improved speech intelligibility. Moreover, the interaural cross-correlation coefficient and early lateral energy fraction were higher and lower, respectively, suggesting that the change in liturgy has made the apparent source width smaller.
Phosphorylated α-Synuclein in Parkinson’s Disease
Authors: Wang Yu , Shi Min , Chung Kathryn A. , Zabetian Cyrus P. , Leverenz James B. , Berg Daniela , Srulijes Karin , Trojanowski John Q. , Lee Virginia M.-Y. , Siderowf Andrew D. , Hurtig Howard , Litvan Irene , Schiess Mya C. , Peskind Elaine R. , Masuda Masami , Hasegawa Masato , Lin Xiangmin , Pan Catherine , Galasko Douglas , Goldstein David S. , Jensen Poul Henning , Yang Hui , Cain Kevin C. , Zhang Jing
Published: February 2012

An assay for detecting phosphorylated α-synuclein in CSF may help to diagnose Parkinson’s disease and determine disease severity.
MicroRNA-21 Promotes Fibrosis of the Kidney by Silencing Metabolic Pathways
Authors: Chau B. Nelson , Xin Cuiyan , Hartner Jochen , Ren Shuyu , Castano Ana P. , Linn Geoffrey , Li Jian , Tran Phong T. , Kaimal Vivek , Huang Xinqiang , Chang Aaron N. , Li Shenyang , Kalra Aarti , Grafals Monica , Portilla Didier , MacKenna Deidre A. , Orkin Stuart H. , Duffield Jeremy S.
Published: February 2012

MicroRNA-21 contributes to fibrosis in the kidney by posttranscriptionally regulating lipid metabolism genes.
The Mutation That Broke the Cell’s Back
Authors: Hong David S.
Published: February 2012

Recent genomic sequencing of pediatric medulloblastoma links catastrophic rearrangements with
TP53
mutations.
Learning, Customized for Your Brain
Authors: Wang Wei
Published: February 2012

Understanding the temporal dynamics of the biochemistry of memory formation can help to design better training methods.
A Microbial Association with Autism
Authors: Benach Jorge L. , Li Ellen , McGovern Margaret M.
Published: February 2012

Autism is a heterogeneous group of complex developmental disabilities that result from a number of possible etiologies. There are a well-known number of comorbidities associated with autism spectrum disorders (ASD), including, commonly, gastrointestinal (GI) pathology, which can include variable combinations of constipation, diarrhea, abdominal pain, gastroesophageal reflux, and vomiting. An American Academy of Pediatrics consensus panel has recommended that prospective studies be carried out to determine the prevalence of GI disorders in ASD and their pathophysiologic basis. In a recent article, Williams et al. [B. L. Williams, M. Hornig, T. Parekh, and W. I. Lipkin, mBio 3(1):e00261-11, 2012] have provided one such study of autism with GI comorbidities by presenting evidence of
Sutterella
species in ileal mucosal biopsy specimens from patients diagnosed with ASD but not in control children with GI symptoms, suggesting a specific role for
Sutterella
in ASD.
Sutterella
sequences represented ~1 to 7% of the total bacterial sequences, and this is a very large effect size on the ileal mucosal composition of the autism phenotype, rivaling or perhaps exceeding the effect size of the ileal Crohn’s disease phenotype. This study opens a new field of investigation to study the etiology or consequences of GI comorbidities in ASD.
Insight into the Transmission Biology and Species-Specific Functional Capabilities of Tsetse (Diptera: Glossinidae) Obligate Symbiont
Wigglesworthia
Authors: Rio Rita V. M. , Symula Rebecca E. , Wang Jingwen , Lohs Claudia , Wu Yi-neng , Snyder Anna K. , Bjornson Robert D. , Oshima Kenshiro , Biehl Bryan S. , Perna Nicole T. , Hattori Masahira , Aksoy Serap
Published: February 2012

Ancient endosymbionts have been associated with extreme genome structural stability with little differentiation in gene inventory between sister species. Tsetse flies (Diptera: Glossinidae) harbor an obligate endosymbiont,
Wigglesworthia
, which has coevolved with the
Glossina
radiation. We report on the ~720-kb
Wigglesworthia
genome and its associated plasmid from
Glossina morsitans morsitans
and compare them to those of the symbiont from
Glossina brevipalpis
. While there was overall high synteny between the two genomes, a large inversion was noted. Furthermore, symbiont transcriptional analyses demonstrated host tissue and development-specific gene expression supporting robust transcriptional regulation in
Wigglesworthia
, an unprecedented observation in other obligate mutualist endosymbionts. Expression and immunohistochemistry confirmed the role of flagella during the vertical transmission process from mother to intrauterine progeny. The expression of nutrient provisioning genes (
thiC
and
hemH
) suggests that
Wigglesworthia
may function in dietary supplementation tailored toward host development. Furthermore, despite extensive conservation, unique genes were identified within both symbiont genomes that may result in distinct metabolomes impacting host physiology. One of these differences involves the chorismate, phenylalanine, and folate biosynthetic pathways, which are uniquely present in
Wigglesworthia morsitans
. Interestingly, African trypanosomes are auxotrophs for phenylalanine and folate and salvage both exogenously. It is possible that
W
.
morsitans
contributes to the higher parasite susceptibility of its host species.

IMPORTANCE
Genomic stasis has historically been associated with obligate endosymbionts and their sister species. Here we characterize the
Wigglesworthia
genome of the tsetse fly species
Glossina morsitans
and compare it to its sister genome within
G
.
brevipalpis
. The similarity and variation between the genomes enabled specific hypotheses regarding functional biology. Expression analyses indicate significant levels of transcriptional regulation and support development- and tissue-specific functional roles for the symbiosis previously not observed in obligate mutualist symbionts. Retention of the genetically expensive flagella within these small genomes was demonstrated to be significant in symbiont transmission and tailored to the unique tsetse fly reproductive biology. Distinctions in metabolomes were also observed. We speculate an additional role for
Wigglesworthia
symbiosis where infections with pathogenic trypanosomes may depend upon symbiont species-specific metabolic products and thus influence the vector competence traits of different tsetse fly host species.
A NEW METHOD FOR MEASURING DIFFUSION COEFFICIENT OF GASES IN LIQUIDS BY PLIF
Authors: JIMENEZ MÉLANIE , DIETRICH NICOLAS , HEBRARD GILLES
Published: February 2012

Gas–liquid mass transfer is a major issue in engineering processes such as wastewater treatment or biogas production since this phenomenon is directly linked to their design and efficiency. In recent years, much research has been done in this area but some gaps still remain in our knowledge of gas–liquid transfer, in particular concerning molecular diffusivity. The determination of molecular diffusivity is commonly based on empirical correlations, such as the widely used Wilke and Chang13 expression, valid under specific conditions and with relatively high uncertainties. In the present work, an innovative and promising technique is proposed to determine diffusion coefficients of gases in liquids. This technique is based on visualizing and quantifying oxygen diffusion across a flat gas–liquid interface, in a Newtonian medium, using planar laser induced fluorescence (PLIF) with inhibition. Particle image velocimetry (PIV) experiments were conducted to confirm the hydrodynamic flow field in the liquid phase. Results included the visualization of oxygen diffusion over time, and the quantification of this visualization. The oxygen diffusivity thus determined is in agreement with values found in the literature.
SIZE RATIO UNIVERSALITY IN CHAOTIC SYSTEMS
Authors: GALA R. D. , PARMANANDA P.
Published: February 2012

In this paper, we attempt to predict the size of the chaotic attractor at the parameter value where the period tends to infinity for nonlinear systems that follow the period doubling route to chaos, and for which the Feigenbaum universalities hold.
MULTIVALUED FRACTALS AND HYPERFRACTALS
Authors: ANDRES JAN , RYPKA MIPOSLAV
Published: February 2012

A new class of fractals called hyperfractals is systematically investigated. Their underlying fractals in supporting spaces are multivalued fractals developed by ourselves in our earlier papers [Andres & Fiser, 2004; Andres et al., 2005]. In the case of uniqueness, they also coincide with the supports of invariant measures of the associated Markov–Feller hyperoperators. We prove their existence by means of fixed point theorems in hyperspaces and calculate, in particular cases of generating hypermaps, their Hausdorff dimension. Two illustrative examples are supplied.
INSTABILITIES IN DIGITALLY CONTROLLED VOLTAGE-MODE SYNCHRONOUS BUCK CONVERTER
Authors: YU DONGSHENG , IU HERBERT H. C. , CHEN HAO , RODRIGUEZ E. , ALARCÓN E. , EL AROUDI A.
Published: February 2012

In this paper, instabilities and bifurcation behavior in a DC–DC digitally controlled voltage-mode synchronous buck converter (SBC) are studied. The bifurcation diagram of the system under a proportional-integral (PI) compensation is presented. Following the system mathematical description in the continuous time domain, the z-domain pulse transfer function is derived in terms of system parameters. The stability range of the design parameter is obtained in closed form by using the Jury test combined with the describing function (DF) method. Experimental measurements from a laboratory prototype are used to validate the theoretical predictions and the numerical simulations.
ON THE CALCULATION OF LYAPUNOV CHARACTERISTIC EXPONENTS FOR CONTINUOUS-TIME LTV DYNAMICAL SYSTEMS USING DYNAMIC EIGENVALUES
Authors: GUTIÉRREZ DE ANDA MIGUEL ÁNGEL
Published: February 2012

The concept of the dynamic eigenvalues may be used, in principle, to formulate in a general way analytic solutions of continuous-time linear time-varying dynamical (LTV) systems. It has also been suggested that the mean value of these quantities may be used to calculate Lyapunov characteristic exponents for the aforementioned systems. In this article, it will be demonstrated that this conjecture is not necessarily valid.
TYPE-ZERO SADDLE-NODE BIFURCATIONS AND STABILITY REGION ESTIMATION OF NONLINEAR AUTONOMOUS DYNAMICAL SYSTEMS
Authors: AMARAL FABÍOLO M. , ALBERTO LUÍS F. C.
Published: February 2012

A complete characterization of the stability boundary of a class of nonlinear dynamical systems that admit energy functions is developed in this paper. This characterization generalizes the existing results by allowing the type-zero saddle-node nonhyperbolic equilibrium points on the stability boundary. Conceptual algorithms to obtain optimal estimates of the stability region (basin of attraction) in the form of level sets of a given family of energy functions are derived. The behavior of the stability region and the corresponding estimates are investigated for parameter variation in the neighborhood of a type-zero saddle-node bifurcation value.
BIFURCATION ANALYSIS FOR A NONLINEAR RECURRENCE RELATION WITH THRESHOLD CONTROL AND PERIODIC COEFFICIENTS
Authors: HOU CHENGMIN , WANG CHUNLAI , CHENG SUI SUN
Published: February 2012

A nonlinear recurrence involving a piecewise constant McCulloch–Pitts function and two 2-periodic coefficient sequences is investigated. By allowing the threshold parameter to vary from 0+ to +∞, we work out a complete bifurcation analysis for the asymptotic behaviors of the corresponding solutions. We show that there are four steady state solutions and that all solutions will tend to one of them. We hope that our results will be useful in further investigating neural networks involving the McCulloch–Pitts function with threshold and more general periodic coefficients.
GLOBAL STABILITY AND HOPF BIFURCATION IN A DELAYED DIFFUSIVE LESLIE–GOWER PREDATOR–PREY SYSTEM
Authors: CHEN SHANSHAN , SHI JUNPING , WEI JUNJIE
Published: February 2012

In this paper, we consider a delayed diffusive Leslie–Gower predator–prey system with homogeneous Neumann boundary conditions. The stability/instability of the coexistence equilibrium and associated Hopf bifurcation are investigated by analyzing the characteristic equations. Furthermore, using the upper and lower solutions method, we give a sufficient condition on parameters so that the coexistence equilibrium is globally asymptotically stable.
TIME-VARYING PERTURBATIONS OF CHAOTIC DISCRETE SYSTEMS
Authors: ZHANG LIJUAN , SHI YUMING
Published: February 2012

This paper is concerned with time-varying discrete dynamical systems in Banach spaces. A criterion of chaos induced by coupled-expansion for time-varying systems is first established and then the persistence of coupled-expansion is considered for time-varying systems under small time-varying perturbations, under which the perturbed system is shown chaotic in the strong sense of Li–Yorke. By applying this result, a map with a regular and nondegenerate snap-back repeller is shown to be still chaotic in the strong sense of Li–Yorke under small time-varying perturbations.
PERIOD ADDING IN PIECEWISE LINEAR MAPS WITH TWO DISCONTINUITIES
Authors: TRAMONTANA FABIO , GARDINI LAURA , AVRUTIN VIKTOR , SCHANZ MICHAEL
Published: February 2012

In this work we consider the border collision bifurcations occurring in a one-dimensional piecewise linear map with two discontinuity points. The map, motivated by an economic application, is written in a generic form and considered in the stable regime, with all slopes between zero and one. We prove that the period adding structures occur in maps with more than one discontinuity points and that the Leonov's method to calculate the bifurcation curves forming these structures is applicable also in this case. We demonstrate the existence of particular codimension-2 bifurcation (big-bang bifurcation) points in the parameter space, from which infinitely many bifurcation curves are issuing associated with cycles involving several partitions. We describe how the bifurcation structure of a map with one discontinuity is modified by the introduction of a second discontinuity point, which causes orbits to appear located on three partitions and organized again in a period-adding structure. We also describe particular codimension-2 bifurcation points which represent limit sets of doubly infinite sequences of bifurcation curves and appear due to the existence of two discontinuities.
A NEW AUTONOMOUS CHAOS GENERATOR FROM STATE CONTROLLED-CELLULAR NEURAL NETWORKS
Authors: GÜNAY ENİS
Published: February 2012

In this study, a new autonomous chaos generator is presented via State Controlled-Cellular Neural Networks (SC-CNNs). From the numerical and circuit simulations, it has been shown that the proposed SC-CNN consisting of three cells can be easily used in chaotic applications as a chaos generator. After presenting the double scroll generation, the presented SC-CNN system is used either in multi-scroll chaotic attractor generation by adding a trigonometric function generator and or to construct a SC-CNN based chaotic masking system with feedback algorithm.
REMOVAL OF STRONTIUM (II) FROM AQUEOUS SOLUTION USING FUNCTIONALIZED CARBON NANOTUBES
Authors: KUMAR RAJESH , JAIN S. K.
Published: February 2012

This study was carried out to evaluate the environmental application of functionalized carbon nanotubes through the experimental removal of strontium (II) from water. The aim was to find the optimal condition for the removal of strontium from water under different conditions such as initial concentration of strontium, contact time and neutral pH. The functionalized multi wall carbon nanotubes (f-MWCNT) were characterized by FT-IR and scanning electron microscopy (SEM). The adsorption isotherms were correlated to Freundlich and Langmuir models and it was found that the adsorption data could be fitted better by Langmuir model than Freundlich one. The kinetic data shows that the adsorption describes well with the pseudo-second order kinetic model. Functionalized MWCNT can be used as good adsorbent for the removal of the strontium ions from polluted water according to results.
g-FRAMES AND MODULAR RIESZ BASES IN HILBERT C*-MODULES
Authors: KHOSRAVI AMIR , KHOSRAVI BEHROOZ
Published: February 2012

In this paper we introduce modular Riesz basis, modular g-Riesz basis in Hilbert C*-modules in a very natural way and we show that they share many properties with Riesz basis and g-Riesz basis in Hilbert spaces.

We also found that by using the fact that every finitely or countably generated Hilbert C*-module over a unital C*-algebra has a standard Parseval frame, we characterize g-frames, modular Riesz bases and modular g-Riesz bases. Finally we obtain a perturbation result for modular g-Riesz bases.
GENERALIZED PALEY–WIENER THEOREMS
Authors: CHEN QIUHUI , LI LUOQING , REN GUANGBIN
Published: February 2012

Non-harmonic Fourier transform is useful for the analysis of transient signals, where the integral kernel is from the boundary value of Möbius transform. In this note, we study the Paley–Wiener type extension theorems for the non-harmonic Fourier transform. Two extension theorems are established by using real variable techniques.
Myocardial macronutrient transporter adaptations in the adult pregestational female intrauterine and postnatal growth-restricted offspring
Authors: Abbasi Afshan , Thamotharan Manikkavasagar , Shin Bo-Chul , Jordan Maria C. , Roos Kenneth P. , Stahl Andreas , Devaskar Sherin U.
Published: February 2012

Associations between exponential childhood growth superimposed on low birth weight and adult onset cardiovascular disease with glucose intolerance/type 2 diabetes mellitus exist in epidemiological investigations. To determine the metabolic adaptations that guard against myocardial failure on subsequent exposure to hypoxia, we compared with controls (CON), the effect of intrauterine (IUGR), postnatal (PNGR), and intrauterine and postnatal (IPGR) calorie and growth restriction ( n = 6/group) on myocardial macronutrient transporter (fatty acid and glucose) -mediated uptake in pregestational young female adult rat offspring. A higher myocardial FAT/CD36 protein expression in IUGR, PNGR, and IPGR, with higher FATP1 in IUGR, FATP6 in PNGR, FABP-c in PNGR and IPGR, and no change in GLUT4 of all groups was observed. These adaptive macronutrient transporter protein changes were associated with no change in myocardial [3H]bromopalmitate accumulation but a diminution in 2-deoxy-[14C]glucose uptake. Examination of the sarcolemmal subfraction revealed higher basal concentrations of FAT/CD36 in PNGR and FATP1 and GLUT4 in IUGR, PNGR, and IPGR vs. CON. Exogenous insulin uniformly further enhanced sarcolemmal association of these macronutrient transporter proteins above that of basal, with the exception of insulin resistance of FATP1 and GLUT4 in IUGR and FAT/CD36 in PNGR. The basal sarcolemmal macronutrient transporter adaptations proved protective against subsequent chronic hypoxic exposure (7 days) only in IUGR and PNGR, with notable deterioration in IPGR and CON of the echocardiographic ejection fraction. We conclude that the IUGR and PNGR pregestational adult female offspring displayed a resistance to insulin-induced translocation of FATP1, GLUT4, or FAT/CD36 to the myocardial sarcolemma due to preexistent higher basal concentrations. This basal adaptation of myocardial macronutrient transporters ensured adequate fatty acid uptake, thereby proving protective against chronic hypoxia-induced myocardial compromise.
Seasonally Perturbed Prey‐Predator Ecological System with the Beddington‐DeAngelis Functional Response
Authors: Yu Hengguo , Zhao Min
Published: February 2012

On the basis of the theories and methods of ecology and ordinary differential equation, a seasonally perturbed prey‐predator system with the Beddington‐DeAngelis functional response is studied analytically and numerically. Mathematical theoretical works have been pursuing the investigation of uniformly persistent, which depicts the threshold expression of some critical parameters. Numerical analysis indicates that the seasonality has a strong effect on the dynamical complexity and species biomass using bifurcation diagrams and Poincaré sections. The results show that the seasonality in three different parameters can give rise to rich and complex dynamical behaviors. In addition, the largest Lyapunov exponents are computed. This computation further confirms the existence of chaotic behavior and the accuracy of numerical simulation. All these results are expected to be of use in the study of the dynamic complexity of ecosystems.