bluuebunny/crossref_metadata_2025 huggingface dataset:
A Parametric Study on Effects of Environmental Loadings on Fatigue Life of Steel Catenary Risers (Using a Nonlinear Cyclic Riser-Soil Interaction Model)
Authors: Kimiaei Mehrdad , Randolph Mark , Ting Ivan
Published: January 2011

Steel catenary risers (SCRs) are often the preferred option for subsea tie-back to floating platforms in deep water due to their conceptual simplicity, ease of construction and installation and simple interface with the flowlines. Fatigue design of SCRs, particularly in the touch down area (TDA), has always been one of the major engineering challenges. Traditionally, fatigue assessment of SCRs has usually been highly conservative, because of lack of precise understanding of the non-linear soil-riser-interaction in the TDA. Most fatigue studies are based on assumed linear stiffness for the seabed, partly because of the lack of robust non-linear riser-seabed interaction models and partly because the linear response simplifies the fatigue study. The recent availability of non-linear seabed response models provides an opportunity to improve fatigue assessment, but it is first necessary to evaluate how best to conduct fatigue studies for such nonlinear systems which can be sensitive to wide range of input parameters. This paper outlines a new advanced numerical model, considering nonlinear cyclic riser-soil interaction behavior, used to determine the contribution of different loading parameters on fatigue damage of SCRs in the TDA in deep water soft sediments. The main loading parameters considered are: different motions of floating vessels, wave heights, wave periods and wave packs ordering. Numerical modeling has shown that over 95% of the fatigue damage corresponds to floating vessel motion parallel to the riser axis at the connection point to the vessel. It is also shown that riser response at TDA is highly influenced with amplitude and period of the environmental loadings.
Vibration Isolation Using Pile Rows in a Layered Poroelastic Half-Space Against the Vibration Due to Harmonic Loads
Authors: Lu Jian-Fei , Xu Bin , Wang Jian-Hua
Published: January 2011

The isolation of the vibration due to a harmonic vertical load using pile rows embedded in a layered poroelastic half-space is investigated in this study. Based on Biot’s theory, the frequency domain fundamental solution for a vertical circular patch load applied in a layered poroelastic half-space is derived via the transmission and reflection matrices (TRM) method. Utilizing Muki and Sternberg’s method, the second kind of Fredholm integral equations describing the dynamic interaction between the pile rows and the layered poroelastic half-space subjected to a harmonic vertical load is constructed. The isolation effect of piles rows for the vibration due to the harmonic vertical load is investigated via numerical solution of the integral equations. Numerical results of this study show that a stiffer upper layer overlying a softer bottom half-space will worsen the vibration isolation effect of pile rows and vice versa. Also, pile rows with large length are preferable for a better vibration isolation effect.
Study on Shear Strength of Artificial Methane Hydrate
Authors: Yu Feng , Song Yongchen , Liu Weiguo , Li Yanghui , Zhao Jiafei
Published: January 2011

The production of methane from hydrate reservoir may induce deformation of the hydrate-bearing strata. The research on mechanical properties of methane hydrate and establishing an efficient methane exploitation technology appear very important. In this paper, a low-temperature high-pressure triaxial test system including pressure crystal device (sample preparation system) was developed. A series of triaxial shear tests were carried out on artificial methane hydrate samples. The mechanical behavior was analyzed. The preliminary results show that the shear strength of methane hydrate increases with the increase of confining pressure and strain rate. While it increases with the decrease of temperature. Moreover, the secant modulus increases with the enhancement of strain rate and the decrease of confining pressure.
Formation and Dissociation of Tetrahydrofuran Hydrate in Porous Media
Authors: Yao Lei , Zhao Jiafei , Cheng Chuanxiao , Liu Yu , Song Yongchen
Published: January 2011

Tetrahydrofuran hydrate has long been used as a proxy of methane hydrate in laboratory studies. This paper investigates the formation and dissociation characters of tetrahydrofuran hydrate in porous media using the magnetic resonance imaging (MRI) technology. Various sized quartz glass beads are used to simulate the sediment. The formation and dissociation processes of THF hydrate are observed. The hydrate saturation during the formation is calculated based on the MRI data. The experimental result indicates that the third surface has an important effect on hydrate formation process. THF hydrate crystals begin to form on the glass beads and in their adjacent area as well as from the wall of the sample container. Furthermore, as the pore size increases, or the formation temperature decreases, the formation rate of THF hydrate gets faster. However, the dissociation rate is mostly dependent on the dissociation temperature rather than the pore size.
Analysis and Design of Advanced Marine Propulsors
Authors: Young Yin L.
Published: January 2011

Recently, there has been a significant interest in the use of composites for marine applications because of their higher strength-to-weight and stiffness-to-weight ratios, better corrosion characteristics, and the ability to be elastically tailored to improve hydrodynamic and/or structural performance. The objective of this work is to review advances made, and discuss current challenges, related to the design and modeling of advanced composite marine propulsors. The areas of focus include 1) the design and application of composite marine propellers, 2) the numerical modeling of the fluid-structure interaction responses and potential failure mechanisms of composite marine propellers, and 3) the scaling of the fluid-structure interaction responses and failure mechanisms of composite marine propellers.
Damage Assessment of Pipelines With Dents and Cracks: Proposal for Methodology for Calculation of Acceptable Dimensions of a Combination of Crack and Dent in Subsea Pipelines
Authors: Hoff Ronny , Berg Espen , Oosterkamp Liljana Djanic
Published: January 2011

This paper presents a proposal for methodology to evaluate the maximum acceptable combination of longitudinal crack and dent in an offshore pipeline. The procedure is based on 2-parameter fracture mechanics FE analyses and fatigue calculations. The reduction in material capacity due to the dent damage is modeled by increasing the driving force by introducing a stress concentration factor to the load. The framework presented in this article represents one possible approach for determining whether a given measured damage to a pipeline must be repaired or if it is sufficient to monitor the damage in the future. Avoiding unnecessary repairs of damaged but viable subsea pipelines is a substantial cost-saving issue.
Dynamics of Vapor Pockets at Phase Boundary: An Application in LNG Sloshing
Authors: Yung Tin-Woo , Minta Moses , He Haiping , Gentry Mark
Published: January 2011

In LNG shipping / offshore offloading, liquid motion within the container sometimes leads to vapor entrapment at the container walls. Dynamic behavior of the entrapped vapor is governed by its thermal or thermodynamic state and profoundly affects LNG sloshing pressure on the container walls. In this paper, the authors will discuss experimental observation of condensable vapor dynamics including steam and natural gas at cryogenic temperatures. Additionally, the authors will also discuss relevant implications in sloshing experiments and the scale up to prototype design.
Ga-doped ZnO grown by pulsed laser deposition in H2: The roles of Ga and H
Authors: Look David C. , Droubay Timothy C. , McCloy John S. , Zhu Zihua , Chambers Scott A.
Published: January 2011

Highly conductive thin films of ZnO doped with Ga were grown by pulsed laser deposition with 10 mTorr of H2 in the growth chamber. Compared with a more conventional method of producing conductive films of ZnO, i.e., growth in O2 followed by annealing in forming gas (5% H2 in Ar), the H2 method requires no postgrowth anneal and also produces higher carrier concentrations and lower resistivities with better depth uniformity. As an example, a 65-nm-thick sample had a room-temperature mobility of 32 cm2/V s, a concentration of 6.8×1020 cm−3, and a resistivity of 2.9×10−4 Ω cm. From a scattering model, the donor and acceptor concentrations were calculated as 8.9×1020 and 2.1×1020 cm−3, respectively, as compared to the Ga and H concentrations of 11×1020 and 1×1020 cm−3. The authors conclude that growth in H2 produces higher Ga-donor concentrations but that H-donors themselves do not play a significant role.
MgZnO/ZnO quantum well nanowire heterostructures with large confinement energies
Authors: Lange M. , Dietrich C. P. , Zúñiga-Pérez J. , von Wenckstern H. , Lorenz M. , Grundmann M.
Published: January 2011

Mg 0.25 Zn 0.75 O / ZnO -quantum well nanowire heterostructures were grown with a three-step pulsed laser deposition process. To avoid shadowing effects during the coating, the ZnO nanowires were grown with a low area density on a ZnO buffer layer deposited on an a-plane sapphire substrate. By using spatially resolved cathodoluminescence measurements, the luminescence of axial and radial quantum wells were clearly distinguished. The large bandgap energy of the Mg0.25Zn0.75O barrier material (≈3.85 eV) made it possible to tune the energy of quantum wells from 3.4 to 3.7 eV. The homogeneity of the radial quantum well along the wire axis was probed, revealing that only small fluctuations of about 4 meV are found in the main part of the nanowire. Near the tip of the nanowire, the energy of the radial quantum well increases due to locally modified growth conditions reducing the growth rate by up to 15%. Furthermore, the growth rates of the axial and radial quantum wells were determined, showing that the one in axial direction is a factor of about 2 larger than the one in radial direction.
C
V
measurements on LaLuO3 stack metal-oxide-semiconductor capacitor using a new three-pulse technique
Authors: Sedghi N. , Mitrovic I. Z. , Hall S. , Lopes J. M. J. , Schubert J.
Published: January 2011

A new three-pulse CV measurement technique has been developed to investigate the trapping and detrapping of negative and positive charges in SiO2/LaLuO3 gate dielectric stacks on p-type silicon. Two types of negative and positive trapped charges have been observed in these devices which are deemed to be related to electron and hole trapping, respectively. The technique has the advantage that trapping and detrapping of both types of charges can be measured independently. The concentrations of trapped charge types, their release times, and their relationship with measurement parameters such as pulse charging/discharging time and pulse amplitude have been investigated. A logarithmic universal relationship was found between the flat-band voltage shifts due to detrapping of positive charges with the discharging time.
Impact of thermal treatment upon morphology and crystallinity of strontium titanate films deposited by atomic layer deposition
Authors: Popovici Mihaela , Van Elshocht Sven , Menou Nicolas , Favia Paola , Bender Hugo , Rosseel Erik , Swerts Johan , Adelmann Christoph , Vrancken Christa , Moussa Alain , Tielens Hilde , Tomida Kazuyuki , Pawlak Malgorzata , Kaczer Ben , Schoofs Geert , Vandervorst Wilfried , Wouters Dirk J. , Kittl Jorge A.
Published: January 2011

Strontium titanate (STO) is a dielectric with a cubic perovskite type structure and of increasing interest for microelectronics, especially in the metal-insulator-metal (MIM) capacitors due to its high dielectric constant. The dielectric constant of the STO films and consequently the performance of the MIM capacitors appear to be strongly influenced by the process conditions. In this work the authors report on the influence of various thermal treatments upon the crystallinity and morphology of strontium titanate crystals. The influence of spike, laser, or rapid thermal anneals on the morphology with respect to grain size and topography of the crystalline stoichiometric STO films is studied. Also, the use of a stack containing a Sr-rich STO (62% Sr) bottom seed layer and a stoichiometric STO top layer in combination with a thermal treatment was found to affect the microstructure of the STO film. A comparison of the electrical properties for various thermal treatments has been made.
Metallic oxygen barrier diffusion applied to high-κ deposition
Authors: Rauwel E. , Rauwel P. , Ducroquet F. , Matko I. , Lourenço A. C.
Published: January 2011

A thin metallic interlayer was deposited on Si and Si/SiO2 substrate prior to the sputtering of HfO2 films. The metallic interlayer, in fact, acts as an oxygen barrier during the HfO2 deposition, preventing the formation of a low-κ layer at the high-κ/Si interface. After annealing, the metal diffuses in the HfO2 film. When the thickness of the metallic interlayer is properly adjusted, with respect to the thickness of the HfO2 film, the interfacial layer at HfO2/Si interface can almost be suppressed, thus improving the electrical properties of the gate stack.
Linearized forward and inverse problems of the resonant ultrasound spectroscopy for the evaluation of thin surface layers
Authors: Růžek Michal , Sedlák Petr , Seiner Hanuš , Kruisová Alena , Landa Michal
Published: January 2011

In this paper, linearized approximations of both the forward and the inverse problems of resonant ultrasound spectroscopy for the determination of mechanical properties of thin surface layers are presented. The linear relations between the frequency shifts induced by the deposition of the layer and the in-plane elastic coefficients of the layer are derived and inverted, the applicability range of the obtained linear model is discussed by a comparison with nonlinear models and finite element method (FEM), and an algorithm for the estimation of experimental errors in the inversely determined elastic coefficients is described. In the final part of the paper, the linearized inverse procedure is applied to evaluate elastic coefficients of a 310 nm thick diamond-like carbon layer deposited on a silicon substrate.
Indications for temporal fine structure contribution to co-modulation masking release
Authors: Pierzycki Robert H. , Seeber Bernhard U.
Published: January 2011

The contribution of temporal fine structure (TFS) information to co-modulation masking release (CMR) was examined by comparing CMR obtained with unprocessed or vocoded stimuli. Tone thresholds were measured in the presence of a sinusoidally amplitude-modulated on-frequency band (OFB) of noise and zero, two, or four flanking bands (FBs) of noise whose envelopes were either co- or anti-modulated with the OFB envelope. Vocoding replaced the TFS of the tone and masker with unrelated TFS of noise or sinusoidal carriers. Maximum CMR of 11 dB was found as the difference between the co- and anti-modulated conditions for unprocessed stimuli. After vocoding, tone thresholds increased by 7 dB, and CMR was reduced to about 4 dB but remained significant. The magnitude of CMR was similar for both the sine and the noise vocoder. Co-modulation improved detection in the vocoded condition despite the absence of the tone-masker TFS interactions; thus CMR appears to be a robust mechanism based on across-frequency processing. TFS information appears to contribute to across-channel CMR since the magnitude of CMR was significantly reduced after vocoding. Since CMR was evidenced despite vocoding, it is hoped that co-modulation would also improve detection in cochlear-implant listening.
Series expansion for the sound field of a ring source
Authors: Carley Michael J.
Published: January 2011

An exact series expansion for the field radiated by a monopole ring source with angular variation in source strength is derived from a previously developed expression for the field from a finite disk. The derived series can be used throughout the field, via the use of a reciprocity relation, and can be readily integrated to find the field radiated by arbitrary circular sources of finite extent, and differentiated to find the field due to higher order sources such as dipoles and quadrupoles.
Ultrasonic airborne insertion loss measurements at normal incidence (L)
Authors: Farley Jayrin , Anderson Brian E.
Published: January 2011

Transmission loss and insertion loss measurements of building materials at audible frequencies are commonly made using plane wave tubes or as a panel between reverberant rooms. These measurements provide information for noise isolation control in architectural acoustics and in product development. Airborne ultrasonic sound transmission through common building materials has not been fully explored. Technologies and products that utilize ultrasonic frequencies are becoming increasingly more common, hence the need to conduct such measurements. This letter presents preliminary measurements of the ultrasonic insertion loss levels for common building materials over a frequency range of 28–90 kHz using continuous-wave excitation.
Diffuse ultrasonic backscatter at normal incidence through a curved interface
Authors: Ghoshal Goutam , Turner Joseph A.
Published: January 2011

Diffuse ultrasonic backscatter techniques are useful for probing heterogeneous materials to extract microstructural parameters and detect flaws which cannot be detected by conventional ultrasonic techniques. Such experiments, usually done using a modified pulse-echo technique, utilize the spatial variance of the signals as a primary measure of microstructure. Quantitative ultrasonic scattering models include components of both transducer beams as well as microstructural scattering information. Of particular interest for interpretation of many experiments is the propagation through a liquid–solid interface. Here, a recent single-scattering model is expanded to include components needed for comparison with experiments. In particular, the Wigner distribution of the displacement profile is derived to model the beam pattern of an ultrasonic transducer through a curved liquid-solid interface. A simple Gaussian beam is used to model the transducer beam pattern. This expression is then used in conjunction with an appropriate scattering operator to complete the derivation. The theory developed is then compared with experimental results for a fine-grained steel using both a planar and a cylindrical interface. These results are anticipated to impact ultrasonic nondestructive evaluation and characterization of heterogeneous media with arbitrary curvatures.
Pulse mode of operation of a spherical piezoceramic transducer filled with liquid and having a correcting electric circuit
Authors: Konovalov S. I. , Kuz’menko A. G.
Published: January 2011

By means of a computational method, the possibility of radiating a short acoustic pulse by a transducer in the form of a piezoceramic sphere internally filled with liquid is investigated. An electric inductive–resistive circuit is connected to the electric input of the transducer. Solution is obtained based on scheme-analogs theory for piezoceramic transducers, and spectral Fourier transform theory. The values of parameters of the system, providing minimal durations of radiated signals, are determined. Computation was carried out for different values of relative thicknesses of the transducer wall. The estimates of durations and amplitudes of the acoustic signals radiated into the external medium are obtained.
Upper limits of auditory rotational motion perception
Authors: Féron François-Xavier , Frissen Ilja , Boissinot Julien , Guastavino Catherine
Published: January 2011

Three experiments are reported, which investigated the auditory velocity thresholds beyond which listeners are no longer able to perceptually resolve a smooth circular trajectory. These thresholds were measured for band-limited noises, white noise, and harmonic sounds (HS), and in different acoustical environments. Experiments 1 and 2 were conducted in an acoustically dry laboratory. Observed thresholds varied as a function of stimulus type and spectral content. Thresholds for band-limited noises were unaffected by center frequency and equal to that of white noise. For HS, however, thresholds decreased as the fundamental frequency of the stimulus increased. The third experiment was a replication of the second in a reverberant concert hall, which produced qualitatively similar results except that thresholds were significantly higher than in the acoustically dry laboratory.
Application of an extended equalization-cancellation model to speech intelligibility with spatially distributed maskers
Authors: Wan Rui , Durlach Nathaniel I. , Colburn H. Steven
Published: January 2011

An extended version of the equalization-cancellation (EC) model of binaural processing is described and applied to speech intelligibility tasks in the presence of multiple maskers. The model incorporates time-varying jitters, both in time and amplitude, and implements the equalization and cancellation operations in each frequency band independently. The model is consistent with the original EC model in predicting tone-detection performance for a large set of configurations. When the model is applied to speech, the speech intelligibility index is used to predict speech intelligibility performance in a variety of conditions. Specific conditions addressed include different types of maskers, different numbers of maskers, and different spatial locations of maskers. Model predictions are compared with empirical measurements reported by Hawley et al. [J. Acoust. Soc. Am. 115, 833–843 (2004)] and by Marrone et al. [J. Acoust. Soc. Am. 124, 1146–1158 (2008)]. The model succeeds in predicting speech intelligibility performance when maskers are speech-shaped noise or broadband-modulated speech-shaped noise but fails when the maskers are speech or reversed speech.
Aging, spatial cues, and single- versus dual-task performance in competing speech perception
Authors: Helfer Karen S. , Chevalier Jamie , Freyman Richard L.
Published: January 2011

Older individuals often report difficulty coping in situations with multiple conversations in which they at times need to “tune out” the background speech and at other times seek to monitor competing messages. The present study was designed to simulate this type of interaction by examining the cost of requiring listeners to perform a secondary task in conjunction with understanding a target talker in the presence of competing speech. The ability of younger and older adults to understand a target utterance was measured with and without requiring the listener to also determine how many masking voices were presented time-reversed. Also of interest was how spatial separation affected the ability to perform these two tasks. Older adults demonstrated slightly reduced overall speech recognition and obtained less spatial release from masking, as compared to younger listeners. For both younger and older listeners, spatial separation increased the costs associated with performing both tasks together. The meaningfulness of the masker had a greater detrimental effect on speech understanding for older participants than for younger participants. However, the results suggest that the problems experienced by older adults in complex listening situations are not necessarily due to a deficit in the ability to switch and/or divide attention among talkers.
Frequency selectivity for frequencies below 100 Hz: Comparisons with mid-frequencies
Authors: Jurado Carlos , Moore Brian C. J.
Published: January 2011

Auditory filter shapes were derived for signal frequencies (fs) between 50 and 1000 Hz, using the notched-noise method. The masker spectrum level (N0) was 50 dB (re 20 μPa). For fs = 63 and 50 Hz, measurements were also made with N0 = 62 dB for the lower band. The data were fitted using a rounded-exponential filter model, with special consideration of the filtering effects of the middle-ear transfer function (METF) at low frequencies. The results showed: (1) For very low values of fs, the lower skirts of the filters were only well defined when N0 = 62 dB for the lower band; (2) the sharpness of both sides of the filters decreased with decreasing fs; (3) the dynamic range of the filters decreased with decreasing fs; (4) the equivalent rectangular bandwidth of the filters decreased with decreasing fs down to fs = 80 Hz, but increased for fs below that; (5) the assumed METF, which includes the shunt effect of the helicotrema for frequencies below 50 Hz, increasingly influenced the low-frequency skirt of the filters as fs decreased; and (6) detection efficiency worsened with decreasing fs for fs between 100 and 500 Hz, but improved slightly below that.
Perceptual learning of fundamental frequency discrimination: Effects of fundamental frequency, harmonic number, and component phase
Authors: Miyazono Hiromitsu , Glasberg Brian R. , Moore Brian C. J.
Published: January 2011

Thresholds (F0DLs) were measured for discrimination of the fundamental frequency (F0) of a group of harmonics (group B) embedded in harmonics with a fixed F0. Miyazono and Moore [(2009). Acoust. Sci. & Tech. 30, 383386] found a large training effect for tones with high harmonics in group B, when the harmonics were added in cosine phase. It is shown here that this effect was due to use of a cue related to pitch pulse asynchrony (PPA). When PPA cues were disrupted by introducing a temporal offset between the envelope peaks of the harmonics in group B and the remaining harmonics, F0DLs increased markedly. Perceptual learning was examined using a training stimulus with cosine-phase harmonics, F0 = 50 Hz, and high harmonics in group B, under conditions where PPA was not useful. Learning occurred, and it transferred to other cosine-phase tones, but not to random-phase tones. A similar experiment with F0 = 100 Hz showed a learning effect which transferred to a cosine-phase tone with mainly high unresolved harmonics, but not to cosine-phase tones with low harmonics, and not to random-phase tones. The learning found here appears to be specific to tones for which F0 discrimination is based on distinct peaks in the temporal envelope.
Minimum radiation force target size for power measurements in focused ultrasonic fields with circular symmetry
Authors: Beissner K.
Published: January 2011

The time-averaged ultrasonic power emitted by medical ultrasonic equipment is mostly measured using a radiation force balance, and the question of the necessary target size is of practical importance. The question is answered here by calculations based on a Rayleigh integral algorithm for fields from circular, focusing transducers. This case occurs particularly in the field of high-intensity therapeutic ultrasound. The calculation yields the necessary size of an absorbing target so that the radiation force is 98% of that exerted on an absorber of infinite lateral size, and this as a function of the transducer-to-target distance, of the transducer radius in comparison with the wavelength and of the focus (half-)angle. Several distributions of the transducer vibration amplitude are considered. The Rayleigh integral strictly applies only to planar transducers, but among the amplitude distributions there is also one that allows the simulation of the spherically curved transducer type often found in practice.
Time-varying spatial spectrum estimation with a maneuverable towed array
Authors: Rogers Jeffrey S. , Krolik Jeffrey L.
Published: January 2011

This paper addresses the problem of field directionality mapping (FDM) or spatial spectrum estimation in dynamic environments with a maneuverable towed acoustic array. Array processing algorithms for towed arrays are typically designed assuming the array is straight, and are thus degraded during tow-ship maneuvers. In this paper, maneuvering the array is treated as a feature allowing for left and right disambiguation as well as improved resolution toward endfire. The Cramér-Rao lower bound is used to motivate the improvement in source localization which can be theoretically achieved by exploiting array maneuverability. Two methods for estimating time-varying field directionality with a maneuvering array are presented: (1) Maximum likelihood (ML) estimation solved using the expectation maximization algorithm and (2) a non-negative least squares (NNLS) approach. The NNLS method is designed to compute the field directionality from beamformed power outputs, while the ML algorithm uses raw sensor data. A multi-source simulation is used to illustrate both the proposed algorithms’ ability to suppress ambiguous towed array backlobes and resolve closely spaced interferers near endfire which pose challenges for conventional beamforming approaches especially during array maneuvers. Receiver operating characteristics are presented to evaluate the algorithms’ detection performance versus signal-to-noise ratio. The results indicate that both FDM algorithms offer the potential to provide superior detection performance when compared to conventional beamforming with a maneuverable array.
Predictions and measurements of sound transmission through a periodic array of elastic shells in air
Authors: Krynkin Anton , Umnova Olga , Yung Boon Chong Alvin , Taherzadeh Shahram , Attenborough Keith
Published: January 2011

Analytical and numerical approaches have been made to the problems of (a) propagation through a doubly periodic array of elastic shells in air, (b) scattering by a single elastic shell in air, and (c) scattering by a finite periodic array of elastic shells in air. Using the Rayleigh identity and the Kirchhoff–Love approximations, a relationship is found between the elastic material parameters and the size of the bandgap below the first Bragg frequency, which results from the axisymmetric resonance of the shells in an array. Predictions and laboratory data confirm that use of a suitably “soft” non-vulcanized rubber results in substantial insertion loss peaks related to the resonances of the shells. Inclusion of viscoelasticity is found to improve the correspondence between predictions and data. In addition the possible influences of inhomogeneity due to the manufacturing of the elastic shells (i.e., the effects of gluing sheet edges together) and of departures from circular cylindrical cross-sections are considered by means of numerical methods.
Bayesian evidence computation for model selection in non-linear geoacoustic inference problems
Authors: Dettmer Jan , Dosso Stan E. , Osler John C.
Published: January 2011

This paper applies a general Bayesian inference approach, based on Bayesian evidence computation, to geoacoustic inversion of interface-wave dispersion data. Quantitative model selection is carried out by computing the evidence (normalizing constants) for several model parameterizations using annealed importance sampling. The resulting posterior probability density estimate is compared to estimates obtained from Metropolis–Hastings sampling to ensure consistent results. The approach is applied to invert interface-wave dispersion data collected on the Scotian Shelf, off the east coast of Canada for the sediment shear-wave velocity profile. Results are consistent with previous work on these data but extend the analysis to a rigorous approach including model selection and uncertainty analysis. The results are also consistent with core samples and seismic reflection measurements carried out in the area.
The effect of native vowel processing ability and frequency discrimination acuity on the phonetic training of English vowels for native speakers of Greek
Authors: Lengeris Angelos , Hazan Valerie
Published: January 2011

The perception and production of nonnative phones in second language (L2) learners can be improved via auditory training, but L2 learning is often characterized by large differences in performance across individuals. This study examined whether success in learning L2 vowels, via five sessions of high-variability phonetic training, related to the learners’ native (L1) vowel processing ability or their frequency discrimination acuity. A group of native speakers of Greek received training, while another completed the pre-/post-tests but without training. Pre-/post-tests assessed different aspects of their L2 and L1 vowel processing and frequency acuity. L2 and L1 vowel processing were assessed via: (a) Natural English (L2) vowel identification in quiet and in multi-talker babble, and natural Greek (L1) vowel identification in babble; (b) the categorization of synthetic English and Greek vowel continua; and (c) discrimination of the same continua. Frequency discrimination acuity was assessed for a nonspeech continuum. Frequency discrimination acuity was related to measures of both L1 and L2 vowel processing, a finding that favors an auditory processing over a speech-specific explanation for individual variability in L2 vowel learning. The most efficient frequency discriminators at pre-test were also the most accurate both in English vowel perception and production after training.
Series expansions of rotating two and three dimensional sound fields
Authors: Poletti M. A.
Published: January 2011

The cylindrical and spherical harmonic expansions of oscillating sound fields rotating at a constant rate are derived. These expansions are a generalized form of the stationary sound field expansions. The derivations are based on the representation of interior and exterior sound fields using the simple source approach and determination of the simple source solutions with uniform rotation. Numerical simulations of rotating sound fields are presented to verify the theory.
Improved space time prewhitener for linear frequency modulation reverberation using fractional Fourier transform
Authors: Wang Ruhang , Huang Jianguo , Ma Tian , Zhang Qunfei
Published: January 2011

This letter presents an improved space time prewhitening method for linear frequency modulation (LFM) reverberation. The proposed method transforms the reverberation to fractional Fourier domain to whiten using fractional Fourier transform. The linear varying frequency in LFM reverberation is focused on a stationary frequency, and the adjacent block signal is used as the reference signal of prewhitening. Finally, experiment results with real reverberation data verify that the proposed method improves the detection performance of active sonar in shallow sea significantly.
Representative environments for reduced estimation time of wide area acoustic performance
Authors: Fabre J. Paquin
Published: January 2011

Advances in ocean modeling have improved such that high-resolution ocean forecasts are becoming available. This facilitates predicted time series of acoustic propagation conditions in the ocean which can greatly improve the planning of acoustic experiments. Modeling of acoustic transmission loss provides variation of acoustic performance with time. It is, however, very time consuming to compute acoustic propagation for many potential source/receiver combinations on an area-wide grid for multiple analysis/forecast times and scenarios of interest. Estimating area performance with a uniform grid can neglect important environmental acoustic features or can over-compute in areas of environmental acoustic isotropy. Two methods are developed to pre-examine an area and time frame to assess environmental acoustic similarities for performance estimation with fewer acoustic model predictions and thus less computation time. The first method is based on critical factors in the environment that typically indicate acoustic response, and the second method is based on a more robust full waveguide mode-based description of the environment. Results are shown for the critical factors method and prove this to be a viable solution for most cases studied. The mode-based method is developed for range independent environments and shows significant promise for future development.
Activation State of the M3 Muscarinic Acetylcholine Receptor Modulates Mammalian Odorant Receptor Signaling
Authors: Li Yun Rose , Matsunami Hiroaki
Published: January 2011

Crosstalk between neurotransmitter signaling and odorant signaling may enhance the sense of smell.
Autonomic Modulation of Olfactory Signaling
Authors: Hall Randy A.
Published: January 2011

Associations between receptors for odorants and acetylcholine result in enhanced odorant receptor signaling.
Scaffold for Infection
Authors: Wong Wei
Published: January 2011

A bacterial effector protein acts as an artificial scaffold for a GTPase and kinase at the Golgi.
Avoiding CO
2
Authors: Gough Nancy R.
Published: January 2011

A free-living nematode relies on a receptor guanylate cyclase and a cGMP-gated channel to move away from carbon dioxide.
Chill Wind
Authors: Hines Pamela J.
Published: January 2011

Spring flowering enabled by a winter chill is regulated by interplay between protein-coding and noncoding RNA transcripts.
Cilia 2010: The Surprise Organelle of the DecadeA report on the conference “The Biology of Cilia and Flagella,” Saxtons River, Vermont, USA, 5 to 10 July 2010.
Authors: Smith Elizabeth F. , Rohatgi Rajat
Published: January 2011

Scientists discussed advances in cilia biology and the role of cilia in development and disease.
Clinical Impact of Antimicrobial Resistance in European Hospitals: Excess Mortality and Length of Hospital Stay Related to Methicillin-Resistant
Staphylococcus aureus
Bloodstream Infections
Authors: de Kraker Marlieke E. A. , Wolkewitz Martin , Davey Peter G. , Grundmann Hajo
Published: January 2011

Antimicrobial resistance is threatening the successful management of nosocomial infections worldwide. Despite the therapeutic limitations imposed by methicillin-resistant
Staphylococcus aureus
(MRSA), its clinical impact is still debated. The objective of this study was to estimate the excess mortality and length of hospital stay (LOS) associated with MRSA bloodstream infections (BSI) in European hospitals. Between July 2007 and June 2008, a multicenter, prospective, parallel matched-cohort study was carried out in 13 tertiary care hospitals in as many European countries. Cohort I consisted of patients with MRSA BSI and cohort II of patients with methicillin-susceptible
S. aureus
(MSSA) BSI. The patients in both cohorts were matched for LOS prior to the onset of BSI with patients free of the respective BSI. Cohort I consisted of 248 MRSA patients and 453 controls and cohort II of 618 MSSA patients and 1,170 controls. Compared to the controls, MRSA patients had higher 30-day mortality (adjusted odds ratio [aOR] = 4.4) and higher hospital mortality (adjusted hazard ratio [aHR] = 3.5). Their excess LOS was 9.2 days. MSSA patients also had higher 30-day (aOR = 2.4) and hospital (aHR = 3.1) mortality and an excess LOS of 8.6 days. When the outcomes from the two cohorts were compared, an effect attributable to methicillin resistance was found for 30-day mortality (OR = 1.8;
P
= 0.04), but not for hospital mortality (HR = 1.1;
P
= 0.63) or LOS (difference = 0.6 days;
P
= 0.96). Irrespective of methicillin susceptibility,
S. aureus
BSI has a significant impact on morbidity and mortality. In addition, MRSA BSI leads to a fatal outcome more frequently than MSSA BSI. Infection control efforts in hospitals should aim to contain infections caused by both resistant and susceptible
S. aureus
.
Importance of Position 170 in the Inhibition of GES-Type β-Lactamases by Clavulanic Acid
Authors: Frase Hilary , Toth Marta , Champion Matthew M. , Antunes Nuno T. , Vakulenko Sergei B.
Published: January 2011

Bacterial resistance to β-lactam antibiotics (penicillins, cephalosporins, carbapenems, etc.) is commonly the result of the production of β-lactamases. The emergence of β-lactamases capable of turning over carbapenem antibiotics is of great concern, since these are often considered the last resort antibiotics in the treatment of life-threatening infections. β-Lactamases of the GES family are extended-spectrum enzymes that include members that have acquired carbapenemase activity through a single amino acid substitution at position 170. We investigated inhibition of the GES-1, -2, and -5 β-lactamases by the clinically important β-lactamase inhibitor clavulanic acid. While GES-1 and -5 are susceptible to inhibition by clavulanic acid, GES-2 shows the greatest susceptibility. This is the only variant to possess the canonical asparagine at position 170. The enzyme with asparagine, as opposed to glycine (GES-1) or serine (GES-5), then leads to a higher affinity for clavulanic acid (

K
i

= 5 μM), a higher rate constant for inhibition, and a lower partition ratio (
r
≈ 20). Asparagine at position 170 also results in the formation of stable complexes, such as a cross-linked species and a hydrated aldehyde. In contrast, serine at position 170 leads to formation of a long-lived
trans
-enamine species. These studies provide new insight into the importance of the residue at position 170 in determining the susceptibility of GES enzymes to clavulanic acid.
Restoration of Chloride Efflux by Azithromycin in Airway Epithelial Cells of Cystic Fibrosis Patients
Authors: Saint-Criq Vinciane , Rebeyrol Carine , Ruffin Manon , Roque Telma , Guillot Loïc , Jacquot Jacky , Clement Annick , Tabary Olivier
Published: January 2011

Azithromycin (AZM) has shown promising anti-inflammatory properties in chronic obstructive pulmonary diseases, and clinical studies have presented an improvement in the respiratory condition of cystic fibrosis (CF) patients. The aim of this study was to investigate, in human airway cells, the mechanism by which AZM has beneficial effects in CF. We demonstrated that AZM did not have any anti-inflammatory effect on CF airway cells but restored Cl
−
efflux.
Decreased Susceptibility to Ciprofloxacin amongShigellaIsolates in the United States, 2006 to 2009
Authors: Folster Jason P. , Pecic Gary , Bowen Anna , Rickert Regan , Carattoli Alessandra , Whichard Jean M.
Published: January 2011

We characterized 20Shigellaisolates with decreased susceptibility to fluoroquinolones. Most patients (80%) from whom a travel history was obtained reported travel to South or Southeast Asia. Mutations within the quinolone resistance determining regions ofgyrAandparCand plasmid-mediated resistance determinants (qnrB,qnrS, andaac(6′)-Ib-cr) were identified. The rise in antimicrobial resistance amongShigellaisolates may necessitate the increased use of extended-spectrum cephalosporins or macrolides in some patients.
Temperature-Dependent Modulation of
Porphyromonas gingivalis
Lipid A Structure and Interaction with the Innate Host Defenses
Authors: Curtis Michael A. , Percival Rimondia S. , Devine Deirdre , Darveau Richard P. , Coats Stephen R. , Rangarajan Minnie , Tarelli Edward , Marsh Philip D.
Published: January 2011

Lipid A structure is a critical determinant of the interaction between pathogens and the innate immune system. Previously, we demonstrated the presence of non- and monophosphorylated tetra-acylated lipid A structures in the outer membrane of
Porphyromonas gingivalis
, an agent of human periodontal disease. These modifications to lipid A structure lead to evasion and suppression of innate defenses mediated by Toll-like receptor 4 (TLR4) and cationic antimicrobial peptides. In this investigation, we examined the influence of growth temperature on
P. gingivalis
lipid A structure and recognition by TLR4 as an example of an environmental influence which is known to vary between healthy and diseased sites in the periodontium. We demonstrate that
P. gingivalis
grown at a normal body temperature produces mainly nonphosphorylated and monophosphorylated tetra-acylated lipid A structures, whereas bacteria grown at 39°C and 41°C intended to mimic increasing levels of inflammation, producing increasing proportions of monophosphorylated, penta-acylated lipid A. The temperature-dependent alteration in lipid A renders the bacterium significantly more potent for activating TLR4 and more susceptible to killing by β-defensins 2 and 3. This is the first report of a lipid A remodeling system linked to temperature shifts associated with a deregulated inflammatory response. Temperature elevation at sites of inflammation in the periodontium may be a significant environmental regulator of the lipid A modification systems of
P. gingivalis
, which will influence the interaction of this organism with the innate host defense.
Global Identification of Multiple Substrates forPlasmodium falciparumSUB1, an Essential Malarial Processing Protease
Authors: Silmon de Monerri Natalie C. , Flynn Helen R. , Campos Marta G. , Hackett Fiona , Koussis Konstantinos , Withers-Martinez Chrislaine , Skehel J. Mark , Blackman Michael J.
Published: January 2011

The protozoan pathogen responsible for the most severe form of human malaria,Plasmodium falciparum, replicates asexually in erythrocytes within a membrane-bound parasitophorous vacuole (PV). Following each round of intracellular growth, the PV membrane (PVM) and host cell membrane rupture to release infectious merozoites in a protease-dependent process called egress. Previous work has shown that, just prior to egress, an essential, subtilisin-like parasite protease called PfSUB1 is discharged into the PV lumen, where it directly cleaves a number of important merozoite surface and PV proteins. These include the essential merozoite surface protein complex MSP1/6/7 and members of a family of papain-like putative proteases called SERA (serine-rich antigen) that are implicated in egress. To determine whether PfSUB1 has additional, previously unrecognized substrates, we have performed a bioinformatic and proteomic analysis of the entire late asexual blood stage proteome of the parasite. Our results demonstrate that PfSUB1 is responsible for the proteolytic processing of a range of merozoite, PV, and PVM proteins, including the rhoptry protein RAP1 (rhoptry-associated protein 1) and the merozoite surface protein MSRP2 (MSP7-related protein-2). Our findings imply multiple roles for PfSUB1 in the parasite life cycle, further supporting the case for considering the protease as a potential new antimalarial drug target.
Branching Network of Proteinaceous Filaments within the Parasitophorous Vacuole of
Encephalitozoon cuniculi
and
Encephalitozoon hellem
Authors: Ghosh Kaya , Nieves Eddie , Keeling Patrick , Pombert Jean-Francois , Henrich Philipp P. , Cali Ann , Weiss Louis M.
Published: January 2011

The microsporidia are a diverse phylum of obligate intracellular parasites that infect all major animal groups and have been recognized as emerging human pathogens for which few chemotherapeutic options currently exist. These organisms infect every tissue and organ system, causing significant pathology, especially in immune-compromised populations. The microsporidian spore employs a unique infection strategy in which its contents are delivered into a host cell via the polar tube, an organelle that lies coiled within the resting spore but erupts with a force sufficient to pierce the plasma membrane of its host cell. Using biochemical and molecular approaches, we have previously identified components of the polar tube and spore wall of the Encephalitozoonidae. In this study, we employed a shotgun proteomic strategy to identify novel structural components of these organelles in
Encephalitozoon cuniculi
. As a result, a new component of the
E. cuniculi
developing spore wall was identified. Surprisingly, using the same approach, a heretofore undescribed filamentous network within the lumen of the parasitophorous vacuole was discovered. This network was also present in the parasitophorous vacuole of
Encephalitozoon hellem
. Thus, in addition to further elucidating the molecular composition of seminal organelles and revealing novel diagnostic and therapeutic targets, proteomic analysis-driven approaches exploring the spore may also uncover unknown facets of microsporidian biology.