bluuebunny/crossref_metadata_2025 huggingface dataset:
Locomotor hindrance of carrying an enlarged sexually selected structure on inclines for male fiddler crabs
Authors: Gerald G. W. , Thiesen K. E.
Published: July 2014

Sexual selection often results in males exhibiting exaggerated traits (e.g. bright colors, elaborate appendages) to attract potential mates and in some cases to also use as a weapon. These traits, however, can impose costs, such as an increase in energy expenditure and a decrease in locomotor performance, which could decrease foraging efficiency and increase an individual's vulnerability to predators. We examined the effect of the enlarged claw in male fiddler crabs Uca pugilator on ecologically relevant performance measures. We measured locomotor performance and kinematics during horizontal, uphill and downhill movements. Speed and stride mechanics were measured for clawed males, males after the claw was removed, and females while running on level (0°), uphill (15 and 30°) and downhill (−15 and −30°) slopes. Endurance capacities were measured on all crabs on horizontal and uphill inclines. Though claw removal had no significant effect on horizontal speeds, removal of the major claw significantly increased uphill speeds of male fiddler crabs at 15 and 30° inclines. Generally, as incline increased, the difference in performance between males with the enlarged claw and those with the claw removed increased. We also found that clawed males exhibit slower downhill speeds compared to clawless males and that claw removal significantly enhanced endurance on all inclines. This study indicates that an assessment of movement on level surfaces alone may not be entirely ecologically relevant when determining the actual costs of sexually selected ornaments.
Effect of toll‐like receptor 7 and 9 targeted therapy to prevent the development of hepatocellular carcinoma
Authors: Mohamed Fatma E. , Al‐Jehani Rajai M. , Minogue Shane S. , Andreola Fausto , Winstanley Alison , Olde Damink Steven W.M. , Habtesion Abeba , Malagó Massimo , Davies Nathan , Luong Tu Vinh , Dhillon Amar P. , Mookerjee Rajeshwar P. , Dhar Dipok K. , Jalan Rajiv
Published: July 2014

Background & Aims

Chronic liver disease is a predisposing factor for development of hepatocellular carcinoma (HCC). Toll‐like receptors play a crucial role in immunity against microbial pathogens and recent evidence suggests that they may also be important in pathogenesis of chronic liver disease. The purpose of this study was to determine whether TLR7 and TLR9 are potential targets for prevention and progression of HCC.

Methods

Tissue microarrays containing liver samples from patients with cirrhosis, viral hepatitis and HCC were examined for expression of TLR7 and TLR9 and the data obtained was validated in liver specimens from the hospital archives. Proliferation of human HCC cell lines was studied following stimulation of TLR7 and TLR9 using agonists (imiquimod and CpG‐ODN respectively) and inhibition with a specific antagonist (IRS‐954) or chloroquine. The effect of these interventions was confirmed in a xenograft model and diethylnitrosamine (DEN)/nitrosomorpholine (NMOR)‐induced model of HCC.

Results

TLR7 and TLR9 expression was up‐regulated in human HCC tissue. Proliferation of HuH7 cells in vitro increased significantly in response to stimulation of TLR7. TLR7 and TLR9 inhibition using IRS‐954 or chloroquine significantly reduced HuH7 cell proliferation in vitro and inhibited tumour growth in the mouse xenograft model. HCC development in the DEN/NMOR rat model was also significantly inhibited by chloroquine (P < 0.001).

Conclusion

The data suggest that inhibiting TLR7 and TLR9 with IRS‐954 or chloroquine could potentially be used as a novel therapeutic approach for preventing HCC development and/or progression in susceptible patients.
Bacterial chemoreceptors of different length classes signal independently
Authors: Herrera Seitz M. Karina , Frank Vered , Massazza Diego A. , Vaknin Ady , Studdert Claudia A.
Published: July 2014

Bacterial chemoreceptors sense environmental stimuli and govern cell movement by transmitting the information to the flagellar motors. The highly conserved cytoplasmic domain of chemoreceptors consists in an alpha‐helical hairpin that forms in the homodimer a coiled‐coil four‐helix bundle. Several classes of chemoreceptors that differ in the length of the coiled‐coil structure were characterized. Many bacterial species code for chemoreceptors that belong to different classes, but how these receptors are organized and function in the same cell remains an open question. E. coli cells normally code for single class chemoreceptors that form extended arrays based on trimers of dimers interconnected by the coupling protein CheW and the kinase CheA. This structure promotes effective coupling between the different receptors in the modulation of the kinase activity. In this work, we engineered functional derivatives of the Tsr chemoreceptor of E. coli that mimic receptors whose cytoplasmic domain is longer by two heptads. We found that these long Tsr receptors did not efficiently mix with the native receptors and appeared to function independently. Our results suggest that the assembly of membrane‐bound receptors of different specificities into mixed clusters is dictated by the length‐class to which the receptors belong, ensuring cooperative function only between receptors of the same class.
NudC Nudix hydrolase from Pseudomonas syringae, but not its counterpart from Pseudomonas aeruginosa, is a novel regulator of intracellular redox balance required for growth, motility and biofilm formation
Authors: Modzelan Marta , Kujawa Martyna , Głąbski Krzysztof , Jagura‐Burdzy Grażyna , Kraszewska Elzbieta
Published: July 2014

Nudix pyrophosphatases, ubiquitous in all organisms, have not been well studied. Recent implications that some of them may be involved in response to stress and in pathogenesis indicate that they play important biological functions. We have investigated NudC Nudix proteins from the plant pathogen Pseudomonas syringae pv. tomato str. DC3000 and from the human pathogen Pseudomonas aeruginosa PAO1161. We found that these homologous enzymes are homodimeric and in vitro preferentially hydrolyse NADH. The P. syringae mutant strain deficient in NudC accumulated NADH and displayed significant defects in growth, motility and biofilm formation. The wild type copy of the nudC gene with its cognate promoter delivered in trans into the nudC mutant restored its fitness. However, introduction of the P. syringae nudC gene under the control of the strong tacp promoter into either P. syringae or P. aeruginosa cells had a toxic effect on both strains. Opposite to P. syringae NudC, the P. aeruginosa NudC deficiency as well as its overproduction had no visible impact on cells. Moreover, P. aeruginosa NudC does not compensate the lack of its counterpart in the P. syringae mutant. These results indicate that NudC from P. syringae, but not from P. aeruginosa is vital for bacteria.
De novo morphogenesis in L‐forms via geometric control of cell growth
Authors: Billings Gabriel , Ouzounov Nikolay , Ursell Tristan , Desmarais Samantha M. , Shaevitz Joshua , Gitai Zemer , Huang Kerwyn Casey
Published: July 2014

In virtually all bacteria, the cell wall is crucial for mechanical integrity and for determining cell shape. Escherichia coli's rod‐like shape is maintained via the spatiotemporal patterning of cell‐wall synthesis by the actin homologue MreB. Here, we transiently inhibited cell‐wall synthesis in E. coli to generate cell‐wall‐deficient, spherical L‐forms, and found that they robustly reverted to a rod‐like shape within several generations after inhibition cessation. The chemical composition of the cell wall remained essentially unchanged during this process, as indicated by liquid chromatography. Throughout reversion, MreB localized to inwardly curved regions of the cell, and fluorescent cell wall labelling revealed that MreB targets synthesis to those regions. When exposed to the MreB inhibitor A22, reverting cells regrew a cell wall but failed to recover a rod‐like shape. Our results suggest that MreB provides the geometric measure that allows E. coli to actively establish and regulate its morphology.
Effects of open and closed suction systems on the haemodynamic parameters in cardiac surgery patients
Authors: Özden Dilek , Görgülü Refia S
Published: July 2014

Aims

This study was carried out to determine the effects of open and closed suction systems on haemodynamic parameters of the patients who underwent open heart surgery.

Background

Nurses should work meticulously and carefully as many complications may develop if the method used to perform suctioning is not appropriate.

Design

The quasi‐experimental study design was used.

Method

The study sample comprised 120 patients who underwent open heart surgery in the cardiovascular surgery intensive care unit of a state hospital in Turkey. Haemodynamic parameters were determined just before, right after, at the 5th and 15th minute after suctioning. The data were evaluated with the One‐Way Analysis of Variance (ANOVA) for Repeated Measures, independent t‐test and Bonferroni's test for further analysis (post hoc).

Results

The difference between heart rate (HR) and mean blood pressure, mean PaO2 and PaCO2, SaO2 and pH values measured before, right after and at the 5th and 15th minute after suctioning was found to be significant in patients who underwent the open suctioning procedure. It was determined that the difference between mean PaO2 values was not significant and that SaO2 versus SpO2 values increased in patients who underwent the closed suctioning procedure. When the open and closed suction systems were compared, statistically significant difference was determined in terms of MAP, SpO2.

Conclusion

It was determined that HR, arterial blood pressure and arterial blood gases of the patients who underwent open heart surgery were negatively affected by the open suction system but did not increase significantly as soon as suctioning was over during the closed suctioning procedure. The data obtained indicate that closed system suctioning, compared with open system suctioning, can be used safely on this patient group.

Relevance to clinical practice

The closed suction system is recommended since it contributes to the enhancement of patient safety and the quality of nursing care.
Spore dispersal of basidiomycete fungi at the landscape scale is driven by stochastic and deterministic processes and generates variability in plant–fungal interactions
Authors: Peay Kabir G. , Bruns Thomas D.
Published: July 2014

Fungi play an important role in plant communities and ecosystem function. As a result, variation in fungal community composition can have important consequences for plant fitness. However, there are relatively few empirical data on how dispersal might affect fungal communities and the ecological processes they mediate.

We established sampling stations across a large area of coastal landscape varying in their spatial proximity to each other and contrasting vegetation types. We measured dispersal of spores from a key group of fungi, the Basidomycota, across this landscape using qPCR and 454 pyrosequencing. We also measured the colonization of ectomycorrhizal fungi at each station using sterile bait seedlings.

We found a high degree of spatial and temporal variability in the composition of Basidiomycota spores. This variability was in part stochastic and in part explained by spatial proximity to other vegetation types and time of year. Variation in spore community also affected colonization by ectomycorrhizal fungi and seedling growth.

Our results demonstrate that fungal host and habitat specificity coupled with dispersal limitation can lead to local variation in fungal community structure and plant–fungal interactions. Understanding fungal communities also requires explicit knowledge of landscape context in addition to local environmental conditions.
Inflation and Market Uncertainty in South Africa
Authors: Burger Philippe
Published: July 2014

Comparison of the movements in the VIX index, the rand – dollar exchange rate and South African CPI inflation reveals a striking resemblance between them, raising the question as to whether or not there is an empirical relationship among them. The aim of this paper is to determine whether or not changes in market uncertainty, as reflected in the VIX index, influence South African inflation. Given that the VIX index reflects market uncertainty, its impact on the inflation rate may differ between times of heightened uncertainty and normality, thus suggesting the presence of multiple regimes. To cater for this possibility, the analysis first uses the general‐to‐specific procedure (including squared and cubed values of dependent and independent variables) with impulse indicator saturation dummies to look for non‐linear behaviour in the form of statistically significant squared and cubed variables and clustered periods of outlier dummies that might reflect an alternative regime. Finding such periods, the analysis next uses a Markov‐switching model to model this non‐linear behaviour explicitly. The results show that market volatility as measured by the VIX indeed explains South African inflation. Moreover, as shown by the second regime of the Markov‐switching model, when market volatility is elevated, its influence on inflation also increases.
Evaluating the Possible Impact of Pension Reforms on Elderly Poverty in Europe
Authors: Grech Aaron
Published: July 2014

Since the 1990s, reforms have changed substantially both the nature of state pension provision and the level of generosity. This article tries to assess the impact of these changes using estimates of pension wealth for a number of hypothetical cases. By focusing on all prospective pension transfers rather than just those at the point of retirement, this approach can provide additional insights, especially on the impact of changes in benefit indexation.

These estimates corroborate existing evidence that reforms have decreased generosity significantly. Moves to link benefits to contributions have made systems less progressive, raising adequacy concerns for certain groups. The reforms have, in particular, strengthened the need of ensuring better access to labour markets, of having in place adequate crediting arrangements and minimum pensions.
Diterpene synthases of the biosynthetic system of medicinally active diterpenoids in Marrubium vulgare
Authors: Zerbe Philipp , Chiang Angela , Dullat Harpreet , O'Neil‐Johnson Mark , Starks Courtney , Hamberger Björn , Bohlmann Jörg
Published: July 2014

Marrubium vulgare (Lamiaceae) is a medicinal plant whose major bioactive compounds, marrubiin and other labdane–related furanoid diterpenoids, have potential applications as anti–diabetics, analgesics or vasorelaxants. Metabolite and transcriptome profiling of M. vulgare leaves identified five different candidate diterpene synthases (diTPSs) of the TPS–c and TPS–e/f clades. We describe the in vitro and in vivo functional characterization of the M. vulgare diTPS family. In addition to MvEKS ent–kaurene synthase of general metabolism, we identified three diTPSs of specialized metabolism: MvCPS3 (+)‐copalyl diphosphate synthase, and the functional diTPS pair MvCPS1 and MvELS. In a sequential reaction, MvCPS1 and MvELS produce a unique oxygenated diterpene scaffold 9,13‐epoxy‐labd‐14‐ene en route to marrubiin and an array of related compounds. In contrast with previously known diTPSs that introduce a hydroxyl group at carbon C–8 of the labdane backbone, the MvCPS1‐catalyzed reaction proceeds via oxygenation of an intermediate carbocation at C–9, yielding the bicyclic peregrinol diphosphate. MvELS belongs to a subgroup of the diTPS TPS–e/f clade with unusual βα–domain architecture. MvELS is active in vitro and in vivo with three different prenyl diphosphate substrates forming the marrubiin precursor 9,13‐epoxy‐labd‐14‐ene, as identified by nuclear magnetic resonance (NMR) analysis, manoyl oxide and miltiradiene. MvELS fills a central position in the biosynthetic system that forms the foundation for the diverse repertoire of Marrubium diterpenoids. Co‐expression of MvCPS1 and MvELS in engineered E. coli and Nicotiana benthamiana offers opportunities for producing precursors for an array of biologically active diterpenoids.
Host PI(3,5)P2 Activity Is Required for Plasmodium berghei Growth During Liver Stage Infection
Authors: Thieleke‐Matos Carolina , da Silva Mafalda Lopes , Cabrita‐Santos Laura , Pires Cristiana F. , Ramalho José S. , Ikonomov Ognian , Seixas Elsa , Shisheva Assia , Seabra Miguel C. , Barral Duarte C.
Published: July 2014

Malaria parasites go through an obligatory liver stage before they infect erythrocytes and cause disease symptoms. In the host hepatocytes, the parasite is enclosed by a parasitophorous vacuole membrane (PVM). Here, we dissected the interaction between the Plasmodium parasite and the host cell late endocytic pathway and show that parasite growth is dependent on the phosphoinositide 5‐kinase (PIKfyve) that converts phosphatidylinositol 3‐phosphate [PI(3)P] into phosphatidylinositol 3,5‐bisphosphate [PI(3,5)P2] in the endosomal system. We found that inhibition of PIKfyve by either pharmacological or non‐pharmacological means causes a delay in parasite growth. Moreover, we show that the PI(3,5)P2 effector protein TRPML1 that is involved in late endocytic membrane fusion, is present in vesicles closely contacting the PVM and is necessary for parasite growth. Thus, our studies suggest that the parasite PVM is able to fuse with host late endocytic vesicles in a PI(3,5)P2‐dependent manner, allowing the exchange of material between the host and the parasite, which is essential for successful infection.
Design and Modeling of an Active Five-Axis Compliant Micromanipulator
Authors: Jayanth G. R. , Menq C. H.
Published: July 2014

This paper presents the design and modeling of an active five-axis compliant micromanipulator whose tip orientation can be independently controlled by large angles about two axes and the tip-position can be controlled in three dimensions. These features enable precise control of the contact point of the tip and the tip–sample interaction forces with three-dimensional nanoscale objects, including those features that are conventionally inaccessible. Control of the tip-motion is realized by means of electromagnetic actuation combined with a novel kinematic and structural design of the micromanipulator, which, in addition, also ensures compatibility with existing high-resolution motion-measurement systems. The design and analysis of the manipulator structure and those of the actuation system are first presented. Quasi-static and dynamic lumped-parameter (LP) models are then derived for the five-axis compliant micromanipulator. Finite element (FE) analysis is employed to validate these models, which are subsequently used to study the effects of tip orientation on the mechanical characteristics of the five-axis micromanipulator. Finally, a prototype of the designed five-axis manipulator is fabricated by means of focused ion-beam milling (FIB).
Analytical Study of Flow Instability in a Natural Circulation Pressurized Water Reactor Auxiliary Feedwater System1
Authors: Chull Jo Jong , Moody Frederick J. , Sik Do Kyu
Published: July 2014

A pressurized water reactor (PWR) incorporates a passive auxiliary feedwater system (PAFS), a closed natural circulation loop which is aligned to feed condensed water to its corresponding steam generator (SG). During its operation, saturated steam in the SG secondary side moves up due to buoyancy force and passes through a steam line, and then flows into a tube-tank type passive condensation heat exchanger (PCHX) where steam is condensed inside the tubes while the tube outer surfaces are cooled by the pool water. The condensate water is passively fed into the bottom of the SG secondary side by gravity. Because a natural circulation loop is susceptible to two-phase flow instability, it is requisite to confirm the system is designed adequately to avoid the potential challenges to its operational safety due to the instability. This paper presents an analytical approach for assessing if the PAFS has possible thermal and fluid mechanical characteristics which could lead to an undesirable unstable or oscillating condensate water level in the vertical pipe section. Both steady and unsteady analytical solutions for a simplified natural circulation loop model of the PAFS were derived in terms of the condensate water level and velocity in the vertical pipe section. From the solutions, the criteria for determining a potential for flow instability in the system were obtained.
Forces on Nets With Bending Stiffness—An Experimental Study on the Effects of Flow Speed and Angle of Attack
Authors: Gansel L. C. , Jensen Ø. , Lien E. , Endresen P. C.
Published: July 2014

This study investigates the effects of changes in flow speed and angle of attack on drag and lift forces on nets with bending stiffness. Today most fish cage nets are made from nylon, but new cage materials are proposed in order to improve the stability of cages in currents and waves, to reduce biofouling, prevent escapes, and to secure fish from predator attacks. The use of some of these materials leads to nets with bending stiffness in at least one direction. However, not much is known about the performance of such nets in currents and waves. In this study, three different nets with bending stiffness were tested together with nylon nets. Net panels were subjected to different flow speeds at different angles between flow direction and net plane, and the forces on the nets were measured with a multi-axis force/torque sensor system. Based on the experiments, drag, and lift coefficients were determined for the different net materials and compared to existing theory with which they are in reasonably good agreement for the nets with low solidity. However, for nets with higher solidity the results are significantly lower than the drag and lift coefficients provided other authors. Also, the change of drag coefficient with changing flow speed and angle of attack was different for a monofilament and a multifilament net with similar solidity and aperture form and size. These differences may partly be due to differences in twine structures and net construction between the monofilament and multifilament net and between nets used by other authors and in the present study.
Two-Dimensional Model for Pore Pressure Accumulations in the Vicinity of a Buried Pipeline
Authors: Zhao H.-Y. , Jeng D.-S. , Guo Z. , Zhang J.-S.
Published: July 2014

In this paper, we presented an integrated numerical model for the wave-induced residual liquefaction around a buried offshore pipeline. In the present model, unlike previous investigations, two new features were added in the present model: (i) new definition of the source term for the residual pore pressure generations was proposed and extended from 1D to 2D; (ii) preconsolidation due to self-weight of the pipeline was considered. The present model was validated by comparing with the previous experimental data for the cases without a pipeline and with a buried pipeline. Based on the numerical model, first, we examined the effects of seabed, wave and pipeline characteristics on the pore pressure accumulations and residual liquefaction. The numerical results indicated a pipe with a deeper buried depth within the seabed with larger consolidation coefficient and relative density can reduce the risk of liquefaction around a pipeline. Second, we investigated the effects of a trench layer on the wave-induced seabed response. It is found that the geometry of the trench layer (thickness and width), as well as the backfill materials (permeability K and relative density Dr) have significant effect on the development of liquefaction zone around the buried pipeline. Furthermore, under certain conditions, partially backfill the trench layer up to one pipeline diameter is sufficient to protect the pipelines from the wave-induced liquefaction.
Experimental Assessment of a New Fuzzy Controller Applied to a Flexible Rotor Supported by Active Magnetic Bearings
Authors: Defoy Benjamin , Alban Thomas , Mahfoud Jarir
Published: July 2014

The aim of this study was to develop and implement a new control approach dedicated to turbomachinery. The new, fuzzy based controller utilizes inputs expressed in polar coordinates. Its originality is that it manages two significant physical quantities, namely, tangential and radial velocities, associated with steady-state and transient behaviors, respectively. Three controllers are compared for the control of a flexible rotor supported by active magnetic bearings (AMBs): proportional-integral-derivative (PID), single-input and single-output (SISO) fuzzy and the new controller. The assessment was performed using an academic test rig and the results obtained with the new controller show that performances were enhanced with equivalent levels of stability and robustness.
Modeling the Energy Yield Enhancement From a Wind Turbine at a Deep Offshore Low Wind Site Through Combined Power and Thermocline Energy Production
Authors: Sant Tonio , Farrugia Robert N.
Published: July 2014

This paper presents steady-state performance modeling and analysis of a novel wind powered system that concurrently exploits thermocline thermal energy through deep sea water extraction in conjunction with offshore wind energy for combined power and thermal energy production. A single offshore wind turbine rotor directly coupled to a large positive displacement pump is modeled to supply deep sea water at high pressure to a land-based plant, the latter consisting of a hydro-electric generator coupled to a heat exchanger. The steady-state power-wind speed characteristics for the system are derived from a numerical thermofluid model. The latter integrates the hydraulic characteristics of the wind turbine-pump combination and a numerical code to simulate the heat gained/lost by deep sea water as it flows through a pipeline to shore. The model was applied to a hypothetical megawatt-scale wind turbine installed at a deep offshore low wind site in the vicinity of the Central Mediterranean island of Malta. One year of wind speed and ambient measurements were used in conjunction with marine thermocline data to estimate the time series electricity and thermal energy yields. The total energy yield from the system was found to be significantly higher than that from a conventional offshore wind turbine generator (OWTG) that only produces electricity. It could be shown that at sites having less energetic wind behavior and high ambient temperatures as a result of a hotter climate, the cooling energy component that can be delivered from such a system is relatively high even at periods of low wind speeds.
Numerical Simulation of Aerodynamic Instabilities in a Multistage High-Speed High-Pressure Compressor on Its Test Rig—Part II: Deep Surge
Authors: Crevel Flore , Gourdain Nicolas , Ottavy Xavier
Published: July 2014

Aerodynamic instabilities such as stall and surge may occur in compressors, possibly leading to mechanical failures so their avoidance is crucial. A better understanding of those phenomena and an accurate prediction are necessary to improve both the performance and the safety. A surge event in a compressor threatens the mechanical integrity of the aircraft engine, and this remains true for a research compressor on a test rig. As a result, few experimental data on surge are available. Moreover, there are technological, restrictive constraints that exist on test rigs and limit severely the type of data obtainable experimentally. This partially explains why numerical simulation has become a usual, complementary and convenient tool to collect data in a compressor, as it does not disturb the flow nor does it encounter technological limits. Despite the inherent difficulties, an entire surge cycle has been simulated in a high-speed, high-pressure, multistage research compressor, using an implicit, time-accurate, 3D compressible unsteady Reynolds-averaged Navier–Stokes solver. First, the paper presents the main features of the surge cycle obtained, along with those from the experimental cycle, for a validation purpose. Four phases compose the surge cycle: surge inception, the reversed-flow phase, the recovery phase, and the repressurization of the compressor flow. All of them are described, and focus is put on surge inception and the reversed-flow phase, as they induce greater risk for the mechanical integrity of the machine.
Using Axiomatic Design Theory for Selection of the Optimum Design Solution and Manufacturing Process Plans of a Limited Angle Torque Motor
Authors: Roohnavazfar M. , Houshmand M. , Nasiri-Zarandi R. , Mirsalim M.
Published: July 2014

The brushless dc limited angle torque motor (LATM) has been widely used in areas of aerospace equipments, robot drives, optical scanning systems and any drive systems that require limited motion, ranging from the simple ON-OFF servo valves to the accurate tracking of a reference signal. This paper presents the optimum design procedure of a brushless direct current LATM to satisfy the functional requirements (FRs) and constraints using Independence axiom in axiomatic design (AD) approach. Also, to select the best manufacturing process plan, we consider both cost and thermal performance as two effective criteria, and evaluate available alternatives by computing information content in Information axiom. Finally, finite element method is employed to validate the results obtained by optimizations as well as experimental outcomes extracted from the manufactured prototype of the device.
Passive localization of noise-producing targets using a compact volumetric array
Authors: Gebbie John , Siderius Martin , Nielsen Peter L. , Miller James
Published: July 2014

A technique is presented for passively localizing multiple noise-producing targets by cross-correlating the elevation beams of a compact volumetric array on separate bearings. A target's multipath structure inherently contains information about its range; however, unknown, random noise waveforms make time separation of individual arrivals difficult. Ocean ambient noise has previously been used to measure multipath delays to the seabed by cross-correlating the beams of a vertical line array [Siderius, Song, Gerstoft, Hodgkiss, Hursky, and Harrison, J. Acoust. Soc. Am. 127, 2193–2200 (2010)], but this methodology has not been applied to distant noise sources having non-vertical arrivals. The technique presented in this paper uses a compact volumetric array mounted to an autonomous underwater vehicle to measure the three-dimensional directionality and time delays of multipath arrivals, while adaptively rejecting clutter and multi-target interference. This is validated with experimental results in a shallow ocean environment in which a small workboat maneuvered in the vicinity. Short ranges could be estimated reliably using straight ray paths, but longer ranges required accounting for ray refraction.
Principal component analysis reveals differential attentional modulation of the vocal response to pitch perturbation
Authors: Okazaki Shuntaro , Mori Koichi , Okada Minae
Published: July 2014

The auditory-vocal system modifies voice fundamental frequency (F0) with auditory feedback. The responses to F0 changes in auditory feedback are known to depend on the task. The hypothesis explored in this study is that the task dependency is the result of multiple components of the F0 responses differently modulated with different tasks. Attention to audition was manipulated by task condition by the instruction to ignore or to count the number of the F0 shifts heard during vocalization. A synthetic voice with pitch shifts was used as auditory pseudo-feedback. The upward and downward shifts evoked very similar vocal F0 response patterns with polarity reversal. Attention to the auditory feedback caused a reduction in the grand-average response amplitude. By decomposing the F0 responses with principal component analysis (PCA), three principal components (PCs) with different peak latencies were found to have contributions above the criterion of 5%, totaling to 74%. All three PCs contributed to a compensatory response under the “ignore” condition. The slowest PC changed its polarity and the intermediate PC was reduced to almost zero under the “count” condition. Thus, the task-dependency of the F0 response to auditory feedback can be described in terms of different sensitivities of components to attention.
Multichannel filtering and reconstruction of ultrasonic guided wave fields using time intercept-slowness transform
Authors: Tran Tho N. H. T. , Le Lawrence H. , Sacchi Mauricio D. , Nguyen Vu-Hieu , Lou Edmond H. M.
Published: July 2014

Multichannel ultrasonic axial-transmission data are multimodal by nature. As guided waves are commonly used in nondestructive material testing, wave field filtering becomes important because the analysis is usually limited to a few lower-order modes and requires their extraction. An application of the Radon transform to enhance signal-to-noise ratio and separate wave fields in ultrasonic records is presented. The method considers guided wave fields as superpositions of plane waves defined by ray parameters (p) and time intercepts (τ) and stacks the amplitudes along linear trajectories, mapping time-offset (t−x) data to a τ−p or Radon panel. The transform is implemented using a least-squares strategy with Cauchy-norm regularization that serves to enhance the focusing power. The method was verified using simulated data and applied to an uneven spatially sampled bovine-bone-plate data set. The results demonstrate the Radon panels show isolated amplitude clusters and the Cauchy-norm constraint provides a more focused Radon image than the damped least-squares regularization. Wave field separation can be achieved by selectively windowing the τ−p signals and inverse transformation, which is illustrated by the successful extraction of the A0 mode in bone plate. In addition, the method effectively attenuates noise, enhances the coherency of the guided wave modes, and reconstructs the missing records. The proposed transform presents a powerful signal-enhancement tool to process guided waves for further analysis and inversion.
Measurement of the sound transmission characteristics of normal neck tissue using a reflectionless uniform tube
Authors: Wu Liang , Xiao Ke , Dong Jiaqi , Wang Supin , Wan Mingxi
Published: July 2014

Understanding the sound transmission of the neck tissue is necessary and important in areas such as vocal function evaluation and electrolarynx improvement. In this paper, a simple method using a reflectionless tube was proposed to measure the neck frequency response function (NFRF) of ten normal subjects (five males and five females) during Mandarin vowel production. The NFRFs across different subjects producing different vowels were measured at different neck positions and compared to confirm the effectiveness of the method, and determine the NFRF variations in normal subjects. The results showed that the proposed method offered an easy and effective way to obtain an accurate NFRF. For normal subjects, the neck tissue can be treated as a low-pass filter, with a maximum gain at 310 Hz and a roll-off at a slope of −8.4 dB/octave, flattening out above 2000 Hz. The measurement position on the neck did not influence the shape of the NFRF, but did change the overall gains of the NFRF. In addition, there was a significant gender difference in NFRFs at the low frequencies. Finally, some potential applications of this method and the results are suggested.
Comparison of sound reproduction using higher order loudspeakers and equivalent line arrays in free-field conditions
Authors: Poletti Mark A. , Betlehem Terence , Abhayapala Thushara D.
Published: July 2014

Higher order sound sources of Nth order can radiate sound with 2N + 1 orthogonal radiation patterns, which can be represented as phase modes or, equivalently, amplitude modes. This paper shows that each phase mode response produces a spiral wave front with a different spiral rate, and therefore a different direction of arrival of sound. Hence, for a given receiver position a higher order source is equivalent to a linear array of 2N + 1 monopole sources. This interpretation suggests performance similar to a circular array of higher order sources can be produced by an array of sources, each of which consists of a line array having monopoles at the apparent source locations of the corresponding phase modes. Simulations of higher order arrays and arrays of equivalent line sources are presented. It is shown that the interior fields produced by the two arrays are essentially the same, but that the exterior fields differ because the higher order sources produces different equivalent source locations for field positions outside the array. This work provides an explanation of the fact that an array of L Nth order sources can reproduce sound fields whose accuracy approaches the performance of (2N + 1)L monopoles.
A role for amplitude modulation phase relationships in speech rhythm perception
Authors: Leong Victoria , Stone Michael A. , Turner Richard E. , Goswami Usha
Published: July 2014

Prosodic rhythm in speech [the alternation of “Strong” (S) and “weak” (w) syllables] is cued, among others, by slow rates of amplitude modulation (AM) within the speech envelope. However, it is unclear exactly which envelope modulation rates and statistics are the most important for the rhythm percept. Here, the hypothesis that the phase relationship between “Stress” rate (∼2 Hz) and “Syllable” rate (∼4 Hz) AMs provides a perceptual cue for speech rhythm is tested. In a rhythm judgment task, adult listeners identified AM tone-vocoded nursery rhyme sentences that carried either trochaic (S-w) or iambic patterning (w-S). Manipulation of listeners' rhythm perception was attempted by parametrically phase-shifting the Stress AM and Syllable AM in the vocoder. It was expected that a 1π radian phase-shift (half a cycle) would reverse the perceived rhythm pattern (i.e., trochaic → iambic) whereas a 2π radian shift (full cycle) would retain the perceived rhythm pattern (i.e., trochaic → trochaic). The results confirmed these predictions. Listeners judgments of rhythm systematically followed Stress-Syllable AM phase-shifts, but were unaffected by phase-shifts between the Syllable AM and the Sub-beat AM (∼14 Hz) in a control condition. It is concluded that the Stress-Syllable AM phase relationship is an envelope-based modulation statistic that supports speech rhythm perception.
Theoretical analysis of warping operators for non-ideal shallow water waveguides
Authors: Niu Haiqiang , Zhang Renhe , Li Zhenglin
Published: July 2014

Signals propagating in waveguides can be decomposed into normal modes that exhibit dispersive characteristics. Based on the dispersion analysis, the warping transformation can be used to improve the modal separability. Different from the warping transformation defined using an ideal waveguide model, an improved warping operator is presented in this paper based on the beam-displacement ray-mode (BDRM) theory, which can be adapted to low-frequency signals in a general shallow water waveguide. For the sake of obtaining the warping operators for the general waveguides, the dispersion formula is first derived. The approximate dispersion relation can be achieved with adequate degree of accuracy for the waveguides with depth-dependent sound speed profiles (SSPs) and acoustic bottoms. Performance and accuracy of the derived formulas for the dispersion curves are evaluated by comparing with the numerical results. The derived warping operators are applied to simulations, which show that the non-linear dispersion structures can be well compensated by the proposed warping operators.
Measuring particle concentration in multiphase pipe flow using acoustic backscatter: Generalization of the dual-frequency inversion method
Authors: Rice Hugh P. , Fairweather Michael , Hunter Timothy N. , Mahmoud Bashar , Biggs Simon , Peakall Jeff
Published: July 2014

A technique that is an extension of an earlier approach for marine sediments is presented for determining the acoustic attenuation and backscattering coefficients of suspensions of particles of arbitrary materials of general engineering interest. It is necessary to know these coefficients (published values of which exist for quartz sand only) in order to implement an ultrasonic dual-frequency inversion method, in which the backscattered signals received by transducers operating at two frequencies in the megahertz range are used to determine the concentration profile in suspensions of solid particles in a carrier fluid. To demonstrate the application of this dual-frequency method to engineering flows, particle concentration profiles are calculated in turbulent, horizontal pipe flow. The observed trends in the measured attenuation and backscatter coefficients, which are compared to estimates based on the available quartz sand data, and the resulting concentration profiles, demonstrate that this method has potential for measuring the settling and segregation behavior of real suspensions and slurries in a range of applications, such as the nuclear and minerals processing industries, and is able to distinguish between homogeneous, heterogeneous, and bed-forming flow regimes.
The stability of perceptual compensation for coarticulation within and across individuals: A cross-validation study
Authors: Yu Alan C. L. , Lee Hyunjung
Published: July 2014

Perceptual compensation for coarticulation (PCCA) refers to listener responses consistent with perceptual reduction of the acoustic effects of the coarticulatory context on a target sound. The robustness of PCCA across individuals and across tasks have not been studied together previously. This study reports the results of two experiments designed to determine the robustness of perceptual compensation for vocalic influence on sibilant perception across tasks and the stability of such compensatory response within an individual. Identification and discrimination data, collected in the laboratory and on Amazon's Mechanical Turk, showed that individuals are moderately stable in their PCCA responses across tasks and the level of stability is consistent across both the lab-based and the internet-based cohorts, although some differences are observed.
A low-order reduced model for the long range propagation of infrasounds in the atmosphere
Authors: Bertin Michael , Millet Christophe , Bouche Daniel
Published: July 2014

This paper considers a class of low-order, range-dependent propagation models obtained from the normal mode decomposition of infrasounds in complex atmospheres. The classical normal mode method requires calculating eigenvalues for large matrices making the computation expensive even though some modes have little influence on the numerically obtained results. By decomposing atmospheric perturbations into a wavelet basis, it is shown that the most sensitive eigenvalues provide the best reduced model for infrasound propagation. These eigenvalues lie on specific curves in the complex plane that can be directly deduced from atmospheric data through a WKB approach. The computation cost can be reduced by computing the invariant subspace associated with the most sensitive eigenvalues. The reduction method is illustrated in the case of the Fukushima explosion (12 March 2011). The implicitly restarted Arnoldi algorithm is used to compute the three most sensitive modes, and the correct tropospheric arrival is found with a cost of 2% of the total run time. The cost can be further reduced by using a stationary phase technique. Finally, it is shown that adding uncertainties triggers a stratospheric arrival even though the classical criteria, based on the ratio of stratospheric sound speed to that at ground level, is not satisfied.
Dolphin biosonar target detection in noise: Wrap up of a past experiment
Authors: Au Whitlow W. L.
Published: July 2014

The target detection capability of bottlenose dolphins in the presence of artificial masking noise was first studied by Au and Penner [J. Acoust. Soc. Am. 70, 687–693 (1981)] in which the dolphins’ target detection threshold was determined as a function of the ratio of the echo energy flux density and the estimated received noise spectral density. Such a metric was commonly used in human psychoacoustics despite the fact that the echo energy flux density is not compatible with noise spectral density which is averaged intensity per Hz. Since the earlier detection in noise studies, two important parameters, the dolphin integration time applicable to broadband clicks and the dolphin's auditory filter shape, were determined. The inclusion of these two parameters allows for the estimation of the received energy flux density of the masking noise so that the dolphin target detection can now be determined as a function of the ratio of the received energy of the echo over the received noise energy. Using an integration time of 264 μs and an auditory bandwidth of 16.7 kHz, the ratio of the echo energy to noise energy at the target detection threshold is approximately 1 dB.
Effect of level, duration, and inter-pulse interval of 1–2 kHz sonar signal exposures on harbor porpoise hearing
Authors: Kastelein Ronald A. , Hoek Lean , Gransier Robin , Rambags Martijn , Claeys Naomi
Published: July 2014

Safety criteria for underwater low-frequency active sonar sounds produced during naval exercises are needed to protect harbor porpoise hearing. As a first step toward defining criteria, a porpoise was exposed to sequences consisting of series of 1-s, 1–2 kHz sonar down-sweeps without harmonics (as fatiguing noise) at various combinations of average received sound pressure levels (SPLs; 144–179 dB re 1 μPa), exposure durations (1.9–240 min), and duty cycles (5%–100%). Hearing thresholds were determined for a narrow-band frequency-swept sine wave centered at 1.5 kHz before exposure to the fatiguing noise, and at 1–4, 4–8, 8–12, 48, 96, 144, and 1400 min after exposure, to quantify temporary threshold shifts (TTSs) and recovery of hearing. Results show that the inter-pulse interval of the fatiguing noise is an important parameter in determining the magnitude of noise-induced TTS. For the reported range of exposure combinations (duration and SPL), the energy of the exposure (i.e., cumulative sound exposure level; SELcum) can be used to predict the induced TTS, if the inter-pulse interval is known. Exposures with equal SELcum but with different inter-pulse intervals do not result in the same induced TTS.
Simulation of ultrasound beam formation of baiji (Lipotes vexillifer) with a finite element model
Authors: Wei Chong , Zhang Yu , Au Whitlow W. L.
Published: July 2014

The baiji (Lipotes vexillifer) of the Yangtze River possesses a sophisticated biosonar system. In this study, a finite element approach was used to numerically investigate the propagation of acoustic waves through the head of the Yangtze River dolphin, which possesses an inhomogeneous and complex structure. The acoustic intensity distribution predicted from models with and without the melon and/or skull showed that the emitted sound beam was narrow and formed a highly directed acoustic beam, and the skull and melon significantly enhanced the directional characteristics of the emitted sound. Finally, for a short duration impulsive source, the emitted sound pressure distributions were also simulated at different propagation times. The results provide useful information for better understanding the operation of the biosonar system in this rare and perhaps extinct animal.