bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechano‐ and chemosensitivity of rat nodose neurones – selective excitatory effects of prostacyclin
Authors: Snitsarev Vladislav , Whiteis Carol A. , Chapleau Mark W. , Abboud François M.
Published: May 2007

Nodose ganglion sensory neurones exert a significant reflex autonomic influence. We contrasted their mechanosensitivity, excitability and chemosensitivity in response to the stable prostacyclin (PGI2) analogue carbacyclin (cPGI) in culture. Under current clamp conditions we measured changes in membrane potential (ΔmV) and action potential (AP) responses to mechanically induced depolarizations and depolarizing current injections before and after superfusion of cPGI (1 μmand 10 μm). Chemosensitivity was indicated by augmentation of AP firing frequency and increased maximum gain of AP frequency (max. dAP/dΔmV), during superfusion with cPGI. Results indicate that two groups of neurones, A and B, are mechanosensitive (MS) and one group, C, is mechanoinsensitive (MI). Group A shows modest depolarization without AP generation during mechanical stimulation, and no increase in max. dAP/dΔmV, despite a marked increase in electrical depolarization with cPGI. Group B shows pronounced mechanical depolarization accompanied by enhanced AP discharge with cPGI, and an increase in max. dAP/dΔmV. Group C remains MI after cPGI but is more excitable and markedly chemosensitive (CS) with a pronounced enhancement of max. dAP/dΔmV with cPGI. The effect of cPGI on ionic conductances indicates that it does not sensitize the mechanically gated depolarizing degenerin/epithelial Na+channels (DEG/ENaC), but it inhibits two voltage‐gated K+currents, Maxi‐K and M‐current, causing enhanced AP firing frequency and depolarization, respectively. We conclude that MS nodose neurones may be unimodal MS or bimodal MS/CS, and that MI neurones are unimodal CS, and much more CS to cPGI than MS/CS neurones. We suggest that the known excitatory effect of PGI2on baroreceptor and vagal afferent fibres is mediated by inhibition of voltage‐gated K+channels (Maxi‐K and M‐current) and not by an effect on mechanically gated DEG/ENaC channels.
SNARE proteins and ‘membrane rafts’
Authors: Lang Thorsten
Published: May 2007

The original ‘lipid raft’ hypothesis proposed that lipid‐platforms/rafts form in the exoplasmic plasmalemmal leaflet by tight clustering of sphingolipids and cholesterol. Their physical state, presumably similar to liquid‐ordered phases in model membranes, would confer detergent resistance to rafts and enriched proteins therein. Based on this concept, detergent resistant membranes (DRMs) from solubilized cells were considered to reflect pre‐existing ‘lipid rafts’ in live cells. To date, more than 200 proteins were found in DRMs including also members of the SNARE superfamily, which are small membrane proteins involved in intracellular fusion steps. Their raft association indicates that they are not uniformly distributed, and, indeed, microscopic studies revealed that SNAREs concentrate in submicrometre‐sized, cholesterol‐dependent clusters at which vesicles fuse. However, the idea that SNARE clusters are ‘lipid rafts’ was challenged, as they do not colocalize with raft markers, and SNAREs are excluded from liquid‐ordered phases in model membranes. Independent from this disagreement, in recent years the solubilization criterion has been criticized for several reasons, calling for a more exact definition of rafts. At a recent consensus on a revised raft model, the term ‘lipid rafts’ was replaced by ‘membrane rafts’ that were defined as ‘small (10–200 nm), heterogeneous, highly dynamic, sterol‐ and sphingolipid‐enriched domains that compartmentalize cellular processes’. As a result, after dismissing the terms ‘detergent resistant’ and ‘liquid‐ordered’, it now appears that SNARE clusters are bona fide‘membrane rafts’.
Frequency‐dependent myofilament Ca2+ desensitization in failing rat myocardium
Authors: Lamberts Regis R. , Hamdani Nazha , Soekhoe Tenoedj W. , Boontje Nicky M. , Zaremba Ruud , Walker Lori A. , De Tombe Pieter P. , Van Der Velden Jolanda , Stienen Ger J. M.
Published: May 2007

The positive force–frequency relation, one of the key factors modulating performance of healthy myocardium, has been attributed to an increased Ca2+ influx per unit of time. In failing hearts, a blunted, flat or negative force–frequency relation has been found. In healthy and failing hearts frequency‐dependent alterations in Ca2+ sensitivity of the myofilaments, related to different phosphorylation levels of contractile proteins, could contribute to this process. Therefore, the frequency dependency of force, intracellular free Ca2+ ([Ca2+]i), Ca2+ sensitivity and contractile protein phosphorylation were determined in control and monocrotaline‐treated, failing rat hearts. An increase in frequency from 0.5 to 6 Hz resulted in an increase in force in control (14.3 ± 3.0 mN mm−2) and a decrease in force in failing trabeculae (9.4 ± 3.2 mN mm−2), whereas in both groups the amplitude of [Ca2+]i transient increased. In permeabilized cardiomyocytes, isolated from control hearts paced at 0 and 9 Hz, Ca2+ sensitivity remained constant with frequency (pCa50: 5.55 ± 0.02 and 5.58 ± 0.01, respectively, P > 0.05), whereas in cardiomyocytes from failing hearts Ca2+ sensitivity decreased with frequency (pCa50: 5.62 ± 0.01 and 5.57 ± 0.01, respectively, P < 0.05). After incubation of the cardiomyocytes with protein kinase A (PKA) this frequency dependency of Ca2+ sensitivity was abolished. Troponin I (TnI) and myosin light chain 2 (MLC2) phosphorylation remained constant in control hearts but both increased with frequency in failing hearts. In conclusion, in heart failure frequency‐dependent myofilament Ca2+ desensitization, through increased TnI phosphorylation, contributes to the negative force–frequency relation and is counteracted by a frequency‐dependent MLC2 phosphorylation. We propose a novel role for PKC‐mediated TnI phosphorylation in modulating the force–frequency relation.
Nutrient signalling in the regulation of human muscle protein synthesis
Authors: Fujita Satoshi , Dreyer Hans C. , Drummond Micah J. , Glynn Erin L. , Cadenas Jerson G. , Yoshizawa Fumiaki , Volpi Elena , Rasmussen Blake B.
Published: May 2007

The mammalian target of rapamycin (mTOR) and AMP‐activated protein kinase (AMPK) are important nutrient‐ and energy‐sensing and signalling proteins in skeletal muscle. AMPK activation decreases muscle protein synthesis by inhibiting mTOR signalling to regulatory proteins associated with translation initiation and elongation. On the other hand, essential amino acids (leucine in particular) and insulin stimulate mTOR signalling and protein synthesis. We hypothesized that anabolic nutrients would be sensed by both AMPK and mTOR, resulting in an acute and potent stimulation of human skeletal muscle protein synthesis via enhanced translation initiation and elongation.

We measured muscle protein synthesis and mTOR‐associated upstream and downstream signalling proteins in young male subjects (n= 14) using stable isotopic and immunoblotting techniques. Following a first muscle biopsy, subjects in the ‘Nutrition’ group ingested a leucine‐enriched essential amino acid–carbohydrate mixture (EAC). Subjects in the Control group did not consume nutrients. A second biopsy was obtained 1 h later. Ingestion of EAC significantly increased muscle protein synthesis, modestly reduced AMPK phosphorylation, and increased Akt/PKB (protein kinase B) and mTOR phosphorylation (P < 0.05). mTOR signalling to its downstream effectors (S6 kinase 1 (S6K1) and 4E‐binding protein 1 (4E‐BP1) phosphorylation status) was also increased (P < 0.05). In addition, eukaryotic elongation factor 2 (eEF2) phosphorylation was significantly reduced (P < 0.05). Protein synthesis and cell signalling (phosphorylation status) was unchanged in the control group (P > 0.05).

We conclude that anabolic nutrients alter the phosphorylation status of both AMPK‐ and mTOR‐associated signalling proteins in human muscle, in association with an increase in protein synthesis not only via enhanced translation initiation but also through signalling promoting translation elongation.
Thermal stability of nonhydrogenated multilayer amorphous carbon prepared by the filtered cathodic vacuum arc technique
Authors: Teo Edwin H. T. , Lee M. L. , Lee C. K. , Ee C. L. , Tay B. K. , Chua Daniel H. C.
Published: May 2007

Through discrete modulation of the deposition biasing conditions, multilayered nonhydrogenated diamondlike amorphous carbon films were prepared by the filtered cathodic vacuum arc technique. Films deposited under different conditions were divided into two groups in order to study how the modulation as well as sublayer content affect various mechanical and material properties as deposited and after annealing in vacuum. A 30% decrease in the residual stress of the multilayer films from 4.3to2.8GPa was observed with only marginal (5%) changes in the hardness. The frictional characteristics of the multilayer films were also studied and shown to be excellent, having a coefficient of friction of 0.1 and stable with annealing. A larger decrease in the resistance to wear was observed in multilayer films richer in soft sublayers which was linked to the decreased in sp3 content in the films.
Infrared absorber for pyroelectric detectors
Authors: Thompson M. P. , Troxell J. R. , Murray M. E. , Thrush C. M. , Mantese J. V.
Published: May 2007

A quarter-wavelength absorber structure was developed for pyroelectric detector applications in the 2.5–3.5μm range. The absorber consisting of Pt and plasma-enhanced chemical vapor deposited SiO2 layers was fabricated using standard clean-room processes. It exhibited a minimum reflectance of 2%.
Electron and ion kinetics in magnetized capacitively coupled plasma source
Authors: Lee S. H. , You S. J. , Chang H. Y. , Lee J. K.
Published: May 2007

One-dimensional particle-in-cell Monte Carlo collision simulations of magnetized argon plasmas in an asymmetric capacitively coupled plasma reactor are presented. At low pressure (10mTorr), electron kinetics are strongly affected by the magnetic field and transitions from nonlocal to local kinetic property occur with increasing magnetic field which are reflected in spatially resolved calculations of the electron-energy probability function. For high-energy electrons, the transition takes place when the energy-relaxation length is smaller than the system length. For low-energy electrons, however, the transition occurs when the electron-diffusion time scale in the energy space is shorter than the spatial-diffusion time scale in coordinate space. These observations are in agreement with experimental data and theoretical calculations deduced from the Boltzmann equation. The ion energy distribution function (IEDF) on the driven electrode changes from the ion-neutral collisional type to the ion-neutral collisionless type with increasing magnetic field strength. The maximum ion energy in the IEDF decreases and the angular spread in the ion angle distribution function slightly increases with increasing magnetic field strength. These changes are explained in terms of the ratio of the ion-transit time to rf frequency, the sheath length, and the mean potential difference between the driven electrode and the plasma. At high pressure (218mTorr), electron-neutral collisions disrupt electron gyromotion so that the effects of the magnetic field on electron and ion kinetics are greatly reduced.
NiCr etching in a reactive gas
Authors: Ritter J. , Boucher R. , Morgenroth W. , Meyer H. G.
Published: May 2007

The authors have etched NiCr through a resist mask using Cl∕Ar based chemistry in an electron cyclotron resonance etch system. The optimum gas mixture and etch parameters were found for various ratios of Ni to Cr, based on the etch rate, redeposits, and the etch ratio to the mask. The introduction of O2 into the chamber, which is often used in the etching of Cr, served to both increase and decrease the etch rate depending explicitly on the etching parameters. Etch rates of >50nmmin−1 and ratios of >1 (NiCr:Mask) were achieved for NiCr (80:20). Pattern transfer from the mask into the NiCr was achieved with a high fidelity and without redeposits for a Cl∕Ar mix of 10% Ar (90%Cl2) at an etch rate of ≈50nmmin−1 and a ratio of 0.42 (NiCr:ZEP 7000 e-beam mask).
Zinc deposition experiments for validation of direct-simulation Monte Carlo calculations of rarefied internal gas flows
Authors: Dorsman R. , Kleijn C. R. , Velthuis J. F. M. , Zijp J. P. , van Mol A. M. B.
Published: May 2007

Specially designed experiments were performed for the validation of direct simulation Monte Carlo calculations of rarefied internal gas flows. Hot zinc vapor was released into a cold-wall deposition chamber filled with a background gas at low pressure in which two silicon wafers were mounted. The deposited zinc layers on these wafers have been measured in four different experiments, with varying background gas species (argon and helium) and background pressures (0.031–0.25Pa). The background gas conditions were chosen such that the Knudsen numbers based on the zinc mean free path range from 0.34 to 2.8. The experimental results have been compared to simulation results.
Mass fractionation of carbon and hydrogen secondary ions upon Cs+ and O2+ bombardment of organic materials
Authors: Harton Shane E. , Zhu Zhengmao , Stevie Frederick A. , Griffis Dieter P. , Ade Harald
Published: May 2007

A phenomenon known as mass fractionation has been probed in organic materials using secondary ion mass spectrometry (SIMS). Mass fractionation occurs because two isotopes of a particular species (i.e., identical number of protons, but different number of neutrons) do not have identical secondary ion yields in a constant chemical environment. Two primary ion probes, Cs+ and O2+, have been utilized with detection of negative and positive secondary ions, respectively, using a magnetic sector mass spectrometer. These two analysis conditions have been found to yield considerably different mass fractionation effects as a result of different sputtering and ionization mechanisms. Also, as determined previously with SIMS analysis of inorganic materials, the lower molecular weight species carbon and hydrogen are particularly susceptible to mass fractionation effects. Because organic materials are primarily composed of carbon and hydrogen, and because isotopic labeling is often utilized to accurately analyze such materials, knowledge of these effects in organic materials is essential for quantitative SIMS analysis.
Radiative wafer heating during plasma deposition process
Authors: Bosch R. C. M. , Kant C. H. , van Erven A. J. M. , Stals W. T. M. , Bijker M. D.
Published: May 2007

Wafer heating with visible and infrared radiation is a well established method used in plasma deposition reactors used for solar cell production. A detailed study on radiative heat transfer as presented in this article gives a quantitative description by considering the spectral absorption of radiation in optical components, contamination of these components during plasma growth, the spectral emissivity of the silicon solar cell, and the effect of heat buffer components. Even with a clever implementation of heaters the net power incident on the wafer is shown to decrease to 60%. The wafer temperature ramp up time is shown to be dependent on the surface roughness and dopant level of the silicon solar cell, whereas the steady-state temperature during plasma growth is independent on these properties. Due to contamination during plasma growth, the wafer temperature decreases by 80K within one production shift, but this decrease can be minimized to 10–20K by implementing heat buffer components.
Femtomolar isothermal desorption using microhotplate sensors
Authors: Shirke Amol G. , Cavicchi Richard E. , Semancik Steve , Jackson Robert H. , Frederick Brian G. , Clayton Wheeler M.
Published: May 2007

The authors describe a technique that utilizes the fast heating rates (106K∕s) of a microhotplate sensor along with a calibrated thermal desorption system to determine the initial coverage and kinetic parameters using isothermal desorption on a millisecond time scale. Models for isothermal desorption including both pumping and desorption rate effects are presented for zero, first, and second order kinetics. Analysis of the first order model illustrates the domain of the desorption, pumping speed, and heating rate time constants that permit the desorption parameters to be estimated from the mass spectrometer signal. The technique is demonstrated using isothermal temperature programed desorption of benzoic acid from a single SnO2 covered microhotplate at surface temperatures ranging from 296to347K. The data indicate that desorption is best represented by first order kinetics. The first order preexponential factor and the desorption energy in the zero coverage limit are determined to be 1×1017s−1 and 97kJ∕mol, respectively, from desorption of 108molecules which corresponds to an initial coverage of 1012cm−2 (⩽0.005 ML).
Enhancement of thermal stability of Ta∕Si(100) film by a Ta–Si interlayer
Authors: Ahn D. C. , Lee H. H. , Kim S. S. , Kim T. C. , Noh D. Y. , Kim D. H.
Published: May 2007

Thermal stability of Ta films grown on Si(100) was investigated by in situ x-ray scattering and ex situ cross-sectional transmission electron microscopy. As a Ta∕Si(100) film was annealed at around 500°C, a uniform Ta–Si interlayer was formed at the interface. This interlayer acts as a diffusion barrier. The Ta film with the interlayer is thermally stable up to 700°C. Meanwhile, Ta films directly annealed to above 640°C exhibit no interlayer formation and transform to randomly nucleated tantalum-silicide phases. Maintaining a uniform interlayer is a critical factor for enhancing thermal stability of Ta∕Si(100) films.
Compound semiconductor bonded to AlN heat spreader substrate using graded intermediate layer
Authors: Jagannadham K.
Published: May 2007

The present work illustrates a novel method of bonding compound semiconductor wafers to AlN or AlN/diamond heat spreaders using a graded intermediate layer. The procedure is illustrated using In–Ga solder to bond GaSb (111) wafer to commercial AlN substrate. Thermal conductivity of three bonded structures was evaluated using the 3-ω method. The experimental measurements of thermal conductivity of the multilayer were simulated using the analysis applicable to a layered structure. The results illustrate that the thin intermediate graded layer has a thermal conductivity above that of GaSb and therefore does not form an insulating layer. Bonding ZnO (002) wafer to commercial AlN substrate using zinc film that is subsequently oxidized is illustrated. The advantages of the graded intermediate layer to bond the heat spreaders such AlN or AlN/diamond are highlighted.
Effects of deposition parameters on the structure of AlN coatings grown by reactive magnetron sputtering
Authors: Khanna Atul , Bhat Deepak G.
Published: May 2007

AlN films were deposited on microscopy glass slide and silicon (111 orientation) substrates by reactive ac magnetron sputtering using two nitrogen concentrations and three discharge powers of 1.5, 2.5, and 5.0kW. X-ray diffraction studies showed that films prepared on glass and Si substrates were of hexagonal wurtizite phase. Films on Si substrates also contained small amounts of the cubic phase of AlN besides the predominantly hexagonal wurtizite phase. AlN coatings on glass substrates were textured towards the (00∙2) plane; this preferred orientation of crystals was found to decrease with increase in sputtering power. Scanning electron microscopy studies showed that AlN films prepared at higher nitrogen concentration have a microstructure consisting of pebblelike crystals, some of which were hexagonal in shape. The crystal size in the coatings increased with sputtering power and was in the range of 70–230nm.
Optimization of the incident angle in infrared spectroscopic ellipsometry: Spectra of C18-alkylthiol monolayers
Authors: Hu Z. G. , Hess P.
Published: May 2007

A detailed analysis of the features of C18-alkylthiol/gold (silver) spectra is presented to interpret the results obtained by infrared spectroscopic ellipsometry (IRSE). The interactions between neighboring vibrational bands, the effect of different incident angles, and the Berreman effect are discussed to clarify assignments, intensities, and shifts of absorption peaks. IRSE spectra of octadecanethiol self-assembled monolayers on gold and silver films were measured at different angles of incidence. The symmetric and asymmetric methylene and methyl stretching vibrations show no frequency variation with increasing angle of incidence of the IR beam. The relative tanΨf∕tanΨ0 spectral patterns are similar to those observed in infrared reflection-absorption spectroscopy. The results suggest that weak bands of organic films on metals can be treated with the Lorentz-oscillator model, taking into account the coincidence of parallel and perpendicular modes and the surface selection rule.
Quantifying the flux and spatial distribution of atomic hydrogen generated by a thermal source using atomic force microscopy to measure the chemical erosion of highly ordered pyrolytic graphite
Authors: Wnuk Joshua D. , Gorham Justin M. , Smith Billy A. , Shin Mi , Fairbrother D. Howard
Published: May 2007

A new method has been developed to quantify the flux and spatial distribution of atomic hydrogen (AH) produced from a thermal source. Experimentally, a partially masked highly ordered pyrolytic graphite (HOPG) substrate was chemically etched by AH under vacuum conditions. The resultant erosion profile (step edge) created on the HOPG substrate was analyzed ex situ with atomic force microscopy. By measuring the variation in the average step height as a function of exposure time, the AH source was shown to produce an average flux of 1.3×1017Hatoms∕scm2 at a source-sample distance of 3.5cm and a hydrogen pressure PH2 of 1.0×10−4Torr. Results demonstrating the ability of this method to measure the spatial distribution of AH flux on a solid substrate as well as the influence of different operating conditions on the average AH flux are also presented.
Resonant soft x-ray reflectivity of organic thin films
Authors: Wang Cheng , Araki Tohru , Watts Benjamin , Harton Shane , Koga Tadanori , Basu Saibal , Ade Harald
Published: May 2007

At photon energies close to absorption edges in the soft x-ray range, the complex index of refraction, n=1−δ−iβ, of organic materials varies rapidly as a function of photon energy in a manner that strongly depends on the chemical moieties and functionalities present in the material. The authors present details of how these molecular structure specific variations in the complex index of refraction can be utilized to enhance and tune the contrast in reflectivity experiments of organic films. This near edge contrast enhancement mimics the specific contrast achieved through deuterium labeling in neutron reflectivity (NR). This relatively new x-ray approach, resonant soft x-ray reflectivity (RSoXR), thus combines aspects of NR and conventional x-ray reflectivity (XR), yet does not require special chemical procedures. The capabilities of RSoXR are exemplified using a number of polymeric bi- and multilayers. Furthermore, a direct comparison of RSoXR to conventional x-ray reflectivity and NR for polystyrene and poly(methyl methacrylate) bilayers verifies that RSoXR is an excellent alternative tool for the characterization of organic thin films. The influence of the longitudinal and transverse coherence properties as well as the divergence of the x-ray or neutron beam on the capabilities and limitations of each reflectivity variant is discussed.
Dental-to-velar perceptual assimilation: A cross-linguistic study of the perception of dental stop+/l/ clusters
Authors: Hallé Pierre A. , Best Catherine T.
Published: May 2007

French listeners perceive illegal /tl/ and /dl/ clusters as legal /kl/ and /gl/, suggesting that /dl, tl/ undergo “phonotactic perceptual assimilation” to the phonetically most similar permissible clusters [Hallé et al., J. Exp. Psychol. Hum. Percept. Perform. (1998)]. However, without a comparison to native speakers of a language allowing initial /tl, dl/, other explanations remain open (e.g., universal phonetic biases). Experiment 1 compared native French and Hebrew listeners on perception of Hebrew /tl/-/kl/ and /dl/-/gl/. On a language-specific phonotactics account, these contrasts should be difficult for listeners whose language disallows initial /tl, dl/ while allowing /kl, gl/ (French), but not for listeners whose language permits all four clusters (Hebrew). Indeed, French but not Hebrew listeners showed difficulty discriminating /tl/-/kl/, and tended to categorize the initial consonant of /tl/ as /k/; analogous effects for /dl/-/gl/ were weaker. Experiment 2 tested speakers of American English, which also disallows initial /tl, dl/ but realizes stop-voicing differently than French or Hebrew, to examine possible contributions of language-specific phonetic settings. Their performance was similar to that of French listeners, though they had significantly greater difficulty with /dl-/gl/. The results support the proposal of language-specific phonotactic perceptual assimilation, with modest contributions from language-specific phonetic settings.
Scala vestibuli pressure and three-dimensional stapes velocity measured in direct succession in gerbil
Authors: Decraemer W. F. , de La Rochefoucauld O. , Dong W. , Khanna S. M. , Dirckx J. J. J. , Olson E. S.
Published: May 2007

It was shown that the mode of vibration of the stapes has a predominant piston component but rotations producing tilt of the footplate are also present. Tilt and piston components vary with frequency. Separately it was shown that the pressure gain between ear canal and scala vestibuli was a remarkably flat and smooth function of frequency. Is tilt functional contributing to the pressure in the scala vestibuli and helping in smoothing the pressure gain? In experiments on gerbil the pressure in the scala vestibuli directly behind the footplate was measured while recording simultaneously the pressure produced by the sound source in the ear canal. Successively the three-dimensional motion of the stapes was measured in the same animal. Combining the vibration measurements with an anatomical shape measurement from a micro-CT (CT: computed tomography) scan the piston-like motion and the tilt of the footplate was calculated and correlated to the corresponding scala vestibuli pressure curves. No evidence was found for the hypothesis that dips in the piston velocity are filled by peaks in tilt in a systematic way to produce a smooth middle ear pressure gain function. The present data allowed calculations of the individual cochlear input impedances.
The minimum glottal airflow to initiate vocal fold oscillation
Authors: Jiang Jack J. , Tao Chao
Published: May 2007

Phonation threshold flow (PTF) is proposed as a new aerodynamic parameter of the speech production system in this study. PTF is defined as the minimum airflow that can initiate stable vocal fold vibration. Because the glottal airflow can be noninvasively measured, it is suggested that the aerodynamic parameter PTF may be more practical for clinical vocal disease assessment. In order to investigate the relationship between PTF and phonatory system properties, the stability of the body-cover vocal fold model was analyzed. The study has theoretically shown that PTF is a sensitive aerodynamic parameter dependent on tissue properties, glottal configuration, and vocal tract loading. It was predicted that PTF can be reduced by decreasing tissue viscosity, decreasing mucosal wave velocity, increasing vocal fold thickness, or decreasing prephonatory glottal area. Furthermore, it was predicted that a divergent glottis or low vocal tract resistance lead to a reduced PTF. Also discussed is the potential significance of PTF in investigating the energy distribution in a vocal fold vibration system and related clinical applications.
Noise level correlates with manatee use of foraging habitats
Authors: Miksis-Olds Jennifer L. , Donaghay Percy L. , Miller James H. , Tyack Peter L. , Nystuen Jeffrey A.
Published: May 2007

The introduction of anthropogenic sound to coastal waters is a negative side effect of population growth. As noise from boats, marine construction, and coastal dredging increases, environmental and behavioral monitoring is needed to directly assess the effect these phenomena have on marine animals. Acoustic recordings, providing information on ambient noise levels and transient noise sources, were made in two manatee habitats: grassbeds and dredged habitats. Recordings were made over two 6-month periods from April to September in 2003 and 2004. Noise levels were calculated in one-third octave bands at nine center frequencies ranging from 250Hzto64kHz. Manatee habitat usage, as a function of noise level, was examined during four time periods: morning, noon, afternoon, and night. Analysis of sightings data in a variety of grassbeds of equal species composition and density indicate that manatees select grassbeds with lower ambient noise for frequencies below 1kHz. Additionally, grassbed usage was negatively correlated with concentrated boat presence in the morning hours; no correlation was observed during noon and afternoon hours. This suggests that morning boat presence and its associated noise may affect the use of foraging habitat on a daily time scale.
Diversity in ambient noise in European freshwater habitats: Noise levels, spectral profiles, and impact on fishes
Authors: Wysocki Lidia Eva , Amoser Sonja , Ladich Friedrich
Published: May 2007

The detectability of acoustic signals depends on the hearing abilities of receivers and the prevailing ambient noise in a given habitat. Ambient noise is inherent in all terrestrial and aquatic habitats and has the potential to severely mask relevant acoustic signals. In order to assess the detectability of sounds to fishes, the linear equivalent sound pressure levels (LLeq) of twelve European freshwater habitats were measured and spectra of the ambient noise recordings analyzed. Stagnant habitats such as lakes and backwaters are quiet, with noise levels below 100dB re 1μPa (LLeq) under no-wind conditions. Typically, most environmental noise is concentrated in the lower frequency range below 500Hz. Noise levels in fast-flowing waters were typically above 110dB and peaked at 135dB (Danube River in a free-flowing area). Contrary to stagnant habitats, high amounts of sound energy were present in the high frequency range above 1kHz, leaving a low-energy “noise window” below 1kHz. Comparisons between the habitat noise types presented here and prior data on auditory masking indicate that fishes with enhanced hearing abilities are only moderately masked in stagnant, quiet habitats, whereas they would be considerably masked in fast-flowing habitats.
Boundary element method for the acoustic characterization of a machine in bounded noisy environment
Authors: Langrenne Christophe , Melon Manuel , Garcia Alexandre
Published: May 2007

In this article, a boundary element method is used to recover free field conditions from noisy bounded space situations. The proposed approach is based on the Helmholtz integral formulation. The method requires the knowledge of double layer pressure fields on two parallel closed surfaces surrounding the source. First, the outgoing and ingoing pressure field are separated using Helmholtz integral. Then, the incident field scattered by the tested source is subtracted from the outgoing field to recover the pressure field which would have been radiated in free space. To simplify the process, rigid body approximation for the source is used. The method is numerically tested in the following conditions: the chosen sound source is the upper spherical cap of a rigid sphere, the source is located at the center of a rigid spherical cavity, and a monopole secondary source is added to blur the primary pressure field. Simulations give good results for ka up to 5 when the discretization of the surfaces is sufficient.
Perceptual rate normalization in naturally produced rate-varied speech
Authors: Nagao Kyoko , de Jong Kenneth
Published: May 2007

The perception of voicing categories is affected by speaking rate, so that listeners’ category boundaries on a VOT continuum shift to a lower value when syllable duration decreases [Miller and Volaitis, Percept. Psychophys. 46, 505–512 (1989); Volaitis and Miller, J. Acoust. Soc. Am. 92, 723–735 (1992)]. Previous rate normalization effects have been found using artificially varied stimuli. This study examines the effect of speech rate on voicing categorization in naturally produced rate-varied speech. The stimuli contained natural decreases in VOT with faster speech rates so that VOT values for /b/ and /p/ overlapped at the fastest rates. Consonant identification results showed that the rate effects on the perceptual boundary between /p/ and /b/ very closely matched the effects of rate on the productions, though there was a small mismatch with fast rate productions whereby voiced stops were systematically miscategorized as voiceless. Another group of listeners judged the goodness of the consonant, indicating that best exemplars were rate-varied and shifted away from the /p/-/b/ boundary. These results are discussed in light of exemplar-based and abstractionist models of speech perception.
Auditory short-term memory persistence for tonal signals in a songbird
Authors: Zokoll Melanie A. , Klump Georg M. , Langemann Ulrike
Published: May 2007

This paper presents an animal model for studying the persistence of auditory memory for tonal signals. Five European starlings (Sturnus vulgaris) were trained in a Go∕NoGo delayed nonmatching-to-sample task to discriminate between a series of identical “sample stimuli” and a single “test stimulus.” Frequencies of sample and test stimuli should be classified as being either the same or different. The performance of the birds is measured as the percentage of correct classifications. Three parameters were varied: The delay between sample and test stimuli, the number of sample stimuli presented before the test stimulus, and the salience of the difference between sample and test stimuli. Auditory memory persistence time was estimated as a function of the delay between the last sample stimulus and the test stimulus. The performance of the birds deteriorated with increasing delay before the test stimulus. Increasing the number of sample stimuli in the series of tones presented before the test stimulus improved performance. Performance was also better for more salient differences between sample and test stimuli. The individual auditory memory persistence time varied between 4 and 20s.
Acoustic propagation under tidally driven, stratified flow
Authors: Finette Steven , Oba Roger , Shen Colin , Evans Thomas
Published: May 2007

Amplitude and phase variability in acoustic fields are simulated within a canonical shelf-break ocean environment using sound speed distributions computed from hydrodynamics. The submesoscale description of the space and time varying environment is physically consistent with tidal forcing of stratified flows over variable bathymetry and includes the generation, evolution and propagation of internal tides and solibores. For selected time periods, two-dimensional acoustic transmission examples are presented for which signal gain degradation is computed between 200 and 500Hz on vertical arrays positioned both on the shelf and beyond the shelf break. Decorrelation of the field is dominated by the phase contribution and occurs over 2–3min, with significant recorrelation often noted for selected frequency subbands. Detection range is also determined in this frequency band. Azimuth-time variations in the acoustic field are illustrated for 100Hz sources by extending the acoustic simulations to three spatial dimensions. The azimuthal and temporal structure of both the depth-averaged transmission loss and temporal correlation of the acoustic fields under different environmental conditions are considered. Depth-averaged transmission loss varies up to 4dB, depending on a combination of source depth, location relative to the slope and tidally induced volumetric changes in the sound speed distribution.
A mechano-electro-acoustical model for the cochlea: Response to acoustic stimuli
Authors: Ramamoorthy Sripriya , Deo Niranjan V. , Grosh Karl
Published: May 2007

A linear, physiologically based, three-dimensional finite element model of the cochlea is developed. The model integrates the electrical, acoustic, and mechanical elements of the cochlea. In particular, the model includes interactions between structures in the organ of Corti (OoC), piezoelectric relations for outer hair cell (OHC) motility, hair bundle (HB) conductance that changes with HB deflection, current flow in the cross section and along the different scalae, and the feed-forward effect. The parameters in the model are based on guinea-pig data as far as possible. The model is vetted using a variety of experimental data on basilar membrane motion and data on voltages and currents in the OoC. Model predictions compare well, qualitatively and quantitatively, with experimental data on basilar membrane frequency response, impulse response, frequency glides, and scala tympani voltage. The close match of the model predictions with experimental data demonstrates the validity of the model for simulating cochlear response to acoustic input and for testing hypotheses of cochlear function. Analysis of the model and its results indicates that OHC somatic motility is capable of powering active amplification in the cochlea. At the same time, the model supports a possible synergistic role for HB motility in cochlear amplification.
Characteristics of whistles from resident bottlenose dolphins (Tursiops truncatus) in southern Brazil
Authors: Azevedo Alexandre F. , Oliveira Alvaro M. , Rosa L. Dalla , Lailson-Brito J.
Published: May 2007

Little is known of the whistles produced by bottlenose dolphins in the South Atlantic Ocean. A total of 788 whistles were recorded from free-ranging bottlenose dolphins in Patos Lagoon estuary, southern Brazil. The mean number of whistles emitted per minute per animal was 0.8. Bottlenose dolphins emitted a varied repertoire of whistles, in which those with more than one inflection point were the most frequent and there was no predominance of ascending or descending whistles. Whistles recorded had a great frequency range, between 1.2 and 22.3kHz. Whistle duration was 553.3 (±393.9ms) and 66.6% of the whistles lasted <800ms. Differences in the mean values of the whistles' characters were found between this study and other values previously reported for Tursiops. Bottlenose dolphins in the Patos Lagoon estuary emitted repeated whistle contours and individuals may be sharing some whistle types, as it has been suggested for Tursiops.
Acoustic signals of Chinese alligators (Alligator sinensis): Social communication
Authors: Wang Xianyan , Wang Ding , Wu Xiaobing , Wang Renping , Wang Chaolin
Published: May 2007

This paper reports the first systematic study of acoustic signals during social interactions of the Chinese alligator (Alligator sinensis). Sound pressure level (SPL) measurements revealed that Chinese alligators have an elaborate acoustic communication system with both long-distance signal—bellowing—and short-distance signals that include tooting, bubble blowing, hissing, mooing, head slapping and whining. Bellows have high SPL and appear to play an important role in the alligator’s long range intercommunion. Sounds characterized by low SPL are short-distance signals used when alligators are in close spatial proximity to one another. The signal spectrographic analysis showed that the acoustic signals of Chinese alligators have a very low dominant frequency, less than 500Hz. These frequencies are consistent with adaptation to a habitat with high density vegetation. Low dominant frequency sound attenuates less and could therefore cover a larger spatial range by diffraction in a densely vegetated environment relative to a higher dominant frequency sound.
Statistical voice activity detection based on integrated bispectrum likelihood ratio tests for robust speech recognition
Authors: Ramírez J. , Górriz J. M. , Segura J. C.
Published: May 2007

Currently, there are technology barriers inhibiting speech processing systems that work in extremely noisy conditions from meeting the demands of modern applications. These systems often require a noise reduction system working in combination with a precise voice activity detector (VAD). This paper shows statistical likelihood ratio tests formulated in terms of the integrated bispectrum of the noisy signal. The integrated bispectrum is defined as a cross spectrum between the signal and its square, and therefore a function of a single frequency variable. It inherits the ability of higher order statistics to detect signals in noise with many other additional advantages: (i) Its computation as a cross spectrum leads to significant computational savings, and (ii) the variance of the estimator is of the same order as that of the power spectrum estimator. The proposed approach incorporates contextual information to the decision rule, a strategy that has reported significant benefits for robust speech recognition applications. The proposed VAD is compared to the G.729, adaptive multirate, and advanced front-end standards as well as recently reported algorithms showing a sustained advantage in speech/nonspeech detection accuracy and speech recognition performance.
An efficient high-order algorithm for acoustic scattering from penetrable thin structures in three dimensions
Authors: Anand Akash , Reitich Fernando
Published: May 2007

This paper presents a high-order accelerated algorithm for the solution of the integral-equation formulation of volumetric scattering problems. The scheme is particularly well suited to the analysis of “thin” structures as they arise in certain applications (e.g., material coatings); in addition, it is also designed to be used in conjunction with existing low-order FFT-based codes to upgrade their order of accuracy through a suitable treatment of material interfaces. The high-order convergence of the new procedure is attained through a combination of changes of parametric variables (to resolve the singularities of the Green function) and “partitions of unity” (to allow for a simple implementation of spectrally accurate quadratures away from singular points). Accelerated evaluations of the interaction between degrees of freedom, on the other hand, are accomplished by incorporating (two-face) equivalent source approximations on Cartesian grids. A detailed account of the main algorithmic components of the scheme are presented, together with a brief review of the corresponding error and performance analyses which are exemplified with a variety of numerical results.
Biosonar signals impinging on the target during interception by big brown bats, Eptesicus fuscus
Authors: Saillant Prestor A. , Simmons James A. , Bouffard Frederick H. , Lee David N. , Dear Steven P.
Published: May 2007

Big brown bats (Eptesicus fuscus) were videotaped in the dark with a night-vision lens and infrared illumination while flying repeatedly along the same straight course to seize a tethered mealworm or a small electret microphone used to record biosonar signals impinging on the target. Bats emitted frequency-modulated sounds with first to third harmonics covering frequencies from 23to105kHz. As the bats neared the target, the first harmonic shifted lower in frequency while the third harmonic strengthened and the fourth harmonic, and sometimes the fifth harmonic, appeared. Incident-sound bandwidth remained broad throughout the maneuver, a feature not seen in field recordings of rapidly moving bats due to propagation losses and uncontrolled directional effects. Sound pressures at the microphone increased by about 20dB during approach from 2.5m down to 50cm and then leveled off, indicating that emitted amplitudes were approximately constant until the terminal stage, when they progressively decreased for the remainder of the maneuver. Interpulse intervals decreased from 80–100ms down to about 6–7ms and then stabilized throughout the terminal stage, while durations decreased smoothly from 3–4ms (limited by adjacent wall) down to 0.5ms during the terminal stage, which ended with capture.
Detection and localization of rib detachment in thin metal and composite plates by inversion of laser Doppler vibrometry scans
Authors: Romano Anthony J. , Bucaro Joseph A. , Vignola Joseph F. , Abraham Phillip B.
Published: May 2007

The laboratory implementation of a fault detection and localization method based on inversion of dynamic surface displacements measured by a scanned laser Doppler vibrometer (SLDV) was investigated. The technique uses flexural wave and generalized force inversion algorithms which have previously been demonstrated using simulated noise-free vibration data generated for thick plates with a finite element model. Here these inversion algorithms to SLDV measurements made in the laboratory on a thin nickel plate and a thin carbon fiber composite plate, both having attached reinforcing ribs with intentional de-bonding of the rib/plate interface at a specific location on each structure are applied. The inverted displacement maps clearly detect and locate the detachment, whereas direct observation of the surface displacements does not. It is shown that the technique is relatively robust to the choice of frequency and to the presence of noise.
Characterization of uncertainty in outdoor sound propagation predictions
Authors: Wilson D. Keith , Andreas Edgar L , Weatherly John W. , Pettit Chris L. , Patton Edward G. , Sullivan Peter P.
Published: May 2007

Predictive skill for outdoor sound propagation is assessed using high-resolution atmospheric fields from large-eddy simulations (LES). Propagation calculations through the full LES fields are compared to calculations through subsets of the LES fields that have been processed in typical ways, such as mean vertical profiles and instantaneous vertical profiles synchronized to the sound propagation. It is found that mean sound pressure levels can be predicted with low errors from the mean profiles, except in refractive shadow regions. Prediction of sound pressure levels for short-duration events is much less accurate, with errors of 8–10dB for near-ground propagation being typical.
Tone recognition in continuous Cantonese speech using supratone models
Authors: Qian Yao , Lee Tan , Soong Frank K.
Published: May 2007

This paper studies automatic tone recognition in continuous Cantonese speech. Cantonese is a major Chinese dialect that is known for being rich in tones. Tone information serves as a useful knowledge source for automatic speech recognition of Cantonese. Cantonese tone recognition is difficult because the tones have similar shapes of pitch contours. The tones are differentiated mainly by their relative pitch heights. In natural speech, the pitch level of a tone may shift up and down and the F0 ranges of different tones overlap with each other, making them acoustically indistinguishable within the domain of a syllable. Our study shows that the relative pitch heights are largely preserved between neighboring tones. A novel method of supratone modeling is proposed for Cantonese tone recognition. Each supratone model characterizes the F0 contour of two or three tones in succession. The tone sequence of a continuous utterance is formed as an overlapped concatenation of supratone units. The most likely tone sequence is determined under phonological constraints on syllable-tone combinations. The proposed method attains an accuracy of 74.68% in speaker-independent tone recognition experiments. In particular, the confusion among the tones with similar contour shapes is greatly resolved.