bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and Installation Aspects of the Kikeh TAD/SPAR Lashing System
Authors: Wan Jianan Jay , Edelson David , Chabot Luc
Published: January 2011

The Kikeh field, owned by Murphy and Petronas Carigali was the first time to use a Spar platform outside of the Gulf of Mexico and also the first time to use a semi-submersible Tender Assist Drilling Unit (TADU) for drilling along a Spar. This paper presents the design and installation aspects of the lashing system of the TADU and the Dry Tree Unit (DTU) Spar for the Kikeh project. The utilization of the TADU in the Kikeh field significantly reduces the weight and cost of the topsides of the Spar and increases the drilling efficiency. In the mean time it has posed a challenging job for the engineers to design the lashing system for the two floaters. This paper will discuss the TADU/DTU concept and benefits along with TADU lashing system design philosophy, design criteria and environment. Different phases of the design process will be discussed in detail, including concept selection, numerical analysis and model test. Several design concepts including the selected design and other alternatives will be explored with pros and cons of each concept explained. Characteristics of the two body motions and lashing tensions will be demonstrated. The selection of the nylon rope and hardware for the lashing system will be discussed. Analysis methodology and modeling of the TADU/DTU lashing system will be discussed. Model test results will be compared with the analytical predictions. Due to the complex nature of the systems and limitation of the analytical tools, model test served as an important tool in the design process. We will show how the results influenced the design of the gangway between the TADU and the DTU. The installation procedures of the TADU mooring and lashing systems will also be presented.
Electron field emission from a gold tip under laser irradiation at the plasmon-resonant wavelength
Authors: Iwami Kentaro , Iizuka Arata , Umeda Norihiro
Published: January 2011

Electron field emission properties of a sharp gold tip under continuous wave laser irradiation at the plasmon-resonant wavelength are investigated. A gold-coated tungsten emitter with a tip radius of 100 nm is used. The plasmon-resonant wavelength of the tip obtained by a finite-difference time-domain calculation is around 530 nm. Thus, I-V characteristics of the tip under laser irradiations at 442, 532, and 633 nm were measured. The intensity of 10 mW, 532 nm irradiation at the focal point was 13.9 kW/cm2. TE-polarized 532 nm irradiation shows the maximum current enhancement despite its smaller photon energy and intensity compared with the irradiation at 442 nm. The current enhancement factor ranged from 13.7 to 217. From the energy dispersive x-ray analysis, these results can be attributed to plasmon resonance. The possible mechanisms of plasmon-resonant current enhancement are considered to be the effective photoassisted field emission and thermal field emission.
Visible-light induced electron emission from carbon nanotube forests
Authors: Yaghoobi Parham , Moghaddam Mehran Vahdani , Michan Mario , Nojeh Alireza
Published: January 2011

The authors report electron emission from forests of vertically aligned multiwalled carbon nanotubes under irradiation by continuous wave green and blue lasers with relatively low power and intensity (maximum intensity of ∼320 W cm−2). The electron emission shows nonlinear increase with laser power for both laser wavelengths of 488 and 532 nm. Thermionic emission and photofield-emission appear to play a role in different sections of the current-voltage characteristics.
Interconnected alternating-current light-emitting diode arrays isolated by laser micromachining
Authors: Mak Giuseppe Y. , Lam Edmund Y. , Choi H. W.
Published: January 2011

The fabrication and operation of a monolithic InGaN alternating-current light-emitting diode (LED) based on the bridge rectifier design are demonstrated. The device consists of on-chip interconnected LED elements that have been isolated by direct-write laser micromachining, a powerful tool well-suited for rapid device prototyping. The effects of capacitors coupled to the dc path of the rectifier have been investigated. Although an increase of radiant flux can be achieved through capacitive voltage smoothening, the wall-plug efficiency drops as a result. The device can be applied to 12 Vrms lighting applications.
Effect of tonal native language on voice fundamental frequency responses to pitch feedback perturbations during sustained vocalizations
Authors: Liu Hanjun , Wang Emily Q. , Chen Zhaocong , Liu Peng , Larson Charles R. , Huang Dongfeng
Published: January 2011

The purpose of this cross-language study was to examine whether the online control of voice fundamental frequency (F0) during vowel phonation is influenced by language experience. Native speakers of Cantonese and Mandarin, both tonal languages spoken in China, participated in the experiments. Subjects were asked to vocalize a vowel sound /u/ at their comfortable habitual F0, during which their voice pitch was unexpectedly shifted (±50, ±100, ±200, or ±500 cents, 200 ms duration) and fed back instantaneously to them over headphones. The results showed that Cantonese speakers produced significantly smaller responses than Mandarin speakers when the stimulus magnitude varied from 200 to 500 cents. Further, response magnitudes decreased along with the increase in stimulus magnitude in Cantonese speakers, which was not observed in Mandarin speakers. These findings suggest that online control of voice F0 during vocalization is sensitive to language experience. Further, systematic modulations of vocal responses across stimulus magnitude were observed in Cantonese speakers but not in Mandarin speakers, which indicates that this highly automatic feedback mechanism is sensitive to the specific tonal system of each language.
Effects of the use of personal music players on amplitude modulation detection and frequency discrimination
Authors: Vinay S. N. , Moore Brian C. J.
Published: January 2011

Measures of auditory performance were compared for an experimental group who listened regularly to music via personal music players (PMP) and a control group who did not. Absolute thresholds were similar for the two groups for frequencies up to 2 kHz, but the experimental group had slightly but significantly higher thresholds at higher frequencies. Thresholds for the frequency discrimination of pure tones were measured for a sensation level (SL) of 20 dB and center frequencies of 0.25, 0.5, 1, 2, 3, 4, 5, 6, and 8 kHz. Thresholds were significantly higher (worse) for the experimental than for the control group for frequencies from 3 to 8 kHz, but not for lower frequencies. Thresholds for detecting sinusoidal amplitude modulation (AM) were measured for SLs of 10 and 20 dB, using four carrier frequencies 0.5, 3, 4, and 6 kHz, and three modulation frequencies 4, 16, and 50 Hz. Thresholds were significantly lower (better) for the experimental than for the control group for the 4- and 6-kHz carriers, but not for the other carriers. It is concluded that listening to music via PMP can have subtle effects on frequency discrimination and AM detection.
Force generation characteristics of standard heavyweight impact sources used in the sound generation of building floors
Authors: Park Buhm , Jeon Jin Yong , Park Junhong
Published: January 2011

Several heavyweight impact sources have been used in applying standardized excitation forces to evaluate the noise generation characteristics of building floors. In this study, heavyweight sources (a bang machine and an impact ball) were filmed with a high-speed camera on the period of deformation and restitution of the impact. The generated impact force was measured, and the effects of the taken deforming shapes were investigated. Experimental modal analysis was performed to determine the natural frequencies and mode shapes of the impact sources. With respect to deforming shapes during impacts, the influence of the mode shapes was clearly demonstrated, especially for the impact ball. Using the measured modal properties, the impact force was predicted and compared to the measured excitation force. By comparing the transient variation of the excitation force and its frequency spectrum, the influence of the modal characteristics of the source on the generated impact force was investigated.
The effects of external acoustic pressure fields on a free-running supercavitating projectile
Authors: Cameron Peter J. K. , Rogers Peter H. , Doane John W.
Published: January 2011

Proliferation of supercavitating torpedoes has motivated research on countermeasures against them as well as on the fluid phenomenon which makes them possible. The goal of this research was to investigate an envisaged countermeasure, an acoustic field capable of slowing or diverting the weapon by disrupting the cavitation envelope. The research focused on the interactions between high pressure amplitude sound waves and a supercavity produced by a small free-flying projectile. The flight dynamics and cavity geometry measurements were compared to control experiments and theoretical considerations were made for evaluating the effects. Corrugations on the cavity/water interface caused by the pressure signal have been observed and characterized. Results also show that the accuracy of a supercavitating projectile can be adversely affected by the sound signal. This research concludes with results that indicate that it is acoustic cavitation in the medium surrounding the supercavity, caused by the high pressure amplitude sound, that is responsible for the reduced accuracy. A hypothesis has been presented addressing the means by which the acoustic cavitation could cause this effect.
Sound transmission through finite lightweight multilayered structures with thin air layers
Authors: Dijckmans A. , Vermeir G. , Lauriks W.
Published: January 2011

The sound transmission loss (STL) of finite lightweight multilayered structures with thin air layers is studied in this paper. Two types of models are used to describe the vibro-acoustic behavior of these structures. Standard transfer matrix method assumes infinite layers and represents the plane wave propagation in the layers. A wave based model describes the direct sound transmission through a rectangular structure placed between two reverberant rooms. Full vibro-acoustic coupling between rooms, plates, and air cavities is taken into account. Comparison with double glazing measurements shows that this effect of vibro-acoustic coupling is important in lightweight double walls. For infinite structures, structural damping has no significant influence on STL below the coincidence frequency. In this frequency region, the non-resonant transmission or so-called mass-law behavior dominates sound transmission. Modal simulations suggest a large influence of structural damping on STL. This is confirmed by experiments with double fiberboard partitions and sandwich structures. The results show that for thin air layers, the damping induced by friction and viscous effects at the air gap surfaces can largely influence and improve the sound transmission characteristics.
Dynamic acoustoelastic testing of weakly pre-loaded unconsolidated water-saturated glass beads
Authors: Renaud Guillaume , Callé Samuel , Defontaine Marielle
Published: January 2011

Dynamic acoustoelastic testing is applied to weakly pre-loaded unconsolidated water-saturated glass beads. The gravitational acceleration produces, on the probed beads, a static stress of order 130 Pa, thus the granular medium is close to the jamming transition. A low-frequency (LF) acoustic wave gently disturbs the medium, inducing successively slight expansion and compaction of the granular packing expected to modulate the number of contacts between beads. Ultrasound (US) pulses are emitted simultaneously to dynamically detect the induced modification of the granular skeleton. US propagation velocity and attenuation both increase when the LF pressure increases. The quadratic nonlinear elastic parameter β, related to the pressure dependence of US propagation velocity, was measured in the range 60–530 if water-saturated glass beads are considered as an effective medium. A dynamic modification of US scattering induced by beads is proposed to modulate US attenuation. Complex hysteretic behaviors and tension-compression asymmetry are also observed and analyzed by time-domain and spectral analyses. Furthermore acoustic nonlinearities are measured in cases of quasi-static and dynamic variations of the LF wave amplitude, providing quantitatively similar acoustic nonlinearities but qualitatively different.
Analysis of a simplified normalized covariance measure based on binary weighting functions for predicting the intelligibility of noise-suppressed speech
Authors: Chen Fei , Loizou Philipos C.
Published: January 2011

The normalized covariance measure (NCM) has been shown previously to predict reliably the intelligibility of noise-suppressed speech containing non-linear distortions. This study analyzes a simplified NCM measure that requires only a small number of bands (not necessarily contiguous) and uses simple binary (1 or 0) weighting functions. The rationale behind the use of a small number of bands is to account for the fact that the spectral information contained in contiguous or nearby bands is correlated and redundant. The modified NCM measure was evaluated with speech intelligibility scores obtained by normal-hearing listeners in 72 noisy conditions involving noise-suppressed speech corrupted by four different types of maskers (car, babble, train, and street interferences). High correlation (r = 0.8) was obtained with the modified NCM measure even when only one band was used. Further analysis revealed a masker-specific pattern of correlations when only one band was used, and bands with low correlation signified the corresponding envelopes that have been severely distorted by the noise-suppression algorithm and/or the masker. Correlation improved to r = 0.84 when only two disjoint bands (centered at 325 and 1874 Hz) were used. Even further improvements in correlation (r = 0.85) were obtained when three or four lower-frequency (<700 Hz) bands were selected.
Real-time near-field acoustic holography for continuously visualizing nonstationary acoustic fields
Authors: Thomas J.-H. , Grulier V. , Paillasseur S. , Pascal J.-C. , Le Roux J.-C.
Published: January 2011

Near-field acoustic holography (NAH) is an effective tool for visualizing acoustic sources from pressure measurements made in the near-field of sources using a microphone array. The method involving the Fourier transform and some processing in the frequency-wavenumber domain is suitable for the study of stationary acoustic sources, providing an image of the spatial acoustic field for one frequency. When the behavior of acoustic sources fluctuates in time, NAH may not be used. Unlike time domain holography or transient method, the method proposed in the paper needs no transformation in the frequency domain or any assumption about local stationary properties. It is based on a time formulation of forward sound prediction or backward sound radiation in the time-wavenumber domain. The propagation is described by an analytic impulse response used to define a digital filter. The implementation of one filter in forward propagation and its inverse to recover the acoustic field on the source plane implies by simulations that real-time NAH is viable. Since a numerical filter is used rather than a Fourier transform of the time-signal, the emission on a point of the source may be rebuilt continuously and used for other post-processing applications.
Temporal envelope compensation for robust phoneme recognition using modulation spectrum
Authors: Ganapathy Sriram , Thomas Samuel , Hermansky Hynek
Published: January 2011

A robust feature extraction technique for phoneme recognition is proposed which is based on deriving modulation frequency components from the speech signal. The modulation frequency components are computed from syllable-length segments of sub-band temporal envelopes estimated using frequency domain linear prediction. Although the baseline features provide good performance in clean conditions, the performance degrades significantly in noisy conditions. In this paper, a technique for noise compensation is proposed where an estimate of the noise envelope is subtracted from the noisy speech envelope. The noise compensation technique suppresses the effect of additive noise in speech. The robustness of the proposed features is further enhanced by the gain normalization technique. The normalized temporal envelopes are compressed with static (logarithmic) and dynamic (adaptive loops) compression and are converted into modulation frequency features. These features are used in an automatic phoneme recognition task. Experiments are performed in mismatched train/test conditions where the test data are corrupted with various environmental distortions like telephone channel noise, additive noise, and room reverberation. Experiments are also performed on large amounts of real conversational telephone speech. In these experiments, the proposed features show substantial improvements in phoneme recognition rates compared to other speech analysis techniques. Furthermore, the contribution of various processing stages for robust speech signal representation is analyzed.
Spatial perception and adaptive sonar behavior
Authors: Aytekin Murat , Mao Beatrice , Moss Cynthia F.
Published: January 2011

Bat echolocation is a dynamic behavior that allows for real-time adaptations in the timing and spectro-temporal design of sonar signals in response to a particular task and environment. To enable detailed, quantitative analyses of adaptive sonar behavior, echolocation call design was investigated in big brown bats, trained to rest on a stationary platform and track a tethered mealworm that approached from a starting distance of about 170 cm in the presence of a stationary sonar distracter. The distracter was presented at different angular offsets and distances from the bat. The results of this study show that the distance and the angular offset of the distracter influence sonar vocalization parameters of the big brown bat, Eptesicus fuscus. Specifically, the bat adjusted its call duration to the closer of two objects, distracter or insect target, and the magnitude of the adjustment depended on the angular offset of the distracter. In contrast, the bat consistently adjusted its call rate to the distance of the insect, even when this target was positioned behind the distracter. The results hold implications for understanding spatial information processing and perception by echolocation.
Nonlinear propagation of spark-generated N-waves in air: Modeling and measurements using acoustical and optical methods
Authors: Yuldashev Petr , Ollivier Sébastien , Averiyanov Mikhail , Sapozhnikov Oleg , Khokhlova Vera , Blanc-Benon Philippe
Published: January 2011

The propagation of nonlinear spherically diverging N-waves in homogeneous air is studied experimentally and theoretically. A spark source is used to generate high amplitude (1.4 kPa) short duration (40 μs) N-waves; acoustic measurements are performed using microphones (3 mm diameter, 150 kHz bandwidth). Numerical modeling with the generalized Burgers equation is used to reveal the relative effects of acoustic nonlinearity, thermoviscous absorption, and oxygen and nitrogen relaxation on the wave propagation. The results of modeling are in a good agreement with the measurements in respect to the wave amplitude and duration. However, the measured rise time of the front shock is ten times longer than the calculated one, which is attributed to the limited bandwidth of the microphone. To better resolve the shock thickness, a focused shadowgraphy technique is used. The recorded optical shadowgrams are compared with shadow patterns predicted by geometrical optics and scalar diffraction model of light propagation. It is shown that the geometrical optics approximation results in overestimation of the shock rise time, while the diffraction model allows to correctly resolve the shock width. A combination of microphone measurements and focused optical shadowgraphy is therefore a reliable way of studying evolution of spark-generated shock waves in air.
A two-dimensional cochlear fluid model based on conformal mapping
Authors: Lüling Hannes , Franosch Jan-Moritz P. , Leo van Hemmen J.
Published: January 2011

Using conformal mapping, fluid motion inside the cochlear duct is derived from fluid motion in an infinite half plane. The cochlear duct is represented by a two-dimensional half-open box. Motion of the cochlear fluid creates a force acting on the cochlear partition, modeled by damped oscillators. The resulting equation is one-dimensional, more realistic, and can be handled more easily than existing ones derived by the method of images, making it useful for fast computations of physically plausible cochlear responses. Solving the equation of motion numerically, its ability to reproduce the essential features of cochlear partition motion is demonstrated. Because fluid coupling can be changed independently of any other physical parameter in this model, it allows the significance of hydrodynamic coupling of the cochlear partition to itself to be quantitatively studied. For the model parameters chosen, as hydrodynamic coupling is increased, the simple resonant frequency response becomes increasingly asymmetric. The stronger the hydrodynamic coupling is, the slower the velocity of the resulting traveling wave at the low frequency side is. The model’s simplicity and straightforward mathematics make it useful for evaluating more complicated models and for education in hydrodynamics and biophysics of hearing.
Effects of differences in fundamental frequency on across-formant grouping in speech perception
Authors: Summers Robert J. , Bailey Peter J. , Roberts Brian
Published: January 2011

In an isolated syllable, a formant will tend to be segregated perceptually if its fundamental frequency (F0) differs from that of the other formants. This study explored whether similar results are found for sentences, and specifically whether differences in F0 (ΔF0) also influence across-formant grouping in circumstances where the exclusion or inclusion of the manipulated formant critically determines speech intelligibility. Three-formant (F1 + F2 + F3) analogues of almost continuously voiced natural sentences were synthesized using a monotonous glottal source (F0 = 150 Hz). Perceptual organization was probed by presenting stimuli dichotically (F1 + F2C + F3; F2), where F2C is a competitor for F2 that listeners must resist to optimize recognition. Competitors were created using time-reversed frequency and amplitude contours of F2, and F0 was manipulated (ΔF0 = ±8, ±2, or 0 semitones relative to the other formants). Adding F2C typically reduced intelligibility, and this reduction was greatest when ΔF0 = 0. There was an additional effect of absolute F0 for F2C, such that competitor efficacy was greater for higher F0s. However, competitor efficacy was not due to energetic masking of F3 by F2C. The results are consistent with the proposal that a grouping “primitive” based on common F0 influences the fusion and segregation of concurrent formants in sentence perception.
A mode matching method for modeling dissipative silencers lined with poroelastic materials and containing mean flow
Authors: Nennig Benoit , Perrey-Debain Emmanuel , Ben Tahar Mabrouk
Published: January 2011

A mode matching method for predicting the transmission loss of a cylindrical shaped dissipative silencer partially filled with a poroelastic foam is developed. The model takes into account the solid phase elasticity of the sound-absorbing material, the mounting conditions of the foam, and the presence of a uniform mean flow in the central airway. The novelty of the proposed approach lies in the fact that guided modes of the silencer have a composite nature containing both compressional and shear waves as opposed to classical mode matching methods in which only acoustic pressure waves are present. Results presented demonstrate good agreement with finite element calculations provided a sufficient number of modes are retained. In practice, it is found that the time for computing the transmission loss over a large frequency range takes a few minutes on a personal computer. This makes the present method a reliable tool for tackling dissipative silencers lined with poroelastic materials.
Auditory masking of a 10 kHz tone with environmental, comodulated, and Gaussian noise in bottlenose dolphins (Tursiops truncatus)
Authors: Trickey Jennifer S. , Branstetter Brian K. , Finneran James J.
Published: January 2011

The pattern of auditory masking derived from Gaussian noise is often cited and used to predict the detrimental effects of masking noise on marine mammals. However, environmental noise (both anthropogenic and natural) may not always be Gaussian distributed. Some noise sources are highly structured with complex amplitude fluctuations that extend across frequency regions, which are often termed comodulated noise. Recent evidence with bottlenose dolphins using comodulated noise demonstrated a significant release from masking compared to Gaussian maskers of the same bandwidth and pressure spectral density level, a result known as comodulation masking release. The present study demonstrates a pattern of masking where both temporally fluctuating comodulated noise and environmental noise produce lower masked thresholds compared to Gaussian noise of the same spectral density level and bandwidth. Furthermore, a threshold reduction or “masking release” occurred when the environmental noise bandwidth increased beyond a critical band. These results provide further evidence that conventional models of auditory masking using Gaussian maskers (i.e., the power spectrum model) do not fully describe the masking effects that occur in realistic environments.
Monitoring underwater explosions in the habitat of resident bottlenose dolphins
Authors: dos Santos Manuel E. , Couchinho Miguel N. , Rita Luís Ana , Gonçalves Emanuel J.
Published: January 2011

Maintenance work on the harbor of Setúbal, in Portugal, required the removal of a 14-m deep rocky outcrop at the ship maneuver area, using about 35 kg of Gelamonite, a nitroglycerin-based high-explosive. This important harbor is located in the Sado estuary, a biologically rich environment and an important feeding area for a resident community of bottlenose dolphins. Using different safe range calculation models, a mitigation and monitoring plan was developed that minimized the risks of these underwater explosions for the dolphins. At our monitoring station, at 2 km from the demolition site, acoustic pressure levels in excess of 170 dB re 1 μPa (root-mean-square) were measured. Samples of dead fish collected at the site were indicative of shock trauma from the blasts.
Processing strategies of the auditory system for improving the detection of masked signals
Authors: Epp Bastian
Published: January 2011

The processing of the auditory system allows the separation of complex acoustical scenes into so-called auditory objects. The goal of this thesis was to shed some light on the ability of the auditory system to use combined across-frequency and binaural cues for the analysis of complex auditory environments. The first and second part of the thesis addresses the investigation of the processing of combined across-frequency and binaural signal properties in normally hearing listeners using psychoacoustical techniques and signal processing strategies. The third part concentrates on the influence of cochlear processing on psychoacoustic effects using a physical nonlinear and active model of the cochlea. The results of this thesis point out that the auditory system is able to process comodulation across frequency and interaural phase differences independently and over a broad frequency range. Hence, improvements of masked thresholds can be used in an optimal manner. The ability of the developed cochlea model to account for psychoacoustical data provides the basis to separate peripheral contributions to psychoacoustical effects from neural contributions. Contact: Bastian.Epp@uni-oldenburg.de.
Sex-related differences in vocal responses to pitch feedback perturbations during sustained vocalization
Authors: Chen Zhaocong , Liu Peng , Jones Jeffery A. , Huang Dongfeng , Liu Hanjun
Published: January 2011

The present study assessed the effect of sex on voice fundamental frequency (F0) responses to pitch feedback perturbations during sustained vocalization. Sixty-four native-Mandarin speakers heard their voice pitch feedback shifted at ±50, ±100, or ±200 cents for 200 ms, five times during each vocalization. The results showed that, as compared to female speakers, male speakers produced significantly larger but slower vocal responses to the pitch-shifted stimuli. These findings reveal a modulation of vocal response as a function of sex, and suggest that there may be a differential processing of vocal pitch feedback perturbations between men and women.
A representation for Green’s function retrieval by multidimensional deconvolution
Authors: Wapenaar Kees , van der Neut Joost
Published: January 2011

Green’s function retrieval by crosscorrelation may suffer from irregularities in the source distribution, asymmetric illumination, intrinsic losses, etc. Multidimensional deconvolution (MDD) may overcome these limitations. A unified representation for Green’s function retrieval by MDD is proposed. From this representation, it follows that the traditional crosscorrelation method gives a Green’s function of which the source is smeared in space and time. This smearing is quantified by a space–time point-spread function (PSF), which can be retrieved from measurements at an array of receivers. MDD removes this PSF and thus deblurs and deghosts the source of the Green’s function obtained by correlation.
Long-range multi-carrier acoustic communications in shallow water based on iterative sparse channel estimation
Authors: Kang Taehyuk , Song H. C. , Hodgkiss W. S. , Soo Kim Jea
Published: January 2011

Long-range orthogonal frequency division multiplexing (OFDM) acoustic communications is demonstrated using data from the Kauai Acomms MURI 2008 (KAM08) experiment carried out in about 106 m deep shallow water west of Kauai, HI, in June 2008. The source bandwidth was 8 kHz (12–20 kHz), and the data were received by a 16-element vertical array at a distance of 8 km. Iterative sparse channel estimation is applied in conjunction with low-density parity-check decoding. In addition, the impact of diversity combining in a highly inhomogeneous underwater environment is investigated. Error-free transmission using 16-quadtrative amplitude modulation is achieved at a data rate of 10 kb/s.
Signaling by Neuronal Swelling
Authors: Fields R. Douglas
Published: January 2011

Physical changes associated with the electrical activity of neurons mediate intercellular signaling.
Combination Therapy with Paromomycin-Associated Stearylamine-Bearing Liposomes Cures Experimental Visceral Leishmaniasis through Th1-Biased Immunomodulation
Authors: Banerjee Antara , De Manjarika , Ali Nahid
Published: January 2011

Visceral leishmaniasis (VL) caused by the parasiteLeishmania donovaniis a potentially fatal disease. Available limited drugs are toxic, require prolonged treatment duration, and are costly. A low-cost parenteral formulation of paromomycin sulfate (PM) has recently been approved for the treatment of VL. Monotherapy with PM runs the risk of development of resistance. Hence, efforts are needed to develop a combination therapy of PM with other drugs to shorten the duration of treatment and prolong the effective life of the drug. PM was formulated with leishmanicidal stearylamine (SA)-bearing phosphatidylcholine (PC) liposomes for low-dose therapy.In vitroandin vivoantileishmanial effects of the combination drug were determined. The immunomodulatory role of PC-SA-PM was determined using enzyme-linked immunosorbent assay (ELISA) and flow cytometry. Excluding the spleen, for which the therapeutic effect was additive, a remarkable synergistic activity toward cure and prophylaxis with a single-shot low-dose treatment with PC-SA-associated PM was achieved with BALB/c mice. PC-SA-PM showed an immunomodulatory effect on CD4+and CD8+T cells for gamma interferon (IFN-γ) production and downregulated disease-associated interleukin-10 (IL-10) and transforming growth factor β (TGF-β) to almost negligible levels. Such combination chemotherapy may provide a promising alternative for the cure of leishmaniasis, with a plausible conversion of the host immune response from a disease-promoting pattern to a Th1-biased response indicative of long-term resistance.
Antimicrobial Resistance in More than 100,000
Escherichia coli
Isolates According to Culture Site and Patient Age, Gender, and Location
Authors: Sahuquillo-Arce José Miguel , Selva María , Perpiñán Hèctor , Gobernado Miguel , Armero Carmen , López-Quílez Antonio , González Francisco , Vanaclocha Hermelinda
Published: January 2011

Escherichia coli
and the antimicrobial pressure exerted on this microorganism can be modulated by factors dependent on the host. In this paper, we describe the distribution of antimicrobial resistance to amikacin, tobramycin, ampicillin, amoxicillin clavulanate, cefuroxime, cefoxitin, cefotaxime, imipenem, ciprofloxacin, fosfomycin, nitrofurantoin, and trimetoprim-sulfametoxazole in more than 100,000
E. coli
isolates according to culture site and patient age, gender, and location. Bayesian inference was planned in all statistical analysis, and Markov chain Monte Carlo simulation was employed to estimate the model parameters. Our findings show the existence of a marked difference in the susceptibility to several antimicrobial agents depending on from where
E. coli
was isolated, with higher levels of resistance in isolates from medical devices, the respiratory system, and the skin and soft tissues; a higher resistance percentage in men than in women; and the existence of a clear difference in antimicrobial resistance with an age influence that cannot be explained merely by means of an increase of resistance after exposure to antimicrobials. Both men and women show increases in resistance with age, but while women show constant levels of resistance or slight increases during childbearing age and greater increases in the premenopausal age, men show a marked increase in resistance in the pubertal age. In conclusion, an overwhelming amount of data reveals the great adaptation capacity of
E. coli
and its close interaction with the host. Sex, age, and the origin of infection are determining factors with the ability to modulate antimicrobial resistances.
Therapeutic Efficacy of Halocidin-Derived Peptide HG1 in a Mouse Model of Surgical Wound Infection with Methicillin-Resistant
Staphylococcus aureus
Authors: Lee Young Shin , Shin Yong Pyo , Shin Seo Hwa , Park Seungmi , Kim Myung Hwa , Lee In Hee
Published: January 2011

We evaluated the therapeutic potential of HG1, an antimicrobial peptide, as a novel topical antibiotic by the use of a mouse surgical wound model of infection with methicillin-resistant
Staphylococcus aureus
. First, we attempted to determine whether or not HG1 infiltrated into the dermis when topically administered. Second, we evaluated the antibiotic effects of HG1 on skin infection via bacterial-enumeration and microscopic analyses. The results showed that topically administered HG1 was capable of penetrating into the dermis at the infection site, where it exerted its antimicrobial effects.
Panton-Valentine Leukocidin-Positive and Toxic Shock Syndrome Toxin 1-Positive Methicillin-Resistant
Staphylococcus aureus
: a French Multicenter Prospective Study in 2008
Authors: Robert Jérôme , Tristan Anne , Cavalié Laurent , Decousser Jean-Winoc , Bes Michèle , Etienne Jerome , Laurent Frédéric
Published: January 2011

The epidemiology of community-acquired methicillin-resistant
Staphylococcus aureus
(CA-MRSA) differs from country to country. We assess the features of the ST80 European clone, which is the most prevalent PVL-positive CA-MRSA clone in Europe, and the TSST-1 ST5 clone that was recently described in France. In 2008, all MRSA strains susceptible to fluoroquinolones and gentamicin and resistant to fusidic acid that were isolated in 104 French laboratories were characterized using
agr
alleles,
spa
typing, and the staphylococcal cassette chromosome
mec
element and PCR profiling of 21 toxin genes. Three phenotypes were defined: (i) kanamycin resistant, associated with the ST80 clone; (ii) kanamycin and tobramycin resistant, associated with the ST5 clone; and (iii) aminoglycoside susceptible, which was less frequently associated with the ST5 clone. Among the 7,253 MRSA strains isolated, 91 (1.3%) were ST80 CA-MRSA (89 phenotype 1) and 190 (2.6%) were ST5 CA-MRSA (146 phenotype 2, 42 phenotype 3). Compared to the latter, ST80 CA-MRSAs were more likely to be community acquired (80% versus 46%) and found in young patients (median age, 26.0 years versus 49.5 years) with deep cutaneous infections (48% versus 6%). They were less likely to be tetracycline susceptible (22% versus 85%) and to be isolated from respiratory infections (6% versus 27%). The TSST-1 ST5 clone has rapidly emerged in France and has become even more prevalent than the ST80 European clone, whose prevalence has remained stable. The epidemiological and clinical patterns of the two clones differ drastically. Given the low prevalence of both among all staphylococcal infections, no modification of antibiotic recommendations is required yet.
Efficacy of the New Lantibiotic NAI-107 in Experimental Infections Induced by Multidrug-Resistant Gram-Positive Pathogens
Authors: Jabés Daniela , Brunati Cristina , Candiani GianPaolo , Riva Simona , Romanó Gabriella , Donadio Stefano
Published: January 2011

NAI-107 is a novel lantibiotic active against Gram-positive bacteria, including methicillin-resistant
Staphylococcus aureus
(MRSA), glycopeptide-intermediate
S. aureus
(GISA), and vancomycin-resistant enterococci (VRE). The aim of this study was to evaluate the
in vivo
efficacy of NAI-107 in animal models of severe infection. In acute lethal infections induced with a penicillin-intermediate
Streptococcus pneumoniae
strain in immunocompetent mice, or with MRSA, GISA, and VRE strains in neutropenic mice, the 50% effective dose (ED
50
) values of NAI-107 were comparable or lower than those of reference compounds, irrespective of the strain and immune status (0.51 to 14.2 mg/kg of body weight for intravenous [i.v.] NAI-107, 5.1 to 22.4 for oral linezolid, and 22.4 for subcutaneous [s.c.] vancomycin). In
t
he granuloma pouch model induced in rats with a MRSA strain, intravenous NAI-107 showed a dose-proportional bactericidal activity that, at a single 40-mg/kg dose, compared with 2 20-mg/kg doses at a 12-h or 24-h interval, caused a 3-log
10
-CFU/ml reduction of viable MRSA in exudates that persisted for more than 72 h. Rat endocarditis was induced with a MRSA strain and treated for five consecutive days. In a first experiment, using 5, 10, or 20 mg/kg/day, and in a second experiment, when 10 mg/kg at 12-h intervals was compared to 20 mg/kg/day, intravenous NAI-107 was effective in reducing the bacterial load in heart vegetations in a dose-proportional manner. Trough plasma levels, as determined on days 2 and 5, were several times higher than the NAI-107 minimal bactericidal concentration (MBC). NAI-107 binding to rat and human serum ranges between 93% and 98.6%. The rapid bactericidal activity of NAI-107 observed
in vitro
was thus confirmed by the efficacy in several models of experimental infection induced by Gram-positive pathogens, supporting further investigation of the compound.
In Vitro
Antibacterial Activity of Modithromycin, a Novel 6,11-Bridged Bicyclolide, against Respiratory Pathogens, Including Macrolide-Resistant Gram-Positive Cocci
Authors: Sato Takafumi , Tateda Kazuhiro , Kimura Soichiro , Iwata Morihiro , Ishii Yoshikazu , Yamaguchi Keizo
Published: January 2011

The
in vitro
activities of modithromycin against Gram-positive and -negative respiratory pathogens, including macrolide-resistant cocci with different resistance mechanisms, were compared with those of other macrolide and ketolide agents. MICs were determined by the broth microdilution method. All 595 test strains used in this study were isolated from Japanese medical facilities. The
erm
(ribosome methylase) and/or
mef
(efflux pump) gene, which correlated with resistance to erythromycin as well as clarithromycin and azithromycin, was found in 81.8%, 21.3%, and 23.2% of
Streptococcus pneumoniae
,
Streptococcus pyogenes
, and methicillin-susceptible
Staphylococcus aureus
(MSSA) strains, respectively. Modithromycin showed MIC
90
s of 0.125 μg/ml against these three cocci, including macrolide-resistant strains. In particular, the MIC of modithromycin against
ermB
-carrying
S. pyogenes
was ≥32-fold lower than that of telithromycin. The activities of modithromycin as well as telithromycin were little affected by the presence of
mefA
or
mefE
in both streptococci. Against Gram-negative pathogens, modithromycin showed MIC
90
s of 0.5, 8, and 0.031 μg/ml against
Moraxella catarrhalis
,
Haemophilus influenzae
, and
Legionella
spp., respectively. The MICs of modithromycin against
M. catarrhalis
and
H. influenzae
were higher than those of telithromycin and azithromycin. However, modithromycin showed the most potent anti-
Legionella
activity among the macrolide and ketolide agents tested. These results suggested that the bicyclolide agent modithromycin is a novel class of macrolides with improved antibacterial activity against Gram-positive cocci, including telithromycin-resistant streptococci and intracellular Gram-negative bacteria of the
Legionella
species.
Resolution of
Staphylococcus aureus
Biofilm Infection Using Vaccination and Antibiotic Treatment
Authors: Brady Rebecca A. , O'May Graeme A. , Leid Jeff G. , Prior Megan L. , Costerton J. William , Shirtliff Mark E.
Published: January 2011

Staphylococcus aureus
infections, particularly those from methicillin-resistant strains (i.e., MRSA), are reaching epidemic proportions, with no effective vaccine available. The vast number and transient expression of virulence factors in the infectious course of this pathogen have made the discovery of protective antigens particularly difficult. In addition, the divergent planktonic and biofilm modes of growth with their accompanying proteomic changes also demonstrate significant hindrances to vaccine development. In this study, a multicomponent vaccine was evaluated for its ability to clear a staphylococcal biofilm infection. Antigens (glucosaminidase, an ABC transporter lipoprotein, a conserved hypothetical protein, and a conserved lipoprotein) were chosen since they were found in previous studies to have upregulated and sustained expression in a biofilm, both
in vitro
and
in vivo
. Antibodies against these antigens were first used in microscopy studies to localize their expression in
in vitro
biofilms. Each of the four antigens showed heterogeneous production in various locations within the complex biofilm community in the biofilm. Based upon these studies, the four antigens were delivered simultaneously as a quadrivalent vaccine in order to compensate for this varied production. In addition, antibiotic treatment was also administered to clear the remaining nonattached planktonic cells since the vaccine antigens may have been biofilm specific. The results demonstrated that when vaccination was coupled with vancomycin treatment in a biofilm model of chronic osteomyelitis in rabbits, clinical and radiographic signs of infection significantly reduced by 67 and 82%, respectively, compared to infected animals that were either treated with vancomycin or left untreated. In contrast, vaccination alone resulted in a modest, and nonsignificant, decrease in clinical (34% reduction) and radiographic signs (9% reduction) of infection, compared to nonvaccinated animal groups untreated or treated with vancomycin. Lastly, MRSA biofilm infections were significantly cleared in 87.5% of vaccinated and antibiotic-treated animals, while antibiotics or vaccine alone could not significantly clear infection compared to controls (55.6, 22.2, and 33.3% clearance rates, respectively). This approach to vaccine development may lead to the generation of vaccines against other pathogenic biofilm bacteria.
Prevalence of Coxiella burnetii infection in Dutch dairy herds based on testing bulk tank milk and individual samples by PCR and ELISA
Authors: Muskens J. , van Engelen E. , van Maanen C. , Bartels C. , Lam T. J. G. M.
Published: January 2011

A study using an ELISA and a real‐time PCR assay based on the detection of the repetitive transposon‐like gene of Coxiella burnetii revealed that infection with the bacterium was widespread among Dutch dairy herds, with antibodies detected in bulk tank milk (BTM) from 268 of 341 herds (78.6 per cent) and bacterial DNA detected in 193 of 341 herds (56.6 per cent). The BTM samples were taken in November and December 2007. Serological and molecular studies in young and adult cattle selected from 100 herds showed that antibodies were present in the blood of 470 of 2936 (16.0 per cent) lactating cows but only in 19 of 1831 (1.0 per cent) young animals. Bacterial DNA was detected in the milk of 254 of 2925 (8.7 per cent) lactating cows; bacterial DNA was not detected in any of the faecal samples obtained from youngstock. The blood and milk samples were taken from the cattle in the period January to April 2008.
Sterilisation of hybrid Galapagos tortoises (Geochelone nigra) for island restoration. Part 1: endoscopic oophorectomy of females under ketamine‐medetomidine anaesthesia
Authors: Knafo S. E. , Divers S. J. , Rivera S. , Cayot L. J. , Tapia‐Aguilera W. , Flanagan J.
Published: January 2011

An endoscopic sterilisation technique for use in Galapagos tortoises (Geochelone nigra) was developed as part of a conservation and ecosystem restoration project. Fifteen female giant Galapagos tortoises were anaesthetised, intubated and positioned in dorsal recumbency. A bilateral prefemoral approach was made and the ovaries were identified using a 5 mm × 33 cm rigid telescope. In the case of endoscope‐assisted oophorectomy, the ovaries were exteriorised through the same incision, the vasculature was ligated and the mesovarium was transected. Two tortoises had immature ovaries that could not be exteriorised. In these animals, endoscopic oophorectomy was performed using radiosurgery. Closure of the incisions was routine. All tortoises except one recovered well from surgery. There were no reported complications six weeks and six months postoperatively, and all were successfully released on to Pinta Island in May 2010.
GRAVITATION, THERMODYNAMICS, AND THE FINE-STRUCTURE CONSTANT
Authors: HOD SHAHAR
Published: January 2011

The dimensionless fine-structure constant α ≡ e2/ℏc ≃ 1/137.036 has fascinated many scientists since its introduction by Sommerfeld almost a century ago. Dirac and Feynman have conjectured that this important physical constant may be composed of fundamental mathematical quantities like π. In this essay we argue that, the interplay between gravity, quantum theory, and thermodynamics may shed much light on the origins of this mysterious constant. In particular, we show that a unified quantum theory of gravity may set a lower bound on the value of the fine-structure constant, α > ln 3/48π ≃ 1/137. 3.