bluuebunny/crossref_metadata_2025 huggingface dataset:
Macro, Meso, and Micro‐Efficiencies in Water Resources Management: A New Framework Using Water Balance1
Authors: Haie Naim , Keller Andrew A.
Published: November 2011

Haie, Naim and Andrew A. Keller, 2012. Macro, Meso, and Micro‐Efficiencies in Water Resources Management: A New Framework Using Water Balance. Journal of the American Water Resources Association (JAWRA) 48(2): 235‐243. DOI: 10.1111/j.1752‐1688.2011.00611.x

Abstract:  One of the most important performance indicators for water resources systems (WRSs) management is efficiency. Here, water balance, based on mass conservation, is utilized to systemically develop three levels of composite efficiency indicators for a WRS, which are configurable based on two types of water totals: total inflow and total consumption (outflow that effectively is not available for reuse). The indices characterize hydrology of an area by including in their formulations the flow dynamics at three integrated levels. Furthermore, the usefulness of water is incorporated into the indicators by defining two weights: one for quality, and the other for beneficial attributes of water use. Usefulness Criterion is the product of quality and beneficial weights, emphasizing the equal significance of the two dimensions. Both of these weights depend on the system itself and the priorities of the supervising organization, which also are shaped by the objectives and values of the given society. These concepts lead to the definition of Macro, Meso, and Micro‐Efficiencies, which form a set of integrated indicators that explicitly promotes stakeholder involvement in evaluation and design of WRSs. Macro, Meso, and Micro‐Efficiencies should be maximized for both water totals, which is an integrated prerequisite for sustainability and is less promoted by competing stakeholders. To demonstrate this new framework, it is applied to published data for urban and agricultural cases and some results are explained.
Antimicrobial use in a critical care unit: a prospective observational study
Authors: Candeloro Christina L , Kelly Lynne M , Bohdanowicz Elk , Martin Claudio M , Bombassaro Anne Mari
Published: November 2011

Objective

The purpose of this study was to describe antimicrobial utilization, consumption, indications and microbial resistance in a medical-surgical-trauma intensive care unit (ICU) of a teaching hospital to identify potential targets for antimicrobial stewardship.

Methods

This was a 30-day prospective observational study enrolling adults admitted to the ICU for at least 24 h and having received antimicrobial therapy. Primary endpoints included utilization as percentage use of antimicrobials by class and agent, consumption measured as days of therapy per 1000 patient days (DOT/1000PD), indications for use and prescriber. Secondary endpoints included reasons for modifications to therapy and microbial resistance.

Key findings

Eighty-three patients were screened and 61 enrolled, receiving 133 courses of antimicrobial therapy, mainly intravenously and prescribed by ICU staff. The most frequently prescribed agents were piperacillin/tazobactam (20%), cefazolin (17%) and vancomycin (13%). The indications for therapy were empirical (50%), directed (27%) and prophylactic (23%). Overall consumption was 1368.54 DOT/1000PD and was mainly attributed to empirical therapy (734.25). Prolonged durations were noted for carbapenems and for surgical prophylaxis. There were 86 therapy modifications involving indication (36), efficacy (25), safety (18) and route (7). Suboptimal or excessive dosing were common contributors to efficacy and safety modifications, respectively. Infections due to microorganisms with notable resistance included methicillin-resistant Staphylococcus aureus (5), Pseudomonas aeruginosa (1) and Streptococcus pneumoniae (1).

Conclusions

Antimicrobial utilization and consumption based on DOT/1000PD were prospectively determined providing a comparator for other ICUs. Potential targets identified for antimicrobial stewardship initiatives include empirical therapy, treatment duration, dosing and route.
Development of tactical deception from 4 to 8 years of age
Authors: Smith Rachelle M. , LaFreniere Peter J.
Published: November 2011

One hundred eighteen children, divided into three age groups (4‐, 6‐, and 8‐year‐olds) participated in a competitive game designed to explore advances in children's deceptive abilities. Success in the game required children to inhibit useful information or provide misinformation in their communication with an adult opponent. Age trends were evident for all dependent variables, including success at the task, strategic behaviours, and interview data. Four‐year‐olds were non‐strategic and rarely successful, 6‐year‐olds were increasingly strategic and successful, and 8‐year‐olds were significantly more subtle in their strategies, more successful at the task, and more likely to verbalize an understanding of their opponent's expectations than younger age groups.
Epithelial Na+ channel proteins are mechanotransducers of myogenic constriction in rat posterior cerebral arteries
Authors: Kim Eok‐Cheon , Ahn Duck‐Sun , Yeon Soo‐In , Lim Mihwa , Lee Young‐Ho
Published: November 2011

It has been suggested that mechanosensitive ion channels initiate myogenic responses in vessels; however, the molecular identity of the mechanosensitive ion channel complex is unknown. Although previous reports have suggested that epithelial Na+ channel (ENaC) proteins are mechanotransducers in arteries, experimental evidence demonstrating that ENaC proteins are mechanotransducers are not fully elucidated. The goal of the present study was to determine whether the ENaC is a mechanotransducer for the myogenic response by providing supporting evidence in the rat posterior cerebral artery (PCA). We measured the effect of ENaC inhibition on the pressure‐induced myogenic response, Ca2+ concentration and 20 kDa myosin light chain (MLC20) phosphorylation. We detected expression of βENaC and γENaC subunits in rat PCA by Western blots and immunofluorescence. Inhibition of ENaCs with amiloride, ethyl isopropyl amiloride or benzamil blocked the myogenic response. Moreover, the myogenic response was inhibited in rat PCA transfected with βENaC and γENaC small interfering RNA. The myogenic response was inhibited by elimination of external Na+, which was replaced with N‐methyl‐d‐glucamine. Amiloride and nifedipine inhibited the pressure‐induced increase in Ca2+ concentration. Finally, MLC20 increased when the intraluminal pressure was raised, and the pressure‐induced increase in MLC20 phosphorylation was inhibited by pretreatment with amiloride, and in arteries transfected with βENaC or γENaC small interfering RNA. Our results suggest that ENaCs may play an important role as mechanosensitive ion channels initiating pressure‐induced myogenic responses in rat PCA.
Cardiovascular determinants of exercise capacity in the Paralympic athlete with spinal cord injury
Authors: Theisen Daniel
Published: November 2011

This report briefly summarizes the cardiovascular factors that influence exercise physiology and, eventually, sports performance of athletes with a spinal cord injury (SCI). The consequences of an SCI are numerous and concern voluntary muscle function, deep and superficial sensitivity, and autonomic function to a degree determined by the level and completeness of the spinal lesion. Athletes with SCI perform with their upper body, which limits their maximal exercise capacity and puts them at a disadvantage compared with leg exercise in terms of mechanical efficiency and physiological adaptations to exercise. Studies generally find that maximal oxygen consumption and mechanical power output are inversely related to spinal lesion level. Athletes with cervical or dorsal lesions down to Th6 have limited maximal heart rates owing to a lack of sympathetic drive to the heart. Blood redistribution from body areas lacking autonomic control is impaired, thus reducing venous return and limiting cardiac stroke volume during exercise. Thermoregulatory function is affected through a lack of afferent neural feedback and limited efferent vasomotor and sudomotor control below the lesion. Strategies to support venous return and to promote body cooling potentially improve physiological responses and athletic performance, especially in individuals with high lesion levels. The latter are subject to autonomic dysreflexia, a generalized sympathetic vasoconstriction below the lesion resulting from nociceptive stimulations in insensate body regions. Acute episodes induce high blood pressure, may enhance exercise performance and must be treated as a clinical emergency. Deliberate triggering of this reflex is prohibited by the International Paralympic Committee.
Design and Experimental Assessment of an Elastically Averaged Binary Manipulator Using Pneumatic Air Muscles for Magnetic Resonance Imaging Guided Prostate Interventions
Authors: Proulx Sylvain , Plante Jean-Sébastien
Published: November 2011

Early diagnostic and treatment of prostate cancer could be achieved using magnetic resonance imaging (MRI) to improve tumor perceptibility. Nonetheless, performing intra-MRI interventions present significant challenges due to intense magnetic fields and limited patient access. This paper presents an MRI-compatible manipulator using elastically averaged binary pneumatic air muscles (PAMs) to orient a needle into a targeted region of the prostate under the command of a physician. The proposed manipulator is based on an all-polymer compliant mechanism designed to make a completely MRI-compatible positioning system. A model based on the PAMs deformation energy is used to design the manipulator so that its discrete workspace, stiffness, and size meet clinically relevant design requirements. The model is also used to study the motion of the device during a state shift. A laboratory prototype of the device shows that the covered workspace, stiffness, and size of the manipulator can meet clinical requirements. Repeatability and accuracy are also acceptable with values of 0.5 mm and 1.7 mm, respectively. Finally, the manipulator’s behavior during state shift describes a hook-shaped motion that is both analytically predicted and experimentally observed.
A Creep Model for Solder Alloys
Authors: Lee Yongchang , Basaran Cemal
Published: November 2011

Demand for long-term reliability of electronic packaging has lead to a large number of studies on viscoplastic behavior of solder alloys. Various creep models for solder alloys have been proposed. They range from purely empirical to mechanism based models where dislocation motion and diffusion processes are taken into account. In this study, most commonly used creep models are compared with the test data and implemented in ABAQUS to compare their performance in cycling loading. Finally, a new creep model is proposed that combines best features of many models. It is also shown that, while two creep models may describe the same material stress–strain rate curves equally well, they may yield very different results when utilized for cycling loading. One interesting observation of this study is that the stress exponent, n., also depends on the grain size.
Investigating the effect of off-state stress on trap densities in AlGaN/GaN high electron mobility transistors
Authors: Liu L. , Ren F. , Pearton S. J. , Fitch R. C. , Walker D. E. , Chabak K. D. , Gillespie J. K. , Kossler M. , Trejo M. , Via David , Crespo A.
Published: November 2011

The temperature dependence of sub-threshold drain current versus gate voltage at a constant drain bias voltage were used to determine the trap densities in AlGaN/GaN high electron mobility transistors (HEMTs) before and after the off-state stress. Two different trap densities were obtained for the measurements conducted at 300–493 K and 493–573 K, respectively. The trap density at the lower temperature range almost doubled from 1.64 × 1012 to 3.3 × 1012/cm2–eV after a critical voltage for degradation of HEMTs was reached during the off-state drain voltage step-stress. The trap density at the higher temperature range only slightly increased from 8.1 × 1012 and 9.2× 1012/cm2–eV after the device stress. The trap densities were also strongly dependent on drain bias voltage; measurements conducted at higher drain bias voltages exhibited larger trap density due to more hot electrons generated at these conditions.
High temperature focused ion beam response of graphite resulting in spontaneous nanosheet formation
Authors: Langegger Rupert , Lugstein Alois , Glaser Markus , Bertagnolli Emmerich , Steiger-Thirsfeld Andreas
Published: November 2011

This work presents an experimental study of a novel combination of a focused ion beam (FIB) with a heating stage to produce real-time microstructural imaging at elevated substrate temperatures from FIB exposed highly ordered pyrolytic graphite (HOPG). The surface modifications achieved by different angles of ion beam incidence and various substrate temperatures were investigated in situ by field emission scanning electron microscopy and afterwards by atomic force microscopy. The authors studied the formation and self-organization of ripples, porous structures, and graphite nanosheets (GNS), which appear spontaneously during FIB irradiation of HOPG. Here the evolution of pseudoperiodical ripples from small amplitudes to nanospikes with increasing ion fluences and the transformation into disorganized porous structures at higher temperatures was observed and further investigated. Moreover, the authors were able to induce the spontaneous formation of sheet like carbon nanostructures at substrate temperatures above T = 500 °C by controlling the scan speed and the ion fluence. These high aspect ratio crystalline GNS, several micrometers high and thinner than 60 nm, can be formed at predefined sites on the HOPG surface.
Shear strain from irrotational tissue displacements near bubbles
Authors: Carstensen Edwin , Gracewski Sheryl M. , Dalecki Diane
Published: November 2011

Particle displacements can be much greater near bubbles than they would be in a homogeneous liquid or tissue when exposed to an acoustic wave. In a plane wave, shear and bulk strains are of the same order of magnitude. In contrast, for a bubble oscillating close to its resonance frequency, the shear strain in the medium near the bubble is roughly four orders of magnitude greater than the bulk strain. This can lead to shear strains of a few percent even with acoustic excitation pressures far below the pressure thresholds required to cause inertial cavitation. High shear strains near oscillating bubbles could potentially be the cause of bioeffects. After acoustic exposures at audio frequencies, hemorrhages in tissues as diverse as lung, liver, and kidney have been observed at shear strains on the order of 1%.
Acoustic characterization of echogenic liposomes: Frequency-dependent attenuation and backscatter
Authors: Kopechek Jonathan A. , Haworth Kevin J. , Raymond Jason L. , Douglas Mast T. , Perrin Stephen R. , Klegerman Melvin E. , Huang Shaoling , Porter Tyrone M. , McPherson David D. , Holland Christy K.
Published: November 2011

Ultrasound contrast agents (UCAs) are used clinically to aid detection and diagnosis of abnormal blood flow or perfusion. Characterization of UCAs can aid in the optimization of ultrasound parameters for enhanced image contrast. In this study echogenic liposomes (ELIPs) were characterized acoustically by measuring the frequency-dependent attenuation and backscatter coefficients at frequencies between 3 and 30 MHz using a broadband pulse-echo technique. The experimental methods were initially validated by comparing the attenuation and backscatter coefficients measured from 50-μm and 100-μm polystyrene microspheres with theoretical values. The size distribution of the ELIPs was measured and found to be polydisperse, ranging in size from 40 nm to 6 μm in diameter, with the highest number observed at 65 nm. The ELIP attenuation coefficients ranged from 3.7 ± 1.0 to 8.0 ± 3.3 dB/cm between 3 and 25 MHz. The backscatter coefficients were 0.011 ± 0.006 (cm str)−1 between 6 and 9 MHz and 0.023 ± 0.006 (cm str)−1 between 13 and 30 MHz. The measured scattering-to-attenuation ratio ranged from 8% to 22% between 6 and 25 MHz. Thus ELIPs can provide enhanced contrast over a broad range of frequencies and the scattering properties are suitable for various ultrasound imaging applications including diagnostic and intravascular ultrasound.
Regimes of bubble volume oscillations in a pipe
Authors: Jeurissen Roger , Wijshoff Herman , van den Berg Marc , Reinten Hans , Lohse Detlef
Published: November 2011

The effect of an acoustically driven bubble on the acoustics of a liquid-filled pipe is theoretically analyzed and the dimensionless groups of the problem are identified. The different regimes of bubble volume oscillations are predicted theoretically with these dimensionless groups. Three main regimes can be identified: (1) For small bubbles and weak driving, the effect of the bubble oscillations on the acoustic field can be neglected. (2) For larger bubbles and still small driving, the bubble affects the acoustic field, but due to the small driving, a linear theory is sufficient. (3) For large bubbles and large driving, the two-way coupling between the bubble and the flow dynamics requires the solution of the full nonlinear problem. The developed theory is then applied to an air bubble in a channel of an inkjet printhead. A numerical model is developed to test the predictions of the theoretical analysis. The Rayleigh-Plesset equation is extended to include the influence of the bubble volume oscillations on the acoustic field and vice versa. This modified Rayleigh-Plesset equation is coupled to a channel acoustics calculation and a Navier-Stokes solver for the flow in the nozzle. The numerical simulations indeed confirm the predictions of the theoretical analysis.
Clutter suppression and classification using twin inverted pulse sonar in ship wakes
Authors: Leighton T. G. , Finfer D. C. , Chua G. H. , White P. R. , Dix J. K.
Published: November 2011

Twin inverted pulse sonar (TWIPS) is here deployed in the wake of a moored rigid inflatable boat (RIB) with propeller turning, and then in the wake of a moving tanker of 4580 dry weight tonnage (the Whitchallenger). This is done first to test its ability to distinguish between scatter from the wake and scatter from the seabed, and second to test its ability to improve detectability of the seabed through the wake, compared to conventional sonar processing techniques. TWIPS does this by distinguishing between linear and nonlinear scatterers and has the further property of distinguishing those nonlinear targets which scatter energy at the even-powered harmonics from those which scatter in the odd-powered harmonics. TWIPS can also, in some manifestations, require no range correction (and therefore does not require the a priori environment knowledge necessary for most remote detection technologies).
Validation of an approximate model for the thermal behavior in acoustically driven bubbles
Authors: Stricker Laura , Prosperetti Andrea , Lohse Detlef
Published: November 2011

The chemical production of radicals inside acoustically driven bubbles is determined by the local temperature inside the bubbles. Therefore, modeling of chemical reaction rates in bubbles requires an accurate evaluation of the temperature field and the heat exchange with the liquid. The aim of the present work is to compare a detailed partial differential equation model in which the temperature field is spatially resolved with an ordinary differential equation model in which the bubble contents are assumed to have a uniform average temperature and the heat exchanges are modeled by means of a boundary layer approximation. The two models show good agreement in the range of pressure amplitudes in which the bubble is spherically stable.
Modeling cavitation nucleation from laser-illuminated nanoparticles subjected to acoustic stress
Authors: Wu Tianming , Farny Caleb H. , Roy Ronald A. , Holt R. G.
Published: November 2011

In an earlier work by Farny et al. [ARLO 6, 138–143 (2005).] it was demonstrated that the acoustic cavitation threshold in a tissue mimicking gel phantom can be lowered from 4.5 to ∼1 MPa by “seeding” the optically transparent phantom with light absorptive gold nanoparticles and irradiating these absorbers with nanosecond pulses of laser light at intensities less than 10 mJ/cm2. As a follow-up study, a three-stage numerical model was developed to account for prenucleation heating, the nucleation and formation of the vapor cavity, and the resulting vapor bubble dynamics. Through examination of the radius–time evolution of the cavity, the combined thresholds for laser radiant exposure and acoustic peak pressure required to induce inertial cavitation are deduced. It is found that the threshold pressure decreases when laser exposure increases; but the rate depends on exposure levels and the size of the particle. Investigations of the roles of particle size and laser pulse length are performed and optimum choices for these parameters determined in order to obtain inertial cavitation at the lowest possible acoustic pressure and laser intensity.
Ambient acceleration dependence of single-bubble sonoluminescence
Authors: Thomas Charles R. , Roy Ronald A. , Holt R. Glynn
Published: November 2011

Much of the research performed to study SBSL deals with the influence of external parameters (e.g., the host water temperature, the ambient pressure, the type and amount of dissolved gas in the liquid, to name a few) on the bubble dynamics and light emission. In the current paper, work carried out to study the influence of another external parameter—ambient acceleration—is described. The experiments described here were performed on the NASA KC-135 which provided both periods of reduced gravity (10−3 g) and increased gravity (1.8 g) by flying repeated parabolic maneuvers. The resulting measurements are compared with the predictions of a numerical model and can be understood in the context of the changing hydrostatic head pressure and buoyant force acting on the bubble.
Controlled tissue emulsification produced by high intensity focused ultrasound shock waves and millisecond boiling
Authors: Khokhlova Tatiana D. , Canney Michael S. , Khokhlova Vera A. , Sapozhnikov Oleg A. , Crum Lawrence A. , Bailey Michael R.
Published: November 2011

In high intensity focused ultrasound (HIFU) applications, tissue may be thermally necrosed by heating, emulsified by cavitation, or, as was recently discovered, emulsified using repetitive millisecond boiling caused by shock wave heating. Here, this last approach was further investigated. Experiments were performed in transparent gels and ex vivo bovine heart tissue using 1, 2, and 3 MHz focused transducers and different pulsing schemes in which the pressure, duty factor, and pulse duration were varied. A previously developed derating procedure to determine in situ shock amplitudes and the time-to-boil was refined. Treatments were monitored using B-mode ultrasound. Both inertial cavitation and boiling were observed during exposures, but emulsification occurred only when shocks and boiling were present. Emulsified lesions without thermal denaturation were produced with shock amplitudes sufficient to induce boiling in less than 20 ms, duty factors of less than 0.02, and pulse lengths shorter than 30 ms. Higher duty factors or longer pulses produced varying degrees of thermal denaturation combined with mechanical emulsification. Larger lesions were obtained using lower ultrasound frequencies. The results show that shock wave heating and millisecond boiling is an effective and reliable way to emulsify tissue while monitoring the treatment with ultrasound.
Combined optical and acoustical detection of single microbubble dynamics
Authors: Sijl Jeroen , Vos Hendrik J. , Rozendal Timo , de Jong Nico , Lohse Detlef , Versluis Michel
Published: November 2011

A detailed understanding of the response of single microbubbles subjected to ultrasound is fundamental to a full understanding of the contrast-enhancing abilities of microbubbles in medical ultrasound imaging, in targeted molecular imaging with ultrasound, and in ultrasound-mediated drug delivery with microbubbles. Here, single microbubbles are isolated and their ultrasound-induced radial dynamics recorded with an ultra-high-speed camera at up to 25 million frames per second. The sound emission is recorded simultaneously with a calibrated single element transducer. It is shown that the sound emission can be predicted directly from the optically recorded radial dynamics, and vice versa, that the nanometer-scale radial dynamics can be predicted from the acoustic response recorded in the far field.
Cross-language acoustic similarity predicts perceptual assimilation of Canadian English and Canadian French vowels
Authors: Escudero Paola , Vasiliev Polina
Published: November 2011

Monolingual Peruvian Spanish listeners identified natural tokens of the Canadian French (CF) and Canadian English (CE) /ɛ/ and /æ/, produced in five consonantal contexts. The results demonstrate that while the CF vowels were mapped to two different native vowels, /e/ and /a/, in all consonantal contexts, the CE contrast was mapped to the single native vowel /a/ in four out of five contexts. Linear discriminant analysis revealed that acoustic similarity between native and target language vowels was a very good predictor of context-specific perceptual mappings. Predictions are made for Spanish learners of the /ɛ/-/æ/ contrast in CF and CE.
Consistency in statistical moments as a test for bubble cloud clustering
Authors: Weber Thomas C. , Lyons Anthony P. , Bradley David L.
Published: November 2011

Frequency dependent measurements of attenuation and/or sound speed through clouds of gas bubbles in liquids are often inverted to find the bubble size distribution and the void fraction of gas. The inversions are often done using an effective medium theory as a forward model under the assumption that the bubble positions are Poisson distributed (i.e., statistically independent). Under circumstances in which single scattering does not adequately describe the pressure field, the assumption of independence in position can yield large errors when clustering is present, leading to errors in the inverted bubble size distribution. It is difficult, however, to determine the existence of clustering in bubble clouds without the use of specialized acoustic or optical imaging equipment. A method is described here in which the existence of bubble clustering can be identified by examining the consistency between the first two statistical moments of multiple frequency acoustic measurements.
Prediction of the influence of reverberation on binaural speech intelligibility in noise and in quiet
Authors: Rennies Jan , Brand Thomas , Kollmeier Birger
Published: November 2011

Reverberation usually degrades speech intelligibility for spatially separated speech and noise sources since spatial unmasking is reduced and late reflections decrease the fidelity of the received speech signal. The latter effect could not satisfactorily be predicted by a recently presented binaural speech intelligibility model [Beutelmann et al. (2010). J. Acoust. Soc. Am. 127, 2479–2497]. This study therefore evaluated three extensions of the model to improve its predictions: (1) an extension of the speech intelligibility index based on modulation transfer functions, (2) a correction factor based on the room acoustical quantity “definition,” and (3) a separation of the speech signal into useful and detrimental parts. The predictions were compared to results of two experiments in which speech reception thresholds were measured in a reverberant room in quiet and in the presence of a noise source for listeners with normal hearing. All extensions yielded better predictions than the original model when the influence of reverberation was strong, while predictions were similar for conditions with less reverberation. Although model (3) differed substantially in the assumed interaction of binaural processing and early reflections, its predictions were very similar to model (2) that achieved the best fit to the data.
Measuring static thermal permeability and inertial factor of rigid porous materials (L)
Authors: Sadouki M. , Fellah M. , Fellah Z. E. A. , Ogam E. , Sebaa N. , Mitri F. G. , Depollier C.
Published: November 2011

An acoustic method based on sound transmission is proposed for deducing the static thermal permeability and the inertial factor of porous materials having a rigid frame at low frequencies. The static thermal permeability of porous material is a geometrical parameter equal to the inverse trapping constant of the solid frame [Lafarge et al., J. Acoust. Soc. Am. 102, 1995 (1997)] and is an important characteristic of the porous material. The inertial factor [Norris., J. Wave Mat. Interact. 1, 365 (1986)] describes the fluid structure interactions in the low frequency range (1-3 kHz). The proposed method is based on a temporal model of the direct and inverse scattering problems for the propagation of transient audible frequency waves in a homogeneous isotropic slab of porous material having a rigid frame. The static thermal permeability and the inertial factor are determined from the solution of the inverse problem. The minimization between experiment and theory is made in the time domain. Tests are performed using industrial plastic foams. Experimental and theoretical data are in good agreement. Furthermore, the prospects are discussed. This method has the advantage of being simple, rapid, and efficient.
Nonlinear progressive wave equation for stratified atmospheres
Authors: Edward McDonald B. , Piacsek Andrew A.
Published: November 2011

The nonlinear progressive wave equation (NPE) [McDonald and Kuperman, J. Acoust. Soc. Am. 81, 1406–1417 (1987)] is expressed in a form to accommodate changes in the ambient atmospheric density, pressure, and sound speed as the time-stepping computational window moves along a path possibly traversing significant altitude differences (in pressure scale heights). The modification is accomplished by the addition of a stratification term related to that derived in the 1970s for linear range-stepping calculations and later adopted into Khokhlov-Zabolotskaya-Kuznetsov-type nonlinear models. The modified NPE is shown to preserve acoustic energy in a ray tube and yields analytic similarity solutions for vertically propagating N waves in isothermal and thermally stratified atmospheres.
MP3 player listening sound pressure levels among 10 to 17 year old students
Authors: Keith Stephen E. , Michaud David S. , Feder Katya , Haider Ifaz , Marro Leonora , Thompson Emma , Marcoux Andre M.
Published: November 2011

Using a manikin, equivalent free-field sound pressure level measurements were made from the portable digital audio players of 219 subjects, aged 10 to 17 years (93 males) at their typical and “worst-case” volume levels. Measurements were made in different classrooms with background sound pressure levels between 40 and 52 dBA. After correction for the transfer function of the ear, the median equivalent free field sound pressure levels and interquartile ranges (IQR) at typical and worst-case volume settings were 68 dBA (IQR = 15) and 76 dBA (IQR = 19), respectively. Self-reported mean daily use ranged from 0.014 to 12 h. When typical sound pressure levels were considered in combination with the average daily duration of use, the median noise exposure level, Lex, was 56 dBA (IQR = 18) and 3.2% of subjects were estimated to exceed the most protective occupational noise exposure level limit in Canada, i.e., 85 dBA Lex. Under worst-case listening conditions, 77.6% of the sample was estimated to listen to their device at combinations of sound pressure levels and average daily durations for which there is no known risk of permanent noise-induced hearing loss, i.e., ≤ 75 dBA Lex. Sources and magnitudes of measurement uncertainties are also discussed.
Experimental testing of the variable rotated elastic parabolic equation
Authors: Simpson Harry J. , Collis Jon M. , Soukup Raymond J. , Collins Michael D. , Siegmann William L.
Published: November 2011

A series of laboratory experiments was conducted to obtain high-quality data for acoustic propagation in shallow water waveguides with sloping elastic bottoms. Accurate modeling of transmission loss in these waveguides can be performed with the variable rotated parabolic equation method. Results from an earlier experiment with a flat or sloped slab of polyvinyl chloride (PVC) demonstrated the necessity of accounting for elasticity in the bottom and the ability of the model to produce benchmark-quality agreement with experimental data [J. M. Collis et al., J. Acoust. Soc. Am. 122, 1987–1993 (2007)]. This paper presents results of a second experiment, using two PVC slabs joined at an angle to create a waveguide with variable bottom slope. Acoustic transmissions over the 100–300 kHz band were received on synthetic horizontal arrays for two source positions. The PVC slabs were oriented to produce three different simulated waveguides: flat bottom followed by downslope, upslope followed by flat bottom, and upslope followed by downslope. Parabolic equation solutions for treating variable slopes are benchmarked against the data.
Linking multiple relaxation, power-law attenuation, and fractional wave equations
Authors: Näsholm Sven Peter , Holm Sverre
Published: November 2011

The acoustic wave attenuation is described by an experimentally established frequency power law in a variety of complex media, e.g., biological tissue, polymers, rocks, and rubber. Recent papers present a variety of acoustical fractional derivative wave equations that have the ability to model power-law attenuation. On the other hand, a multiple relaxation model is widely recognized as a physically based description of the acoustic loss mechanisms as developed by Nachman et al. [J. Acoust. Soc. Am. 88, 1584–1595 (1990)]. Through assumption of a continuum of relaxation mechanisms, each with an effective compressibility described by a distribution related to the Mittag-Leffler function, this paper shows that the wave equation corresponding to the multiple relaxation approach is identical to a given fractional derivative wave equation. This work therefore provides a physically based motivation for use of fractional wave equations in acoustic modeling.
The Timbre Toolbox: Extracting audio descriptors from musical signals
Authors: Peeters Geoffroy , Giordano Bruno L. , Susini Patrick , Misdariis Nicolas , McAdams Stephen
Published: November 2011

The analysis of musical signals to extract audio descriptors that can potentially characterize their timbre has been disparate and often too focused on a particular small set of sounds. The Timbre Toolbox provides a comprehensive set of descriptors that can be useful in perceptual research, as well as in music information retrieval and machine-learning approaches to content-based retrieval in large sound databases. Sound events are first analyzed in terms of various input representations (short-term Fourier transform, harmonic sinusoidal components, an auditory model based on the equivalent rectangular bandwidth concept, the energy envelope). A large number of audio descriptors are then derived from each of these representations to capture temporal, spectral, spectrotemporal, and energetic properties of the sound events. Some descriptors are global, providing a single value for the whole sound event, whereas others are time-varying. Robust descriptive statistics are used to characterize the time-varying descriptors. To examine the information redundancy across audio descriptors, correlational analysis followed by hierarchical clustering is performed. This analysis suggests ten classes of relatively independent audio descriptors, showing that the Timbre Toolbox is a multidimensional instrument for the measurement of the acoustical structure of complex sound signals.
A neurocognitive model of recognition and pitch segregation
Authors: McLachlan Neil
Published: November 2011

This paper describes a neurocognitive model of pitch segregation in which it is proposed that recognition mechanisms initiate early in auditory processing pathways so that long-term memory templates may be employed to segregate and integrate auditory features. In this model neural representations of pitch height are primed by the location and pattern of excitation across auditory filter channels in relation to long-term memory templates for common stimuli. Since waveform driven pitch mechanisms may produce information at multiple frequencies for tonal stimuli, pitch priming was assumed to include competitive inhibition that would allow only one pitch estimation at any time. Consequently concurrent pitch information must be relayed to short-term memory via a parallel mechanism that employs pitch information contained in the long-term memory template of the chord. Pure tones, harmonic complexes and two pitch chords of harmonic complexes were correctly classified by the correlation of templates comprising auditory nerve excitation and off-frequency inhibition with the excitation patterns of stimuli. The model then replicated behavioral data for pitch matching of concurrent vowels. Comparison of model outputs to the behavioral data suggests that inability to recognize a stimulus was associated with poor pitch segregation due to the use of inappropriate pitch priming strategies.
Effects of inducer continuity on auditory stream segregation: Comparison of physical and perceived continuity in different contexts
Authors: Haywood Nicholas R. , Roberts Brian
Published: November 2011

The factors influencing the stream segregation of discrete tones and the perceived continuity of discrete tones as continuing through an interrupting masker are well understood as separate phenomena. Two experiments tested whether perceived continuity can influence the build-up of stream segregation by manipulating the perception of continuity during an induction sequence and measuring streaming in a subsequent test sequence comprising three triplets of low and high frequency tones (LHL-…). For experiment 1, a 1.2-s standard induction sequence comprising six 100-ms L-tones strongly promoted segregation, whereas a single extended L-inducer (1.1 s plus 100-ms silence) did not. Segregation was similar to that following the single extended inducer when perceived continuity was evoked by inserting noise bursts between the individual tones. Reported segregation increased when the noise level was reduced such that perceived continuity no longer occurred. Experiment 2 presented a 1.3-s continuous inducer created by bridging the 100-ms silence between an extended L-inducer and the first test-sequence tone. This configuration strongly promoted segregation. Segregation was also increased by filling the silence after the extended inducer with noise, such that it was perceived like a bridging inducer. Like physical continuity, perceived continuity can promote or reduce test-sequence streaming, depending on stimulus context.
Voice segregation by difference in fundamental frequency: Evidence for harmonic cancellation
Authors: Deroche Mickael L. D. , Culling John F.
Published: November 2011

Two experiments investigated listeners’ ability to use a difference of two semitones in fundamental frequency (F0) to segregate a target voice from harmonic complex tones, with speech-like spectral profiles. Masker partials were in random phase (experiment 1) or in sine phase (experiment 2) and stimuli were presented over headphones. Target’s and masker’s harmonicity were each distorted by F0 modulation and reverberation. The F0 of each source was manipulated (monotonized or modulated by 2 semitones at 5 Hz) factorially. In addition, all sources were presented from the same location in a virtual room with controlled reverberation, assigned factorially to each source. In both experiments, speech reception thresholds increased by about 2 dB when the F0 of the masker was modulated and increased by about 6 dB when, in addition to F0 modulation, the masker was reverberant. Masker partial phases did not influence the results. The results suggest that F0-segregation relies upon the masker’s harmonicity, which is disrupted by rapid modulation. This effect is compounded by reverberation. In addition, F0-segregation was found to be independent of the depth of masker envelope modulations.
Effects of the selective disruption of within- and across-channel cues to comodulation masking release
Authors: Goldman Simon A. , Baer Thomas , Moore Brian C. J.
Published: November 2011

In many experiments on comodulation masking release (CMR), both across- and within-channel cues may be available. This makes it difficult to determine the mechanisms underlying CMR. The present study compared CMR in a flanking-band (FB) paradigm for a situation in which only across-channel cues were likely to be available [FBs placed distally from the on-frequency band (OFB)] and a situation where both across- and within-channel cues might have been available (proximally spaced FBs, for which larger CMRs have previously been observed). The use of across-channel cues was selectively disrupted using a manipulation of auditory grouping factors, following Dau et al. [J. Acoust. Soc. Am. 125, 2182–2188(2009)] and the use of within-channel cues was selectively disrupted using a manipulation called “OFB reversal,” following Goldman et al. [J. Acoust. Soc. Am. 129, 3181–3193 (2011)]. The auditory grouping manipulation eliminated CMR for the distal-FB configuration and reduced CMR for the proximal-FB configuration. This may indicate that across-channel cues are available for proximal FB placement. CMR for the proximal-FB configuration persisted when both manipulations were used together, which suggests that OFB reversal does not entirely eliminate within-channel cues.
Comparison of fundamental, second harmonic, and superharmonic imaging: A simulation study
Authors: van Neer Paul L. M. J. , Danilouchkine Mikhail G. , Verweij Martin D. , Demi Libertario , Voormolen Marco M. , van der Steen Anton F. W. , de Jong Nico
Published: November 2011

In medical ultrasound, fundamental imaging (FI) uses the reflected echoes from the same spectral band as that of the emitted pulse. The transmission frequency determines the trade-off between penetration depth and spatial resolution. Tissue harmonic imaging (THI) employs the second harmonic of the emitted frequency band to construct images. Recently, superharmonic imaging (SHI) has been introduced, which uses the third to the fifth (super) harmonics. The harmonic level is determined by two competing phenomena: nonlinear propagation and frequency dependent attenuation. Thus, the transmission frequency yielding the optimal trade-off between the spatial resolution and the penetration depth differs for THI and SHI. This paper quantitatively compares the concepts of fundamental, second harmonic, and superharmonic echocardiography at their optimal transmission frequencies. Forward propagation is modeled using a 3D-KZK implementation and the iterative nonlinear contrast source (INCS) method. Backpropagation is assumed to be linear. Results show that the fundamental lateral beamwidth is the narrowest at focus, while the superharmonic one is narrower outside the focus. The lateral superharmonic roll-off exceeds the fundamental and second harmonic roll-off. Also, the axial resolution of SHI exceeds that of FI and THI. The far-field pulse-echo superharmonic pressure is lower than that of the fundamental and second harmonic. SHI appears suited for echocardiography and is expected to improve its image quality at the cost of a slight reduction in depth-of-field.
Two-dimensional virtual array for ultrasonic nondestructive evaluation using a time-reversal chaotic cavity
Authors: Choi Youngsoo , Lee Hunki , Hong Hyun , Ohm Won-Suk
Published: November 2011

Despite its introduction more than a decade ago, a two-dimensional ultrasonic array remains a luxury in nondestructive evaluation because of the complexity and cost associated with its fabrication and operation. This paper describes the construction and performance of a two-dimensional virtual array that solves these problems. The virtual array consists of only two transducers (one each for transmit and receive) and an aluminum chaotic cavity, augmented by a 10 × 10 matrix array of rectangular rods. Each rod, serving as an elastic waveguide, is calibrated to emit a collimated pulsed sound beam centered at 2.5 MHz using the reciprocal time reversal. The resulting virtual array is capable of pulse-echo interrogation of a solid sample in direct contact along 10 × 10 scan lines. Three-dimensional imaging of an aluminum test piece, the nominal thickness of which is in the order of 1 cm, is successfully carried out using the virtual array.
Effect of decision weights and internal noise on the growth of d′ with N
Authors: Lutfi Robert A. , Gilbertson Lynn
Published: November 2011

A general finding of psychoacoustic studies is that detectability d' of a noisy signal grows less than optimally with the number N of independent observations of the signal. Competing accounts implicate internal noise common to all observations or nonoptimal decision weights given to observations. A discriminant analysis of listeners’ trial-by-trial responses in a multitone level-discrimination task favored the latter account.
Interaural spectral asymmetry and sensitivity to interaural time differences
Authors: Brown Christopher A. , Yost William A.
Published: November 2011

Listeners’ ability to discriminate interaural time difference (ITD) changes in low-frequency noise was determined as a function of differences in the noise spectra delivered to each ear. An ITD was applied to Gaussian noise, which was bandpass filtered using identical high-pass, but different low-pass cutoff frequencies across ears. Thus, one frequency region was dichotic, and a higher-frequency region monotic. ITD thresholds increased as bandwidth to one ear (i.e., monotic bandwidth) increased, despite the fact that the region of interaural spectral overlap remained constant. Results suggest that listeners can process ITD differences when the spectra at two ears are moderately different.
Comment on “Global Trends in Wind Speed and Wave Height”
Authors: Wentz Frank J. , Ricciardulli Lucrezia
Published: November 2011

Young
et al
. (Reports, 22 April 2011, p. 451) reported trends in global mean wind speed much larger than found by other investigators. Their report fails to reference these other investigations and does not discuss the consequences that such large wind trends would have on global evaporation and precipitation. The difference between their altimeter and buoy trends suggests a relatively large trend error.
When More Is More
Authors: Giraldeau Luc-Alain
Published: November 2011

Whether contextual information is helpful in making decisions depends on the situation.
The Energy Research Imperative
Authors: Gates Bill
Published: November 2011

As someone now working full time in global health and development, I see firsthand how the U.S. government's support for scientific research has improved people's lives. That support is vital in another area—affordable, clean energy. I believe it is imperative that the government commit to clean energy innovation at a level similar to its research investments in health and defense.
Research Projects Could Be Roadkill in Revision of Massive Highway Bill
Authors: Malakoff David
Published: November 2011

A federal highway program that has funded archaeological and environmental restoration projects faces serious opposition in the U.S. House of Representatives from lawmakers who consider it to be wasteful and unnecessary spending.
China Looks to Balance Its Carbon Books
Authors: Jiao Li , Stone Richard
Published: November 2011

As nations grope for a consensus on how to rein in carbon dioxide emissions, China is pressing ahead on its own to sharply reduce energy intensity by shuttering inefficient coal-fired power plants and capping energy use.
An Unsung Carbon Sink
Authors: Larson Christina
Published: November 2011

Soil scientists in China are measuring calcium and bicarbonate ions in karst in an effort to figure out how much carbon dioxide has been taken out of the air. Karst could be a substantial inorganic carbon sink, experts say.