bluuebunny/crossref_metadata_2025 huggingface dataset:
Risk of Recurrent Stroke before Carotid Endarterectomy: The ANSYSCAP Study
Authors: Johansson E. P. , Arnerlöv C. , Wester P.
Published: April 2012

Background

Carotid endarterectomy yields greater risk reduction for ipsilateral ischemic stroke when performed within two-weeks of the last cerebrovascular symptom than when performed two-weeks or more after the last symptom. However, additional benefit might be gained if carotid endarterectomy is performed earlier than within two-weeks.

Aims

To investigate the 90-day risk of ipsilateral ischemic stroke recurrence after amaurosis fugax, retinal artery occlusion, transient ischemic attack, or minor ischemic stroke in patients with 50–99% carotid stenosis before carotid endarterectomy, with emphasis on the first 14 days.

Methods

Prospective cohort study. 230 consecutive patients with symptomatic 50–99% carotid stenosis (North American Symptomatic Carotid Endarterectomy Trial grading method) who underwent evaluation before carotid endarterectomy. Of these, 183 underwent carotid endarterectomy; the median delay to carotid endarterectomy was 29 days. Blood pressure lowering medication was used by 93% and lipid-lowering medication by 90%.

Results

The risk of ipsilateral ischemic stroke recurrence before carotid endarterectomy was 5·2% ( n = 12) within two-days, 7·9% ( n = 18) within seven-days, 11·2% ( n = 25) within 14 days, and 18·6% ( n = 33) within 90 days of the presenting event. The risk of ipsilateral ischemic stroke recurrence was higher if the presenting event was a stroke (adjusted hazard ratio 12·4, P = 0·015) or transient ischemic attack (adjusted hazard ratio 10·2, P = 0·026) compared with an amaurosis fugax.

Discussion

The risk of recurrent ipsilateral ischemic stroke was high within the first days of the presenting event. Many recurrences would likely have been avoided if carotid endarterectomy had been performed within the first days of the presenting event.
Epileptic Encephalitis: The Role of the Innate and Adaptive Immune System
Authors: Bauer Jan , Vezzani Annamaria , Bien Christian G.
Published: April 2012

Seizures are a prominent clinical feature of encephalitis. Recent data suggest the adaptive as well as innate immune system to be involved directly in the pathomechanism of epileptogenesis. Cytotoxic T‐cells and antibody‐mediated complement activation are major components of the adaptive immune system, which can induce neurodegeneration, thereby probably contributing to epileptic encephalitis. The innate immune system operates via interleukin‐1 and toll‐like receptor‐associated mechanisms and was shown to play a direct role in epileptogenesis. Here, we review neuropathology hallmarks of various encephalitis conditions such as Rasmussen encephalitis (RE) but also introduce the more recently discovered antibody‐associated voltage‐gated potassium channel complex (VGKC), N‐methyl‐D‐aspartate receptor (NMDAR) or glutamic acid decarboxylase (GAD) 65 encephalitides. Neuropathological investigations are used to determine specific cellular components and molecular mechanisms used by the immune system to provoke neurodegeneration and to promote epileptogenesis. Based on recent findings, we propose concepts for the stratification of epileptic encephalitis. Knowledge of the role of the innate immunity has already translated into clinical treatment strategies and may help to discover novel drug targets for these epileptic disorders.
Long‐Term Epilepsy‐Associated Tumors
Authors: Thom Maria , Blümcke Ingmar , Aronica Eleonora
Published: April 2012

The term long‐term epilepsy associated tumor (LEAT) encompasses lesions identified in patients investigated for long histories (often 2 years or more) of drug‐resistant epilepsy. They are generally slowly growing, low grade, cortically based tumors, more often arising in younger age groups and in many cases exhibit neuronal in addition to glial differentiation. Gangliogliomas and dysembryoplastic neuroepithelial tumors predominate in this group. LEATs are further united by cyto‐architectural changes that may be present in the adjacent cortex which have some similarities to developmental focal cortical dysplasias (FCD); these are now grouped as FCD type IIIb in the updated International League Against Epilepsy (ILAE) classification. In the majority of cases, surgical treatments are beneficial from both perspectives of managing the seizures and the tumor. However, in a minority, seizures may recur, tumors may show regrowth or recurrence, and rarely undergo anaplastic progression. Predicting and identifying tumors likely to behave less favorably are key objectives of the neuropathologist. With immunohistochemistry and modern molecular pathology, it is becoming increasingly possible to refine diagnostic groups. Despite this, some LEATs remain difficult to classify, particularly tumors with “non‐specific” or diffuse growth patterns. Modification of LEAT classification is inevitable with the goal of unifying terminological criteria applied between centers for accurate clinico‐pathological‐molecular correlative data to emerge. Finally, establishing the epileptogenic components of LEAT, either within the lesion or perilesional cortex, will elucidate the cellular mechanisms of epileptogenesis, which in turn will guide optimal surgical management of these lesions.
Effects of Onion (Allium cepa L.) and Garlic (Allium sativum L.) Essential Oils on the Aspergillus versicolor Growth and Sterigmatocystin Production
Authors: Kocić‐Tanackov Sunčica , Dimić Gordana , Lević Jelena , Tanackov Ilija , Tepić Aleksandra , Vujičić Biserka , Gvozdanović‐Varga Jelica
Published: April 2012

Abstract:  In the present study the effects of individual and combined essential oils (EOs) extracted from onion (Allium  cepa L.) bulb and garlic (Allium sativum L.) clove on the growth of Aspergillus versicolor and sterigmatocystin (STC) production were investigated. The EOs obtained by hydrodistillation were analyzed by GC/MS. Twenty one compounds were identified in onion EO. The major components were: dimethyl‐trisulfide (16.64%), methyl‐propyl‐trisulfide (14.21%), dietil‐1,2,4‐tritiolan (3R,5S‐, 3S,5S‐ and 3R,5R‐ isomers) (13.71%), methyl‐(1‐propenyl)‐disulfide (13.14%), and methyl‐(1‐propenyl)‐trisulfide (13.02%). The major components of garlic EO were diallyl‐trisulfide (33.55%), and diallyl‐disulfide (28.05%). The mycelial growth and the STC production were recorded after 7, 14, and 21 d of the A. versicolor growth in Yeast extract sucrose (YES) broth containing different EOs concentrations. Compared to the garlic EO, the onion EO showed a stronger inhibitory effect on the A. versicolor mycelial growth and STC production. After a 21‐d incubation of fungi 0.05 and 0.11 μg/mL of onion EO and 0.11 μg/mL of garlic EO completely inhibited the A. versicolor mycelial growth and mycotoxins biosynthesis. The combination of EOs of onion (75%) and garlic (25%) had a synergistic effect on growth inhibition of A. versicolor and STC production.

Practical Application:  A substitution of synthetic preservatives with natural antimicrobial compounds in food safety to control fungal contamination and mycotoxin production.
Integrating Racial and Ethnic Identity Research Into Developmental Understanding of Adolescents
Authors: Williams Joanna Lee , Tolan Patrick H. , Durkee Myles I. , Francois, Amir G. , Anderson Riana E.
Published: April 2012

This article calls for a fuller integration of racial and ethnic identity (REI) as a fundamental topic of developmental research. Reviewing common, youth‐focused models of REI, it suggests the need for understanding the underlying assumptions of each when undertaking research in this domain. It then proposes that youth development research will be enhanced by further testing of the relation of REI to developmental progress in other dimensions of youth's identity and by developmentally conceptualized testing that incorporates social‐ecological perspectives. Relevant findings from studies of adolescents are used throughout to support these contentions. The article argues that new directions can promote the integration of REI research into the mainstream and inform the supports that bolster resilience for youth.
Melanoma‐derived conditioned media efficiently induce the differentiation of monocytes to macrophages that display a highly invasive gene signature
Authors: Wang Tao , Ge Yingbin , Xiao Min , Lopez‐Coral Alfonso , Azuma Rikka , Somasundaram Rajasekharan , Zhang Gao , Wei Zhi , Xu Xiaowei , Rauscher Frank J. , Herlyn Meenhard , Kaufman Russel E.
Published: April 2012

The presence of tumor‐associated macrophages (TAMs) in melanomas is correlated with a poor clinical prognosis. However, there is limited information on the characteristics and biological activities of human TAMs in melanomas. In this study, we developed an in vitro method to differentiate human monocytes to macrophages using modified melanoma‐conditioned medium (MCM). We demonstrate that factors from MCM‐induced macrophages (MCMI‐Mφ) express both M1‐Mφ and M2‐Mφ markers and inhibit melanoma‐specific T‐cell proliferation. Furthermore, microarray analyses reveal that the majority of genes up‐regulated in MCMI‐Mφ are associated with tumor invasion. The most strikingly up‐regulated genes are CCL2 and MMP‐9. Consistent with this, blockade of both CCL‐2 and MMPs diminish MCMI‐Mφ‐induced melanoma invasion. Finally, we demonstrated that both MCMI‐Mφ and in vivo TAMs express the pro‐invasive, melanoma‐associated gene, glycoprotein non‐metastatic melanoma protein B. Our study provides a framework for understanding the mechanisms of cross‐talk between TAMs and melanoma cells within the tumor microenvironment.
Local airborne particulate concentration is associated with visible tracheal mucus in Thoroughbred racehorses
Authors: MILLERICK‐MAY M. L. , KARMAUS W. , DERKSEN F. J. , BERTHOLD B. , HOLCOMBE S. J. , ROBINSON N. E.
Published: April 2012

Reason for performing study:Accumulations of tracheal mucus assessed by endoscopic examination are associated with poor performance in racehorses. The air quality in horses' stalls may contribute to this visible tracheal mucus.

Objectives:To determine whether the concentration and number of airborne particulates in stalls are associated with visible accumulations of tracheal mucus and with the number of inflammatory cells in tracheal aspirates.

Methods:We studied 107 racehorses from 3 stables, in 3 different months, and measured airborne particulate matter 3 times daily in each of the stalls. On each monthly visit, horse airways were examined endoscopically and assigned a mucus score, and tracheal lavage was performed. Bivariate procedures, general estimating equations and linear mixed models were applied to estimate the association between PM and the presence of accumulations of mucus and number of inflammatory cells.

Results:Stable, stall, month and PM were all significantly associated with the presence of accumulations of tracheal mucus, which had an overall prevalence of 67%. The odds of horses having visible accumulation of mucus were increased when horses occupied enclosed stables or stalls with higher particulate concentrations, and when concentrations of larger particles (≤10 µm in diameter) were elevated. Sixty‐eight percent of tracheal wash samples contained more than 20% neutrophils. Increased numbers of neutrophils were associated with the concentration of smaller particles (≤2.5 µm in diameter).

Potential relevance:Careful consideration of stable construction and management practices focused on maintaining the lowest possible dust concentrations throughout the day should reduce the prevalence of visible accumulations of tracheal mucus, potentially improving racing performance.
Advanced Combined Cycle Systems Based on Methanol Indirect Combustion
Authors: Deng Shimin , Hynes Rory
Published: April 2012

In this paper, two new combined cycle systems with/without CO2 capture based on methanol indirect combustion are developed, which have significantly higher efficiency than methanol fueled conventional combined cycle. The performance of the new systems is compared with conventional combined cycle to identify the potential of methanol indirect combustion. The systems are modeled by using Aspen PlusTM and GTProTM. Exergy analysis and the principle of cascade utilization of chemical exergy reasonably explain the improved efficiency of the new systems. Other merits of the combined cycle systems based on methanol indirect combustion are discussed and their promising commercial application aspects are pointed out.
Prediction of Rotordynamic Coefficients for Short Labyrinth Gas Seals Using Computational Fluid Dynamics
Authors: Pugachev Alexander O. , Kleinhans Ulrich , Gaszner Manuel
Published: April 2012

The analysis is presented for the computational fluid dynamics (CFD)-based modeling of short labyrinth gas seals. Seal leakage performance can be reliably predicted with CFD for a wide operating range and various sealing configurations. Prediction of seal influence on the rotordynamic stability, however, is a challenging task requiring relatively high computer processing power. A full 3D eccentric CFD model of a short staggered three-tooth-on-stator labyrinth seal is built in ANSYS CFX. An extensive grid independence study is carried out showing influence of the grid refinement on the stiffness coefficients. Three methods for the prediction of stiffness and damping coefficients as well as the effect of turbulence modeling, boundary conditions, and solver parameters are presented. The rest of the paper shows the results of a parameter variation (inlet pressure, preswirl, and shaft rotational speed) for two labyrinth seals with a tooth radial clearance of 0.5 mm and 0.27 mm, respectively. The latter was compared with experimental data in Pugachev and Deckner, 2010, “Analysis of the Experimental and CFD-Based Theoretical Methods for Studying Rotordynamic Characteristics of Labyrinth Gas Seals,” Proceedings of ASME Turbo Expo 2010, Paper No. GT2010-22058.
Development of Al-Alloy Coating for Advanced Nuclear Systems Using Lead Alloys
Authors: Kurata Yuji , Yokota Hitoshi , Suzuki Tetsuya
Published: April 2012

Small and medium reactors using lead alloys as coolants are one of the promising reactor concepts with improved safety because of their thermal-physical and chemical properties. This paper focuses on the development of Al-alloy coating for nuclear systems using liquid lead-bismuth eutectic (LBE). Since corrosion attack becomes severe against structural steels at high temperatures in liquid LBE, it is necessary to improve the corrosion resistance of steels. An Al-alloy coating method using Al, Ti, and Fe powders, and laser beam heating has been developed. The main defects formed in the Al-powder-alloy coating process are surface defects and cracks. The conditions required to avoid these defects are the employment of the laser beam scanning rate of 20 mm/min and the adjustment of the Al concentration in the coating layer. According to the results of the corrosion tests at 550ÃÂ °C in liquid LBE, the Al-alloy coating layers on 316SS prevent severe corrosion attack such as grain boundary corrosion and LBE penetration observed in the 316SS without coating. The good corrosion resistance of the Al-alloy coating is based on the thin Al-oxide film, which can be regenerated in liquid LBE. From the viewpoint of the soundness of the produced Al-powder-alloy coating layers and the preservation of their corrosion resistance, it is estimated that the range of adequate Al concentration in the coating layer is from 4 to 12 wt. %.
Bobillier Formula for One Parameter Motions in the Complex Plane
Authors: Ersoy Soley , Bayrak Nurten
Published: April 2012

This is a brief note expanding on the aspect of Fayet (2002, “Bobillier Formula as a Fundamental Law in Planar Motion,” Z. Angew. Math. Mech., 82(3), pp. 207–210), which investigates the Bobillier formula by considering the properties up to the second order planar motion. In this note, the complex number forms of the Euler Savary formula for the radius of curvature of the trajectory of a point in the moving complex plane during one parameter planar motion are taken into consideration and using the geometrical interpretation of the Euler Savary formula, Bobillier formula is established for one parameter planar motions in the complex plane. Moreover, a direct way is chosen to obtain Bobillier formula without using the Euler Savary formula in the complex plane. As a consequence, the Euler Savary given in the complex plane will appear as a particular case of Bobillier formula.
Influence of Contact Geometry on Local Friction Energy and Stiffness of Revolute Joints
Authors: Gummer Alexander , Sauer Bernd
Published: April 2012

Revolute joints (also called pin joints or hinge joints) are used in many different mechanical systems such as robotic arms, door hinges, folding mechanisms, or hydraulic shovels. Since they transmit forces and give a rotational degree of freedom to the connected parts, revolute joints have a major impact on the dynamic behavior of the system into which they are built. Two main characteristics of these elements are their stiffness and their clearance. Both of them change as the wear between the joint’s pin and the rod hole increases during operation. In order to consider these aspects in a multibody simulation an analytical, numerically effective method has been developed to calculate the stiffness of a revolute joint in dependence of the geometry and the wear state. In addition, the calculation algorithm allows for for the analysis of the local friction energy that occurs in the contact zone. In this paper, the calculation approach is presented together with the results for two different steady loaded revolute joints.
An Efficient 3D Model of Heterogeneous Materials for Elastic Contact Applications Using Multigrid Methods
Authors: Boffy Hugo , Baietto Marie-Christine , Sainsot Philippe , Lubrecht Antonius A.
Published: April 2012

A 3D graded coating/substrate model based on multigrid techniques within a finite difference frame work is presented. Localized refinement is implemented to optimize memory requirement and computing time. Validation of the solver is performed through a comparison with analytical results for (i) a homogeneous material and (ii) a graded material. The algorithm performance is analyzed through a parametric study describing the influence of layer thickness (0.01 < t/a < 10) and mechanical properties (0.005 < Ec/Es < 10) of the coating on the contact parameters (Ph, a). Three-dimensional examples are then presented to illustrate the efficiency and the large range of possibilities of the model. The influence of different gradations of Young’s modulus, constant, linear and sinusoidal, through the coating thickness on the maximum tensile stress is analyzed, showing that the sinusoidal gradation best accommodates the property mismatch of two successive layers. A final case is designed to show that full 3D spatial property variations can be accounted for. Two spherical inclusions of different size made from elastic solids with Young’s modulus and Poisson’s ratio are embedded within an elastically mismatched finite domain and the stress field is computed.
A Computational Fluid Dynamics/Bulk-Flow Hybrid Method for Determining Rotordynamic Coefficients of Annular Gas Seals
Authors: Migliorini Patrick J. , Untaroiu Alexandrina , Wood Houston G. , Allaire Paul E.
Published: April 2012

This paper presents a new computational fluid dynamics (CFD)/bulk-flow hybrid method to determine the rotordynamic characteristics of annular gas seals. The method utilizes CFD analysis to evaluate the unperturbed base state flow, an averaging method to determine the base state bulk-flow variables, and a bulk-flow perturbation method to solve for the fluid forces acting on an eccentric, whirling rotor. In this study the hybrid method is applied to a hole-pattern seal geometry and compared with experimental data and numerical and analytical methods. The results of this study show that the dynamic coefficients predicted by the hybrid method agree well with the experimental data, producing results that are comparable with a full, three-dimensional, transient, whirling rotor CFD method. Additionally, the leakage rate predicted by the hybrid method is more agreeable with experiment than the other methods. The benefit of the present method is the ability to calculate accurate rotordynamic characteristics of annular seals that are comparable to results produced by full, transient CFD analyses with a simulation time on the order of bulk-flow analyses.
Simple Activities to Improve Students' Understanding of Microscopic Friction
Authors: Corpuz Edgar de Guzman , Rebello N. Sanjay
Published: April 2012

We are currently on the verge of several breakthroughs in nanoscience and technology, and we need to prepare our citizenry to be scientifically literate about the microscopic world. Previous research1 shows that students' mental models of friction at the atomic level are significantly influenced by their macroscopic ideas. Most students see friction at the microscopic scale as due to the meshing of bumps and valleys and rubbing of atoms. Furthermore, for most students, what is true macroscopically should also be true microscopically. Friction provides a very good context for making students aware of the disparity between the macroscopic and microscopic worlds. In the proceeding sections we will present a series of activities that teachers can use to refine students' ideas of friction at the microscopic level. Several teaching interviews2 were conducted to develop and validate these activities and to establish the concepts/ideas that students adopt as they go through each of the activities.
On the Definition of Mass in Mechanics: Why Is It So Difficult?
Authors: Coelho Ricardo Lopes
Published: April 2012

In spite of the concerted efforts of physicists, philosophers, mathematicians, and logicians, no final clarification of the concept of mass has been reached. So concludes Jammer in his book on the history of the concept.1 The Nobel laureate Wilczek called our attention to the problem in his papers on the concepts of the fundamental equation of dynamics.2 In 2005, Roche wrote a paper whose title asks the question “What is mass?”3 Hecht sums up the situation in textbooks in the title of his article “There Is No Really Good Definition of Mass.”4 Where the difficulty in defining mass in classical mechanics lies is the question addressed in the present paper. Before dealing with this topic, it is important to make explicit what the problem consists of, since sometimes people think that there is no problem with mass at all.
Mode separation of Lamb waves based on dispersion compensation method
Authors: Xu Kailiang , Ta Dean , Moilanen Petro , Wang Weiqi
Published: April 2012

Ultrasonic Lamb modes typically propagate as a combination of multiple dispersive wave packets. Frequency components of each mode distribute widely in time domain due to dispersion and it is very challenging to separate individual modes by traditional signal processing methods. In the present study, a method of dispersion compensation is proposed for the purpose of mode separation. This numerical method compensates, i.e., compresses, the individual dispersive waveforms into temporal pulses, which thereby become nearly un-overlapped in time and frequency and can thus be extracted individually by rectangular time windows. It was further illustrated that the dispersion compensation also provided a method for predicting the plate thickness. Finally, based on reversibility of the numerical compensation method, an artificial dispersion technique was used to restore the original waveform of each mode from the separated compensated pulse. Performances of the compensation separation techniques were evaluated by processing synthetic and experimental signals which consisted of multiple Lamb modes with high dispersion. Individual modes were extracted with good accordance with the original waveforms and theoretical predictions.
A Bayesian approach to sound source reconstruction: Optimal basis, regularization, and focusing
Authors: Antoni Jérôme
Published: April 2012

The reconstruction of acoustical sources from discrete field measurements is a difficult inverse problem that has been approached in different ways. Classical methods (beamforming, near-field acoustical holography, inverse boundary elements, wave superposition, equivalent sources, etc.) all consist—implicitly or explicitly—in interpolating the measurements onto some spatial functions whose propagation are known and in reconstructing the source field by retropropagation. This raises the fundamental question as whether, for a given source topology and array geometry, there exists an optimal interpolation basis which minimizes the reconstruction error. This paper provides a general answer to this question, by proceeding from a Bayesian formulation that is ideally suited to combining information of physical and probabilistic natures. The main findings are the followings: (1) The optimal basis functions are the M eigen-functions of a specific continuous-discrete propagation operator, with M being the number of microphones in the array. (2) The a priori inclusion of spatial information on the source field causes super-resolution according to a phenomenon coined “Bayesian focusing.” (3) The approach is naturally endowed with an internal regularization mechanism and results in a robust regularization criterion with no more than one minimum. (4) It admits classical methods as particular cases.
Rapid head-related transfer function adaptation using a virtual auditory environment
Authors: Parseihian Gaëtan , Katz Brian F. G.
Published: April 2012

The paper reports on the ability of people to rapidly adapt in localizing virtual sound sources in both azimuth and elevation when listening to sounds synthesized using non-individualized head-related transfer functions (HRTFs). Participants were placed within an audio-kinesthetic Virtual Auditory Environment (VAE) platform that allows association of the physical position of a virtual sound source with an alternate set of acoustic spectral cues through the use of a tracked physical ball manipulated by the subject. This set-up offers a natural perception-action coupling, which is not limited to the visual field of view. The experiment consisted of three sessions: an initial localization test to evaluate participants’ performance, an adaptation session, and a subsequent localization test. A reference control group was included using individual measured HRTFs. Results show significant improvement in localization performance. Relative to the control group, participants using non-individual HRTFs reduced localization errors in elevation by 10° with three sessions of 12 min. No significant improvement was found for azimuthal errors or for single session adaptation.
The development of acoustic cues to coda contrasts in young children learning American English
Authors: Song Jae Yung , Demuth Katherine , Shattuck-Hufnagel Stefanie
Published: April 2012

Research on children’s speech perception and production suggests that consonant voicing and place contrasts may be acquired early in life, at least in word-onset position. However, little is known about the development of the acoustic correlates of later-acquired, word-final coda contrasts. This is of particular interest in languages like English where many grammatical morphemes are realized as codas. This study therefore examined how various non-spectral acoustic cues vary as a function of stop coda voicing (voiced vs. voiceless) and place (alveolar vs. velar) in the spontaneous speech of 6 American-English-speaking mother-child dyads. The results indicate that children as young as 1;6 exhibited many adult-like acoustic cues to voicing and place contrasts, including longer vowels and more frequent use of voice bar with voiced codas, and a greater number of bursts and longer post-release noise for velar codas. However, 1;6-year-olds overall exhibited longer durations and more frequent occurrence of these cues compared to mothers, with decreasing values by 2;6. Thus, English-speaking 1;6-year-olds already exhibit adult-like use of some of the cues to coda voicing and place, though implementation is not yet fully adult-like. Physiological and contextual correlates of these findings are discussed.
Development of a theoretical model describing sonoporation activity of cells exposed to ultrasound in the presence of contrast agents
Authors: Forbes Monica M. , O’Brien William D.
Published: April 2012

Sonoporation uses ultrasound, with the aid of ultrasound contrast agents (UCAs), to enhance cell permeabilization, thereby allowing delivery of therapeutic compounds noninvasively into specific target cells. The objective of this study was to determine if a computational model describing shear stress on a cell membrane due to microstreaming would successfully reflect sonoporation activity with respect to the peak rarefactional pressure. The theoretical models were compared to the sonoporation results from Chinese hamster ovary cells using Definity® at 0.9, 3.15, and 5.6 MHz and were found to accurately describe the maximum sonoporation activity, the pressure where a decrease in sonoporation activity occurs, and relative differences between maximum activity and the activity after that decrease. Therefore, the model supports the experimental findings that shear stress on cell membranes secondary to oscillating UCAs results in sonoporation.
Transient-evoked otoacoustic emission generators in a nonlinear cochlea
Authors: Moleti Arturo , Botti Teresa , Sisto Renata
Published: April 2012

This study focuses on the theoretical prediction and experimental evaluation of the latency of transient-evoked otoacoustic emissions. Response components with different delay have been identified in several studies. The main generator of the transient response is assumed to be coherent reflection from cochlear roughness near the resonant place. Additional components of different latency can be generated by different mechanisms. Experimental data are re-analyzed in this study to evaluate the dependence of the latency on stimulus level, for each component of the response, showing that previous estimates of the otoacoustic emission latency were affected by systematic errors. The latency of the emission from each generator changes very little with stimulus level, whereas their different growth rate causes sharp changes of the single-valued latency, estimated as the time of the absolute maximum of the bandpass filtered response. Results of passive linear models, in which gain and bandwidth of the cochlear amplifier are strictly related, are incompatible with the observations. Although active linear models including delayed stiffness terms do predict much slower dependence of latency on the stimulus level, a suitable nonlinear model should be designed, capable of decoupling more effectively the dependence on stimulus level of amplitude and phase of the otoacoustic response.
Bayesian geoacoustic inversion using wind-driven ambient noise
Authors: Quijano Jorge E. , Dosso Stan E. , Dettmer Jan , Zurk Lisa M. , Siderius Martin , Harrison Chris H.
Published: April 2012

This paper applies Bayesian inversion to bottom-loss data derived from wind-driven ambient noise measurements from a vertical line array to quantify the information content constraining seabed geoacoustic parameters. The inversion utilizes a previously proposed ray-based representation of the ambient noise field as a forward model for fast computations of bottom loss data for a layered seabed. This model considers the effect of the array’s finite aperture in the estimation of bottom loss and is extended to include the wind speed as the driving mechanism for the ambient noise field. The strength of this field relative to other unwanted noise mechanisms defines a signal-to-noise ratio, which is included in the inversion as a frequency-dependent parameter. The wind speed is found to have a strong impact on the resolution of seabed geoacoustic parameters as quantified by marginal probability distributions from Bayesian inversion of simulated data. The inversion method is also applied to experimental data collected at a moored vertical array during the MAPEX 2000 experiment, and the results are compared to those from previous active-source inversions and to core measurements at a nearby site.
Channel selection in the modulation domain for improved speech intelligibility in noise
Authors: Wójcicki Kamil K. , Loizou Philipos C.
Published: April 2012

Background noise reduces the depth of the low-frequency envelope modulations known to be important for speech intelligibility. The relative strength of the target and masker envelope modulations can be quantified using a modulation signal-to-noise ratio, (S/N)mod, measure. Such a measure can be used in noise-suppression algorithms to extract target-relevant modulations from the corrupted (target + masker) envelopes for potential improvement in speech intelligibility. In the present study, envelopes are decomposed in the modulation spectral domain into a number of channels spanning the range of 0–30 Hz. Target-dominant modulations are identified and retained in each channel based on the (S/N)mod selection criterion, while modulations which potentially interfere with perception of the target (i.e., those dominated by the masker) are discarded. The impact of modulation-selective processing on the speech-reception threshold for sentences in noise is assessed with normal-hearing listeners. Results indicate that the intelligibility of noise-masked speech can be improved by as much as 13 dB when preserving target-dominant modulations, present up to a modulation frequency of 18 Hz, while discarding masker-dominant modulations from the mixture envelopes.
Rapid crystallization from acoustically levitated droplets
Authors: Cao Hui-Ling , Yin Da-Chuan , Guo Yun-Zhu , Ma Xiao-Liang , He Jin , Guo Wei-Hong , Xie Xu-Zhuo , Zhou Bo-Ru
Published: April 2012

This paper reports on an ultrasonic levitation system developed for crystallization from solution in a containerless condition. The system has been proven to be able to levitate droplets stably and grow crystals rapidly and freely from a levitated droplet. Crystals of four samples, including NaCl, NH4Cl, lysozyme, and proteinase K, were obtained successfully utilizing the system. The studies showed that the crystals obtained from the acoustically levitated droplets all exhibited higher growth rates, larger sizes, better shapes, fewer crystals, as well as fewer twins and shards, compared with the control on a vessel wall. The results indicated that containerless ultrasonic levitation could play a key role in improving the crystallization of both inorganic salts and proteins. The ultrasonic levitation system could be used as a ground-based microgravity simulation platform, which could swiftly perform crystallization and screening of crystallization conditions for space crystallization and other ground-based containerless techniques. Moreover, the approach could also be conveniently applied to researching the dynamics and mechanism of crystallization. In addition, the device could be used for the preparation of high-purity materials, analysis of minute or poisonous samples, study of living cells, environmental monitoring, and so on.
Frequency discrimination under conditions of comodulation masking release (L)
Authors: Buss Emily , Grose John H. , Hall Joseph W.
Published: April 2012

Masked detection thresholds can often be improved by introducing coherent masker amplitude modulation across frequency, a phenomenon referred to as comodulation masking release (CMR). While CMR can be large for detection, it is smaller for supra-threshold tasks, such as intensity discrimination. In this experiment, frequency discrimination for a 1000-Hz tone near threshold was found to be poorer in an amplitude-modulated than a steady bandpass noise. These results parallel previous findings for intensity discrimination. Although this study examined the relatively simple task of frequency discrimination, the results may have implications for more complex tasks, such as speech recognition in fluctuating noise.
Role of community tolerance level (CTL) in predicting the prevalence of the annoyance of road and rail noise
Authors: Schomer Paul , Mestre Vincent , Fidell Sanford , Berry Bernard , Gjestland Truls , Vallet Michel , Reid Timothy
Published: April 2012

Fidell et al. [(2011), J. Acoust. Soc. Am. 130(2), 791-806] have shown (1) that the rate of growth of annoyance with noise exposure reported in attitudinal surveys of the annoyance of aircraft noise closely resembles the exponential rate of change of loudness with sound level, and (2) that the proportion of a community highly annoyed and the variability in annoyance prevalence rates in communities are well accounted for by a simple model with a single free parameter: a community tolerance level (abbreviated CTL, and represented symbolically in mathematical expressions as Lct), expressed in units of DNL. The current study applies the same modeling approach to predicting the prevalence of annoyance of road traffic and rail noise. The prevalence of noise-induced annoyance of all forms of transportation noise is well accounted for by a simple, loudness-like exponential function with community-specific offsets. The model fits all of the road traffic findings well, but the prevalence of annoyance due to rail noise is more accurately predicted separately for interviewing sites with and without high levels of vibration and/or rattle.
Anechoic coatings obtained from two- and three-dimensional monopole resonance diffraction gratings
Authors: Ivansson Sven M.
Published: April 2012

Underwater sound reflections can be reduced in magnitude by a rubber coating including three-dimensional (3-D) cavities forming a doubly periodic diffraction grating. A monopole resonance for sphere-like cavities enhances absorption in the surrounding rubber solid. A corresponding resonance for an infinite cylinder is studied in the present paper. Appearing at a considerably lower frequency than for a sphere with the same radius, it suggests the possibility of much thinner anechoic coatings including cylindrical cavities, with axes in a lateral direction, forming a diffraction grating with a single period. This is effectively a 2-D case, because of invariance in the axial direction. Subsequent coating design computations, using the layer-multiple-scattering method and including cavities of different sizes, show improved reflection reduction with coatings only about one third as thick. Still accounting for multiple scattering among the cavities and capturing the essential physics, the monopole approximation is applied to advance the analytic study of the reflection reduction. An energy decomposition relation is derived and used to quantify the absorption of the incident sound energy by cavities of different sizes. Coatings based on filled inclusions and other resonance effects are briefly considered. Again, the 2-D alternative with cylinders of mixed sizes gives thinner coatings.
A study of high front vowels with articulatory data and acoustic simulations
Authors: Jackson Michel T.-T. , McGowan Richard S.
Published: April 2012

The purpose of this study is to test a methodology for describing the articulation of vowels. High front vowels are a test case because some theories suggest that high front vowels have little cross-linguistic variation. Acoustic studies appear to show counterexamples to these predictions, but purely acoustic studies are difficult to interpret because of the many-to-one relation between articulation and acoustics. In this study, vocal tract dimensions, including constriction degree and position, are measured from cinéradiographic and x-ray data on high front vowels from three different languages (North American English, French, and Mandarin Chinese). Statistical comparisons find several significant articulatory differences between North American English /i/ and Mandarin Chinese and French /i/. In particular, differences in constriction degree were found, but not constriction position. Articulatory synthesis is used to model the acoustic consequences of some of the significant articulatory differences, finding that the articulatory differences may have the acoustic consequences of making the latter languages’ /i/ perceptually sharper by shifting the frequencies of F2 and F3 upwards. In addition, the vowel /y/ has specific articulations that differ from those for /i/, including a wider tongue constriction, and substantially different acoustic sensitivity functions for F2 and F3.
Perception of urban park soundscape
Authors: Tse Man Sze , Chau Chi Kwan , Choy Yat Sze , Tsui Wai Keung , Chan Chak Ngai , Tang Shiu Keung
Published: April 2012

A number of studies have been initiated to explore how to improve the soundscape quality in urban parks. However, good soundscape quality in parks cannot be provided without a thorough understanding of the complex relationships among sound, environment, and individuals. As acoustic comfort is considered to be an important outcome of soundscape quality, this study investigates the relative impacts of the factors influencing acoustic comfort evaluation by formulating a multivariate ordered logit model. This study also explores the inter-relationships among acoustic comfort evaluation, acceptability of the environment, and preference to stay in a park using a path model. A total of 595 valid responses were obtained from interview surveys administered in four parks in Hong Kong while objective sound measurements were carried out at the survey spots concurrently. The findings unveil that acoustic comfort evaluation, besides visual comfort evaluation of landscape, also plays an important role on users’ acceptability of the urban park environment. Compared with all the studied acoustic related factors, acoustic comfort evaluation serves as a better proxy for park users’ preference to stay in urban parks. Hearing the breeze will significantly increase the likelihood of individuals in giving high acoustic comfort evaluation. Conversely, hearing the sounds from heavy vehicles or sounds from bikes will significantly reduce the likelihood in giving a high acoustic evaluation.
Vibro-acoustic analysis of a rectangular cavity bounded by a flexible panel with elastically restrained edges
Authors: Du Jing T. , Li Wen L. , Xu Hong A. , Liu Zhi G.
Published: April 2012

A coupled system consisting of an acoustic cavity and an elastic panel is a classical problem in structural acoustics and is typically analyzed using modal approaches based on in vacuo structural modes and the rigidly walled acoustic modes which are pre-determined based on separate component models. Such modeling techniques, however, tend to suffer the following drawbacks or limitations: (a) a panel is only subjected to ideal boundary conditions such as the simply supported, (b) the coupling between the cavity and panel is considered weak, and (c) the particle velocity cannot be correctly predicted from the pressure gradient on the contacting interface, to name a few. Motivated by removing these restrictions, this paper presents a general method for the vibro-acoustic analysis of a three-dimensional (3D) acoustic cavity bounded by a flexible panel with general elastically restrained boundary conditions. The displacement of the plate and the sound pressure in the cavity are constructed in the forms of standard two-dimensional and 3D Fourier cosine series supplemented by several terms introduced to ensure and accelerate the convergence of the series expansions. The unknown expansions coefficients are treated as the generalized coordinates and determined using the Rayleigh–Ritz procedure based on the energy expressions for the coupled structural acoustic system. The accuracy and effectiveness of the proposed method are demonstrated through numerical examples and comparisons with the results available in the literature.
`Spatial impulse response of a rectangular double curved transducer
Authors: Bæk David Böttcher , Jensen Jørgen Arendt , Willatzen Morten
Published: April 2012

Calculation of the pressure field from transducers with both a convex and a concave surface geometry is a complicated assignment that often is accomplished by subdividing the transducer surface into smaller flat elements of which the spatial impulse response is known. This method is often applied to curved transducers because an analytical solution is unknown. In this work a semi-analytical algorithm for the exact solution to a first order in diffraction effect of the spatial impulse response of rectangular-shaped double curved transducers is presented. The solution and an approximation to it are investigated. The approximation reformulates the solution to an analytically integrable expression, which is computationally efficient to solve. Simulation results are compared to FIELD II simulations. Calculating the response from 200 different points yields a mean error for the different approximations ranging from 0.03% to 0.8% relative to a numerical solution for the spatial impulse response. It is also shown that the presented algorithm gives consistent results with FIELD II for a linear flat, a linear focused, and a convex nonfocused element. The solution involved a three-point Taylor expansion and gave an accuracy of 0.01%.
Computational Approaches to Developmental Patterning
Authors: Morelli Luis G. , Uriu Koichiro , Ares Saúl , Oates Andrew C.
Published: April 2012

Computational approaches are breaking new ground in understanding how embryos form. Here, we discuss recent studies that couple precise measurements in the embryo with appropriately matched modeling and computational methods to investigate classic embryonic patterning strategies. We include signaling gradients, activator-inhibitor systems, and coupled oscillators, as well as emerging paradigms such as tissue deformation. Parallel progress in theory and experiment will play an increasingly central role in deciphering developmental patterning.
Using Gene Expression Noise to Understand Gene Regulation
Authors: Munsky Brian , Neuert Gregor , van Oudenaarden Alexander
Published: April 2012

Phenotypic variation is ubiquitous in biology and is often traceable to underlying genetic and environmental variation. However, even genetically identical cells in identical environments display variable phenotypes. Stochastic gene expression, or gene expression “noise,” has been suggested as a major source of this variability, and its physiological consequences have been topics of intense research for the last decade. Several recent studies have measured variability in protein and messenger RNA levels, and they have discovered strong connections between noise and gene regulation mechanisms. When integrated with discrete stochastic models, measurements of cell-to-cell variability provide a sensitive “fingerprint” with which to explore fundamental questions of gene regulation. In this review, we highlight several studies that used gene expression variability to develop a quantitative understanding of the mechanisms and dynamics of gene regulation.
Cell Polarity: Quantitative Modeling as a Tool in Cell Biology
Authors: Mogilner Alex , Allard Jun , Wollman Roy
Published: April 2012

Among a number of innovative approaches that have modernized cell biology, modeling has a prominent yet unusual place. One popular view is that we progress linearly, from conceptual to ever more detailed models. We review recent discoveries of cell polarity mechanisms, in which modeling played an important role, to demonstrate that the experiment-theory feedback loop requires diverse models characterized by varying levels of biological detail and mathematical complexity. We argue that a quantitative model is a tool that has to fit an experimental study, and the model’s value should be judged not by how complex and detailed it is, but by what could be learned from it.