Steady-state Background Research Articles

Comparing Kurtosis-adjusted weighted levels with other metrics to assess the risk of hearing loss from non-Gaussian noise exposures

Several studies have shown that impulsive noise can cause more damage to hearing than steady-state noise of equal energy. As a result, a large body of research has been devoted to evaluating the hazards of impulsive noise. However, work environments often have varying noise patterns, including Gaussian background noise combined with high-level transient noises contributing to the worker's daily dose. Thus, an energy-based noise metric underestimates the risk of hearing loss unless incorporating a temporal structure correction term. Kurtosis has been reported as an effective adjunct to energy for predicting hearing hazards from non-Gaussian noise exposures. In this work, recordings of real impulsive noise were conducted using a portable measuring system at a very high sampling frequency and using high-pressure microphones. Controlled synthetic non-Gaussian noise was generated using these impulsive signals and steady-state background noise. After exploring the detailed temporal structure of the noise, the daily exposure time has been determined using different metrics, including kurtosis-adjusted weighted levels, weighted peak levels, and auditory risk units. The examples presented here aim to demonstrate how kurtosis can help develop more accurate methods to prevent noise-induced hearing loss.

Pebble-driven migration of low-mass planets in the 2D regime of pebble accretion

Pebbles drifting past a disk-embedded low-mass planet develop asymmetries in their distribution and exert a substantial gravitational torque on the planet, thus modifying its migration rate. Our aim is to assess how the distribution of pebbles and the resulting torque change in the presence of pebble accretion, focusing on its 2D regime. First, we performed 2D high-resolution multi-fluid simulations with Fargo3D but found that they are impractical for resolving pebble accretion due to the smoothing of the planetary gravitational potential. To remove the smoothing and directly trace pebbles accreted by the planet, we developed a new code Deneb which evolves an ensemble of pebbles, represented by Lagrangian superparticles, in a steady-state gaseous background. For small and moderate Stokes numbers, $ St pebble accretion creates two underdense regions with a front-rear asymmetry with respect to the planet. The underdensity trailing the planet is more extended. The resulting excess of pebble mass in front of the planet then makes the pebble torque positive and capable of outperforming the negative gas torque. Pebble accretion thus enables outward migration (previously thought to occur mainly for $ St in a larger portion of the parameter space. It occurs for the planet mass pl oplus $ and for all the Stokes numbers considered in our study, $ St $, assuming a pebble-to-gas mass ratio of $Z=0.01$. If some of the observed planets underwent outward pebble-driven migration during their accretion, the formation sites of their progenitor embryos could have differed greatly from the usual predictions of planet formation models. To enable an update of the respective models, we provide a scaling law for the pebble torque that can be readily incorporated in N-body simulations.

Precise Electrochemical Sizing of Individual Electro-Inactive Particles.

Nanoimpact electrochemistry enables the time-resolved in situ characterization (e.g., size, catalytic activity) of single nanomaterial units, providing a means of elucidating heterogeneities that would be masked in ensemble studies. To implement this technique with redox inactive particles, a solution-phase redox reaction is used to produce a steady-state background current on a disk ultramicroelectrode. When a particle adsorbs onto the electrode, it produces a stepwise reduction in the exposed electrode area, which produces, in turn, a stepwise decrease in the current commensurate with the size of the adsorbing species. Historically, however, nanoimpact electrochemistry has suffered from "edge effects," in which the radial diffusion layer formed at the circumference of the ultramicroelectrodes renders the step size dependent not only on the size of the particle but also on where it lands on the electrode. The introduction of electrocatalytic current generation, however, mitigates the heterogeneity caused by edge effects, thus improving the measurement precision. In this approach, termed "electrocatalytic interruption," a substrate that regenerates the redox probe at the diffusion layer is introduced. This shifts the rate-limiting step of the current generation from diffusion to the homogeneous reaction rate constant, thus reducing flux heterogeneity and increasing the precision of particle sizing by an order of magnitude. The protocol described here explains the set-up and data collection employed in nanoimpact experiments implementing this effect for improved precision in the sizing of redox in-active materials.

Particle-in-cell simulations of parallel dynamics of a blob in the scrape-off-layer plasma of a generic medium-size tokamak

In this work we investigate, in a fully-kinetic particle approach, the evolution of a blob inside a flux tube in the scrape-off-layer (SOL) plasma of a generic diverted medium-size tokamak and its contribution to the recorded particle and energy flux densities at the divertor. Initially, a steady-state background plasma is reached, with realistic plasma profiles in the parallel direction. On top of it, a blob source with given intensity and temperature is superimposed at the outer midplane. The blob source is active for 10 in order to emulate a generic blob with 1 cm diameter crossing the magnetic flux tube with a typical 1 km s−1 radial drift velocity. We have observed that most of the blob’s hot electrons are screened off by the cold electrons of the SOL plasma and can travel towards the two divertors free of the initial ambipolar forces. Performing a density scan and having a blob-to-background density ratio in the source region, we observe that due to Coulomb collisions these hot electrons can reach the outer divertor or also the inner one, depending on the density of the background SOL plasma. Consequently, the midplane–divertor potential difference increases and the sheath expands leading to a significant increase in the background ion energy flux density onto the divertor. We also observe that when the blob ions reach the divertor the electron flux density on the divertor increases due to ambipolar forces. Through Coulomb collisions, a part of the thermal energy of the hot blob ions is transferred to the main (background) plasma, depending on the plasma density. Most of the energy deposited into the divertor is brought by the ions and the blob-induced background ion energy flux density becomes comparable (low-density case) or much higher (high-density case) than the blob ion energy flux density.

Finite-time blowup and ill-posedness in Sobolev spaces of the inviscid primitive equations with rotation

Large scale dynamics of the oceans and the atmosphere are governed by the primitive equations (PEs). It is well-known that the three-dimensional viscous PEs is globally well-posed in Sobolev spaces. On the other hand, the inviscid PEs without rotation is known to be ill-posed in Sobolev spaces, and its smooth solutions can form singularity in finite time. In this paper, we extend the above results in the presence of rotation. We construct finite-time blowup solutions to the inviscid PEs with rotation, and establish that the inviscid PEs with rotation is ill-posed in Sobolev spaces in the sense that its perturbation around a certain steady state background flow is both linearly and nonlinearly ill-posed in Sobolev spaces. Its linear instability is of the Kelvin-Helmholtz type similar to the one appears in the context of vortex sheets problem. This implies that the inviscid PEs is also linearly ill-posed in Gevrey class of order s>1, and suggests that a suitable space for the well-posedness is Gevrey class of order s=1, which is exactly the space of analytic functions.

Effect of Spectral Contrast Enhancement on Speech-on-Speech Intelligibility and Voice Cue Sensitivity in Cochlear Implant Users.

Speech intelligibility in the presence of a competing talker (speech-on-speech; SoS) presents more difficulties for cochlear implant (CI) users compared with normal-hearing listeners. A recent study implied that these difficulties may be related to CI users' low sensitivity to two fundamental voice cues, namely, the fundamental frequency (F0) and the vocal tract length (VTL) of the speaker. Because of the limited spectral resolution in the implant, important spectral cues carrying F0 and VTL information are expected to be distorted. This study aims to address two questions: (1) whether spectral contrast enhancement (SCE), previously shown to enhance CI users' speech intelligibility in the presence of steady state background noise, could also improve CI users' SoS intelligibility, and (2) whether such improvements in SoS from SCE processing are due to enhancements in CI users' sensitivity to F0 and VTL differences between the competing talkers. The effect of SCE on SoS intelligibility and comprehension was measured in two separate tasks in a sample of 14 CI users with Cochlear devices. In the first task, the CI users were asked to repeat the sentence spoken by the target speaker in the presence of a single competing talker. The competing talker was the same target speaker whose F0 and VTL were parametrically manipulated to obtain the different experimental conditions. SoS intelligibility, in terms of the percentage of correctly repeated words from the target sentence, was assessed using the standard advanced combination encoder (ACE) strategy and SCE for each voice condition. In the second task, SoS comprehension accuracy and response times were measured using the same experimental setup as in the first task, but with a different corpus. In the final task, CI users' sensitivity to F0 and VTL differences were measured for the ACE and SCE strategies. The benefit in F0 and VTL discrimination from SCE processing was evaluated with respect to the improvement in SoS perception from SCE. While SCE demonstrated the potential of improving SoS intelligibility in CI users, this effect appeared to stem from SCE improving the overall signal to noise ratio in SoS rather than improving the sensitivity to the underlying F0 and VTL differences. A second key finding of this study was that, contrary to what has been observed in a previous study for childlike voice manipulations, F0 and VTL manipulations of a reference female speaker (target speaker) toward male-like voices provided a small but significant release from masking for the CI users tested. The present findings, together with those previously reported in the literature, indicate that SCE could serve as a possible background-noise-reduction strategy in commercial CI speech processors that could enhance speech intelligibility especially in the presence of background talkers that have longer VTLs compared with the target speaker.

Chemical Signaling in the Turbulent Ocean—Hide and Seek at the Kolmogorov Scale

Chemical cues and signals mediate resource acquisition, mate finding, and the assessment of predation risk in marine plankton. Here, we use the chemical properties of the first identified chemical cues from zooplankton together with in situ measurements of turbulent dissipation rates to calculate the effect of turbulence on the distribution of cues behind swimmers as well as steady state background concentrations in surrounding water. We further show that common zooplankton (copepods) appears to optimize mate finding by aggregating at the surface in calm conditions when turbulence do not prevent trail following. This near surface environment is characterized by anisotropic turbulence and we show, using direct numerical simulations, that chemical cues distribute more in the horizontal plane than vertically in these conditions. Zooplankton may consequently benefit from adopting specific search strategies near the surface as well as in strong stratification where similar flow fields develop. Steady state concentrations, where exudation is balanced by degradation develops in a time scale of ~5 h. We conclude that the trails behind millimeter-sized copepods can be detected in naturally occurring turbulence below the wind mixed surface layer or in the absence of strong wind. The trails, however, shorten dramatically at high turbulent dissipation rates, above ~10−3 cm2 s−3 (10−7 W kg−1)

MUX/DEMUX SiC receiver for visible light communications

In this paper we present a MUX/DEMUX device based on a multilayer a-SiC:H optical filter that requires near-ultraviolet steady state optical switches to select desired wavelengths in the visible range. The selector filter is realized by using a two terminal double pi’n/pin a-SiC:H photodetector. Five visible communication channels are transmitted together, each one with a specific bit sequence. The combined optical signal is analyzed by reading out the photocurrent, under near-UV front steady state background. Data shows that 25 current levels are detected and corresponds to the thirty-two on/off possible states. The proximity of the magnitude of consecutive levels causes occasional errors in the decoded information. To minimize the errors, four parity bit are generated and stored along with the data word. The parity of the word is checked after reading the word to detect and correct the transmitted data. Results showed that the background works as a selector in the visible range, shifting the sensor sensitivity and together with the parity check bits allows the identification and decoding of the different input channels. A transmission capability of 60 kbps using the generated codeword was achieved.

Development of a LIBS system for in situ surface measurements during plasma exposure in PISCES-A.

A laser-induced breakdown spectroscopy (LIBS) system has been developed with a Q-switched Nd:YAG laser (wavelength = 1064 nm and pulse width ∼5 ns) to conduct in situ surface measurements during plasma exposure in the PISCES-A linear divertor plasma simulator. The LIBS signal enhancement is obtained with both the magnetic field normal to the surface of a target and steady-state background plasma. Migration of sputtered Ta impurities onto the neighboring Cr surface is identified during He plasma exposure, only when cone structures are formed on the Cr surface. D retention in W during D plasma exposure is observed to decrease with increasing the sample temperature. The temporal evolution of D outgassing from W is measured in a time range of ∼10-420 s right after D plasma exposure. A power law fit, t -α , yields α ∼ 0.34 ± 0.09, which is nearly consistent with calculated and measured values.

General relativity as a unified fluid and field theory

Einstein’s dream for a unified field theory of Nature is attained with a classical fluid theory founded on space, time and spin, rather than on Einstein’s spacetime. An invariant quantum theory for the primordial fluid obeys the homogeneous Klein-Gordon equation, which is the same three-dimensional classical wave equation (CWE) initially tried by Schrödinger to formulate quantum mechanics (QM), but abandoned by linear superposition considerations. Primordial fluid pervades universe, obeys energy and momentum conservation, and is formed by sagions: energy-like, discrete, extended Planck-size objects of finite size, carriers of linear momentum and spin, moving in absolute 3D-curved space with speed C along straightest path. We briefly describe our novel non-harmonic and inherently quantized solutions for CWE in spherical coordinates, discovered in 1995. Solutions include a steady-state background field (possibly related to the CMB, to non-locality, and to action-at-a-distance), quantized helices, and inherently quantized functions exhibiting stable dynamic equilibrium, and isomorphism under many transformations, including the classical Doppler case, and the relativistic Lorentz, Poincaré, and Einstein transformations. Isomorphism pre-empts ab initio a few interpretative issues regarding relativistic and classical transformations. Mathematical fields represent the realistic physical temporal evolution of the primordial fluid in curved 3D-space.

Study of impurity effects on CFETR steady-state scenario by self-consistent integrated modeling

Impurity effects on fusion performance of China fusion engineering test reactor (CFETR) due to extrinsic seeding are investigated. An integrated 1.5D modeling workflow evolves plasma equilibrium and all transport channels to steady state. The one modeling framework for integrated tasks framework is used to couple the transport solver, MHD equilibrium solver, and source and sink calculations. A self-consistent impurity profile constructed using a steady-state background plasma, which satisfies quasi-neutrality and true steady state, is presented for the first time. Studies are performed based on an optimized fully non-inductive scenario with varying concentrations of Argon (Ar) seeding. It is found that fusion performance improves before dropping off with increasing , while the confinement remains at high level. Further analysis of transport for these plasmas shows that low-k ion temperature gradient modes dominate the turbulence. The decrease in linear growth rate and resultant fluxes of all channels with increasing can be traced to impurity profile change by transport. The improvement in confinement levels off at higher . Over the regime of study there is a competition between the suppressed transport and increasing radiation that leads to a peak in the fusion performance at (~2.78 for CFETR). Extrinsic impurity seeding to control divertor heat load will need to be optimized around this value for best fusion performance.

Balancing the detrimental effects of office noise annoyance and distraction on work performance

Broadband, steady-state background noise can improve open office conditions by facilitating speech privacy and reducing distraction caused by intermittent, occupancy-generated noise. The background noise is typically generated by HVAC systems, though can be added with loudspeakers to boost speech masking. However, too high background noise levels can cause annoyance, fatigue, and other noise-related symptoms. It is yet unclear whether noise annoyance or distraction impairs work performance more. This study investigated the trade-off between noise annoyance and distraction, as well as their effects on acoustic dissatisfaction and performance. Subjects performed cognitive tasks while exposed to simulated office acoustic environments reproduced using higher-order Ambisonics. At fixed time intervals, the subjects could change the acoustic environment by adjusting either the background or intermittent noise levels. Lowering background noise caused the intermittent noise to rise, and vice versa. By the end of testing, it was expected that each subject equalized their dissatisfactions of the two noise types. Annoyance and distraction were assessed with a survey at each time interval. Physiological measures, including heart rate variability and skin conductance, were collected to correlate arousal/stress levels with each acoustic environment. The results of the study may provide context to effectively utilize background noise in open-plan offices.

Impact of an alternative steroid on the relative bioavailability and bioequivalence of a novel versus the originator formulation of abiraterone acetate

PurposeThe originator abiraterone acetate (OAA) formulation is used for the treatment of metastatic castration-resistant prostate cancer (mCRPC). This study evaluated the bioavailability and bioequivalence of a novel formulation, abiraterone acetate fine particle (AAFP), versus OAA on a steady-state background of steroids.MethodsThirty-seven healthy male subjects were randomized in a crossover design to receive methylprednisolone (4 mg twice daily) or prednisone (5 mg twice daily) for 12 days in Period 1. On Day 11 of Period 1, subjects given methylprednisolone received a single dose of AAFP 500 mg, and subjects given prednisone received a single dose of OAA 1000 mg under fasted conditions. After a 2-week steroid washout period, subjects received the alternate treatments in Period 2.ResultsThere were no statistical differences regarding area under the curve (AUC) and maximum concentration (Cmax) between AAFP and OAA. The bioavailability of abiraterone from AAFP versus OAA by geometric mean ratio was AUC0–∞, 95.9% (90% confidence interval [CI] 86.0–106.9); AUC0–t, 99.2% (88.7–110.9); and Cmax, 116.8% (102.2–133.4). The coefficient of variation (CV) was smaller for AAFP versus OAA (AUC0–∞, CV 44.23 vs. 55.61%; AUC0–t, 45.17 vs. 58.16%; Cmax, 54.55 vs. 65.65%, respectively). Both treatments were safe and well tolerated.ConclusionsAAFP plus methylprednisolone provided abiraterone exposure that was comparable to OAA plus prednisone with respect to Cmax and AUC. Less drug exposure variability was observed with AAFP compared with OAA. Reduced pharmacokinetic variability may positively influence clinical outcomes and warrants further study in mCRPC patients.

Time-domain Brillouin scattering for the determination of laser-induced temperature gradients in liquids.

We present an optical technique based on ultrafast photoacoustics to determine the local temperature distribution profile in liquid samples in contact with a laser heated optical transducer. This ultrafast pump-probe experiment uses time-domain Brillouin scattering (TDBS) to locally determine the light scattering frequency shift. As the temperature influences the Brillouin scattering frequency, the TDBS signal probes the local laser-induced temperature distribution in the liquid. We demonstrate the relevance and the sensitivity of this technique for the measurement of the absolute laser-induced temperature gradient of a glass forming liquid prototype, glycerol, at different laser pump powers-i.e., different steady state background temperatures. Complementarily, our experiments illustrate how this TDBS technique can be applied to measure thermal diffusion in complex multilayer systems in contact with a surrounding liquid.

VIS/NIR wavelength selector based on a multilayer pi'n/pin a‐SiC:H optical filter

AbstractIn this paper, we present a tandem visible/nearinfrared (VIS/NIR) wavelength selector based on a multilayer a‐SiC:H optical filter that requires appropriate near‐ultraviolet steady states optical switches to select the desired wavelengths in the VIS/NIR ranges. Spectral response measurements are presented and show the feasibility of tailoring the wavelength and bandwidth of a polychromatic mixture of different wavelengths. The selector filter is realized by using a two terminal double pi'n/pin a‐SiC:H photodetector. Five visible/infrared communication channels are transmitted together, each one with a specific bit sequence. The combined optical signal is analysed by reading out the photocurrent, under near‐UV steady state background. Results show that the background side and intensity works as a selector in the infrared/visible regions, shifting the sensor sensitivity. This nonlinearity allows the identification and decoding of the different input channels in the visible/infrared ranges. This concept is extended to implement a 1 by 5 wavelength division multiplexer with channel separation in the VIS/NIR range and a transmission capability of 30 Kbps. The relationship between the optical inputs and the output signal is established and an algorithm to decode the Multiplexed (MUX) signal presented. An optoeletronic model gives insight on the system physics. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Two-dimensional analysis of the stability of conducting medium flows between permeable plane electrodes inclined to the horizon

Flows of a conducting continuous medium due to Joule heat generation in an inclined plane layer in the presence of the gravity force are considered on the basis of the Oberbeck-Boussinesq equations and a thermal discharge model. One-dimensional steady-state background solutions are constructed and volt-ampere characteristics (VAC) are studied for a model temperature dependence (linearly decreasing) of the specific electric resistance of the interelectrode medium. The investigation is carried out taking the electrode permeability into account for a conducting medium in the presence of blowing through a single electrode and suction through the other. An analysis of stability carried out in the electrical engineering (one-dimensional) approximation shows that under certain conditions there exist solutions corresponding to a VAC fragment with negative differential resistance. Flows of the continuous medium corresponding to these solutions can be unstable in the interelectrode discharge gap. The results of calculations of the instability growth rate of a horizontal layer are given in the electrothermal approximation when there are no velocity perturbations.

Stability of conducting medium flows between plane continuous electrodes inclined to the horizon

The mathematical formulation of the problem of analysis of the stability of flows of a conducting continuous medium associated with Joule heat generation in an inclined plane layer in the presence of the gravity force is formulated. A one-dimensional steady-state background solution is found. Volt-ampere characteristics (VAC) are constructed and investigated. It is shown that S-shaped voltage dependences of the current density can exist under certain conditions when three solutions with different current densities are possible for a given voltage. The solution with the mean current density that corresponds to the VAC fragment with a negative differential resistance is unstable. A model of analysis of two-dimensional perturbations based on the Oberbeck-Boussinesq equations and a thermal discharge model is proposed.

Transient Characterization of Hybrid Microfluidic-Thermoelectric Cooling Scheme for Dynamic Thermal Management of Microprocessor

Power dissipated by modern microprocessors is a function of time and continuously changes with the workload, giving rise to temporal hotspots of local areas with very high power dissipation. A hybrid cooling scheme has been proposed, which combines solid-state cooling to remove the dynamically changing hotspots in real time while addressing the steady-state background power dissipation using liquid cooling in embedded microchannels. In this paper, we have investigated the transient behavior of the hybrid scheme through experiments as well as computational modeling. Infrared microscopy, equipped with transient detector, was used to study the transient cooling behavior when a power spike is produced by a microfabricated heater, emulating a hot spot. The results indicate that solid-state superlattice cooling (SLC) offers an extremely fast transient response, having time constant of the order of few tens of microseconds which matches with dynamics of microprocessor power dissipation. The effect of various geometric and operating conditions on the transient behavior of the hybrid scheme has been assessed to provide an insight and guidelines for optimal design and operation of the proposed hybrid cooling scheme.

Hypoxanthine Biosensor Based on Immobilization of Xanthine Oxidase on Modified Pt Electrode and Its Application for Fish Meat

In this study, hypoxanthine biosensor based on immobilization of xanthine oxidase on polyvinylferrocenium perchlorate matrix coated Pt electrode for detection of hypoxanthine was presented. The steady-state background current of the biosensor was measured at+0.5V, which was due to the electrooxidation of enzymatically produced H2O2. The biosensor exhibited a linear range from 2.15 × 10−3mM to 1.03mM (r = 0.9963) with a detection limit of 6.5 × 10−4mM (S/N = 3) for the detection of hypoxanthine. The storage stability of the biosensor, the effect of interference by uric acid, and the applicability to fish sample of the biosensor analysis were also evaluated.

Simulation of Three PPCPs Existed in Major Pearl River with an ASM Model Including a Separate Degrading Microorganism

Hundreds of different pharmaceuticals and personal care products (PPCPs) are usually detected in urban riverine waters, and have long been attracting attention for their potential toxic effect to river ecosystems and even to human beings. Biodegradation and sorption are known as the main mechanisms to remove PPCPs in activated sludge systems, the characteristics of their removal process in rivers, however, are still less known. We developed an ASM-based process model including aerobic growth and decay of a specific PPCPs-degrading microorganism and try to simulate the transformation and conversion process of three main endocrine-disrupting phenols (nonylphenol, bisphenol-A, triclosan) in Major Pearl River Delta, South China. Firstly we aquired the data of river conditions and substances concentrations, then set up a model by WEST software which contains ASM theories, here the form of river system was simplified. Subsequently conducted parameter calibration and operated the simulating process using steady-state background concentrations. Validation results show that when the river is seen as series of aerobic tanks the removal of PPCPs in the system is similar to that traditional organic matters degrading by activated sludge process, and that the transport fate of PPCPs is sensitive to three model parameters of the hypothesized microorganism: concentration in the system, half saturation coefficient and maximum specific growth rate, and that the main effect of PPCPs removal in river is aerobic growth of organisms and that adsorption can be nearly ignored during the process. The proposed model shows considerable success in capturing important characteristics of the observed PPCPs transformation, thus this method could acquainting the knowledge of PPCPs changes in river aquatic environment by adjusting the model parameters according to practical conditions. Further mechanism analysis should be conducted to optimize the model.