bluuebunny/crossref_metadata_2025 huggingface dataset:
A regional registration technique for automated interval change analysis of breast lesions on mammograms
Authors: Sanjay‐Gopal S. , Chan Heang‐Ping , Wilson Todd , Helvie Mark , Petrick Nicholas , Sahiner Berkman
Published: July 2002

Analysis of interval change is a useful technique for detection of abnormalities in mammographic interpretation. Interval change analysis is routinely used by radiologists and its importance is well‐established in clinical practice. As a first step to develop a computerized method for interval change analysis on mammograms, we are developing an automated regional registration technique to identify corresponding lesions on temporal pairs of mammograms. In this technique, the breast is first segmented from the background on the current and previous mammograms. The breast edges are then aligned using a global alignment procedure based on the mutual information between the breast regions in the two images. Using the nipple location and the breast centroid estimated independently on both mammograms, a polar coordinate system is defined for each image. The polar coordinate of the centroid of a lesion detected on the most recent mammogram is used to obtain an initial estimate of its location on the previous mammogram and to define a fan‐shaped search region. A search for a matching structure to the lesion is then performed in the fan‐shaped region on the previous mammogram to obtain a final estimate of its location. In this study, a quantitative evaluation of registration accuracy has been performed with a data set of 74 temporal pairs of mammograms and ground‐truth correspondence information provided by an experienced radiologist. The most recent mammogram of each temporal pair exhibited a biopsy‐proven mass. We have investigated the usefulness of correlation and mutual information as search criteria for determining corresponding regions on mammograms for the biopsy‐proven masses. In 85% of the cases (63/74 temporal pairs) the region on the previous mammogram that corresponded to the mass on the current mammogram was correctly identified. The region centroid identified by the registration technique had an average distance of 2.8±1.9 mm from the centroid of the radiologist‐identified region. These results indicate that our new registration technique may be useful for establishing correspondence between structures on current and previous mammograms. Once such a correspondence is established an interval change analysis could be performed to aid in both detection as well as classification of abnormal breast densities.
DPOAE group delays versus electrophysiological measures of cochlear delay in normal human ears
Authors: Schoonhoven Ruurd , Prijs Vera F. , Schneider Sandra
Published: July 2002

Group delays of 2 f1−f2 distortion product otoacoustic emissions (DPOAEs) were determined using both f1- and f2-sweep paradigms in 24 normal-hearing subjects. These DPOAE group delays were studied in comparison with cochlear delays estimated from derived band VIIIth nerve compound action potentials (CAPs) and auditory brainstem responses (ABRs) in the same subjects. The center frequencies of the derived bands in the electrophysiological experiment were matched with the f2-frequencies in the DPOAE recording to ensure that DPOAEs and derived CAPs and ABRs were generated at the same places along the cochlear partition, thus allowing for a direct comparison. The degree to which DPOAE group delays are larger in the f2- than in the f1-sweep paradigm is consistent with a theoretical analysis of the so-called wave-fixed model. Both DPOAE group delays are highly correlated with CAP- and ABR-derived measures of cochlear delay. The principal result of this study is that “roundtrip” DPOAE group delay in the f1-sweep paradigm is exactly twice as large as the neural estimate of the “forward” cochlear delay. The interpretation of this notion in the context of cochlear wave propagation properties and DPOAE-generating mechanisms is discussed.
Intensity-invariance of fine time structure in basilar-membrane click responses: Implications for cochlear mechanics
Authors: Shera Christopher A.
Published: July 2002

Basilar-membrane and auditory-nerve responses to impulsive acoustic stimuli, whether measured directly in response to clicks or obtained indirectly using cross- or reverse-correlation and/or Fourier analysis, manifest a striking symmetry: near-invariance with stimulus intensity of the fine time structure of the response over almost the entire dynamic range of hearing. This paper explores the origin and implications of this symmetry for cochlear mechanics. Intensity-invariance is investigated by applying the EQ-NL theorem [de Boer, Aud. Neurosci. 3, 377–388 (1997)] to define a family of linear cochlear models in which the strength of the active force generators is controlled by a real-valued, intensity-dependent parameter, γ (with 0⩽γ⩽1). The invariance of fine time structure is conjectured to imply that as γ is varied the poles of the admittance of the cochlear partition remain within relatively narrow bands of the complex plane oriented perpendicular to the real frequency axis. Physically, the conjecture implies that the local resonant frequencies of the cochlear partition are nearly independent of intensity. Cochlear-model responses, computed by extending the model obtained by solution of the inverse problem in squirrel monkey at low sound levels [Zweig, J. Acoust. Soc. Am. 89, 1229–1254 (1991)] with three different forms of the intensity dependence of the partition admittance, support the conjecture. Intensity-invariance of cochlear resonant frequencies is shown to be consistent with the well-known “half-octave shift,” describing the shift with intensity in the peak (or best) frequency of the basilar-membrane frequency response. Shifts in best frequency do not arise locally, via changes in the underlying resonant frequencies of the partition, but globally through the intensity dependence of the driving pressure. Near-invariance of fine time structure places strong constraints on the mechanical effects of force generation by outer hair cells. In particular, the symmetry requires that the feedback forces generated by outer hair cells (OHCs) not significantly affect the natural resonant frequencies of the cochlear partition. These results contradict many, if not most, cochlear models, in which OHC forces produce significant changes in the reactance and resonant frequencies of the partition.
Sound propagation in rigid bends: A multimodal approach
Authors: Félix S. , Pagneux V.
Published: July 2002

The sound propagation in a waveguide with bend of finite constant curvature is analyzed using multimodal decomposition. Two infinite first-order differential equations are constructed for the pressure and velocity in the bend, projected on the local transverse modes. A Riccati equation for the impedance matrix is then derived, which can be numerically integrated after truncation at a sufficient number of modes. An example of validation is considered and results show the accuracy of the method and its suitability for the formulation of radiation conditions. Reflection and transmission coefficients are also computed, showing the importance of higher order mode generation at the junction between the bend and the straight ducts. The case of varying cross-section curved ducts is also considered using multimodal decomposition.
A stability analysis of a decentralized adaptive feedback active control system of sinusoidal sound in free space
Authors: Leboucher E. , Micheau P. , Berry A. , L’Espérance A.
Published: July 2002

In some cases, the implementation of active control of sound in free space requires a large number of secondary sources and error sensors. In terms of control hardware, this may translate into considerable processing power requirement. A practical method to decrease processing power is to decentralize the control; that is, implement many single-input, single-output independent controllers operating simultaneously instead of a large multiple-input, multiple-output system. The main drawback of decentralized control is the risk of global instability. The purpose of this paper is to derive conditions under which globally stable control system behavior can be obtained in the case of adaptive feedback decentralized control for a sinusoidal disturbance. The main objective is to give practical conditions derived from the small gain theorem and the Nyquist criterion for the stability of the control system. These conditions only take into account the geometrical arrangement of the secondary sources and error sensors. This analysis involves a new parameter β called “performance index,” which is associated with both the convergence of the individual controllers and the global stability of the system. Simulation and experimental results are shown to illustrate the effectiveness of the developed analytical tools.
A wide angle and high Mach number parabolic equation
Authors: Lingevitch Joseph F. , Collins Michael D. , Dacol Dalcio K. , Drob Douglas P. , Rogers Joel C. W. , Siegmann William L.
Published: July 2002

Various parabolic equations for advected acoustic waves have been derived based on the assumptions of small Mach number and narrow propagation angles, which are of limited validity in atmospheric acoustics. A parabolic equation solution that does not require these assumptions is derived in the weak shear limit, which is appropriate for frequencies of about 0.1 Hz and above for atmospheric acoustics. When the variables are scaled appropriately in this limit, terms involving derivatives of the sound speed, density, and wind speed are small but can have significant cumulative effects. To obtain a solution that is valid at large distances from the source, it is necessary to account for linear terms in the first derivatives of these quantities [A. D. Pierce, J. Acoust. Soc. Am. 87, 2292–2299 (1990)]. This approach is used to obtain a scalar wave equation for advected waves. Since this equation contains two depth operators that do not commute with each other, it does not readily factor into outgoing and incoming solutions. An approximate factorization is obtained that is correct to first order in the commutator of the depth operators.
On the influence of laryngeal pathologies on acoustic and electroglottographic jitter measures
Authors: Vieira Maurı́lio N. , McInnes Fergus R. , Jack Mervyn A.
Published: July 2002

This study compared acoustic and electroglottographic (EGG) jitter from [a] vowels of 103 dysphonic speakers. The EGG recordings were chosen according to their intensity, signal-to-noise ratio, and percentage of unvoiced intervals, while acoustic signals were selected based on voicing detection and the reliability of jitter extraction. The agreement between jitter measures was expressed numerically as a normalized difference. In 63.1% (65/103) of the cases the differences fell within ±22.5%. Positive differences above +22.5% were associated with increased acoustic jitter and occurred in 12.6% (13/103) of the speakers. These were, typically, cases of small nodular lesions without problems in the posterior larynx. On the other hand, substantial rises in EGG jitter leading to differences below −22.5% took place in 24.3% (25/103) of the speakers and were related to hyperfunctional voices, creaky-like voices, small laryngeal asymmetries affecting the arytenoids, or small-to-moderate glottal chinks. A clinically relevant outcome of the study was the possibility of detecting gentle laryngeal asymmetries among cases of large unilateral increase in EGG jitter. These asymmetries can be linked with vocal problems that are often overlooked in endoscopic examinations.
Ultrasonic wave speed measurement using the time-delay profile of rf-backscattered signals: Simulation and experimental results
Authors: Pereira Fernando R. , Machado João C. , Pereira Wagner C. A.
Published: July 2002

Conventional methods determine the ultrasonic wave speed measuring the medium path length propagated by a pulsed wave and the corresponding time-of-flight. In this work, the wave speed is determined without the need of the path length. A transmit transducer sends a pulsed wave into the medium (wave speed constant along the beam axis) and the backscattered signal is collected by a hydrophone placed at two distinct positions near the transmitted beam. The time-delay profile, between gated windows of the two rf-signals received by the hydrophone, is determined using a cross-correlation method. Also, a theoretical time-delay profile is determined considering the wave speed as a parameter. The estimated wave speed is obtained upon minimization of the rms error between theoretical and experimental time-delay profiles. A PZT conically focused transmitting transducer with center frequency of 3.3 MHz, focal depth of 30 mm, and beam full width (−3 dB) of 2 mm at the focus was used together with a PZT hydrophone (0.8 mm of aperture). The method was applied to three phantoms (wave speed of 1220, 1540, and 1720 m/s) and, in vitro, to fresh bovine liver sample, immersed in a temperature-controlled water bath. The results present a relative speed error less than 3% when compared with the sound speed obtained by a conventional method.
A theoretical study of structural acoustic silencers for hydraulic systems
Authors: Ramamoorthy Sripriya , Grosh Karl , Dodson John M.
Published: July 2002

Theoretical studies show that the introduction of an in-line structural acoustic silencer into a hydraulic system can achieve broadband quieting (i.e., high transmission loss). Strategies for using structural acoustic filters for simultaneously reducing reflection and transmission by tailoring the material properties are studied. A structural acoustic silencer consists of a flexible layer inserted into nominally rigid hydraulic piping. Transmission loss is achieved by two mechanisms—reflection of energy due to an impedance mismatch, and coupling of the incoming acoustic fluctuations to structural vibrations thereby allowing for the extraction of energy through losses in the structure. Structural acoustic finite element simulations are used to determine the transmission loss and evaluate designs. Results based on the interaction of orthotropic and isotropic plates with variable geometry, operating in heavy fluids like water and oil, are presented.
Measurements of ultrasonic pulse distortion produced by human chest wall
Authors: Hinkelman Laura M. , Szabo Thomas L. , Waag Robert C.
Published: July 2002

Ultrasonic wavefront distortion produced by transmission through human chest wall specimens was measured over a two-dimensional aperture. Measured pulse wavefronts were sometimes disrupted by secondary wavefronts produced by interaction between the transmitted pulses and the bone and cartilage structures of the rib cage. The secondary wavefronts produced large distortions in the received waveforms and interfered with the determination of the wavefront distortion caused by soft-tissue inhomogeneities. The effects of secondary wavefronts were minimized by reducing the region of analysis. Differences in arrival time and energy level between these restricted regions and references that account for geometric delay and spreading were computed. Spectral changes were assessed by calculating a waveform similarity factor that is decreased from 1.0 by changes in waveform shape. For 16 different intercostal spaces, the arrival time fluctuations of the measured waveforms had an average (±s.d.) rms value of 21.3 (±8.4) ns and an average correlation length of 2.50 (±0.62) mm. The energy level fluctuations had an average rms value of 1.57 (±0.45) dB and an average correlation length of 1.98 (±0.33) mm, and the average waveform similarity factor was 0.964 (±0.012). For soft-tissue inhomogeneities in chest wall specimens, the average rms arrival time and energy level fluctuations were less than half those measured for the abdominal wall. However, although the average correlation length of the arrival time fluctuations was less than half that found for the abdominal wall, the average correlation length of the energy level fluctuations was similar to that of the abdominal wall.
Seat dip effect: The phenomena and the mechanism
Authors: Takahashi D.
Published: July 2002

The phenomenon of excess attenuation due to audience seating, which is called “seat dip effect (SDE),” have been discussed in the case of a rather short-time interval including a direct sound and early arriving sound. However, it may be expected that the effect is diminished as the time interval increases, owing to the supplement of other arriving sounds. The first aim of this investigation is to clarify the effect of time interval on the SDE as well as the effect of other arriving sounds, by means of 110-scale model experiments. For the mechanism of the phenomenon, a clear explanation has not yet been given. The second aim is to clarify the fundamental mechanism of the SDE. For this aim, a wave-scattering theory for a periodic surface and a simple wave reflection theory for a layered boundary surface are applied, and discussed in comparison with the experimental results. From this investigation, it became clear that the mechanism of the SDE can be easily explained by using these simple analytical models.
Calculation of the dynamic air flow resistivity of fiber materials
Authors: Tarnow Viggo
Published: July 2002

The acoustic attenuation of acoustic fiber materials is mainly determined by the dynamic resistivity to an oscillating air flow. The dynamic resistance is calculated for a model with geometry close to the geometry of real fiber material. The model consists of parallel cylinders placed randomly. Two cases are treated: flow perpendicular to the cylinder axes, and flow parallel to the axes. In each case two new approximate procedures were used. In the first procedure, one solves the equation of flow in a Voronoi cell around the fiber, and averages over the distribution of the Voronoi cells. The second procedure is an extension to oscillating air flow of the Brinkman self-consistent procedure for dc flow. The procedures are valid for volume concentration of cylinders less than 0.1. The calculations show that for the density of fibers of interest for acoustic fiber materials the simple self-consistent procedure gives the same results as the more complicated procedure based on average over Voronoi cells. Graphs of the dynamic resistivity versus frequency are given for fiber densities and diameters typical for acoustic fiber materials.
High modal density approximations for equipment in the time domain
Authors: Cherukuri Aravind , Barbone Paul E.
Published: July 2002

This article considers modeling the effect of complex subsystems on the dynamics of the main structure to which they are attached. It is proposed that the substructure (say a piece of equipment) be replaced by an equivalent set of forces which react back on the main structure. These forces are given as time convolutions of the displacements at the equipment attachment points. The convolution integral, which represents a time domain DtN (Dirichlet-to-Neumann) map, is approximated in the high modal density limit with determined error bounds. This approximation leads to a family of equipment representations. The simplest requires few measured equipment properties, though more information can lead to greater accuracy. Our approximate DtNs are demonstrated numerically in finite element simulations.
Increasing the insertion loss of noise barriers using an active-control system
Authors: Guo Jingnan , Pan Jie
Published: July 2002

In recent studies on active noise control in open space, a multichannel active-control system was used to create the largest quiet zone with the least increase of total sound-power output when its sensors and actuators were optimally arranged. This control system was also applied to increase the insertion loss of noise barriers. The control system was arranged to create quiet zones on the top of the barrier; thus, the sound diffraction along the barrier top was reduced and the insertion loss of the barrier increased. It was found that the control system significantly increases the insertion loss of the noise barrier at low frequencies when the ground on both sides of the barrier is totally nonreflective. In practice, a nearby reflective ground may deteriorate the performance of the active noise-control system. The effects of ground reflection on the effectiveness of the active-noise barrier are considered in this paper. Both simulation and experimental results show that the reflective ground significantly reduces the effectiveness of the active noise-control system on the barrier. Reflection from the ground on the noise-source side has the greatest influence on the control efficiency. This suggests that passive reduction of the reflection from the ground on the source side should be incorporated in the design of the active-control system. Experiments were made for noise with multiple-frequency components in a low-frequency band. The results suggest that the active-control system can be effective at improving the performance of the noise barrier for noise with multiple-frequency components.
Measurements with reticulated vitreous carbon stacks in thermoacoustic prime movers and refrigerators
Authors: Adeff Jay A. , Hofler Thomas J. , Atchley Anthony A. , Moss William C.
Published: July 2002

Reticulated vitreous carbon has been successfully used as a stack material in thermoacoustic prime movers and refrigerators. It is a rigid glassy carbon material, with a porous spongelike structure. Test results indicate peak pressure amplitudes of up to 32% in a prime mover, and refrigeration performance comparable to that of a traditional plastic roll stack.
A new rough surface parabolic equation program for computing low-frequency acoustic forward scattering from the ocean surface
Authors: Rosenberg Allan P.
Published: July 2002

The parabolic equation acoustic propagation program RAM has been extended to handle a rough air–water interface treated as a series of stair steps. Because much finer vertical spacing may be needed to resolve the interface than to propagate a low-frequency acoustic wave accurately in the rest of the domain, an option to use one vertical spacing near the surface and a coarser one in the rest of the ocean has been implemented. The necessary Galerkin approximations of derivatives on an unequally spaced grid have been worked out using computer algebra. The new program, Rrsfc, is efficient enough to compute the frequency spectrum of the field scattered off a moving surface by treating the surface as a sequence of frozen surfaces. A comparison of one such spectrum with actual ocean data is provided. In order to make a more detailed assessment of the program, both the depth-dependent pressure for individual surfaces and the frequency spectrum for sequences of surfaces are compared with the results of numerically exact integral equation calculations for a few constant sound speed test cases.
Annihilation of beam vibrations by shaped piezoelectric actuators: Coupled theory
Authors: Irschik Hans , Krommer Michael , Pichler Uwe
Published: July 2002

Flexural vibrations of smart beams are studied in this paper. Layers made of piezoelectric material are used to perform a distributed actuation of the beam. Special emphasis is given to the following actuator shaping problem: A spatial shape function of the distributed actuator is sought such that vibrations induced by external forces are completely annihilated. The formulation is restricted to forces with a given spatial distribution and an arbitrary time evolution of their intensity. The scope is to derive a class of easy to obtain analytic solutions of this inverse problem. Actuator equations are used in the present contribution which take into account the interaction of mechanical and electrical fields. Extending the preliminary results, the above actuator shaping problem is solved in the context of these coupled equations. Beams with different boundary conditions are considered. Shape functions responsible for nonuniqueness of the shaping problem are also considered. These nilpotent solutions may be added to the above derived solution of the actuator problem without producing any additional vibrations. The presented analytic results are validated by means of coupled finite-element calculations.
Effects of interaction between two bubble scatterers
Authors: Kapodistrias George , Dahl Peter H.
Published: July 2002

The backscattering of sound from two regularly arranged bubble scatterers is studied theoretically and experimentally. In well-controlled laboratory experiments a bistatic system is used to interrogate the scatterers, which are symmetrically placed on a very fine thread at a distance d from the combined beam axis of the set of transducers. The radius of each bubble was 585 μm. The frequency range was 80–140 kHz, and by varying d the variable kd spanned the range 0.3–21, where k is the acoustic wave number. Scattering calculations were carried out using a closed form solution derived from the multiple scattering series. Several experiments were performed and the results are in close agreement with the calculations. It was verified that multiple scattering induces an oscillatory behavior about the exact coherent scattering level, with decreasing amplitude for increasing kd. For kd≊1 the backscattered radiation is maximized, while for kd<1 the radiation is reduced considerably. These and other effects will be presented and discussed. [Work supported by ONR, Code 321 OA.]
Temporary threshold shift in hearing induced by an octave band of continuous noise in the bottlenose dolphin
Authors: Au Whitlow W. L. , Nachtigall Paul E. , Pawloski Jeffery L.
Published: July 2002

Temporary threshold shift in hearing at 7.5 kHz was studied with an Atlantic bottlenose dolphin. Immediately following a threshold measurement, the animal was required to station in a hoop and be exposed to an octave band of continuous noise from 5 to 10 kHz. Noise exposure sessions lasted about 50 min, with the requirement that the animal spend a total of 30 min in the hoop. The dolphin also had two preferred locations both about a meter to the side of the hoop, one at the surface, and the other at the hoop depth. The noise levels at the hoop and to the side were about the same but with different spectra. The noise at the surface was about 3-dB lower. After exposure to the fatiguing stimulus, the animal’s hearing sensitivity was immediately measured. The animal’s hearing was not affected when the noise was 171 dB at 1 μPa with a total energy flux density of 205 dB at 1 μPa2s. Temporary threshold shifts of 12–18 dB were obtained when the noise increased to 179 dB with an energy flux density of 213 dB or 1330 J/m2. The fatiguing stimulus was about 96 dB above the animal’s pure tone threshold of 84 dB. [Work supported by ONR.]
Evaluation of spectral enhancement in hearing aids, combined with phonemic compression
Authors: Franck Bas A. M. , van Kreveld-Bos C. Sidonne G. M. , Dreschler Wouter A. , Verschuure Hans
Published: July 2002

In this study, the separate and combined effects on speech perception of compensation of the reduced dynamic range by compression and compensation of the reduced frequency resolution by spectral enhancement is investigated. The study has been designed to compare the effects of signal processing on monosyllabic consonant–vowel–consonant words for hearing-impaired listeners in conditions of quiet, fluctuating noise, and continuous noise. Speech perception of spectrally enhanced speech was compared with unprocessed speech. In addition, a comparison was made between combinations of spectrally enhanced speech and two types of phonemic compression. In the past, the definition “syllabic compressor” is often used to indicate fast compressors. However, the time constants of the fast compressors used in this study are so short that syllabic has become an inappropriate term. Moreover, intelligibility tests were performed in which scores were acquired of monosyllabic words, and their constituent “phonemic” parts. Therefore, the definitions “phoneme” and phonemic will be used throughout this paper. In one condition, spectral enhancement produced significant improvements for vowel perception. But, this was counteracted by deterioration of the consonant scores for all but one subject. In general, the best overall scores for consonant–vowel–consonant words were obtained in the unprocessed condition. After the spectral enhancement, a single-channel phonemic compressor added no improvement. There are indications that a multichannel phonemic compressor and spectral enhancement have opposite effects, because the scores for this combination are, in general, the lowest.
Experimental demonstration of a band-limited actuator/sensor selection strategy for structural acoustic control
Authors: Clark Robert L. , Cox David E.
Published: July 2002

A band-limited method of selecting actuators and sensors for structural acoustic control is reviewed, and experimental results are presented to demonstrate the approach. The selection methodology is based upon the decomposition of the Hankel singular values of a system model in terms of individual sensor and actuator configurations for lightly damped structures. The technique selects sensor and actuator combinations which couple well to structural modes that radiate efficiently. However, it rejects sensor and actuator combinations which couple well to modes that are inefficient acoustic radiators or are outside of the desired bandwidth of control. Selecting transducer combinations which filter modes outside of the desired bandwidth serves to minimize the potential for spillover and instability associated with unmodeled or poorly modeled dynamics. The approach is computationally efficient since it is based upon open-loop dynamics and does not require iterative nonlinear optimization.
Stochastic properties of cat auditory nerve responses to electric and acoustic stimuli and application to intensity discrimination
Authors: Javel Eric , Viemeister Neal F.
Published: July 2002

Statistical properties of electrically stimulated (ES) and acoustically stimulated (AS) auditory nerve fiber responses were assessed in undeafened and short-term deafened cats, and a detection theory approach was used to determine fibers’ abilities to signal intensity changes. ES responses differed from AS responses in several ways. Rate-level functions were an order of magnitude steeper, and discharge rate normally saturated at the stimulus pulse rate. Dynamic ranges were typically 1–4 dB for 200 pps signals, as compared with 15–30 dB for AS signals at CF, and they increased with pulse rate without improving threshold or changing absolute rate-level function slopes. For both ES and AS responses, variability of spike counts elicited by repeated trials increased with level in accord with Poisson-process predictions until the discharge rate exceeded 20–40 spikes/s. AS variability continued increasing monotonically at higher discharge rates, but more slowly. In contrast, maximum ES variability was usually attained at 100 spikes/s, and at higher discharge rates variability reached a plateau that was either maintained or decreased slightly until discharge rate approached the stimulus pulse rate. Variability then decreased to zero as each pulse elicited a spike. Increasing pulse rate did not substantially affect variability for rates up to 800 pps; rather, higher pulse rates simply extended the plateau region. Spike count variability was unusually high for some ES fibers. This was traced to response nonstationarities that stemmed from two sources, namely level-dependent fluctuations in excitability that occurred at 1–3 s intervals and, for responses to high-rate, high-intensity signals, fatigue that arose when fibers discharged at their maximum possible rates. Intensity discrimination performance was assessed using spike count as the decision variable in a simulated 2IFC task. Neurometric functions (percent correct versus intensity difference) were obtained at several levels of the standard (I), and the intensity difference (ΔI) necessary for 70% correct responses was estimated. AS Weber fractions (10 log ΔI/I) averaged +0.2 dB (ΔIdB=3.1 dB) for 50 ms tones at CF. ES Weber fractions averaged −12.8 dB (ΔIdB=0.23 dB) for 50 ms, 200 pps signals, and performance was approximately constant between 100 and 1000 pps. Intensity discrimination by single cells in ES conditions paralleled human psychophysical performance for similar signals. High ES sensitivity to intensity changes arose primarily from steeper rate-level functions and secondarily from reduced spike count variability.
Energy Dissipation of a Cohesive Soil by the Fourier Transformation of Stress Relaxation Response
Authors: Kondner Robert L. , Ho Michael M. K.
Published: July 2002

The energy dissipation of a cohesive soil is obtained by the Fourier transformation of stress relaxation test data. Energy dissipation is expressed in terms of the loss tangent. The soil response is nonlinear. Because of the difficulty in obtaining a mathematical expression to fit the relaxation data adequately over the entire time scale of interest, an approximate method of evaluating the transform is used. The relaxation response functions are approximated by straight line segments to form a piecewise continuous relation. By using a large number of straight line segments, the error between the actual and approximate transformation can be made negligible. The segment slopes with corresponding values of time are used in a digital computer program to evaluate the transform. The results clearly indicate a decrease of loss tangent with increased applied strain level. For constant strain level, the variation of loss tangent as a function of moisture content is not clearly defined. The loss tangent vs. logarithm of time relation gives a characteristic single peak bell-shaped distribution for each strain level.
Polymer Melt Flow Behavior in the Barrel of a Capillary Rheometer
Authors: Cook N. P. , Furno F. J. , Eirich F. R.
Published: July 2002

A study was made of the flow patterns in a capillary rheometer barrel to determine if there were any phenomena which might affect viscosity determinations. The rheometer barrel was loaded with layer of several different colors of the same plastic. Various percentages of the initial charge were extruded through the capillary using normal techniques at various shear rates and temperatures. At the end of each test, the material remaining in the barrel was frozen and removed as a plug. The plugs were then sectioned and a flow diagram was constructed by measuring the colored layers. Although the expected laminar flow was observed, upward flow at the wall and channeling at the center were also evident. These phenomena were noted even when only a small portion of the charge had been extruded through the capillary. This paper presents these findings in detail, picturing the flow patterns observed and illustrating the effects of temperature and shear rate.
Creep and Recovery Properties of a Zinc Phosphinate Polymer
Authors: Plazek D. J.
Published: July 2002

The investigation of the torsional creep and recovery behavior of a coordination polymer Zn[OP(Ph)(Me)O]2 at five temperatures from 100 to 200°C has revealed an unusual rheological behavior. A high temperature aging effect which appears at least partially reversible is observed. Observed creep deformation which is linear in time, followed by a delayed recovery, is explained as a consequence of a void in the retardation spectrum. Temperature reduction is achieved and the temperature shift factors are analyzed in the light of the WLF equation. The measurements were made with a recently developed creep instrument which employs a magnetically levitated rotor and a drag cup motor for precision torque production.
The Effect of Temperature on the Consistency of Fluids
Authors: Christiansen E. B. , Craig S. E. , Carter T. R.
Published: July 2002

A temperature-reduced form of the Powell-Eyring equation is shown to represent the flow properties as a function of temperature for relatively dilute aqueous carboxymethylcelullose and carboxypolymethylene dispensions, Paraplex G40, and blood over moderate temperature ranges. Convenient methods for determining the activation energy and the equation constants from experimental flow data are presented.
Diameter Effect in the Measurement of the Primary Normal Stress Difference from Jet Expansion
Authors: Powell Robert L. , Middleman Stanley
Published: July 2002

A diameter effect is observed in calculating normal stress differences from observation of the expansion of viscoelastic jets. The possibility that the effect is due to an elastic reaction to the deceleration which accompanies expansion of the jet is raised, and a simple analysis shows this may be plausible.
Parallel Superposition of Simple Shearing and Small Amplitude Oscillatory Motions
Authors: Macdonald I. F.
Published: July 2002

Parallel superposed flow data are presented for four widely studied solutions, three Aroclor solutions of nearly monodisperse polystyrene and a polyisobutylene in Primol solution. Predictions of two integral models, the Bird-Carreau model and the modified OWFS model, are given and found to describe the data quite well. The experimental results are similar to those of other investigators except that they do not support the relation ω0≈0.5γ̇ proposed by Booij where ω0 is the frequency at which the phase shift is 90°.
On High-Frequency Behavior in Superposed Flow
Authors: MacDonald I. F.
Published: July 2002

Parallel and orthogonal superposed flow results have been obtained experimentally. It has been found that at large values of the frequency of oscillation, the dynamic viscosities ηt′ and ηi′ merge with the dynamic viscosity η′ for oscillatory shear alone and the storage moduli Gt′ and Gi′ become parallel to the storage modulus G′ for oscillatory shear alone. Results are presented here showing that the conclusions by Bernstein, Huilgol, and Tanner that the K-BKZ model correctly describes the high-frequency asymptotic behavior are unwarranted and that, consequently, the predictive ability of the K-BKZ theory for these flows remains unknown. The claim by Bernstein and Huilgol that the behavior of the Bird-Carreau model is at variance with the experimental evidence is discussed and formal arguments are presented showing that the Bird-Carreau and M-OWFS model predictions do conform with the experimental data.
Rheological Properties of Aqueous Poly(ethylene Oxide) Solutions in Parallel Superposed Flows
Authors: Powell R. L. , Schwarz W. H.
Published: July 2002

The response of concentrated solutions (0.7 g/dl-2.0 g/dl) of poly(ethylene oxide) (Polyox WSR-301) to in-line shearing oscillations was measured using a Weissenberg Rheogoniometer Model R.18 with the parallel-plate geometry. This physical system was analyzed using the theory of Pipkin and Owen (Phys. Fluids, 10, 836, 1967) for nearly viscometric flows and explicit formulae for rheological parameters in terms of measured quantities were obtained in the limit of negligible fluid density. The data are presented as the complex viscosity, η12*, depending both on strain rate, κ, and frequency, ω and were obtained for 10−2.5<κ<100.5 sec−1 and 10−2.5<ω<101.5 sec−1. The data were interpreted using the mechanical theory of materials with memory developed for both in-line and orthogonal superposed flows. For a fixed κ, the η12′(κ,ω) data have a maximum value as ω→0, viz., η12′(κ,0), and with increasing ω, were found to approach the no-shear data, η′(ω). Also, the theoretical prediction, η12′(κ,0)=[dκη(κ)/dκ], was experimentally confirmed over the entire range of κ measured. For small ω, G12′=γ12(κ)ω2 with γ12(κ)>0, and γ12(κ)→−γ (the second-order fluid normal stress coefficient) as κ→0. Further, the relation, (G12′/ω2)=(σ2−σ1)/(2κ2), was found to be valid to a higher order in κ than predicted by the theory. A material time, τ(κ)=[γ12(κ)/η12′(κ,0)], was used to correlate nondimensionalized forms of the η12′ and G12′ data. Also, the particular strain-rate-dependent stress-relaxation functions ψ12(κ,σ), used to define η12*(κ,ω), were calculated and indicate a decrease in material memory with shear.
The rheology of charge stabilized silica suspensions
Authors: Fagan M. E. , Zukoski C. F.
Published: July 2002

The flow properties of aqueous suspensions of silica particles with diameters ranging from 117 to 780 nm were measured as a function of volume fraction, ionic strength, and continuous phase composition. Dense, aqueous suspensions of all sizes displayed similar behavior with a yield stress in the limit of low shear rate, shear thinning as the stress was raised and, above a critical volume fraction, shear thickening. Master flow curves which are weakly dependent on particle size, volume fraction, surface potential, magnitude of the decay length for the electrostatic forces, or particle size distribution are produced when stress is scaled on the suspension’s elastic modulus, G, and shear rate on G/ηc. Here ηc is the continuous phase viscosity. For suspensions which ordered at rest and of sufficiently high volume faction, shear thickening occurred as a discontinuous decrease in shear rate as the stress increased. This behavior was not observed in suspensions altered so that no order occurred at rest. When the continuous phase viscosity was increased by suspending the particles in a glycerin solution, no evidence for a yield stress or ordering were observed. These suspensions thinned with increasing stress to a minimum viscosity where thickening occurred as a smooth transition. The elastic scaling that successfully produced master curves for the aqueous suspension failed for the glycerin suspensions.
On-line X-ray diffraction for quantitative phase analysis: Application in the Portland cement industry
Authors: Scarlett Nicola V. Y. , Madsen Ian C. , Manias Con , Retallack David
Published: July 2002

The aim of this work was to design, construct, install, and commission an on-line, X-ray diffraction (XRD) analyzer capable of continuously monitoring phase abundances for use in process plant control. This has been achieved through a joint project between CSIRO Minerals and Fuel & Combustion Technology Pty. Ltd. with an instrument designed for use in a Portland cement manufacturing plant. Key factors in tailoring such an instrument to the cement industry were (i) the handling and presentation of a dry sample and (ii) the development of an analytical method suitable for the complex suite of phases contained within Portland cement. The instrument incorporates continuous flow of sample through the diffractometer using a purpose-built sample presentation stage. The XRD data are collected simultaneously using a wide range (120° 2θ) position sensitive detector, thus enabling rapid collection of the full diffraction pattern. The data are then analyzed using a Rietveld analysis method to obtain a quantitative estimate of each of the phases present. The instrument is controlled by a PC linked to the diffractometer through a purpose built interface. The phase abundance information is then transmitted to the central computer in the cement plant where it can be used for the control of mill parameters such as temperature and retention times as well as gypsum feed rate.
Assessment of Patient-Reported Outcome Measures for Maternal Postpartum Depression Using the Consensus-Based Standards for the Selection of Health Measurement Instruments Guideline
Authors: Sultan Pervez , Ando Kazuo , Elkhateb Rania , George Ronald B. , Lim Grace , Carvalho Brendan , Chitneni Ahish , Kawai Ray , Tulipan Tanya , Blake Lindsay , Coker Jessica , O’Carroll James
Published: June 2022

Importance

Maternal depression is frequently reported in the postpartum period, with an estimated prevalence of approximately 15% during the first postpartum year. Despite the high prevalence of postpartum depression, there is no consensus regarding which patient-reported outcome measure (PROM) should be used to screen for this complex, multidimensional construct.

Objective

To evaluate psychometric measurement properties of existing PROMs of maternal postpartum depression using the Consensus-Based Standards for the Selection of Health Measurement Instruments (COSMIN) guideline and identify the best available patient-reported screening measure.

Evidence Review

This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline. PubMed, CINAHL, Embase, and Web of Science were searched on July 1, 2019, for validated PROMs of postpartum depression, and an additional search including a hand search of references from eligible studies was conducted in June 2021. Included studies evaluated 1 or more psychometric measurement properties of the identified PROMs. A risk-of-bias assessment was performed to evaluate methods of each included study. Psychometric measurement properties of each PROM were rated according to COSMIN criteria. A modified Grading of Recommendations Assessment, Development, and Evaluation approach was used to assess the level of evidence supporting each rating, and a recommendation class (A, recommended for use; B, further research required; or C, not recommended) was given based on the overall quality of each included PROM.

Findings

Among 10 264 postpartum recovery studies, 27 PROMs were identified. Ten PROMs (37.0%) met the inclusion criteria and were used in 43 studies (0.4%) involving 22 095 postpartum women. At least 1 psychometric measurement property was assessed for each of the 10 validated PROMs identified. Content validity was sufficient in all PROMs. The Edinburgh Postnatal Depression Scale (EPDS) demonstrated adequate content validity and a moderate level of evidence for sufficient internal consistency (with sufficient structural validity), resulting in a recommendation of class A. The other 9 PROMs evaluated received a recommendation of class B.

Conclusions and Relevance

The findings of this systematic review suggest that the EPDS is the best available patient-reported screening measure of maternal postpartum depression. Future studies should focus on evaluating the cross-cultural validity, reliability, and measurement error of the EPDS to improve understanding of its psychometric properties and utility.
Cryo‐electron microscopy of Na+,K+‐ATPase reveals how the extracellular gate locks in the E2·2K+ state
Authors: Kanai Ryuta , Cornelius Flemming , Vilsen Bente , Toyoshima Chikashi
Published: June 2022

Na+,K+‐ATPase (NKA) is one of the most important members of the P‐type ion‐translocating ATPases and plays a pivotal role in establishing electrochemical gradients for Na+ and K+ across the cell membrane. Presented here is a 3.3 Å resolution structure of NKA in the E2·2K+ state solved by cryo‐electron microscopy. It is a stable state with two occluded K+ after transferring three Na+ into the extracellular medium and releasing inorganic phosphate bound to the cytoplasmic P domain. We describe how the extracellular ion pathway wide open in the E2P state becomes closed and locked in E2·2K+, linked to events at the phosphorylation site more than 50 Å away. We also show, although at low resolution, how ATP binding to NKA in E2·2K+ relaxes the gating machinery and thereby accelerates the transition into the next step, that is, the release of K+ into the cytoplasm, more than 100 times.