bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of endogenous melatonin in the oxidative homeostasis of the extracellular striatal compartment: a microdialysis study in PC12 cells in vitro and in the striatum of freely moving rats
Authors: Rocchitta Gaia , Migheli Rossana , Mura Maria P. , Esposito Giovanni , Marchetti Bianca , Desole Maria S. , Miele Egidio , Serra Pier Andrea
Published: October 2005

Abstract:  A capillary apparatus for in vitro microdialysis was used to investigate melatonin and ascorbic acid effects on dopamine (DA) autoxidation or nitric oxide (NO)‐mediated oxidation in suspended PC12 cells. Following high K+ (KCl 75 mm) infusion, secreted DA underwent a partial autoxidation or peroxynitrite‐mediated oxidation when the potential peroxynitrite generator 3‐morpholinosydnonimine (SIN‐1, 1.0 mm) was co‐infused with KCl. Ascorbic acid was supplied to the medium by means of intracellular reduction of infused dehydroascorbic acid (DHAA) (5.0 mm). Melatonin (50 μm) and DHAA showed a synergistic effect in inhibiting DA autoxidation and peroxynitrite‐mediated DA oxidation. Moreover, melatonin increased dialysate recovery of ascorbic acid released from PC12 cells. Endogenous melatonin was depleted in rats maintained on a 24‐hr light cycle for 1 wk. In melatonin‐depleted rats, baseline levels of dialysate ascorbic acid were lower than controls, while those of DA were unaffected. In these rats, intrastriatal infusion of 5.0 mm SIN‐1 induced DA increases significantly lower than in controls; in addition, dialysate ascorbic acid concentrations exhibited significant decreases. Melatonin co‐infusion restored SIN‐1 effects on dialysate DA and antagonized SIN‐1‐induced ascorbic acid decreases. Melatonin‐depleted rats were allowed to recover. In these rats, striatal baseline ascorbic acid, as well as SIN‐1‐induced increases in dialysate DA did not differ from controls. Taken together, these findings suggest that endogenous melatonin is an active component of the striatal extracellular antioxidant pool, as it maintains endogenous ascorbic acid in its reduced status and co‐operates with ascorbic acid in protecting extracellular DA from exogenous NO‐mediated oxidation.
UV‐A light regulation of arylalkylamine N‐acetyltransferase activity in the chick pineal gland: role of cAMP and proteasomal proteolysis
Authors: Rosiak Jolanta , Michael Iuvone P. , Zawilska Jolanta B.
Published: October 2005

Abstract:  Acute exposure of dark‐adapted, cultured chick pineal glands to UV‐A light significantly decreased the tissue cAMP concentration and the activity of arylalkylamine N‐acetyltransferase (AANAT), the penultimate and key regulatory enzyme in the melatonin biosynthetic pathway. The magnitude of these changes was dependent on the duration of UV‐A exposure. The UV‐A light‐evoked decline in pineal AANAT activity was blocked by cAMP protagonists (forskolin and dibutyryl‐cAMP) and by inhibitors of the proteasomal degradation pathway (MG‐132, proteasome inhibitor I, and lactacystin). These results indicate that the chick pineal gland is directly sensitive to UV‐A light. By analogy to white light, the suppressive action of UV‐A radiation on AANAT activity in the chick pineal gland involves changes in the tissue cAMP level and enhanced proteasomal proteolysis.
Hot Plate Gas Sensors—Are Ceramics Better?
Authors: Kita Jaroslaw , Rettig Frank , Moos Ralf , Drüe Karl‐Heinz , Thust Heiko
Published: October 2005

For modern gas sensors, low power consumption is expected. It is well known that with low temperature cofiring technology (LTCC) small compact sensors can be constructed. Compared with standard devices on alumina such sensors consume less power due to their lower thermal conductivity. However, simple replacement of substrate materials is not sufficient. LTCC offers the possibility to structure unfired tapes easily. Therefore, the sensor substrate may have almost any desired shape. In our first investigations, we showed that ceramic hot plates could be successfully constructed in LTCC technology. In contrast to standard configuration of thick‐film gas sensors on alumina or even on LTCC, the hot plate principle allows to reduce significantly power consumption. Our tests showed possibilities to further decrease power consumption by laser forming of suspended beams. The obtained results were very promising and induced continuation of these works. This article shows recent results of investigations on hot plate structures. Tapes from different manufacturers have been used for sensor construction. The sensors were made by laser structuring of printed unfired LTCC tapes. Samples were evaluated by measurement and analysis of electrical properties as well as by long‐term tests of integrated heaters. Design issues as well as stability issues are discussed in this contribution.
Novel Microsystem Applications with New Techniques in Low‐Temperature Co‐Fired Ceramics
Authors: Peterson K. A. , Patel K. D. , Ho C. K. , Rohde S. B. , Nordquist C. D. , Walker C. A. , Wroblewski B. D. , Okandan M.
Published: October 2005

Low‐temperature co‐fired ceramic (LTCC) enables development and testing of critical elements on microsystem boards as well as nonmicroelectronic meso‐scale applications. We describe silicon‐based microelectromechanical systems packaging and LTCC meso‐scale applications. Microfluidic interposers permit rapid testing of varied silicon designs. The application of LTCC to micro‐high‐performance liquid chromatography (μ‐HPLC) demonstrates performance advantages at very high pressures. At intermediate pressures, a ceramic thermal cell lyser has lysed bacteria spores without damaging the proteins. The stability and sensitivity of LTCC/chemiresistor smart channels are comparable to the performance of silicon‐based chemiresistors. A variant of the use of sacrificial volume materials has created channels, suspended thick films, cavities, and techniques for pressure and flow sensing. We report on inductors, diaphragms, cantilevers, antennae, switch structures, and thermal sensors suspended in air. The development of “functional‐as‐released” moving parts has resulted in wheels, impellers, tethered plates, and related new LTCC mechanical roles for actuation and sensing. High‐temperature metal‐to‐LTCC joining has been developed with metal thin films for the strong, hermetic interfaces necessary for pins, leads, and tubes.
Direct‐Write Laser Exposure of Photosensitive Conductive Inks Using Shaped‐Beam Optics
Authors: Corbett Scott , Strole Jeff , Johnston Kyle , Swenson Edward , Lu Weixiong
Published: October 2005

We present several laser direct‐write patterning technologies for use with photosensitive or non‐photosensitive thick‐film conductive inks. In a first case, a ultraviolet (UV) laser processing system (Electro Scientific Industries) was used to directly expose photodefinable conductive silver ink (Fodel® 6778, Dupont). After developing and further processing, the process yielded patterned traces approximately 25 μm wide. In a second case, the UV laser was used to photo‐ablate the silver conductive ink to form spaces, resulting in line resolution as fine as 8 μm trace width and 12 μm space width (20 μm pitch). In another experiment, the laser was used to pattern pre‐fired conductive gold ink (Heraeus KQ500) covered with photosensitive resist material. After ablation of the resist and underlying gold, the resist was removed yielding well‐defined traces down to 25 μm pitch. We also ablated unfired Heraeus KQ 500 ink followed by post‐firing to produce a well‐defined inductor pattern. The above processes were performed both with a 25 μm Gaussian‐shaped laser beam and a special shaped 10 μm “top hat” square beam, ideal for even laser exposure across the beam aperture. The square‐beam enabled finer line resolution with the ablation process, but was not as effective for the laser exposure process in comparison to the Gaussian beam. Post firing of the Fodel® parts was performed using both a batch box furnace and an infrared belt furnace with multiple heat zones. Both firing methods yielded well‐defined traces with the belt‐firing process supporting slightly finer trace resolution. The laser direct‐write processes enable fine‐line patterning of conductors for single or multilayer ceramic circuit fabrication. Direct laser writing offers the advantage of direct patterning from a computer automated design (CAD) file without requiring a mask and exposure system and can also be used in combination with traditional screen printing or mask lithography to enhance the resolution and accuracy of thick‐film patterning.
A Brief Overview on Automotive Exhaust Gas Sensors Based on Electroceramics
Authors: Moos Ralf
Published: October 2005

Nowadays, ceramic exhaust gas sensors are installed in quantities of millions in automotive exhaust gas systems. Almost any automobile being powered by a gasoline combustion engine is equipped with at least one zirconia exhaust gas oxygen sensor (λ probe) for detection of the air‐to‐fuel ratio λ. The first part of this short overview focuses on potentiometric as well as on amperometric zirconia exhaust gas oxygen sensors. It is remarkable that in the past years a leap in manufacturing technology has occurred from classical ceramic technology to tape and thick‐film technology. The advent of novel combustion concepts like lean‐burn operating gasoline direct injection required novel exhaust gas aftertreatment concepts. It pushed the development of the NOxsensor, which is manufactured in the same technology. It is also shown how development of exhaust gas sensors has always to be considered in interaction with exhaust gas aftertreatment systems. This elucidates why novel sensors have gained in importance just recently when stricter emission regulations were announced, meaning that the time is ripe for novel exhaust gas aftertreatment concepts. Appropriate sensors—ammonia sensors, hydrocarbon sensors, and particulate matter sensors—are still in the R&D stage. Several possible sensor principles are discussed. The materials that are used for sensors in the automotive exhaust are electroceramics. Besides ion‐conducting zirconia and zirconia cermets, electrically insulating alumina is used for substrate purposes. Novel functional materials in the R&D state are strontium–iron titanate for temperature‐independent resistive oxygen sensing and zeolites for selective detection of specific gases like hydrocarbons or ammonia.
Chord‐based versus voxel‐based methods of electron transport in the skeletal tissues
Authors: Shah Amish P. , Jokisch Derek W. , Rajon Didier A. , Watchman Christopher J. , Patton Phillip W. , Bolch Wesley E.
Published: October 2005

Anatomic models needed for internal dose assessment have traditionally been developed using mathematical surface equations to define organ boundaries, shapes, and their positions within the body. Many researchers, however, are now advocating the use of tomographic models created from segmented patient computed tomography (CT) or magnetic resonance (MR) scans. In the skeleton, however, the tissue structures of the bone trabeculae, marrow cavities, and endosteal layer are exceedingly small and of complex shape, and thus do not lend themselves easily to either stylistic representations or in‐vivo CT imaging. Historically, the problem of modeling the skeletal tissues has been addressed through the development of chord‐based methods of radiation particle transport, as given by studies at the University of Leeds (Leeds, UK) using a male subject. We have proposed an alternative approach to skeletal dosimetry in which excised sections of marrow‐intact cadaver spongiosa are imaged directly via microCT scanning. The cadaver selected for initial investigation of this technique was a male subject of nominal body mass index . The objectives of the present study were to compare chord‐based versus voxel‐based methods of skeletal dosimetry using data from the UF male subject. Good agreement between chord‐based and voxel‐based transport was noted for marrow irradiation by either bone surface or bone volume sources up to (depending upon the skeletal site). In contrast, chord‐based models of electron transport yielded consistently lower values of the self‐absorbed fraction to marrow tissues than seen under voxel‐based transport at energies above , a feature directly attributed to the inability of chord‐based models to account for nonlinear electron trajectories. Significant differences were also noted in the dosimetry of the endosteal layer (for all source tissues), with chord‐based transport predicting a higher fraction of energy deposition than given by voxel‐based transport (average factor of about 1.6). The study supports future use of voxel‐based skeletal models which (1) permit nonlinear electron trajectories across the skeletal tissues, (2) do not rely on mathematical algorithms for treating the endosteal tissue layer, and (3) do not implicitly assume independence of marrow and bone trajectories as is the case for chord‐based skeletal models.
The x‐ray time of flight method for investigation of ghosting in amorphous selenium‐based flat panel medical x‐ray imagers
Authors: Rau A. W. , Bakueva L. , Rowlands J. A.
Published: October 2005

Amorphous selenium based real‐time flat‐panel imagers (FPIs) are finding their way into the digital radiology department because they offer the practical advantages of digital x‐ray imaging combined with an image quality that equals or outperforms that of conventional systems. The temporal imaging characteristics of FPIs can be affected by ghosting (i.e., radiation‐induced changes of sensitivity) when the dose to the detector is high (e.g., portal imaging and mammography) or the images are acquired at a high frame rate (e.g., fluoroscopy). In this paper, the x‐ray time‐of‐flight (TOF) method is introduced as a tool for the investigation of ghosting in photoconductor layers. The method consists of irradiating layers of with short x‐ray pulses. From the current generated in the layer, ghosting is quantified and the ghosting parameters (charge carrier generation rate and carrier lifetimes and mobilities) are assessed. The x‐ray TOF method is novel in that (1) x‐ray sensitivity and ghosting parameters can be measured simultaneously, (2) the transport of both holes and electrons can be isolated, and (3) the method is applicable to the practical layer structure with blocking contacts used in FPIs. The x‐ray TOF method was applied to an analysis of ghosting in photoconductor layers under portal imaging conditions, i.e., thick layers, biased at , were irradiated using a LINAC x‐ray beam to a total dose (ghosting dose) of . The initial sensitivity of the layers was . It was found that decreases to 30% of after a ghosting dose of and to 21% after at which point no further change in occurs. At an x‐ray intensity of (instantaneous dose rate during a LINAC x‐ray pulse), the charge carrier generation rate was and, to a first approximation, independent of the ghosting dose. However, both hole and electron transport showed a strong dependence on the ghosting dose: hole transport decreased by 61%, electron transport by up to . Therefore, degradation of both hole and electron transport due to the recombination of mobile charge carriers with trapped carriers (of opposite polarity) were identified as the main cause of ghosting in this study.
Feasibility study of helical tomotherapy for total body or total marrow irradiationa)
Authors: Hui Susanta K. , Kapatoes Jeff , Fowler Jack , Henderson Douglas , Olivera Gustavo , Manon Rafael R. , Gerbi Bruce , Mackie T. R. , Welsh James S.
Published: October 2005

Total body radiation (TBI) has been used for many years as a preconditioning agent before bone marrow transplantation. Many side effects still plague its use. We investigated the planning and delivery of total body irradiation (TBI) and selective total marrow irradiation (TMI) and a reduced radiation dose to sensitive structures using image‐guided helical tomotherapy. To assess the feasibility of using helical tomotherapy, (A) we studied variations in pitch, field width, and modulation factor on total body and total marrow helical tomotherapy treatments. We varied these parameters to provide a uniform dose along with a treatment times similar to conventional TBI . (B) We also investigated limited (head, chest, and pelvis) megavoltage CT (MVCT) scanning for the dimensional pretreatment setup verification rather than total body MVCT scanning to shorten the overall treatment time per treatment fraction. (C) We placed thermoluminescent detectors (TLDs) inside a Rando phantom to measure the dose at seven anatomical sites, including the lungs. A simulated TBI treatment showed homogeneous dose coverage to the whole body. Doses to the sensitive organs were reduced by 35%–70% of the target dose. TLD measurements on Rando showed an accurate dose delivery to the target and critical organs. In the TMI study, the dose was delivered conformally to the bone marrow only. The TBI and TMI treatment delivery time was reduced (by 50%) by increasing the field width from in the inferior–superior direction. A limited MVCT reduced the target localization time 60% compared to whole body MVCT. MVCT image‐guided helical tomotherapy offers a novel method to deliver a precise, homogeneous radiation dose to the whole body target while reducing the dose significantly to all critical organs. A judicious selection of pitch, modulation factor, and field size is required to produce a homogeneous dose distribution along with an acceptable treatment time. In addition, conformal radiation to the bone marrow appears feasible in an external radiation treatment using image‐guided helical tomotherapy.
FTRAC—A robust fluoroscope tracking fiducial
Authors: Jain Ameet Kumar , Mustafa Tabish , Zhou Yu , Burdette Clif , Chirikjian Gregory S. , Fichtinger Gabor
Published: October 2005

‐arm fluoroscopy is ubiquitous in contemporary surgery, but it lacks the ability to accurately reconstruct three‐dimensional (3D) information. A major obstacle in fluoroscopic reconstruction is discerning the pose of the x‐ray image, in 3D space. Optical/magnetic trackers tend to be prohibitively expensive, intrusive and cumbersome in many applications. We present single‐image‐based fluoroscope tracking (FTRAC) with the use of an external radiographic fiducial consisting of a mathematically optimized set of ellipses, lines, and points. This is an improvement over contemporary fiducials, which use only points. The fiducial encodes six degrees of freedom in a single image by creating a unique view from any direction. A nonlinear optimizer can rapidly compute the pose of the fiducial using this image. The current embodiment has salient attributes: small dimensions ; need not be close to the anatomy of interest; and accurately segmentable. We tested the fiducial and the pose recovery method on synthetic data and also experimentally on a precisely machined mechanical phantom. Pose recovery in phantom experiments had an accuracy of in translation and 0.33° in orientation. Object reconstruction had a mean error of with STD. The method offers accuracies similar to commercial tracking systems, and appears to be sufficiently robust for intraoperative quantitative ‐arm fluoroscopy. Simulation experiments indicate that the size can be further reduced to , with only a marginal drop in accuracy.
MOSFET dosimeter depth‐dose measurements in heterogeneous tissue‐equivalent phantoms at diagnostic x‐ray energies
Authors: Jones A. K. , Pazik F. D. , Hintenlang D. E. , Bolch W. E.
Published: October 2005

The objective of the present study was to explore the use of the TN‐1002RD metal‐oxide‐semiconductor field effect transistor (MOSFET) dosimeter for measuring tissue depth dose at diagnostic photon energies in both homogeneous and heterogeneous tissue‐equivalent materials. Three cylindrical phantoms were constructed and utilized as a prelude to more complex measurements within tomographic physical phantoms of pediatric patients. Each cylindrical phantom was constructed as a stack of seven ‐diameter and ‐thick discs of materials radiographically representative of either soft tissue , bone , or lung tissue at diagnostic photon energies. In addition to a homogeneous phantom of soft tissue (SSSSSSS), two heterogeneous phantoms were constructed: SSBBSSS and SBLLBSS. MOSFET dosimeters were then positioned at the interface of each disc, and the phantoms were then irradiated at and . Measured values of absorbed dose at depth were then compared to predicated values of point tissue dose as determined via Monte Carlo radiation transport modeling. At depths exceeding , experimental results matched the computed values of dose with high accuracy regardless of the dosimeter orientation (epoxy bubble facing toward or away from the x‐ray beam). Discrepancies were noted, however, between measured and calculated point doses near the surface of the phantom (surface to depth) when the dosimeters were oriented with the epoxy bubble facing the x‐ray beam. These discrepancies were largely eliminated when the dosimeters were placed with the flat side facing the x‐ray beam. It is therefore recommended that the MOSFET dosimeters be oriented with their flat sides facing the beam when they are used at shallow depths or on the surface of either phantoms or patients.
Sound isolation rating system for use when the sound source is music, machinery, or mechanical equipment
Authors: Roller H. Stanley
Published: October 2005

A rating system is presented for use in the selection of sound isolating components when the sound source is music, machinery, or mechanical equipment. The rating system described is complementary to the STC rating system which works well as a tool for simplifying the selection of components for the isolation of “speech like” sound sources. It is possible by considering both rating numbers to more accurately, and yet simply, compare and evaluate different construction systems as to their appropriateness for the intended use.
Solutions of some problems in duct acoustics, using nonseparable modes
Authors: Vaidya P. G.
Published: October 2005

Almost all closed form solutions of the problems in duct acoustics (and in other branches of acoustics) are obtained by assuming that the eigenfunctions depend on each of the coordinates independently of the other. Such “separable” solutions are impossible if, for example, the boundary conditions are nonuniform. Under these conditions, instead of resorting to ad-hoc numerical procedures, closed form solutions could still be obtained by using nonseparable modes. Examples of circumferentially and/or axially nonuniform boundary conditions are worked out to illustrate this procedure.
The use of clustering result in speaker-independent, isolated-word recognition
Authors: Wei Nien-chih
Published: October 2005

Currently, a test utterance is recognized as word “A” when the distance score of the test utterance to a reference template for word “A” is the lowest among the measured scores between test and all reference utterances. The reference template is generated by: (1) clustering utterances from many speakers and (2) choosing the cluster centers as reference templates. Thus, the distance between the test utterance and the reference template is the distance of the test utterance to the cluster center. This type of distance measure ignores the fact that clusters have different sizes. Using a Gaussian model for the distribution of utterances inside a cluster, this paper proposes a new distance measure based on the size of the cluster. The correlation between the Itakura distance measure and the new distance measure for many utterance (∼1500) is fairly low (∼0.2). This suggests that the new distance measure represents new information. Incorporating this new distance measure can reduce the recognition error rate in half.
A word model based endpoint detector for isolated utterunce recognition
Authors: Hieronymus James L.
Published: October 2005

Endpoint detection is a critical issue for several types of isolated utterance recognizers, because improper endpoints often result in recognition errors. Endpoint errors often stem from nonspeech artifacts, namely lip smacks, tongue and teeth clicks, and breath noise. Endpoint detectors based only on energy thresholds cannot correctly reject these artifacts, but adding a word model allows most of these artifacts to be properly rejected. The rules which implement the word model are (1) the word cannot begin or end with two released plosives, (2) word initial stop gaps are less than 120 ms and word final ones less than 200 ms, (3) a word must contain a vocalic nucleus and be at least 100 ms in length, (4) word final sounds containing only mid-frequency energy are breath noise. The detection algorithm has been implemented on a Heuristics Speech Recognizer and tested using the Texas Instruments isolated word data base. The word model based system substantially reduced the error rate relative to an energy threshold based system.
Schematizing spectrograms for speech recognition
Authors: Riley Michael D.
Published: October 2005

An initial step in wide vocabulary, continuous speech recognition is proposed that roughly consists of a schematization of the features seen in conventional spectrograms—e.g., peaks and edges of spectral energy concentrations, temporal discontinuities, and spectral balance information. In a second step, these features can be mapped onto their acoustic-phonetic correlates—e.g., formant distribution, voice onsets, articulatory closures. A method for locating spectral energy concentrations is given that takes advantage of their usual continuity in time, and thus performs superior to locating peaks in spectral cross sections. It begins with smoothing and flattening convolutions in both the time and frequency dimensions of narrow-band spectrograms to select the appropriate temporal and spectral scales. Ridges in the resulting two-dimensional (time-frequency) surfaces correspond to local spectral energy concentrations. The tops of these ridges are found by the application of a two-dimensional differential operator at each point in the time-frequency plane. The operator's definition in terms of the relationship between the gradient and principal directions will be given, along with justification and examples.
Identification of visual displays of speech: Comparisons of naive and trained observers
Authors: Pisoni David B. , Greene Beth G. , Carrell Thomas D.
Published: October 2005

Two groups of subjects were presented with spectrograms of 50 words they had never seen before and were asked to provide a single monosyllabic English word for each spectrogram. One group had learned to identify a limited set of speech spectrograms after 15 h of training using a study-test procedure which stressed wholistic word identification. A subgroup of participants in a formal course on spectrogram reading at MIT served as a second group of subjects. These subjects learned specific acoustic and phonetic principles and strategies for interpreting spectrograms. Subjects in the first group correctly identified 33% of the possible phonetic segments in spectrograms they had never seen before. The second group of subjects correctly identified 40% of the possible segments in the same set of spectrograms given to the first group. When the data were scored for correct manner class of consonants only, the two groups did not differ significantly. Detailed descriptions of the identification results will be presented. Implications of these findings for developing visual aids for hearing impaired persons and improved phonetic recognition strategies will be discussed. [Supported by NSF.]
A nonsense syllable test designed for articulation index testing
Authors: Studebaker Gerald A. , Pavlovic Chaslav V.
Published: October 2005

The band-importance function developed by Bell Laboratories is not directly applicable to any of the available recorded speech tests. For this reason we developed a test which is like that used by the Bell Laboratories but unlike other available tests in that (1) each CV or VC is a different utterance (2) the phonemes appear with uniform frequency. The same phonemes used by the Bell Laboratories were used. A “test” consists of utterances by one male and one female talker each speaking 152 CV and VC's following a carrier phrase. The frequency spectrum of this material, as well as the procedure used for its estimate, will be described. Practice effects were studied at different magnitudes of distortion. The importance function which is presumably applicable to this material was found valid within the error of measurement for the filtered speech articulation test results. The error in predicting the articulation score will be related to the magnitude of the intrinsic variability of articulation testing. [Work supported by NINCDS.]
Recovery of brief tone thresholds from short duration noise exposure
Authors: Stephenson Mark R. , Wall Lida G.
Published: October 2005

Very few studies have examined temporal integration at threshold following noise exposure. Previous studies [J. Jerger, J. Acoust. Soc. Am. 27, 121–124 (1955) and J. Mills et al., J. Acoust. Soc. Am. 48, 524–535 (1970)] have indicated that temporal integration was reduced following a fatiguing noise exposure. Their results also indicated that the time course for recovery may be different for longer versus shorter duration signals. The purpose of this study was to evaluate the recovery function of two signal durations following a 15-min 100-db narrow-band noise exposure. Specifically, the time course for recovery was evaluated for absolute sensitivity and for temporal integration. Temporal integration was evaluated at a frequency range where the greatest TTS occurred as well as at a frequency range where TTS was not exhibited. The results indicated a different recovery function exists between “short” and “long” duration tones at a frequency range where greatest TTS occurred. Temporal integration was not consistently affected in the adjacent frequency regions.
The effect of noise-induced hearing loss on speech intelligibility in noise and its implications for noise damage risk criteria
Authors: Smoorenburg G. F.
Published: October 2005

Speech reception thresholds for sentences presented both in quiet and in background noise, and tone audiograms were measured for 14 normal ears (7 subjects) and 44 ears (22 subjects) with noise-induced hearing loss (NIHL). For the 22 subjects with NIHL maximum hearing loss was found in the 4–6 kHz region at 40 to 90 dB (losses exceeded by 90% and 10%, respectively). Hearing loss for speech presented in quiet was only 1.8 to 13.4 dB. For speech in noise hearing loss was 1.2 to 7 dB which means that the subjects with NIHL needed a 1.2 to 7 dB higher speech-to-noise ratio than normals to understand the sentences equally well. A 1-dB decrease in speech-to-noise ratio implies a decrease in sentence intelligibility of 15% to 20%. There was virtually no correlation between the hearing loss for speech presented in quiet and the loss for speech presented in background noise. Speech thresholds found in quiet showed the highest correlation with losses in the tone audiogram at 500 Hz whereas speech thresholds in noise showed the highest correlation with the losses at 2–3 kHz. The results for speech perception in noise show that the AAOO fence of 25-dB hearing loss averaged over the losses at 12, 1, and 2 kHz implies a severe handicap. Noise damage risk criteria should not be based on audiometric fences higher than 15-dB hearing loss averaged over the losses at 1, 2, and 3 kHz.
Meaningful and nonmeaningful noise: Effects and aftereffects
Authors: Loeb Michel , Holding Dennis H. , Baker Mary Anne
Published: October 2005

In recent experiments in our laboratory two effects of white noise have been found: (1) With the Norinder, an arithmetic task employed by Frankenhaueser and Lundberg, involving decisions as to whether additions or subtractions are to be performed, 95 dBA noise decreased number of problems attempted for men in the morning but not for men in the afternoon or for women and (2) with COPE, a task involving a decision whether to attempt a more complex task with a greater probability of success or a less complex one with lower success probability, both noise and task-induced fatigue tended to produce choices of the less complex task, and the effects were additive. The present experiment employed two kinds of continuous noise of 95 dBA as well as a control or ambient noise condition (55 dBA), and a different arithmetic task, involving successive additions of columns of numbers, was employed. Preliminary analysis indicates that the effects of noise on this task are different from those on the Norinder. Effects on COPE were inconclusive, for reasons to be discussed.
The effects of noise on a cognitive vigilance task
Authors: Lysaght Robert J. , Warm Joel S. , Dember William N. , Loeb Michel
Published: October 2005

An important aspect of vigilance research has been the impact of environmental factors, such as noise, on performance efficiency. Results from numerous studies indicate that noise influences sustained attention in complex ways. The impact of noise depends upon at least three parameters: (1) the quality of noise; (2) the intensity level of the noise; and (3) the information-processing demand required to perform the vigilance task. These noise effects have been based upon “sensory” vigilance tasks, in which critical signals for detection are physical changes in ongoing stimulation. However, no systematic efforts have been made to assess the joint effects of noise parameters and information-processing demand upon “cognitive” vigilance tasks in which the critical signals for detection are more symbolic than sensory. Such an effort constituted the goal of the present investigation. The results of the study indicated that the effects of noise exposure on “cognitive” vigilance are diverse. With respect to low information-processing demand, the presence of either broadband noise or varied noise seemed to have a negligible impact on the course of vigilance performance over time. By contrast, with a high information-processing demand, noise exposure resulted in an intricate set of findings, in which both noise level and noise quality were important.
Auditory intensity discrimination in human infants
Authors: Sinnott Joan M. , Aslin Richard N.
Published: October 2005

Auditory intensity difference limens were measured in 40 human infants (ages 7–9 months) and several adults using a go, no—go operant head-turning technique and an adaptive staircase (tracking) discrimination procedure. Subjects were visually reinforced for responding to intensity increments in a repeating background signal either a 1.0-kHz tone or a vowel /a/, presented free-field at a level of 60 dB SPL. Stimulus control in infants was monitored through the use of randomly interleaved “probe” and “catch” trials. Infant thresholds ranged from 3.0 to 12.0 dB for tones and from 2.5 to 12.0 dB for vowels, with the most sensitive infants falling within the range of adults. It is noteworthy that we were unsuccessful in training any infants to respond to intensity decrements, although adults experienced no difficulty with this task. [Supported by NIH grant HD 11915.]
Comparative frequency discrimination in primates
Authors: Sinnott Joan M. , Petersen Michael R.
Published: October 2005

Auditory frequency difference limens at 2.0 kHz were measured monaurally in three humans and three Old World monkeys: one Japanese macaque (Macaca fuscata), one vervet (Cercopithecus aethiops), and one De Brazza monkey (Cercopithecus neglectus). A go, no-go, repetitive-standard discrimination procedure was employed with positive reinforcement. In addition to species differences, we examined the effects of presence versus absence of feedback after missed stimuli, changes in sensation level (35 vs 45 dB), and presenting frequency increments versus decrements. Results showed that human ΔFs (4–11 Hz) were superior to those of monkeys (25–99 Hz), and all subjects performed better with feedback after misses. In addition, while the best human thresholds tended to occur with frequency increments at higher sensation levels, the best monkey thresholds tended to occur with frequency decrements at lower sensation levels. Of the three monkeys, the Japanese macaque exhibited performance qualitatively and quantitatively most similar to the humans. [Supported by NSF, Sloan Foundation, and Deafness Research Foundation.]
Comparison of several auditory adaptation techniques
Authors: Weiler E. M. , Nileshwar Neeta , Davis J. M.
Published: October 2005

The present study examined similarities between several auditory adaptation techniques to determine whether one or several effects occur. Four procedures for measuring adaptation were used: The Modified Monaural Magnitude Estimates (M.E.) Procedure (Weiler, Sandman, Pederson, 1981), The Binaural M.E. Procedure From Scharf's Laboratory (Botté et al., 1982), The Reaction Time Method (Weiler and Davis, 1975) and The Classical Simultaneous Dichotic Loudness Balance (S.D.L.B., Hood, 1950). Initial results with 12 graduate students showed adaptation with each procedure. The monaural and binaural M.E. procedures agree generally with Botté et al. As indicated by previous reviews of several studies (Weiler, Sandman, Goldman, Davis, 1982), there do not appear to be significant correlations, except between monaural and binaural M.E. Adaptation (r = 0.55). It appears that the procedures either produce different adaptation effects or measure different aspects of auditory adaptation.
Loudness adaptation of a continuing tone “induced” by nonsimultaneous binaural stimulation
Authors: Cobb Frederick , Pollock V. , Sandman D. , Weiler E. M.
Published: October 2005

Botté, Canévét, and Scharf (1982) induced Magnitude Estimated (M.E.) loudness adaptation of a continuous tone by means of a simultaneous intermittent contralateral tone. The present study investigated the need for simultaneous contralateral stimulation to induce M.E. adaptation. During the pre-test, simultaneous intermittent binaural stimuli were presented at 60 dB SPL, 1 kHz. During the adapting (middle) phase, the tone was presented monaurally and continuously for 7 min. This stimulus continued into the post-test when the contralateral intermittent tone was re-introduced. No change in loudness was reported during the pre-test. A significant cumulative decline in loudness was reported for the monaural 7-min adapting phase. Re-introduction of the binaural contralateral tone resulted in additional adaptation. Simultaneous presentation of the contralateral tone was not necessary to observe loudness adaptation.
Smoothed boundary conditions for low-frequency coherent scatter
Authors: Tolstoy I.
Published: October 2005

The problem of low-frequency coherent scatter from a rough z = 0 plane (kd < kh < 1, d, h being mean roughness height and spacing, k the radiation wavenumber) is equivalent to the wave equation with a smoothed boundary condition ∂φs/∂z = αφ, φs being the perturbation of the total field φ at z = 0 (on the side of incidence), α a coefficient defining the roughness. The problem is to calculate α. There are (1) stochastic models; random roughness profiles are assumed, with small slopes everywhere, giving α = αST (d̄,l̄), d̄,l̄ being mean-square height and correlation distance, with αST of O (k2d̄2), (2) deterministic models in which the roughness is modeled by small bosses of given shape (height d, width 2l⩽h). Steep, even infinite, slopes are allowed in the roughness profile, leading to α = αD (d,l) of O(kd)—which, however, becomes O(k2d2) for small average slopes d/l≪1. For kh < 1 such surfaces are easily randomized through a trivial averaging procedure. In the limit d/l→0, it is shown that αD → αST. Formally the deterministic model differs from the stochastic in fundamental ways; it brings out explicitly the role of monopole and dipole source densities in representing the effect of roughness, and the importance of nonradiative nearfield interaction between neighboring dipoles. This interaction is essential for calculating αD for close-packed scatterers (d/h>0.1)—as demonstrated by boundary-wave experiments [Medwin et al., J. Acoust. Soc. Am. 66, 1131–1134 (1979}]. [Work supported by ONR.]
Effects of volume scatter on spatial coherence
Authors: McCoy John J.
Published: October 2005

We consider a framework that is useful for classifying a wide variety of probabilistic acoustic models according to intended application, nature of stochastic input, and level of mathematical sophistication. The mathematical basis for the several codes developed as part of the Naval Research Laboratory's research program intended for estimating environmental limitations (in this case, due to volume scattering) on array design will be reviewed. Typical outputs of these codes will be presented, and available experimental data will be considered in the light of these outputs.
Vertical spatial coherence of an acoustical signal along a rearm-ray path
Authors: Perkins John S. , McCoy John J.
Published: October 2005

COVERT is a computer model which predicts the effects of stochastic volume scattering on the vertical spatial coherence of an acoustic signal along a single path (as determined by a mean sound-speed field). The propagation path is termed a macro-ray path and is described by a sequence of straight line segments. The program algorithm calculates the effects of scattering over each segment in turn as if it were in a homogeneous medium. The scattering term [J. J. McCoy and M. J. Beran, J. Acoust. Soc. Am. 66, 1468–1481 (1979)] takes into account the angle of the path segment relative to the anisotropic scattering mechanism, and the scattering strength may vary with the depth of the segment. Major advantages of COVERT are that it is easy to use and relatively fast. Its current principal limitations are that it treats a single macro-ray path and does not incorporate coupling between the volume scattering and subsequent effects of refraction and diffraction. Thus, COVERT's main utility is for single-path, high-frequency (above 100 Hz) problems, and as a basis of comparison for more complex models.
A generalized stochastic propagation channel characterization
Authors: Adams Stanley L. , Tappert Fred D.
Published: October 2005

Recent work by the authors has led to an elegant generalized propagation channel characterization. The underwater propagation channel is treated as a transformation of space-time images into space-time images. Propagation of three-dimensional space-time images through random media leads to eight variables, each with independent spreads (or coherencies) in a second-order moment characterization. From this point of view, generalized system input-output equations are developed and generalized ambiguity functions are defined. Examples are drawn from several disciplines to qualitatively demonstrate the characterization.
Perception of stop consonant formant transitions by normal and high-frequency sensorineurally hearing-impaired listeners: Identification and psychoacoustic evidence
Authors: Ochs T. , Humes Larry E. , Ohde Ralph N.
Published: October 2005

Perception of stop consonant formant transitions was examined for normal hearers and subjects with high-frequency hearing loss. In experiment I, subjects identified five-formant synthetic voiced stops /b, d, g/ in the /i/ and /ɑ/ vowel environments. In one condition, short duration stimuli were synthesized with appropriate onset frequency but no F2 transition. Results for the /ɑ/ vowel revealed good identification for both conditions. Identification performance was generally poorer for the /i/ vowel than the /ɑ/ vowel, particularly in hearing-impaired subjects. The presence of formant transitions slightly enhanced identification ability for some conditions. In experiment II, difference limens (DLs) for the F2 transition were determined using selected stops in the /i/ vowel environment. The DL results for F2 transitions showed considerable overlap among the groups, in spite of different identification performance between hearing impaired and normal hearers. Along with previous findings, these results suggest that formant transitions are not necessary for identification of place of articulation in stops.
Initial stop burst place perception for normal- and impaired-hearing listeners
Authors: Revoile S. , Pickett J. M. , Holden-Pitt Lisa
Published: October 2005

This study examined whether hearing-impaired listeners could identify place of articulation for initial stop consonants, using information occurring early in the stop release; for normal-hearing listeners this release information has been implicated as a highly important cue for place perception of initial stops. Place perception for the release bursts of initial stop consonants was tested for impaired-(N = 23) and for normal-hearing (N = 6) listeners. The burst were obtained from ten utterances each of the syllables /pad/, /kad/, /tad/, /bad/, /gad/, /dad/. Three test conditions were used: (1) the entire syllable; (2) the initial release transients alone; and (3) the aspirations following the transients of the voiceless consonants. For the normal-hearing group, consonant perception was 100% when tested for the entire syllable; consonant place perception for the transients only, was 87%, and for the voiceless aspirations 67%. Among the hearing-impaired listeners, mean stop place perception was about 60% when tested for the entire syllable. Tests of the burst segments only, yielded chance performance for the impaired listeners.
The search for invariant visible cues in lipreading
Authors: Montgomery Allen A.
Published: October 2005

In the acoustic speech signal it is well known that at the segmental level constant perception may result from widely differing acoustic signals. The existence of analogous phenomena in lipreading, however, has not been demonstrated. In principle, that demonstration would take the form of determining whether constant visual perception of a viseme (such as the /i,I/ high front vowel) is associated with significantly varying physical properties of the lipshapes in different phonetic contexts. In this study we present an analysis of physical and perceptual data derived from vowel lipreading stimuli aimed at defining appropriate physical measures of vowel lipshapes, examining a database of vowel lipshapes and associated lipreading confusions, and deriving criteria for perceptual invariance and physical cue variance in visible stimuli. Preliminary results based on five vowels in 11 CVC contexts indicate that perceptual constancy analogous to that in auditory perception may exist in lipreading, although further refinement of the physical cues and the definition of viseme are clearly needed. [Work supported by Department of Clinical Investigation, WRAMC.]
Effects of training on vowel production by deaf speakers
Authors: Osberger M. J. , Kent R. D.
Published: October 2005

Five profoundly hearing-impaired children received training for approximately six months to improve production of vowels in monosyllabic words. Spectrographic analyses were used to measure the duration and formant frequencies of vowel nuclei in a corpus of CV (C) words produced before, during, and after training. Preliminary results revealed that vowel duration was abnormally long in all samples, but the duration of the vowels produced in the training sessions were excessively prolonged relative to the duration of the same samples produced in either the pre- or post-training sessions. There tended to be a decrease in duration as training progressed, although there were some individual variations. The pattern of change associated with the frequency locations of F1 and F2 was complex and varied depending on the speaker and target vowel. The largest changes most often involved the frequency location of F1. These findings suggest that the most common maneuver used by the children to achieve a target vowel involved jaw rather than tongue movement, accompanied by excessive prolongation of the vowel. The data also indicate that the processes involved in the development of speech skills can be highly individualized in deaf children. [Work supported by NIH/NINCDS-NS16247.]