bluuebunny/crossref_metadata_2025 huggingface dataset:
Requirement for the Chemokine Receptor Ccr6 in Allergic Pulmonary Inflammation
Authors: Lukacs Nicholas W. , Prosser Dina M. , Wiekowski Maria , Lira Sergio A. , Cook Donald N.
Published: July 2002

Allergic asthmatic responses in the airway are associated with airway hyperreactivity, eosinophil accumulation in the lung, and cytokine production by allergen-specific, T helper cell type 2 (Th2) lymphocytes. Here, we show that in a cockroach antigen (CA) model of allergic pulmonary inflammation, the chemokine macrophage inflammatory protein (MIP)-3α is expressed in the lung within hours of allergen challenge. To determine the biologic relevance of this expression, mice lacking CCR6, the only known receptor for MIP-3α, were studied for their response to CA. CCR6-deficient mice were immunized to the same extent as their wild-type counterparts, as judged by cytokine production in antigen-challenged lymphocytes. However, compared with CA-challenged wild-type mice, challenged CCR6-deficient mice had reduced airway resistance, fewer eosinophils around the airway, lower levels of interleukin 5 in the lung, and reduced serum levels of immunoglobulin E. Together, these data demonstrate that MIP-3α and CCR6 function in allergic pulmonary responses and suggest that these molecules might represent novel therapeutic targets for treatment of asthma.
Regulation of Murine Intestinal Inflammation by Reactive Metabolites of Oxygen and Nitrogen
Authors: Krieglstein Christian F. , Cerwinka Wolfgang H. , Laroux F. Stephen , Salter James W. , Russell Janice M. , Schuermann Guido , Grisham Matthew B. , Ross Christopher R. , Granger D. Neil
Published: July 2002

Several reports have implicated reactive oxygen and nitrogen metabolites (RONS) in the initiation and/or progression of inflammatory bowel diseases (IBDs). We have investigated the role of three key RONS-metabolizing enzymes (inducible nitric oxide synthase [iNOS], superoxide dismutase [SOD], nicotinamide adenine dinucleotide phosphate [NADPH] oxidase) in a murine model of IBD. Mice genetically deficient (−/−) in either iNOS or the p47phox subunit of NADPH oxidase, transgenic (Tg) mice that overexpress SOD, and their respective wild-type (WT) littermates were fed dextran sulfate sodium (DSS) in drinking water for 7 days to induce colitis. In addition, the specific iNOS inhibitor 1400W was used in DSS-treated WT and p47phox−/− mice. WT mice responded to DSS feeding with progressive weight loss, bloody stools, elevated serum NOX and colonic mucosal injury with neutrophil infiltration. Both the onset and severity of colitis were significantly attenuated in iNOS−/− and 1400W-treated WT mice. While the responses to DSS did not differ between WT and p47phox−/− mice, enhanced protection was noted in 1400W-treated p47phox−/− mice. Interestingly, SODTg mice exhibited more severe colitis than their WT littermates. These findings reveal divergent roles for superoxide and iNOS-derived NO in intestinal inflammation.
The Nature of Surround-Induced Depolarizing Responses in Goldfish Cones
Authors: Kraaij D.A. , Spekreijse H. , Kamermans M.
Published: July 2002

Cones in the vertebrate retina project to horizontal and bipolar cells and the horizontal cells feedback negatively to cones. This organization forms the basis for the center/surround organization of the bipolar cells, a fundamental step in the visual signal processing. Although the surround responses of bipolar cells have been recorded on many occasions, surprisingly, the underlying surround-induced responses in cones are not easily detected. In this paper, the nature of the surround-induced responses in cones is studied. Horizontal cells feed back to cones by shifting the activation function of the calcium current in cones to more negative potentials. This shift increases the calcium influx, which increases the neurotransmitter release of the cone. In this paper, we will show that under certain conditions, in addition to this increase of neurotransmitter release, a calcium-dependent chloride current will be activated, which polarizes the cone membrane potential. The question is, whether the modulation of the calcium current or the polarization of the cone membrane potential is the major determinant for feedback-mediated responses in second-order neurons. Depolarizing light responses of biphasic horizontal cells are generated by feedback from monophasic horizontal cells to cones. It was found that niflumic acid blocks the feedback-induced depolarizing responses in cones, while the shift of the calcium current activation function and the depolarizing biphasic horizontal cell responses remain intact. This shows that horizontal cells can feed back to cones, without inducing major changes in the cone membrane potential. This makes the feedback synapse from horizontal cells to cones a unique synapse. Polarization of the presynaptic (horizontal) cell leads to calcium influx in the postsynaptic cell (cone), but due to the combined activity of the calcium current and the calcium-dependent chloride current, the membrane potential of the postsynaptic cell will be hardly modulated, whereas the output of the postsynaptic cell will be strongly modulated. Since no polarization of the postsynaptic cell is needed for these feedback-mediated responses, this mechanism of synaptic transmission can modulate the neurotransmitter release in single synaptic terminals without affecting the membrane potential of the entire cell.
Blocker State Dependence and Trapping in Hyperpolarization-Activated Cation Channels
Authors: Shin Ki Soon , Rothberg Brad S. , Yellen Gary
Published: July 2002

Hyperpolarization-activated cation currents (Ih) are key determinants of repetitive electrical activity in heart and nerve cells. The bradycardic agent ZD7288 is a selective blocker of these currents. We studied the mechanism for ZD7288 blockade of cloned Ih channels in excised inside-out patches. ZD7288 blockade of the mammalian mHCN1 channel appeared to require opening of the channel, but strong hyperpolarization disfavored blockade. The steepness of this voltage-dependent effect (an apparent valence of ∼4) makes it unlikely to arise solely from a direct effect of voltage on blocker binding. Instead, it probably indicates a differential affinity of the blocker for different channel conformations. Similar properties were seen for ZD7288 blockade of the sea urchin homologue of Ih channels (SPIH), but some of the blockade was irreversible. To explore the molecular basis for the difference in reversibility, we constructed chimeric channels from mHCN1 and SPIH and localized the structural determinant for the reversibility to three residues in the S6 region likely to line the pore. Using a triple point mutant in S6, we also revealed the trapping of ZD7288 by the closing of the channel. Overall, the observations led us to hypothesize that the residues responsible for ZD7288 block of Ih channels are located in the pore lining, and are guarded by an intracellular activation gate of the channel.
The Mechanism of Ciliary Stimulation by Acetylcholine
Authors: Zagoory Orna , Braiman Alex , Priel Zvi
Published: July 2002

Stimulation of ciliary cells through muscarinic receptors leads to a strong biphasic enhancement of ciliary beat frequency (CBF). The main goal of this work is to delineate the chain of molecular events that lead to the enhancement of CBF induced by acetylcholine (ACh). Here we show that the Ca2+, cGMP, and cAMP signaling pathways are intimately interconnected in the process of cholinergic ciliary stimulation. ACh induces profound time-dependent increase in cGMP and cAMP concentrations mediated by the calcium–calmodulin complex. The initial strong CBF enhancement in response to ACh is mainly governed by PKG and elevated calcium. The second phase of CBF enhancement induced by ACh, a stable moderately elevated CBF, is mainly regulated by PKA in a Ca2+-independent manner. Inhibition of either guanylate cyclase or of PKG partially attenuates the response to ACh of [Ca2+]i, but completely abolishes the response of CBF. Inhibition of PKA moderately attenuates and significantly shortens the responses to ACh of both [Ca2+]i and CBF. In addition, PKA facilitates the elevation in [Ca2+]i and cGMP levels induced by ACh, whereas an unimpeded PKG activity is essential for CBF enhancement mediated by either Ca2+ or PKA.
Editorial boards: realizing their potential
Authors: Hames Irene
Published: July 2002

Most journals have editorial boards. Their composition, what the individual members do, and how they operate will vary, but they are generally recognized as having certain central roles. What makes a good editor? How can potential editors be identified and then persuaded to join an editorial board? Once on the board, what can be done to keep them happy, committed, and working productively for the journal? What sorts of problems can arise, and how can they be avoided? These are some of the questions dealt with in this article.
The Hausdorff operator is bounded on the real Hardy space 𝐻¹(ℝ)
Authors: Liflyand Elijah , Móricz Ferenc
Published: July 2002

We prove that the Hausdorff operator generated by a function

φ
∈

L

1

(

R

)

\varphi \in L^{1} ({\mathbb {R}})

is bounded on the real Hardy space

H

1

(

R

)

H^{1} ({\mathbb {R}})

. The proof is based on the closed graph theorem and on the fact that if a function

f
f

in

L

1

(

R

)

L^{1} ({\mathbb {R}})

is such that its Fourier transform

f
^

(
t
)

\widehat {f} (t)

equals

0
0

for

t
>
0

t>0

(or for

t
>
0

t>0

), then

f
∈

H

1

(

R

)

f\in H^{1} ({\mathbb {R}})

.
Subquadratic-time factoring of polynomials over finite fields
Authors: Kaltofen Erich , Shoup Victor
Published: July 2002

New probabilistic algorithms are presented for factoring univariate polynomials over finite fields. The algorithms factor a polynomial of degree

n
n

over a finite field of constant cardinality in time

O
(

n

1.815

)

O(n^{1.815})

. Previous algorithms required time

Θ
(

n

2
+
o
(
1
)

)

\Theta (n^{2+o(1)})

. The new algorithms rely on fast matrix multiplication techniques. More generally, to factor a polynomial of degree

n
n

over the finite field

F

q

{\mathbb F}_q

with

q
q

elements, the algorithms use

O
(

n

1.815

log
⁡
q
)

O(n^{1.815} \log q)

arithmetic operations in

F

q

{\mathbb F}_q

. The new “baby step/giant step” techniques used in our algorithms also yield new fast practical algorithms at super-quadratic asymptotic running time, and subquadratic-time methods for manipulating normal bases of finite fields.
A construction of interpolating wavelets on invariant sets
Authors: Chen Zhongying , Micchelli Charles , Xu Yuesheng
Published: July 2002

We introduce the concept of a refinable set relative to a family of contractive mappings on a metric space, and demonstrate how such sets are useful to recursively construct interpolants which have a multiscale structure. The notion of a refinable set parallels that of a refinable function, which is the basis of wavelet construction. The interpolation points we recursively generate from a refinable set by a set-theoretic multiresolution are analogous to multiresolution for functions used in wavelet construction. We then use this recursive structure for the points to construct multiscale interpolants. Several concrete examples of refinable sets which can be used for generating interpolatory wavelets are included.
Restoration of telomerase activity rescues chromosomal instability and premature aging in Terc−/− mice with short telomeres
Authors: Samper Enrique , Flores Juana M , Blasco María A
Published: July 2002

Reconstitution of telomerase activity is proposed as a potential gene therapy to prevent, or rescue, age‐related diseases produced by critical telomere shortening. However, it is not known whether or not short telomeres are irreversibly damaged. We addressed this by re‐introducing telomerase in late generation telomerase‐deficient mice, Terc−/−, which have short telomeres and show severe proliferative defects. For this, we have crossed these mice with Terc+/− mice and analyzed telomere length, chromosomal instability and premature aging of the progeny. The Terc−/− progeny had one set of chromosomes with normal telomeres, whereas the other set remained with critically short telomeres; these mice presented chromosomal instability and premature aging. In contrast, Terc+/− progeny showed all chromosomes with detectable telomeres, and did not show chromosomal instability or premature aging. These results prove that critically short telomeres can be rescued by telomerase, and become fully functional, thus rescuing premature aging. This has important implications for the future design of telomerase‐based gene therapy of age‐related diseases.
PABP1 identified as an arginine methyltransferase substrate using high‐density protein arrays
Authors: Lee Jaeho , Bedford Mark T
Published: July 2002

The arginine methyltransferases CARM1 and PRMT1 associate with the p160 family of nuclear hormone receptor coactivators. This association enhances transcriptional activation by nuclear receptors. We describe a method for identifying arginine N‐methyltransferase substrates using arrayed high‐density protein membranes to perform solid‐phase supported enzyme reactions in the presence of the methyl donor S‐adenosyl‐L‐methionine. Using this screen, we identified distinct substrates for CARM1 and PRMT1. All PRMT1 substrates harbor the expected GGRGG methylation motif, whereas the peptide sequence comparisons of the CARM1 substrates revealed no such motif. The predominant CARM1 substrate identified in this screen was PABP1. We mapped the methylated region of this RNA binding molecule in vitro and demonstrate that PABP1 is indeed methylated in vivo. Prior to these findings, the only known substrate for CARM1 was histone H3. We broaden the number of CARM1 targets and suggest a role for CARM1 in regulating transcription/translation.
The many challenges of facial herpes simplex virus infection
Authors: Esmann Jørgen
Published: July 2002

Infection with herpes simplex virus type 1 (HSV-1) is common throughout the world, with many cases leading to symptomatic facial herpes. Following primary infection, HSV-1 establishes chronic latency, usually in the trigeminal ganglia, from where it reactivates periodically to cause recurrent outbreaks of infection. Recurrent facial herpes episodes vary in severity; they may be asymptomatic or appear as maculo-papular lesions that subsequently regress (abort), or vesicular lesions may develop which then scab prior to healing. Symptomatic lesions usually occur on the lips, cheeks, within the nose or on the nasal septum; they are often painful and unsightly. During asymptomatic or symptomatic outbreaks, HSV-1 is shed and thus there is a risk of transmission to susceptible individuals. Antiviral therapy in oral or topical formulations has been shown to be effective in treating facial herpes outbreaks. Oral therapy may also be used to suppress frequently recurring or severe episodes. For lesions at less readily accessible sites or when the risk of autoinoculation is high, oral therapy is warranted.
The Immune Tolerance Network: tolerance at the crossroads
Authors: Bluestone Jeffrey A. , Matthe Jeffrey
Published: July 2002

Immune tolerance therapies are designed to reprogramme immune cells in a highly specific fashion in order to eliminate pathogenic responses but preserve normal immune function. A concept that has tantalized immunologists for decades, tolerogenic therapies would replace current lifelong immunosuppressive regimens and their often debilitating side–effects with short–term immunosuppressive regimens and their often debilitating side–effects with short–term, effective cures. Significant advances have been made over the past decade that have provided a more detailed understanding of the molecular events associated with T–cell recognition and activation. Unprecedented opportunities to test these approaches in a variety of human diseases have now emerged. As a result of these advances, the Immune Tolerance Network (ITN), a group of 70 expert immunologists spanning multiple disciplines, has been created to identify and promote the use of tolerogenic therapies in the clinic. Using a unique interactive approach designed to speed the development of clinical tolerance therapies, the ITN is examining new and innovative therapeutic approaches and bioassays in a range of autoimmune diseases and transplantation settings, as well as asthma and allergies. This work has been funded by the National Institutes of Health (in collaboration with the Juvenile Diabetes Foundation International).
Elastic proteins: biological roles and mechanical properties
Authors: Gosline J. , Lillie M. , Carrington E. , Guerette P. , Ortlepp C. , Savage K.
Published: July 2002

The term ‘elastic protein’ applies to many structural proteins with diverse functions and mechanical properties so there is room for confusion about its meaning. Elastic implies the property of elasticity, or the ability to deform reversibly without loss of energy; so elastic proteins should have high resilience. Another meaning for elastic is ‘stretchy’, or the ability to be deformed to large strains with little force. Thus, elastic proteins should have low stiffness. The combination of high resilience, large strains and low stiffness is characteristic of rubber–like proteins (e.g. resilin and elastin) that function in the storage of elastic–strain energy. Other elastic proteins play very different roles and have very different properties. Collagen fibres provide exceptional energy storage capacity but are not very stretchy. Mussel byssus threads and spider dragline silks are also elastic proteins because, in spite of their considerable strength and stiffness, they are remarkably stretchy. The combination of strength and extensibility, together with low resilience, gives these materials an impressive resistance to fracture (i.e. toughness), a property that allows mussels to survive crashing waves and spiders to build exquisite aerial filters. Given this range of properties and functions, it is probable that elastic proteins will provide a wealth of chemical structures and elastic mechanisms that can be exploited in novel structural materials through biotechnology.
Superior Formation of Cortical Memory Traces for Melodic Patterns in Musicians
Authors: Tervaniemi Mari , Rytkönen Mika , Schröger Erich , Ilmoniemi Risto J. , Näätänen Risto
Published: July 2002

The human central auditory system has a remarkable ability to establish memory traces for invariant features in the acoustic environment despite continual acoustic variations in the sounds heard. By recording the memory-related mismatch negativity (MMN) component of the auditory electric and magnetic brain responses as well as behavioral performance, we investigated how subjects learn to discriminate changes in a melodic pattern presented at several frequency levels. In addition, we explored whether musical expertise facilitates this learning. Our data show that especially musicians who perform music primarily without a score learn easily to detect contour changes in a melodic pattern presented at variable frequency levels. After learning, their auditory cortex detects these changes even when their attention is directed away from the sounds. The present results thus show that, after perceptual learning during attentive listening has taken place, changes in a highly complex auditory pattern can be detected automatically by the human auditory cortex and, further, that this process is facilitated by musical expertise.
In vivo assessment of trabecular bone structure using fractal analysis of distal radius radiographs
Authors: Majumdar Sharmila , Link Thomas M. , Millard Jacob , Lin John C. , Augat Peter , Newitt David , Lane Nancy , Genant Harry K.
Published: July 2002

Our purpose in this study was (i) to measure trabecular bone structure using fractal analysis of distal radius radiographs in subjects with and without osteoporotic hip fractures, and (ii) to compare these measures with bone mineral density (BMD) as well as with measures of trabecular bone structure derived from high resolution magnetic resonance (MR) images. Distal radius radiographs were obtained using semi‐industrial films (55 kVp, 400 mAs) in 30 postmenopausal patients, who had suffered osteoporotic hip fractures (74.8+/−8.2 years) in the last 24 months and 27 postmenopausal age‐matched (74.6+/−6.6 yr) normal volunteers. Radiographs were digitized at 50 μm. A Fourier power spectrum‐based fractal dimension (FD) characterizing the trabecular pattern was measured in a region of interest proximal to the joint line. The fractal dimension was calculated over two spatial frequency (f) ranges: FD1 was calculated over FD2 over the higher range Trabecular BMD in the radius was obtained using peripheral quantitative computed tomography (pQCT) (Stratec GmbH, Germany). In addition BMD of the proximal femur was determined using dual x‐ray absorptiometry (DXA) (QDR 2000, Hologic, MA). In a subset of patients (16 controls and 18 with hip fractures), high resolution MR imaging of the distal radius (spatial resolution of 156×156×500 μm) was used to obtain measures analogous to bone histomorphometry. There were significant differences between the fracture and nonfracture groups in the total femur BMD (13%), trabecular BMD in the distal radius (4%), and the fractal dimension in the radiographs (FD2) (3%). The correlations between FD2 and the total femur BMD as well as trabecular bone BMD in the distal radius were −0.48 and −0.22 respectively; FD1 increased with BMD and showed lower correlations. FD2 showed good correlations with App. Tb.N (−0.71) and App. Tb.Sp (0.69) moderate correlation with App BV/TV (−0.53) and no significant correlation with App. Tb.Th. The correlations between structural measures and FD1 showed the inverse trend and were typically lower. The odds ratios for a hip fracture were 2.44 for total femur BMD, 1.5 for trabecular BMD (radius), and 1.5 for FD2, respectively. In summary, the fractal measures derived from radiographs of the radius show differences between subjects with and without hip fractures, the predictive power of measures in the distal radius are comparable to radial trabecular BMD but lower than that of total hip BMD.
Temperature monitoring of ultrasonically heated muscle with RARE chemical shift imaging
Authors: Mulkern Robert V. , Chung Andrew H. , Jolesz Ferenc A. , Hynynen Kullervo
Published: July 2002

The ability to monitor tissue temperature in ultrasonically heated rabbit muscle is demonstrated using a chemical shift imaging approach based on the rapid acquisition with relaxation enhancement (RARE) fast imaging method [Hennig et al., Magn. Reson. Med. 3, 823–833 (1986)] applied in a line scan format. A three echo sequence with a 16 Hz spectral resolution with 64 ms echo readouts and 78 ms echo spacings is shown capable of measuring relevantly small water frequency shifts in phantoms. Applied to the in vivo model of ultrasonically heated rabbit muscle, water resonance frequencies at the ultrasonic focal point were found to be linearly related to temperature with a slope of −0.007 ± 0.001 ppm/°C ( studies). Measurements of the frequency shift in unheated tissue located away from the ultrasonically heated tissue varied by approximately 0.011 ppm over the course of the experiments, leading to an estimated temperature accuracy of ±1.6 °C in vivo.
Experimental determination of the convolution kernel for the study of the spatial response of a detector
Authors: Garcı́a‐Vicente F. , Delgado J. M. , Peraza C.
Published: July 2002

One of the most important parameters in the characterization of a detector is its spatial convolution kernel. This kernel contains all of the information about the influence that the detector size has on the measured beam profile. In this paper we present an experimental method for the determination of the spatial convolution kernel for commonly used detectors that are employed in the x‐ray profile measurement: diode, and ionization minichamber. Our work is based on first assuming a step function pattern on a photographic film is known and is a perfect step function. The kernel of the densitometer system was then derived from the deconvolution of the scanned profile to the step function. Next a film was exposed to a penumbra area of an x‐ray beam from a linac. The film was scanned using the same densitometer. The “real profile” that emerges from a linear accelerator was derived by the deconvolution of the scanned profile using the now known kernel of the film densitometer. Under the same irradiation condition the x‐ray profile was measured with other detectors and with this information we obtained the convolution kernels for these detectors by solving numerically their basic convolution integrals. The results show that the Gaussian convolution kernel is the most consistent with the measurements. The best numerical values for the FWHM of the kernels are 1.1 mm, 2.2 mm, and 5.4 mm for densitometer, diode, and minichamber, respectively.
Ionization chamber, electrometer, linear accelerator, field size, and energy dependence of the polarity effect in electron dosimetry
Authors: Ramsey Chester R. , Spencer Kelly M. , Oliver Adrian L.
Published: July 2002

Plane‐parallel ionization chambers are the instrument of choice for use in electron calibration and dosimetry, but these chambers may exhibit large polarity effects. This study concentrates on measuring the dependence of the polarity error at various mean energies using different linear accelerator, field size, ion chamber, and electrometer combinations. The polarity error was shown to increase for all four ionization chambers as the mean energy at depth decreased, but was always less than one percent at Polarity error dependence was also observed for similar plane‐parallel chambers, varying field sizes, and different linear accelerators, but no polarity error dependence was observed for similar cylindrical chambers and different electrometers. Measurements of the polarity error can be used to develop correction factors for future measurements that will help minimize the time spent performing electron dosimetry and calibrations. These correction factors can be used to calculate the correct reading without the need to reverse the chamber bias, thus reducing the number of measurements required.
Macroscopic phenomena and microscopic processes: Student understanding of transients in direct current electric circuits
Authors: Thacker Beth Ann , Ganiel Uri , Boys Donald
Published: July 2002

Studies of student understanding of simple electric dc circuits have shown that many of them find it very difficult to apply qualitative reasoning to explain the observed phenomena. It has been suggested that these difficulties may be due to their failure to construct models of microscopic processes that lead to these phenomena. Indeed, in the traditional courses, such models have generally not been emphasized. In the present study, we compared the performance of different groups of university students in answering a questionnaire designed to probe their understanding of the relationship between macroscopic phenomena of transients in a dc circuit and the microscopic processes that can explain these phenomena. One group studied from a traditional text, the second group used a recently developed text that emphasizes models of microscopic processes. We also conducted detailed interviews with some of the students. From an analysis of the performance of these two groups, and also from a comparison with a previous study on Israeli high school students, we found that most of the students whose instructional experiences included an emphasis on the development of models of microscopic processes developed a better understanding of the transient phenomena studied. They applied qualitative considerations in their analyses and were able to develop coherent models to describe their observations. Overall, they demonstrated a superior understanding of the physical phenomena.
A study of time-domain FXLMS algorithms with control output constraint
Authors: Qiu Xiaojun , Hansen Colin H.
Published: July 2002

A single input, single output active noise control system using the time-domain Filtered-X LMS algorithm with output constraint is investigated. The constraint on the output of the control filter is applied by three different methods: the leakage algorithm based on the transformation method using a penalty function; the re-scaling algorithm based on the active set method; and the simple practical (clipping) algorithm which just clips the output if a constraint is encountered. A comparison of the three algorithms shows that the re-scaling algorithm can usually work successfully under the constraint, while the leakage algorithm usually needs a large leakage coefficient to satisfy the constraint with a resulting performance loss. The clipping algorithm has potential problems both with the stability and convergence speed.
An approximated 3-D model of the Langevin transducer and its experimental validation
Authors: Iula Antonio , Carotenuto Riccardo , Pappalardo Massimo , Lamberti Nicola
Published: July 2002

In this work, an approximated 3-D analytical model of the Langevin transducer is proposed. The model, improving the classical 1-D approach describing the thickness extensional mode, allows us to predict also the radial modes of both the piezoelectric ceramic disk and the loading masses; furthermore, it is able to describe the coupling between radial and thickness extensional modes. In order to validate the model, the computed frequency spectrum is compared with that obtained by measurements carried out on 13 manufactured samples of different thicknesses to diameter ratios. The comparison shows that the model predicts with quite good accuracy the resonance frequencies of the two lowest frequency modes, i.e., those of practical interest, all over the explored range. Finally, the coupling effect between thickness and radial modes on the frontal displacement is measured and discussed.
Age-related changes in temporal gap detection
Authors: Snell Karen B.
Published: July 2002

The purpose of this study was to clarify and extend the results of earlier studies of age-related effects on temporal resolution by precisely matching young and old subjects with normal hearing and measuring gap thresholds in a variety of listening conditions. Younger subjects were between 17 and 40 years of age, older subjects between 64 and 77 years. Signals were noisebursts which varied in upper-cutoff frequency, overall level, and sinusoidal-amplitude-modulation depth. Signals were presented in quiet, in a noise floor, and with a gated-high-frequency masker in a noise floor. Significant main effects were found for signal frequency, intensity, modulation, age, and background condition. Mean gap thresholds ranged between 2.1 and 10.1 ms and were larger for the older subjects in all 24 conditions. In some conditions, introduction of a noise floor increased the gap thresholds of the older subjects relative to those of the younger. Analyses of individual data support the conclusion that the mean differences between groups reflect shifts in the distributions of gap thresholds of the older subjects towards poorer temporal resolution.
Bjerknes force and bubble levitation under single-bubble sonoluminescence conditions
Authors: Matula Thomas J. , Cordry Sean M. , Roy Ronald A. , Crum Lawrence A.
Published: July 2002

Bubble levitation in an acoustic standing wave is re-examined here for the case of single-bubble sonoluminescence. The equilibrium position of the bubble is calculated by equating the average Bjerknes force with the average buoyancy force. The predicted values, as a function of pressure amplitude, are compared with experimental measurements. Our measurements indicate that the equilibrium position of the bubble shifts away from the pressure antinode as the drive pressure increases, in qualitative agreement with calculations, but unexpected when only linear theory is considered [A. Eller, J. Acoust. Soc. Am. 43, 170 (1968)]. The Bjerknes force also provides an upper limit to the drive pressure in which a bubble can be levitated near (and above) a pressure antinode, even in the absence of shape instabilities.
Pronunciation proficiency in L1 and L2 among Korean–English bilinguals: The effect of age of arrival in the U.S
Authors: Yeni-Komshian Grace H. , Flege James E. , Liu Hua
Published: July 2002

Pronunciation proficiency in the first (L1=Korean) and the second (L2=English) languages of bilinguals who had emigrated to the U.S. was examined. The focus of this presentation is on the effect of age of arrival (AOA) in the U.S. on pronunciation in L1 and in L2. The subject pool consisted of 240 Korean–English bilinguals classified into ten subgroups (ages 2–22) based on AOA. Two groups of monolingual subjects were also tested: 24 Korean and 24 English speakers. The bilingual subjects produced sentences in their L1 and L2 and the monolingual subjects produced sentences in their L1’s. Native listeners from each language group rated the speakers’ pronunciation on a 9-point scale. The results show a positive correlation between AOA and Korean pronunciation (0.74) and a negative correlation between AOA and English pronunciation (−0.85). In each language group and regardless of AOA, the monolingual subjects were rated better in pronunciation than the bilingual subjects. The implications of these findings to second language acquisition and first language retention will be discussed. [Work supported by NIH.]
Speech articulator measurements using low power EM-wave sensors
Authors: Holzrichter J. F. , Burnett G. C. , Ng L. C. , Lea W. A.
Published: July 2002

Very low power electromagnetic (EM) wave sensors are being used to measure speech articulator motions as speech is produced. Glottal tissue oscillations, jaw, tongue, soft palate, and other organs have been measured. Previously, microwave imaging (e.g., using radar sensors) appears not to have been considered for such monitoring. Glottal tissue movements detected by radar sensors correlate well with those obtained by established laboratory techniques, and have been used to estimate a voiced excitation function for speech processing applications. The noninvasive access, coupled with the small size, low power, and high resolution of these new sensors, permit promising research and development applications in speech production, communication disorders, speech recognition and related topics.
Adapting to supernormal auditory localization cues. I. Bias and resolution
Authors: Shinn-Cunningham Barbara G. , Durlach Nathaniel I. , Held Richard M.
Published: July 2002

Head-related transfer functions (HRTFs) were used to create spatialized stimuli for presentation through earphones. Subjects performed forced-choice, identification tests during which allowed response directions were indicated visually. In each experimental session, subjects were first presented with auditory stimuli in which the stimulus HRTFs corresponded to the allowed response directions. The correspondence between the HRTFs used to generate the stimuli and the directions was then changed so that response directions no longer corresponded to the HRTFs in the natural way. Feedback was used to train subjects as to which spatial cues corresponded to which of the allowed responses. Finally, the normal correspondence between direction and HRTFs was reinstated. This basic experimental paradigm was used to explore the effects of the type of feedback provided, the complexity of the simulated acoustic scene, the number of allowed response positions, and the magnitude of the HRTF transformation subjects had to learn. Data showed that (1) although subjects may not adapt completely to a new relationship between physical stimuli and direction, response bias decreases substantially with training, and (2) the ability to resolve different HRTFs depends both on the stimuli presented and on the state of adaptation of the subject.
A wave field extrapolation approach to acoustical modeling in enclosed spaces
Authors: Berkhout A. J. , de Vries D. , Baan J. , van den Oetelaar B. W.
Published: July 2002

In practice, impulse responses in enclosed spaces are calculated with algorithms that are based on the ray tracing model, the mirror image source model, or a mixture of both. Using those algorithms, however, the wave character of sound propagation is not properly taken into account and complex boundaries cannot be included. This paper presents an alternative approach adopted from the seismic imaging field. The proposed model is based on the concept of wave field extrapolation. Absorption properties of the boundaries can be specified in detail by means of reflection matrices. Propagation between boundaries is formulated by propagation matrices. Impulse responses along an array of receivers are numerically simulated by executing a sequence of matrix multiplications that can be interpreted as generalized spatial convolutions. Diffraction phenomena due to the finiteness and irregularity of the boundaries are correctly taken into account. The proposed algorithm is illustrated on a two-dimensional configuration. Results are compared with those of conventional models and with measured data. A discussion on computing time is included. In addition, the proposed algorithm leads to new directions in the analysis of measurements in enclosed spaces. The proposed algorithm implies a new concept for dereverberation of recordings that are made in complex acoustic surroundings, using microphone arrays.
Auditory localization of nearby sources. II. Localization of a broadband source
Authors: Brungart Douglas S. , Durlach Nathaniel I. , Rabinowitz William M.
Published: July 2002

Although many researchers have examined auditory localization for relatively distant sound sources, little is known about the spatial perception of nearby sources. In the region within 1 m of a listener’s head, defined as the “proximal region,” the interaural level difference increases dramatically as the source approaches the head, while the interaural time delay is roughly independent of distance. An experiment has been performed to evaluate proximal-region localization performance. An auditory point source was moved to a random position within 1 m of the subject’s head, and the subject responded by pointing to the perceived location of the sound with an electromagnetic position sensor. The overall angular error (17°) was roughly comparable to previously measured results in distal-region experiments. Azimuth error increased slightly as the sound source approached the head, but elevation performance was essentially independent of source distance. Distance localization performance was generally better than has been reported in distal-region experiments and was strongly dependent on azimuth, with the stimulus–response correlation ranging from 0.85 to the side of the head to less than 0.4 in the median plane. The results suggest that the enlarged binaural difference cues found in the head-related transfer function (HRTF) for nearby sources are important to auditory distance perception in the proximal region.
Memory for pitch versus memory for loudness
Authors: Clément Sylvain , Demany Laurent , Semal Catherine
Published: July 2002

The decays of pitch traces and loudness traces in short-term auditory memory were compared in forced-choice discrimination experiments. The two stimuli presented on each trial were separated by a variable delay (D); they consisted of pure tones, series of resolved harmonics, or series of unresolved harmonics mixed with lowpass noise. A roving procedure was employed in order to minimize the influence of context coding. During an initial phase of each experiment, frequency and intensity discrimination thresholds [P(C)=0.80] were measured with an adaptive staircase method while D was fixed at 0.5 s. The corresponding physical differences (in cents or dB) were then constantly presented at four values of D: 0.5, 2, 5, and 10 s. In the case of intensity discrimination, performance (d′) markedly decreased when D increased from 0.5 to 2 s, but was not further reduced when D was longer. In the case of frequency discrimination, the decline of performance as a function of D was significantly less abrupt. This divergence suggests that pitch and loudness are processed in separate modules of auditory memory.
Relationships among age-related differences in gap detection and word recognition
Authors: Snell Karen B. , Frisina D. Robert
Published: July 2002

The relationships among age-related differences in gap detection and word recognition in subjects with normal hearing or mild sensorineural hearing loss were explored in two studies. In the first study, gap thresholds were obtained for 40 younger and 40 older subjects. The gaps were carried by 150-ms, modulated, low-pass noise bursts with cutoff frequencies of 1 or 6 kHz. The noise bursts were presented at an overall level of 80 dB SPL in three background conditions. Mean gap thresholds ranged between 2.6 and 7.8 ms for the younger age group and between 3.4 and 10.0 ms for the older group. Mean gap thresholds were significantly larger for the older group in all six conditions. Gap thresholds were not significantly correlated with audiometric thresholds in either age group but the 1-kHz gap thresholds increased with age in the younger group. In the second study, the relationships among gap thresholds, spondee-in-babble thresholds, and audiometric thresholds of 66 subjects were examined. Compared with the older subjects, the younger group recognized the spondees at significantly lower (more difficult) spondee-to-babble ratios. In the younger group, spondee-in-babble thresholds were significantly correlated with gap thresholds in conditions of high-frequency masking. In the older group, spondee-in-babble thresholds, gap thresholds, and audiometric thresholds were not significantly correlated, but the spondee-in-babble thresholds and two audiometric thresholds increased significantly with age. These results demonstrate that significant age-related changes in auditory processing occur throughout adulthood. Specifically, age-related changes in temporal acuity may begin decades earlier than age-related changes in word recognition.
Couette Flow of a Polar Fluid
Authors: Pennington C. J. , Cowin S. C.
Published: July 2002

The problem considered is that of steady laminar flow of an incompressible polar fluid between two parallel plates, one of which is in motion relative to the second. It is shown that the effective viscosity, defined as the shear stress applied to the plates times the distance between the plates divided by the relative velocity of the plates, depends upon the distance between the plates. That is to say, if the applied shear stress is held constant, then as the plates are moved closer together their relative velocity will become slower. The velocity distribution in the polar fluid will change accordingly. It is also shown that at the two extremes of closely spaced plates and widely spaced plates the Couette flow of a polar fluid coincides with the Couette flow of Newtonian fluids, but the Newtonian fluids are of different viscosities. Experimental evidence for the increased viscosity of real fluids between narrowly spaced parallel plates is cited.
An Experimental Study of Rheological Properties of Polymer Melts in Laminar Shear Flow and of Interface Deformation and Its Mechanisms in Two-Phase Stratified Flow
Authors: Lee Biing-Lin , White James L.
Published: July 2002

The stress state of four rheologically characterized polymer melts—low-density polyethylene (LDPE), high-density polyethylene (HDPE), polystyrene (PS), and poly(methyl methacrylate) (PMMA)—in laminar shearing flow was completely determined by measuring the non-Newtonian viscosity μ and the first and second normal stress differences N1 and N2. The mean N2 function was negative and about 0.1–0.3 the value of N1. The measurements were made in a Weissenberg rheogoniometer using cone- and parallel-plate geometries. Additional viscosity measurements were made in a capillary rheometer. An experimental study of interface distortion in the stratified two-phase flow has been carried out using these melts. It was found in the stratified flow experiments that the lower viscosity melts exhibited concave interfaces and encapsulated the higher viscosity melts irrespective of the relative values of N1 and N2. The rate of interface distortion and encapsulation increases with increasing viscosity differences. The pressure losses for stratified flow tended to be close to the values for the lower viscosity phase, especially for long dies. The problem of instabilities at the interface between the two melts is briefly discussed.
Stress–strain behavior of polymers in tension, compression, and shear
Authors: Chow T. S.
Published: July 2002

Equations are developed to predict the influence of external stresses on the stress–strain relationships of glassy polymers. Different stress fields applied to a polymer result in different domain sizes of those polymer segments which have to move as a whole in order for plastic deformation to occur. These domains are the components of an activation volume tensor, which is a key parameter in describing the nonlinear relaxation time. The shape of the stress–strain curves depends on the time scales in which the solid polymer is relaxed and measured. The yield stresses, yield strains, and stress–strain curves of polystyrene in tension, compression, and shear are calculated and discussed.
Characterization of hydroxyl-bearing magnesium fluoride containing physically bound water
Authors: Booster J. L. , Voncken J. H. L. , van Sandwijk A. , Reuter M. A.
Published: July 2002

Most electrolytic zinc plants have to deal with dissolved magnesium in their process liquors, as zinc sulphide concentrates contain small amounts of magnesium. Applied magnesium bleed methods are generally expensive and environmentally unfriendly. Recently, a new approach was suggested and discussed, which involves selective magnesium fluoride precipitation from purified zinc sulphate solutions. X-ray fluorescence measurements of these precipitates indicated that the ratio Mg:F is not 1:2 as would be expected if the precipitate was MgF2, which should be formed on a theoretical basis. It was inferred that fluoride was partly substituted by hydroxyl groups. Analytical techniques such as infrared absorption spectrometry, X-ray diffraction, and thermogravimetry were combined in order to verify this hypothesis. The precipitate indeed appeared to be a magnesium fluoro- hydroxide compound containing physically bound water. The results contribute to the understanding of the required operating conditions of the proposed process.
Ultrafast visible-light photochromic properties of naphthalenediimide-based coordination polymers for the visual detection/filtration of blue light
Authors: Hao Pengfei , Gao Bohong , Li Gaopeng , Shen Junju , Fu Yunlong
Published: April 2022

Two naphthalenediimide-based coordination polymers exhibit ultrafast visible-light photochromic properties for blue light detection/filtration.