bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonreceptor Tyrosine Kinase c-Yes Interacts with Occludin during Tight Junction Formation in Canine Kidney Epithelial Cells
Authors: Chen Yan-Hua , Lu Qun , Goodenough Daniel A. , Jeansonne Beverly
Published: July 2002

Occludin is an integral membrane protein that is tyrosine phosphorylated when localized at tight junctions. When Ca2+was depleted from the culture medium, occludin tyrosine phosphorylation was diminished from Madin-Darby canine kidney epithelial cells in 2 min. This dephosphorylation was correlated with a significant reduction in transepithelial electrical resistance (TER), indicating a global loss of the tight junction barrier function. Reconstitution of Ca2+resulted in a robust tyrosine rephosphorylation of occludin that was temporally associated with an increase in TER. Moreover, we demonstrate in this study that occludin was colocalized with the nonreceptor tyrosine kinase c-Yes at cell junction areas and formed an immunoprecipitable complex with c-Yes in vivo. This complex dissociated when the cells were incubated in medium without Ca2+or treated with a c-Yes inhibitor, CGP77675. In the presence of CGP77675 after Ca2+repletion, occludin tyrosine phosphorylation was completely abolished and both tight junction formation and the increase of the TER were inhibited. Our study thus provides strong evidence that occludin tyrosine phosphorylation is tightly linked to tight junction formation in epithelial cells, and that the nonreceptor tyrosine kinase c-Yes is involved in the regulation of this process.
DNA sequence quality trimming and vector removal
Authors: Chou Hui-Hsien , Holmes Michael H.
Published: July 2002

Motivation: Most sequence comparison methods assume that the data being compared are trustworthy, but this is not the case with raw DNA sequences obtained from automatic sequencing machines. Nevertheless, sequence comparisons need to be done on them in order to remove vector splice sites and contaminants. This step is necessary before other genomic data processing stages can be carried out, such as fragment assembly or EST clustering. A specialized tool is therefore needed to solve this apparent dilemma.

Results: We have designed and implemented a program that specifically addresses the problem. This program, called Lucy, has been in use since 1998 at The Institute for Genomic Research (TIGR). During this period, many rounds of experience-driven modifications were made to Lucy to improve its accuracy and its ability to deal with extremely difficult input cases. We believe we have finally obtained a useful program which strikes a delicate balance among the many issues involved in the raw sequence cleaning problem, and we wish to share it with the research community.

Availability: Lucy is available directly from TIGR (http://www.tigr.org/softlab). Academic users can download Lucy after accepting a free academic use license. Business users may need to pay a license fee to use Lucy for commercial purposes.

Contact: Questions regarding the quality assessment module of Lucy should be directed to Michael Holmes (mholmes@tigr.org). Questions regarding other aspects of Lucy should be directed to Hui-Hsien Chou (hhchou@iastate.edu).
The influence of Carboniferous palaeoatmospheres on plant function: an experimental and modelling assessment
Authors: Beerling D. J. , Woodward F. I. , Lomas M. R. , Wills M. A. , Quick W. P. , Valdes P. J.
Published: July 2002

Geochemical models of atmospheric evolution predict that during the late Carboniferous,
ca
. 300 Ma, atmospheric oxygen and carbon dioxide concentrations were 35% and 0.03%, respectively. Both gases compete with each other for ribulose–1,5–bisphosphate carboxylase/oxygenase–the primary C–fixing enzyme in C
3
land plants: and the absolute concentrations and the ratio of the two in the atmosphere have the potential to strongly influence land–plant function. The Carboniferous therefore represents an era of potentially strong feedback between atmospheric composition and plant function. We assessed some implications of this ratio of atmospheric gases on plant function using experimental and modelling approaches. After six weeks growth at 35% O
2
and 0.03% carbon dioxide, no photosynthetic acclimation was observed in the woody species
Betula pubescens
and
Hedera helix
relative to those plants grown at 21% O
2
. Leaf photosynthetic rates were 29% lower in the high O
2
environment compared to the controls. A global–scale analysis of the impact of the late Carboniferous climate and atmospheric composition on vegetation function was determined by driving a process–based vegetation–biogeochemistry model with a Carboniferous global palaeoclimate simulated by the Universities Global Atmospheric Modelling Programme General Circulation Model. Global patterns of net primary productivity, leaf area index and soil carbon concentration for the equilibrium model solutions showed generally low values everywhere, compared with the present day, except for a central band in the northern land mass extension of Gondwana, where high values were predicted. The areas of high soil carbon accumulation closely match the known distribution of late Carboniferous coals. Sensitivity analysis with the model indicated that the increase in O
2
concentration from 21% to 35% reduced global net primary productivity by 18.7% or by 6.3 GtC yr
–1
. Further work is required to collate and map at the global scale the distribution of vegetation types, and evidence for wildfires, for the late Carboniferous to test our predictions.
Properties of fast endocytosis at hippocampal synapses
Authors: Kavalali Ege T. , Klingauf Jürgen , Tsien Richard W.
Published: July 2002

Regulation of synaptic transmission is a widespread means for dynamic alterations in nervous system function. In several cases, this regulation targets vesicular recycling in presynaptic terminals and may result in substantial changes in efficiency of synaptic transmission. Traditionally, experimental accessibility of the synaptic vesicle cycle in central neuronal synapses has been largely limited to the exocytotic side, which can be monitored with electrophysiological responses to neurotransmitter release. Recently, physiological measurements on the endocytotic portion of the cycle have been made possible by the introduction of styryl dyes such as FM1–43 as fluorescent markers for recycling synaptic vesicles. Here we demonstrate the existence of fast endocytosis in hippocampal nerve terminals and derive its kinetics from fluorescence measurements using dyes with varying rates of membrane departitioning. The rapid mode of vesicular retrieval was greatly speeded by exposure to staurosporine or elevated extracellular calcium. The effective time–constant for retrieval can be <2 seconds under appropriate conditions. Thus, hippocampal synapses capitalize on efficient mechanisms for endocytosis and their vesicular retrieval is subject to modulatory control.
Functional mapping in the human brain using high magnetic fields
Authors: Ugurbil Kamil , Xiaoping Hu , Wei Chen , Zhu Xiao-Hong , Kim Seong-Gi , Georgopoulos Apostolos
Published: July 2002

An avidly pursued new dimension in magnetic resonance imaging (MRI) research is the acquisition of physiological and biochemical information non–invasively using the nuclear spins of the water molecules in the human body. In this trial, a recent and unique accomplishment was the introduction of the ability to map human brain function non–invasively. Today, functional images with subcentimetre resolution of the entire human brain can be generated in single subjects and in data acquisition times of several minutes using 1.5 tesla (T) MRI scanners that are often used in hospitals for clinical purposes. However, there have been accomplishments beyond this type of imaging using significantly higher magnetic fields such as 4 T. Efforts for developing high magnetic field human brain imaging and functional mapping using MRI (fMRI) were undertaken at about the same time. It has been demonstrated that high magnetic fields result in improved contrast and, more importantly, in elevated sensitivity to capillary level changes coupled to neuronal activity in the blood oxygenation level dependent (BOLD) contrast mechanism used in fMRI. These advantages have been used to generate, for example, high resolution functional maps of ocular dominance columns, retinotopy within the small lateral geniculate nucleus, true single–trial fMRI and early negative signal changes in the temporal evolution of the BOLD signal. So far these have not been duplicated or have been observed as significantly weaker effects at much lower field strengths. Some of these high–field advantages and accomplishments are reviewed in this paper.
The conformational cycle of kinesin
Authors: Cross R. A. , Crevel I. , Carter N. J. , Alonso M. C. , Hirose K. , Amos L. A.
Published: July 2002

The stepping mechanism of kinesin can be thought of as a programme of conformational changes. We briefly review protein chemical, electron microscopic and transient kinetic evidence for conformational changes, and working from this evidence, outline a model for the mechanism. In the model, both kinesin heads initially trap Mg.ADP. Microtubule binding releases ADP from one head only (the trailing head). Subsequent ATP binding and hydrolysis by the trailing head progressively accelerate attachment of the leading head, by positioning it closer to its next site. Once attached, the leading head releases its ADP and exerts a sustained pull on the trailing head. The rate of closure of the molecular gate which traps ADP on the trailing head governs its detachment rate. A speculative but crucial coordinating feature is that this rate is strain sensitive, slowing down under negative strain and accelerating under positive strain.
Developmental genetics in primitive chordates
Authors: Sordino Paolo , Belluzzi Lisa , Santis Rosaria De , Smith William C.
Published: July 2002

Recent advances in the study of the genetics and genomics of urochordates testify to a renewed interest in this chordate subphylum, believed to be the most primitive extant chordate relatives of the vertebrates. In addition to their primitive nature, many features of their reproduction and early development make the urochordates ideal model chordates for developmental genetics. Many urochordates spawn large numbers of transparent and externally developing embryos on a daily basis. Additionally, the embryos have a defined and well–characterized cell lineage until the end of gastrulation. Furthermore, the genomes of the urochordates have been estimated to be only 5–10% of the size of the vertebrates and to have fewer genes and less genetic redundancy than vertebrates. Genetic screens, which are powerful tools for investigating developmental mechanisms, have recently become feasible due to new culturing techniques in ascidians. Because hermaphrodite ascidians are able to self–fertilize, recessive mutations can be detected in a single generation. Several recent studies have demonstrated the feasibility of applying modern genetic techniques to the study of ascidian biology.
Flies, clocks and evolution
Authors: Rosato Ezio , Kyriacou Charalambos P.
Published: July 2002

The negative feedback model for gene regulation of the circadian mechanism is described for the fruitfly,Drosophila melanogaster. The conservation of function of clock molecules is illustrated by comparison with the mammalian circadian system, and the apparent swapping of roles between various canonical clock gene components is highlighted. The role of clock gene duplications and divergence of function is introduced via thetimelessgene. The impressive similarities in clock gene regulation between flies and mammals could suggest that variation between more closely related species within insects might be minimal. However, this is not borne out because the expression of clock molecules in the brain of the giant silk moth,Antheraea pernyi, is not easy to reconcile with the negative feedback roles of theperiodandtimelessgenes. Variation in clock gene sequences between and within fly species is examined and the role of co-evolution between and within clock molecules is described, particularly with reference to adaptive functions of the circadian phenotype.
Modern human origins: progress and prospects
Authors: Stringer Chris
Published: July 2002

The question of the mode of origin of modern humans (Homo sapiens) has dominated palaeoanthropological debate over the last decade. This review discusses the main models proposed to explain modern human origins, and examines relevant fossil evidence from Eurasia, Africa and Australasia. Archaeological and genetic data are also discussed, as well as problems with the concept of ‘modernity’ itself. It is concluded that a recent African origin can be supported forH. sapiens, morphologically, behaviourally and genetically, but that more evidence will be needed, both from Africa and elsewhere, before an absolute African origin for our species and its behavioural characteristics can be established and explained.
Advanced Integrated Mouse YAC Map Including BAC Framework
Authors: Schalkwyk Leonard C. , Cusack Brian , Dunkel Ilona , Hopp Martina , Kramer Markus , Palczewski Stefanie , Piefke Jutta , Scheel Sabine , Weiher Michael , Wenske Gunther , Lehrach Hans , Himmelbauer Heinz
Published: July 2002

Functional characterization of the mouse genome requires the availability of a comprehensive physical map to obtain molecular access to chromosomal regions of interest. Positional cloning remains a crucial way of linking phenotype with particular genes. A key step and frequent stumbling block in positional cloning is making a contig of a genetically defined candidate region. The most efficient first step is isolating YAC (Yeast Artificial Chromosome) clones. A robust, detailed YAC contig map is thus an important tool. Employing Interspersed Repetitive Sequence (IRS)-PCR genomics, we have generated an advanced second-generation YAC contig map of the mouse genome that doubles both the depth of clones and the density of markers available. In addition to the primarily YAC-based map, we located 1942 BAC (Bacterial Artificial Chromosome) clones. This allows us to present for the first time a dense framework of BACs spanning the genome of the mouse, which, for instance, can serve as a nucleus for genomic sequencing. Four large-insert mouse YAC libraries from three different strains are included in our data, and our analysis incorporates the data of Hunter et al. and Nusbaum et al. There is a total of 20,205 markers on the final map, 12,033 from our own data, and a total of 56,093 YACs, of which 44,401 are positive for more than one marker.

[The sequence data described in this paper have been submitted to the GenBank data library under accession nos. BH174059–BH175013.]
Changes in Gene Expression Profiles in Developing B Cells of Murine Bone Marrow
Authors: Hoffmann Reinhard , Seidl Thomas , Neeb Martin , Rolink Antonius , Melchers Fritz
Published: July 2002

Gene expression profiles of five consecutive stages of mouse B cell development were generated with high-density oligonucleotide arrays from as few as 2 × 104 ex vivo isolated and flow-cytometrically purified cells. Between 2.8% and 6.8% of all genes change on differentiation from one cellular stage to the next by at least twofold. The entire pathway involves differential expression of 10.7% of all genes. Previously known expression patterns of 15 genes (like surrogate light chain, RAG-1/2, MHC class II, mel-14 antigen) are confirmed. The gene expression patterns of the proliferating pre-BI and large pre-BII cells on the one hand, and the resting immature and mature B cells on the other hand, are most similar to each other. Small pre-BII cells display a pattern that is transitional between these two groups. Most of the genes expressed in early precursors are involved in general processes, like protein folding or cell cycle regulation, whereas more mature precursors express genes involved in more specific molecular programs (cell surface receptors, secreted factors, and adhesion molecules, among others). Between 19 and 139 genes share a given expression pattern. Combining knowledge about gene function and expression pattern allows identification of novel candidate genes potentially involved in self-maintenance of pre-BI cells, allelic exclusion and pre-B cell receptor signaling in large pre BII cells, cell-cycle arrest of small pre-BII cells, propensity toward apoptosis or anergization in immature B cells, propensity toward cell division and activation in mature B cells, and stage-specific interactions with stromal cells in the bone marrow.

[The sequence data described in this paper have been submitted to the Gene Expression Omnibus (GEO) at the National Center for Biotechnology Information (NCBI) under accession number GSE13. Online supplementary material available at www.genome.org.]
Knowledge‐based computer‐aided detection of masses on digitized mammograms: A preliminary assessment
Authors: Chang Yuan‐Hsiang , Hardesty Lara A. , Hakim Christiane M. , Chang Thomas S. , Zheng Bin , Good Walter F. , Gur David
Published: July 2002

The purpose of this work was to develop and evaluate a computer‐aided detection (CAD) scheme for the improvement of mass identification on digitized mammograms using a knowledge‐based approach. Three hundred pathologically verified masses and 300 negative, but suspicious, regions, as initially identified by a rule‐based CAD scheme, were randomly selected from a large clinical database for development purposes. In addition, 500 different positive and 500 negative regions were used to test the scheme. This suspicious region pruning scheme includes a learning process to establish a knowledge base that is then used to determine whether a previously identified suspicious region is likely to depict a true mass. This is accomplished by quantitatively characterizing the set of known masses, measuring “similarity” between a suspicious region and a “known” mass, then deriving a composite “likelihood” measure based on all “known” masses to determine the state of the suspicious region. To assess the performance of this method, receiver‐operating characteristic (ROC) analyses were employed. Using a leave‐one‐out validation method with the development set of 600 regions, the knowledge‐based CAD scheme achieved an area under the ROC curve of 0.83. Fifty‐one percent of the previously identified false‐positive regions were eliminated, while maintaining 90% sensitivity. During testing of the 1000 independent regions, an area under the ROC curve as high as 0.80 was achieved. Knowledge‐based approaches can yield a significant reduction in false‐positive detections while maintaining reasonable sensitivity. This approach has the potential of improving the performance of other rule‐based CAD schemes.
Influence of cavity size on the response of cavity chambers to 25‐ and 45‐MeV neutrons
Authors: Newhauser W. D. , Brede H. J.
Published: July 2002

We calculated the response of gas‐cavity dosimeters to 25‐ and 45‐MeV neutrons in order to estimate the portion of the response that originates from neutron interactions within the gas cavity. This affords insight into the validity of the Bragg–Gray theory for dosimeters with finite cavities and also provides a basis for modifying gas‐to‐wall absorbed dose conversion factors deduced from the Bragg–Gray theory for use with small‐cavity dosimeters. For a typical ionization chamber, e.g., with a propane‐based tissue‐equivalent gas at standard temperature and pressure, the fraction of the total absorbed dose to the gas cavity from neutron interactions within the gas is 0.09% at 25‐MeV and 0.006% at 45‐MeV neutron energies. For microdosimetric detectors, the neutron interactions within the gas are negligible above 25 MeV.
Classification of compressed breast shapes for the design of equalization filters in x‐ray mammography
Authors: Goodsitt Mitchell M. , Chan Heang‐Ping , Liu Bob , Guru Shankar V. , Morton A. Ray , Keshavmurthy Shyam , Petrick Nick
Published: July 2002

We are developing an external filter method for equalizing the x‐ray exposure in mammography. Each filter is specially designed to match the shape of the compressed breast border and to preferentially attenuate the x‐ray beam in the peripheral region of the breast. To be practical, this method should require the use of only a limited number of custom built filters. It is hypothesized that this would be possible if compressed breasts can be classified into a finite number of shapes. A study was performed to determine the number of shapes. Based on the parabolic appearances of the outer borders of compressed breasts in mammograms, the borders were fit with the polynomial equations and The goodness‐of‐fit of these equations was compared. The and coefficients were employed in a K‐Means clustering procedure to classify 470 CC‐view and 484 MLO‐view borders into 2–10 clusters. The mean coefficients of the borders within a given cluster defined the “filter” shape, and the individual borders were translated and rotated to best match that filter shape. The average rms differences between the individual borders and the “filter” were computed as were the standard deviations of those differences. The optimally shifted and rotated borders were refit with the above polynomial equations, and plotted for visual evaluation of clustering success. Both polynomial fits were adequate with rms errors of about 2 mm for the 2‐coefficient equation, and about 1 mm for the 3‐coefficient equation. Although the fits to the original borders were superior for the 3‐coefficient equation, the matches to the “filter” borders determined by clustering were not significantly improved. A variety of modified clustering methods were developed and utilized, but none produced major improvements in clustering. Results indicate that 3 or 4 filter shapes may be adequate for each mammographic projection (CC and MLO‐view). To account for the wide variations in exposures observed at the peripheral regions of breasts classified to be of a particular shape, it may be necessary to employ different filters for thin, medium and thick breasts. Even with this added requirement, it should be possible to use a small number of filters as desired.
Thermoacoustic computed tomography–technical considerations
Authors: Kruger Robert A. , Reinecke Daniel R. , Kruger Gabe A.
Published: July 2002

We have constructed a thermoacoustic computed tomography scanner for imaging soft tissue in the human body. Thermoacoustic signals are induced in soft tissue by irradiation with 434 MHz rf energy. The thermoacoustic signals are detected by an array of transducers mounted on a hemispherical bowl. A three‐dimensional, filtered backprojection algorithm is used to reconstruct rf absorption patterns within soft tissue. We have demonstrated soft tissue differentiation sufficient to delineate the normal internal structures of an excised lamb kidney using safe levels of rf radiation.
Two-particle Schrödinger equation animations of wave packet–wave packet scattering
Authors: Maestri Jon J. V. , Landau Rubin H. , Páez Manuel J.
Published: July 2002

A simple and explicit technique for the numerical solution of the two-particle, time-dependent Schrödinger equation is assembled and tested. The technique can handle interparticle potentials that are arbitrary functions of the coordinates of each particle, arbitrary initial and boundary conditions, and multidimensional equations. Plots and animations are given here and on the World Wide Web of the scattering of two wave packet in one dimension.
Super classical quantum mechanics: The best interpretation of nonrelativistic quantum mechanics
Authors: Lamb Willis E.
Published: July 2002

It has been shown that Newtonian classical mechanics (NCM) suffers from several kinds of chaotic indeterminacies. That means, a large set of problems treated with NCM gives results which are in wild disagreement with observation. In the present paper, these shortcomings are repaired in a simple, obvious, and essentially unique manner. The NCM theory is thereby transformed into a new theory which is fully equivalent to the Heisenberg, Schrödinger, and Dirac nonrelativistic quantum mechanics, with the vital addition of Born’s probabilistic interpretation of the wave function built in from the start. I call this new theory “super classical quantum mechanics” (SCQM). Using Ehrenfest’s theorem of 1927, the classical limit of the new theory, SCQM, is seen to give exactly the results expected of the repaired Newtonian theory of classical mechanics.
Variability in the passive ranging of acoustic sources in air using a wavefront curvature technique
Authors: Ferguson Brian G.
Published: July 2002

Simultaneous time delay measurements from two adjacent pairs of sensors are used to estimate the “instantaneous” range and bearing of both stationary and moving broadband sources of continuous sound in air. The random fluctuations in the estimated source position are due to random errors in the time delay measurements. The variances of both the short time-scale and long time-scale random errors in the time delay estimates are quantified for different sensor separation distances and for different source positions. After normalization, the observed variances of the short time-scale random errors in the bearing and range estimates are found to agree with the theoretical results predicted for various sensor-source configurations where the independent variable is the length of the effective intersensor baseline. Increasing the intersensor separation distance by an order of magnitude reduces the bearing error variance by two orders of magnitude and the range error variance by four orders of magnitude.
Analysis of the asymmetric triple-layered piezoelectric bimorph using equivalent circuit models
Authors: Ha Sung Kyu
Published: July 2002

An eight-port impedance matrix and an equivalent circuit are presented for the analysis of an asymmetric triple-layered piezoelectric bimorph with separate electrical ports. The separate electric ports for the top and bottom piezoelectric layers operate independently of each other: they generate and/or sense the coupled extensional and flexural motions. Taking into account shear and rotatory inertia, the eight-port impedance model is first obtained for the bimorph. The electromechanical behavior of the piezoelectric layers, and the mechanical motions of the bimorph, are separately represented by equivalent circuits with common ports. Connecting the circuits through the common ports then leads to the overall equivalent circuit. It is demonstrated that the resonance/antiresonance frequencies and the sensor-to-actuator signal of the cantilevered bimorph for various length-to-thickness ratios can be effectively calculated by the application of the electrical network theory to the equivalent circuit. It is also shown that the electric circuit conditions on the piezoelectric layers can alter the resonance frequencies of the bimorph without changing the mechanical conditions. All the results by the present method are in excellent agreement with those by three-dimensional finite-element methods.
Time-lapse nondestructive assessment of shock wave damage to kidney stones in vitro using micro-computed tomography
Authors: Cleveland Robin O. , McAteer James A. , Müller Ralph
Published: July 2002

To better understand how lithotripter shock waves break kidney stones, we treated human calcium oxalate monohydrate (COM) kidney stones with shock waves from an electrohydraulic lithotripter and tracked the fragmentation of the stones using micro-computed tomography (μCT). A desktop μCT scanning system, with a nominal resolution of 17 μm, was used to record scans of stones at 50-shock wave intervals. Each μCT scan yielded a complete three-dimensional map of the internal structure of the kidney stone. The data were processed to produce either two- or three-dimensional time-lapse images that showed the progression of damage inside the stone and at the surface of the stone. The high quality and excellent resolution of these images made it possible to detect separate patterns of damage suggestive of failure by cavitation and by spall. Nondestructive assessment by μCT holds promise as a means to determine the mechanisms of stone fragmentation in SWL in vitro.
Source levels of clicks from free-ranging white-beaked dolphins (Lagenorhynchus albirostris Gray 1846) recorded in Icelandic waters
Authors: Rasmussen Marianne H. , Miller Lee A. , Au Whitlow W. L.
Published: July 2002

This study reports the source levels of clicks recorded from free-ranging white-beaked dolphins (Lagenorhynchus albirostris Gray 1846). A four-hydrophone array was used to obtain sound recordings. The hydrophone signals were digitized on-line and stored in a portable computer. An underwater video camera was used to visualize dolphins to help identify on-axis recordings. The range to a dolphin was calculated from differences in arrival times of clicks at the four hydrophones, allowing for calculations of source levels. Source levels in a single click train varied from 194 to 211 dB peak-to-peak (p-p) re: 1 μPa. The source levels varied linearly with the log of range. The maximum source levels recorded were 219 dB (p-p) re: 1 μPa.
Perception of synthetic /ba/–/wa/ speech continuum by budgerigars (Melopsittacus undulatus)
Authors: Dent Micheal L. , Brittan-Powell Elizabeth F. , Dooling Robert J. , Pierce Alisa
Published: July 2002

Other than humans, extensive vocal learning has only been widely demonstrated in birds. Moreover, there are only a handful of avian species that are known to be good mimics of human speech. One such species is the budgerigar (Melopsittacus undulatus), which is a popular mimic of human speech and learns new vocalizations throughout adult life. Using operant conditioning procedures with a repeating background task, we tested budgerigars on the discrimination of tokens from two synthetic /ba/–/wa/ speech continua that differed in syllable, but not transition, duration. Budgerigars showed a significant improvement in discrimination performance on both continua near the phonetic boundary for humans. Budgerigars also showed a shift in the location of the phonetic boundary with a change in syllable length, similar to what has been described for humans and other primates. These results on a nonmammalian species provide support for the operation of a general, nonphonetic, auditory process as one mechanism which can lead to the well-known stimulus-length effect in humans.
Acoustic scattering by a hard or soft body across a wide frequency range by the Helmholtz integral equation method
Authors: Yang Shih-An
Published: July 2002

In this paper, the acoustic scattering by an obstacle across a wide frequency range of sound waves is investigated on the basis of the Helmholtz integral formulation. To overcome the nonuniqueness difficulties, the methods proposed by Burton [NPL Report NAC 30 (Jan 1973)] and by Burton and Miller [Proc. R. Soc. London, Ser. A 323, 201–210 (1971)] are adopted for the Dirichlet and Neumann problems, respectively. The aim of this paper is twofold. The first is to bring together completely regular formulations of the Helmholtz integral equation and its normal derivative. The second is to extend these formulations to treat the higher-frequency problems. The weakly singular integrals are regularized by subtracting out one term and adding it back. Depending on the problem concerned, the additional integral can finally be expressed in an explicit form or results in solving a surface source distribution of the equipotential body. The hypersingular kernels are regularized by the method of using some properties of the associated Laplace equation, originally proposed by Chien et al. [J. Acoust. Soc. Am. 88, 918–937 (1990)]. The completely regularized integral equations are amenable to computation by direct use of the standard quadrature methods. To study the acoustic scattering due to higher-frequency waves, Filon’s quadrature method [Proc. R. Soc. Edinburgh 49, 38–47 (1928)] is extended to treat the rapidly oscillatory integrands. Numerical examples consist of acoustic scattering from a hard or soft sphere of radius a across a wide spectrum of wave numbers ka=π–20π. Comparisons of the numerical results with the exact solutions demonstrate the validity and efficiency of the implementation.
Sound propagation from a point source over extended-reaction ground
Authors: Li Kai Ming , Waters-Fuller Tim , Attenborough Keith
Published: July 2002

Through comparisons with numerical predictions, with data from laboratory experiments and with outdoor data obtained over snow, heuristic modifications of the classical analytical approximation for the field due to a point source above an impedance plane are shown to be adequate for predicting sound propagation from a point source close to layered porous media with extended reaction. The main deficiencies are for extremely low flow resistivities and at close ranges. It is shown that multiple layering offers a possible explanation for previously reported difficulties in obtaining theoretical fits to propagation data over snow [J. Acoust. Soc. Am. 77, 67–73 (1985)].
Minimum variance distortionless response beamforming of acoustic array data
Authors: Ferguson Brian G.
Published: July 2002

An array of hydrophones is towed below the sea surface so as to sample the underwater acoustic pressure field in both space and time, while a land-based array of microphones is used to sense the atmospheric acoustic environment which, at the time, was dominated by a single source of broadband energy. After transformation from the time domain to the frequency domain, the sensor outputs from each array are weighted and combined in the spatial domain (beamformed) so as to produce a frequency–wave number power spectrum, which displays the power spectral density distribution of the various signal and noise sources as a joint function of frequency and wave number. The frequency-domain beamforming (or spatial filtering) process enables both conventional and optimal estimation of the frequency–wave number power spectrum. The optimal spatial filtering technique used here is commonly referred to as the Minimum Variance Distortionless Response (MVDR) beamformer which requires inversion of the observed narrow-band cross-power spectral matrix at each frequency of interest. A comparison of the frequency–wave number power spectra estimated by the two spatial filtering techniques shows that the MVDR beamformer enables the various sources of acoustic energy to be more clearly delineated in frequency–wave number space. The MVDR beamformer is a data-adaptive spatial filter which is observed to suppress sidelobes, to enhance the spatial resolution of an array through narrower beamwidths, and to provide superdirective array gain at frequencies well below the design frequency of an array. By extending the processing to include the data from another type of towed array, it is shown that frequency–wave number analysis, when incorporated with MVDR beamforming, constitutes a powerful diagnostic tool for studying the self-noise characteristics of towed arrays.
A deconvolution method for force reconstruction in rods under axial impact
Authors: Wu Enboa , Tsai Cheng-Zorn , Tseng Ling-Hsien
Published: July 2002

A deconvolution method to extract the force history exerted axially on one end of a rod using the responses recorded remotely from the impact location is presented in this paper. The traditional Green’s function is completely eliminated in the solution process. To apply the developed method, another set of force and response data, at the same locations as in the impact event in which the force is to be reconstructed, needs to be obtained either from measurement or from a theoretical/numerical solution. The latter was adopted in bar impact events due to the fact that the signals have very wide frequency bands, and the theoretical responses were calculated separately using the Love theory and the Pochhammer–Chree equation. Using optimization algorithms to search for the force from the input signals that were recorded by multiple gauges and were contaminated with noises, the method has been demonstrated to be robust. Further, to show that the developed method is general, an example for extracting the impact force exerted on a complicated sandwich structure using the recorded strain signals as the input data are also presented. This further demonstrates that the method can be applied to an impact event in which the Green’s function is very difficult to construct.
Validity of rating scale measures of voice quality
Authors: Kreiman Jody , Gerratt Bruce R.
Published: July 2002

The validity of perceptual measures of vocal quality has been neglected in studies of voice, which focus more commonly on rater reliability. Validity depends in part on reliability, because an unreliable test does not measure what it is intended to measure. However, traditional measures of rating reliability only partially represent interrater agreement, because they cannot reflect variations or patterns of agreement for specific voice samples. In this paper the likelihood that two raters would agree in their ratings of a single voice is examined, for each voice in five previously gathered data sets. Results do not support the continued assumption that traditional rating procedures produce useful indices of listeners’ perceptions. Listeners agreed very poorly in the midrange of scales for breathiness and roughness, and mean ratings in the midrange of such scales did not represent the extent to which a voice possesses a quality, but served only to indicate that listeners disagreed. Techniques like analysis by synthesis or judgment of similarity avoid decomposing quality into constituent dimensions, and do not require a listener to compare an external stimulus to an unstable internal representation, thus decreasing the error in measures of quality. Modeling individual differences in perception can increase the variance accounted for in models of quality, further reducing the error in perceptual measures. Thus such techniques may provide valid alternatives to current approaches.
Absolute pitch is demonstrated in speakers of tone languages
Authors: Deutsch Diana , Henthorn Trevor , Dolson Mark
Published: July 2002

In two experiments, Vietnamese and Mandarin speakers manifested a precise form of absolute pitch in reading lists of words. In one experiment, seven Vietnamese speakers read out a list of ten words twice, on two separate days. The average pitch of each word was determined by computer analysis, and for each speaker comparisons were made between the average pitches produced by the same word on different days. Remarkable correspondences were obtained: For most speakers, the signed pitch difference, averaged across words, was well within a semitone. In another experiment, 15 Mandarin speakers read out a list of 12 words twice within a session, with the 2 readings separated by roughly 20 s; and in 2 sessions which were held on different days. Again, comparing across sessions, for most speakers the signed pitch difference, averaged across words, was well within a semitone. Furthermore, the differences were no greater when the pitches were compared across sessions than within sessions. These findings demonstrate that tone language speakers are able to refer to a remarkably precise and stable absolute pitch template in producing words. Relationships to other work on absolute pitch are discussed, and the findings are illustrated by sound recordings.
Range discrimination by big brown bats (Eptesicus fuscus) using altered model echoes: Implications for signal processing
Authors: Masters W. Mitchell , Raver K. A. S.
Published: July 2002

The sonar emissions of two big brown bats (Eptesicus fuscus) were modeled to create a “normal” echolocation signal for each bat which was then used as an artificial echo to synthesize a phantom target. The bat’s task was to indicate which of two phantom targets (presented singly) was the “near” target and which the “far” target. Threshold range discrimination at a nominal target distance of 80 cm was about 0.6 cm for both bats. The normal signal was then modified to change the relative energy in each harmonic, the signal duration, the curvature of the frequency sweep, the absolute frequency, the phase of the second and third harmonics relative to the first, or the Doppler shift of the signal. To determine which modifications affected ranging performance, the altered models were used in tests of range discrimination that were interleaved on a day-to-day basis with tests using the normal model. Of the 12 modifications tested, only those changing the curvature of the frequency sweep affected performance. This result appears not to be predicted by current models of echo processing in FM bats. Eptesicus may be able to compensate for certain types of distortions of a returning echo, an ability possibly related to Doppler tolerance or to the characteristics of the natural variation in a bat’s emissions.
A dual passive cavitation detector for localized detection of lithotripsy-induced cavitation in vitro
Authors: Cleveland Robin O. , Sapozhnikov Oleg A. , Bailey Michael R. , Crum Lawrence A.
Published: July 2002

A passive cavitation detector (PCD) identifies cavitation events by sensing acoustic emissions generated by the collapse of bubbles. In this work, a dual passive cavitation detector (dual PCD), consisting of a pair of orthogonal confocal receivers, is described for use in shock wave lithotripsy. Cavitation events are detected by both receivers and can be localized to within 5 mm by the nature of the small intersecting volume of the focal areas of the two receivers in association with a coincidence detection algorithm. A calibration technique, based on the impulse response of the transducer, was employed to estimate radiated pressures at collapse near the bubble. Results are presented for the in vitro cavitation fields of both a clinical and a research electrohydraulic lithotripter. The measured lifetime of the primary growth-and-collapse of the cavitation bubbles increased from 180 to 420 μs as the power setting was increased from 12 to 24 kV. The measured lifetime compared well with calculations based on the Gilmore–Akulichev formulation for bubble dynamics. The radiated acoustic pressure 10 mm from the collapsing cavitation bubble was measured to vary from 4 to 16 MPa with increasing power setting; although the trends agreed with calculations, the predicted values were four times larger than measured values. The axial length of the cavitation field correlated well with the 6-dB region of the acoustic field. However, the width of the cavitation field (10 mm) was significantly narrower than the acoustic field (25 mm) as bubbles appeared to be drawn to the acoustic axis during the collapse. The dual PCD also detected signals from “rebounds,” secondary and tertiary growth-and-collapse cycles. The measured rebound time did not agree with calculations from the single-bubble model. The rebounds could be fitted to a Rayleigh collapse model by considering the entire bubble cloud as an effective single bubble. The results from the dual PCD agreed well with images from high-speed photography. The results indicate that single-bubble theory is sufficient to model lithotripsy cavitation dynamics up to time of the main collapse, but that upon collapse bubble cloud dynamics becomes important.
Integration of modeling and acoustic microscopy measurements for thin films
Authors: Guo Zhiqi , Achenbach J. D. , Madan Anita , Martin Keith , Graham M. E.
Published: July 2002

A model for measuring the V(z) curve by line-focus acoustic microscopy contains the reflectance function of the specimen as a principal component. In this paper the reflectance function has been analyzed for multilayered thin films on a substrate for both fast-on-slow and slow-on-fast systems. The phase velocities of modes of surface acoustic wave propagation and their associated mode reflection coefficients can be obtained from the reflectance function. This information can be used together with estimates of the elastic constants to determine suitable frequency ranges for measuring the V(z) curve. Minimization of the difference between phase velocities obtained from measured and calculated V(z) curves is used to determine the elastic constants. Results are presented for TiN films on M2 high-speed steel substrates.
Time-frequency representation of Lamb waves using the reassigned spectrogram
Authors: Niethammer Marc , Jacobs Laurence J. , Qu Jianmin , Jarzynski Jacek
Published: July 2002

This brief note reports on a study that applies the reassigned spectrogram (the reassigned energy density spectrum of the short-time Fourier transform [STFT]) to develop the dispersion curves for multimode Lamb waves propagating in an aluminum plate. The proposed procedure first uses the spectrogram to operate on a single, laser-generated and detected waveform to develop the dispersion relationship for this plate. Next, a reassignment procedure is used to refine the time-frequency resolution of the calculated dispersion curves. This reassignment operation clarifies the definition of the measured modes. This study demonstrates that the reassigned spectrogram is capable of distinguishing multiple, closely spaced Lamb modes in the ultrasonic frequency range.
Tensile Creep of Polystyrene at Elevated Temperatures. Part I.
Authors: Karam Henry J. , Bellinger John C.
Published: July 2002

The tensile creep behavior of polystyrene was studied at elevated temperature of 70 to 240°C. This paper will describe in detail experimental techniques and apparatus to obtain the zero shear viscosity of the polymer in this temperature range. Data will be compared with similar information obtained by other experimental techniques. Possible explanations for the discrepancies in the two sets of data are discussed. The paper will indicate, however will not discuss in detail how one can obtain melt elasticity, creep function, and compliance function of an amorphous polymer in the temperature range of 70 to 240°C, by creep experiments.
The Effect of Pressure on the Mechanical Properties of Polymers
Authors: Fillers R. W. , Tschoegl N. W.
Published: July 2002

Stress relaxation measurements were made as a function of temperature and hydrostatic pressure on two lightly filled elastomers (Hypalon 40 and Viton B), one highly filled elastomer (Neoprene WB), and on an EPDM rubber. The latter was not piezorheologically simple. The lightly filled elastomers showed piezorheologically simple behavior, i.e., their response curves under different hydrostatic pressures could be superposed empirically by a simple horizontal shift along the logarithmic axis. The filled elastomer was piezorheologically simple only in the rubbery region and in the beginning of the transition region. The dependence of the empirical shift distances, log ap, on P could not be described by either the Ferry-Stratton or the Bueche-O'Reilly equation. By considering the bulk modulus to be linearly related to pressure, a new equation has been developed for log aT,P which describes the pressure dependence well and contains the WLF equation as a limiting case. Published data on the response of poly(vinyl chloride) under superposed hydrostatic pressure are shown to obey the new equation also. The theoretical importance of the new equation lies in the fact that combination of the usual isobaric measurements at atmospheric pressure as function of temperature with isothermal measurements as function of pressure allows, in principle, all the molecular parameters required by the free volume theory to be determined unambiguously.