bluuebunny/crossref_metadata_2025 huggingface dataset:
The 3.7 Å projection map of the glycerol facilitator GlpF: a variant of the aquaporin tetramer
Authors: Braun Thomas , Philippsen Ansgar , Wirtz Sabine , Borgnia Mario J. , Agre Peter , Kühlbrandt Werner , Engel Andreas , Stahlberg Henning
Published: July 2002

GlpF, the glycerol facilitator protein of Escherichia coli, is an archetypal member of the aquaporin superfamily. To assess its structure, recombinant histidine‐tagged protein was overexpressed, solubilized in octylglucoside and purified to homogeneity. Negative stain electron microscopy of solubilized GlpF protein revealed a tetrameric structure of ∼80 Å side length. Scanning transmission electron microscopy yielded a mass of 170 kDa, corroborating the tetrameric nature of GlpF. Reconstitution of GlpF in the presence of lipids produced highly ordered two‐dimensional crystals, which diffracted electrons to 3.6 Å resolution. Cryoelectron microscopy provided a 3.7 Å projection map exhibiting a unit cell comprised of two tetramers. In projection, GlpF is similar to AQP1, the erythrocyte water channel. However, the major density minimum within each monomer is distinctly larger in GlpF than in AQP1.
Regulation of epidermal growth factor receptor endocytosis by wortmannin through activation of Rab5 rather than inhibition of phosphatidylinositol 3‐kinase
Authors: Chen Xinmei , Wang Zhixiang
Published: July 2002

The involvement of phosphatidylinositol 3‐kinase (PI3K) in membrane trafficking in mammalian cells has largely come from experiments with wortmannin. This compound inhibits endosome fusion in vitro, possibly by inhibiting the production of phosphatidylinositol (PtdIns)‐3‐P, which co‐regulates EEA1 with Rab5. However, the results from wortmannin inhibition experiments performed in vivo differ significantly. We have recently shown that wortmannin enlarges endosomes containing the epidermal growth factor receptor (EGFR) and enhances the lysosomal degradation of EGFR. In this report, we demonstrate that addition of the PI3K reaction products does not suppress wortmannin‐induced enlargement of EGFR‐containing endosomes and enhancement of EGFR degradation. Moreover, the effects of wortmannin on the intracellular trafficking of EGFR mimic those of the permanently activated Rab5 mutant, Rab5 Q79L, which stimulates endosome fusion. We also found that an inactive Rab5 mutant, Rab5 S34N, blocks wortmannin‐induced endosome enlargement and that wortmannin stimulates the activation of Rab5. We further showed that wortmannin reduced the membrane association of p120 Ras GTPase‐activating protein (GAP) and inhibited the interaction between Rab5 and p120 Ras GAP. We conclude that wortmannin alters intracellular trafficking of EGFR by activating Rab5 rather than by inhibiting PI3K.
Dynamic modules and heterogeneity of function: a lesson from tyrosine kinase receptors in endothelial cells
Authors: Bussolino Federico , Serini Guido , Mitola Stefania , Bazzoni Gianfranco , Dejana Elisabetta
Published: July 2002

An important unresolved issue related to tyrosine kinase receptor signaling pathways is the lack of specificity of the molecular effectors involved. The specificity of the biological responses that are nevertheless elicited may be explained by differences in activation thresholds, as well as by temporal (transient versus sustained) and topographical aspects of receptor activation. On the basis of recent lessons from endothelial cells, we argue that an additional strategy can be adopted to generate specificity, i.e. tyrosine kinase receptors may form distinct signaling modules with other transmembrane proteins, such as adhesive receptors, to elicit different biological programs in stimulated cells.
A Ras subfamily GTPase shows cell cycle‐dependent nuclear localization
Authors: Sutherland Brent W , Spiegelman George B , Weeks Gerald
Published: July 2002

Previously characterized Ras subfamily proteins have been found tobe predominantly associated with the plasma membrane where they function in signal transduction pathways to convey extracellular signals to intracellular targets. Here, we provide evidence that the Dictyostelium Ras subfamily protein RasB has a novel subcellular localization and function. The protein is predominantly localized in the nucleus during most of the cell cycle. Furthermore, during mitosis and cytokinesis RasB assumes a diffuse cellular localization despite the fact that the nuclear membrane stays intact. The linkage between the position of RasB in the cell and division suggests that it may have a role in nuclear division. Consistent with this idea, rasB− cells exhibit severe growth defects and cells overexpressing an activated version of RasB are multinucleate.
The cystic fibrosis transmembrane conductance regulator (CFTR) inhibits ENaC through an increase in the intracellular Cl− concentration
Authors: König Jens , Schreiber Rainer , Voelcker Thilo , Mall Marcus , Kunzelmann Karl
Published: July 2002

Activation of the CFTR Cl− channel inhibits epithelial Na+ channels (ENaC), according to studies on epithelial cells and overexpressing recombinant cells. Here we demonstrate that ENaC is inhibited during stimulation of the cystic fibrosis transmembrance conductance regulator (CFTR) in Xenopus oocytes, independent of the experimental set‐up and the magnitude of the whole‐cell current. Inhibition of ENaC is augmented at higher CFTR Cl− currents. Similar to CFTR, ClC‐0 Cl− currents also inhibit ENaC, as well as high extracellular Na+ and Cl−in partially permeabilized oocytes. Thus, inhibition of ENaC is not specific to CFTR and seems to be mediated by Cl−.
Locating a mate in 3D: the case of Temora longicornis
Authors: Doall Michael H. , Colin Sean P. , Strickler J. Rudi , Yen Jeannette
Published: July 2002

Using laser optics to illuminate high–resolution video–recordings, we revealed behavioural mechanisms through which males of the calanoid copepod species
Temora longicornis
locate females. Males of
T. longicornis
swam at significantly faster speeds than females along more sinuous routes, possibly reflecting adaptations to increase encounter with females. Upon approaching within 2 mm (i.e. two bodylengths) of a female's swimming path, males accelerated to significantly higher pursuit speeds. Pursuit trajectories closely traced the trajectories of females, suggesting that males were following detectable trails created by swimming females. Males of
T. longicornis
detected female trails up to at least 10 s old, and tracked trails for distances exceeding 13 cm, or 130 bodylengths. Females were positioned up to 34.2 mm away from males (i.e. reactive distance) when males initiated ‘mate–tracking’. It was always the males of
T. longicornis
that detected and pursued mates. In rare events, males pursued other males. Behavioural flexibility was exhibited by males during mate–tracking. Males generally tracked the trails of ‘cruising’ (i.e. fast–swimming) females with high accuracy, while the pursuits of ‘hovering’ (i.e. slow–swimming) females often included ‘casting’ behaviour, in which males performed sharp turns in zigzag patterns within localized volumes. This casting by males suggested that hovering females create more dispersed trails than cruising females. Casting behaviour also was initiated by males near locations where females had hopped, suggesting that rapid movements by females disrupt the continuity of their trails. Males were inefficient at choosing initial tracking directions, following trails in the incorrect direction in 27 of the 67 (40%) mating pursuits observed. Males usually attempted to correct misguided pursuits by ‘back–tracking’ along trails in the correct direction. Males were observed to detect and track their own previous trajectories without females present, suggesting the possibility that males follow their own trails during back–tracking. Observations of males tracking their own trails and the trails of other males bring into question the specificity of trails as a mechanism promoting reproductive isolation among co–occurring planktonic copepods.
Disease conditions and subclinical infections of the platypus (Ornithorhynchus anatinus)
Authors: Munday B. L. , Whittington R. J. , Stewart N. J.
Published: July 2002

Before the arrival of European settlers in Australia, the platypus,Ornithorhynchus anatinus, probably suffered from little disease. Among other things, European settlement has involved substantial environmental perturbation, introduction of large predators, introduction of motor vehicles and translocation of potential pathogens. As a result, platypuses are now killed by motor vehicles, dogs, foxes and discarded plastic litter. Information programmes targeting appropriate segments of the public would help reduce these unnecessary deaths. The enigmatic disease, ulcerative mycosis, caused byMucor amphibiorum, has been the subject of scientific investigation in Tasmania for the past 15 years. The apparent recent acceleration in its spread has sounded a warning and more intensive investigation is warranted. The possibility that this pathogen has been translocated from subtropical to temperate Tasmania, Australia, with green tree frogs in banana shipments further emphasizes the role of humans in threatening the welfare of the platypus. Recommendations are made in relation to appropriate measures that could be taken to ameliorate disease and trauma in this species.
Multimodal sensory integration in the strike–feeding behaviour of predatory fishes
Authors: New John G. , Kang Peter Y.
Published: July 2002

The search for useful model systems for the study of sensory processing in vertebrate nervous systems has resulted in many neuroethological studies investigating the roles played by a single sensory modality in a given behaviour. However, behaviours relying solely upon information from one sensory modality are relatively rare. Animals behaving in a complex, three–dimensional environment receive a large amount of information from external and internal receptor arrays. Clearly, the integration of sensory afference arising from different modalities into a coherent ‘gestalt’ of the world is essential to the behaviours of most animals. In the last several years our laboratory team has examined the roles played by the visual and lateral line sensory systems in organizing the feeding behaviour of two species of predatory teleost fishes, the largemouth bass,Micropterus salmoides, and the muskellunge,Esox masquinongy. The free–field feeding behaviours of these fishes were studied quantitatively in intact animals and compared to animals in which the lateral line and visual systems had been selectively suppressed. All groups of animals continued to feed successfully, but significant differences were observed between each experimental group, providing strong clues as to the relative role played by each sensory system in the organization of the behaviour. Furthermore, significant differences exist between the two species. The differences in behaviour resulting when an animal is deprived of a given sensory modality reflect the nature of central integrative sensory processes, and these behavioural studies provide a foundation for further neuroanatomical and physiological studies of sensory integration in the vertebrate central nervous system.
Cell cycle–regulated phosphorylation of p220NPATby cyclin E/Cdk2 in Cajal bodies promotes histone gene transcription
Authors: Ma Tianlin , Van Tine Brian A. , Wei Yue , Garrett Michelle D. , Nelson David , Adams Peter D. , Wang Jin , Qin Jun , Chow Louise T. , Harper J. Wade
Published: July 2002

Cyclin E/Cdk2 acts at the G1/S-phase transition to promote the E2F transcriptional program and the initiation of DNA synthesis. To explore further how cyclin E/Cdk2 controls S-phase events, we examined the subcellular localization of the cyclin E/Cdk2 interacting protein p220NPATand its regulation by phosphorylation. p220 is localized to discrete nuclear foci. Diploid fibroblasts in Go and G1 contain two p220 foci, whereas S- and G2-phase cells contain primarily four p220 foci. Cells in metaphase and telophase have no detectable focus. p220 foci contain cyclin E and are coincident with Cajal bodies (CBs), subnuclear organelles that associate with histone gene clusters on chromosomes 1 and 6. Interestingly, p220 foci associate with chromosome 6 throughout the cell cycle and with chromosome 1 during S phase. Five cyclin E/Cdk2 phosphorylation sites in p220 were identified. Phospho-specific antibodies against two of these sites react with p220 within CBs in a cell cycle–specific manner. The timing of p220 phosphorylation correlates with the appearance of cyclin E in CBs at the G1/S boundary, and this phosphorylation is maintained until prophase. Expression of p220 activates transcription of the histone H2B promoter. Importantly, mutation of Cdk2 phosphorylation sites to alanine abrogates the ability of p220 to activate the histone H2B promoter. Collectively, these results strongly suggest that p220NPATlinks cyclical cyclin E/Cdk2 kinase activity to replication-dependent histone gene transcription.
Predicting Gene Ontology Functions from ProDom and CDD Protein Domains
Authors: Schug Jonathan , Diskin Sharon , Mazzarelli Joan , Brunk Brian P. , Stoeckert Christian J.
Published: July 2002

A heuristic algorithm for associating Gene Ontology (GO) defined molecular functions to protein domains as listed in the ProDom and CDD databases is described. The algorithm generates rules for function-domain associations based on the intersection of functions assigned to gene products by the GO consortium that contain ProDom and/or CDD domains at varying levels of sequence similarity. The hierarchical nature of GO molecular functions is incorporated into rule generation. Manual review of a subset of the rules generated indicates an accuracy rate of 87% for ProDom rules and 84% for CDD rules. The utility of these associations is that novel sequences can be assigned a putative function if sufficient similarity exists to a ProDom or CDD domain for which one or more GO functions has been associated. Although functional assignments are increasingly being made for gene products from model organisms, it is likely that the needs of investigators will continue to outpace the efforts of curators, particularly for nonmodel organisms. A comparison with other methods in terms of coverage and agreement was performed, indicating the utility of the approach. The domain-function associations and function assignments are available from our websitehttp://www.cbil.upenn.edu/GO.
Comprehensive quality assurance for the delivery of intensity modulated radiotherapy with a multileaf collimator used in the dynamic mode
Authors: LoSasso Thomas , Chui Chen‐Shou , Ling C. Clifton
Published: July 2002

The delivery of intensity modulated radiation therapy (IMRT) using dynamic multileaf collimation (DMLC) accounts for about 40% of all treatments on eight multileaf collimator (MLC)‐equipped linacs currently at the central and satellite facilities of the Memorial Sloan Kettering Cancer Center (MSKCC). These numbers have been steadily growing for the past 6 years. Treatment with IMRT has been used for a variety of cancers, including tumors of the prostate, head and neck, breast, paraspinal regions, and brain. To ensure that patients are treated in an accurate, efficient, and safe manner, we have developed a comprehensive QA program including mechanical quality assurance, which monitors known potential weaknesses in the MLC device itself, and verification of patient‐specific treatments, to confirm the reliability of new software and to identify errors introduced through human interaction with individual patient's plans. This paper presents the reasoning, methodology, and results for mechanical, dosimetric, and electronic tests that are conducted at MSKCC.
Intensity modulated radiotherapy dose delivery error from radiation field offset inaccuracy
Authors: Kung J. H. , Chen G. T. Y.
Published: July 2002

In Intensity Modulated Radiotherapy (IMRT), irradiation is delivered in a number of small aperture subfields. The fluences shaped by these small apertures are highly sensitive to inaccuracies in multileaf collimator (MLC) calibration. The Radiation Field Offset (RFO) is the difference between a radiation and a light field at the Source to Axis Distance (SAD) for a MLC. An Intensity Modulated Radiotherapy (IMRT) system must incorporate a RFO by closing in all leaf openings. In IMRT, RFO inaccuracy will result in a dose error to the interior of a target volume. We analyze dosimetric consequences of incorporating a wrong RFO into the CORVUS, 1 cm×1 cm, step and shoot, IMRT system. The following method was employed. First an IMRT plan is generated for a target volume in a phantom, which produces a set of dynamic MLC (DMLC) files with the correct RFO value. To simulate delivery with a wrong RFO value, we wrote a computer code that reads in the DMLC file with the correct RFO value and produces another DMLC with an incorrect RFO specified by a user. Finally the phantom was irradiated with the correct and the incorrect RFO valued DMLC files, and the doses were measured with an ionization chamber. The method was applied to 9 fields, 6 MV, IMRT plans. We measured Dose Error Sensitivity Factor (DESF) for each plan, which ranged from (0–8)% mm−1. The is defined as a fractional dose error to a point (x) in a target volume per mm of the RFO error, i.e., Therefore, we concluded that for CORVUS, 6 MV, 1 cm×1 cm, step and shoot IMRT, RFO must be determined within an accuracy of 0.5 mm if a fractional dose error to a target volume is to be less than 4%. We propose an analytic framework to understand the measured DESF's. From the analysis we conclude that a large DESF was associated with an DMLC file with small average leaf openings. For 1 cm×1 cm, step and shoot IMRT, the largest possible DESF is predicted to be 20% mm−1. In addition, we wrote computer code that can calculate a DESF of a DMLC file. The code was written in Mathematica 3.0. The code can be used to screen patient IMRT plans that are highly sensitive to a RFO error.
Teaching quantum mechanics on an introductory level
Authors: Müller Rainer , Wiesner Hartmut
Published: July 2002

We present a new research-based course on quantum mechanics in which the conceptual issues of quantum mechanics are taught at an introductory level. In the context of virtual laboratories, the students discover from the very beginning how quantum phenomena deviate from our classical everyday experience. The results of the evaluation of the course show that most of the students acquired appropriate quantum mechanical conceptions, and that many of the common misconceptions encountered in traditional instruction have been avoided.
The vibration behavior of railway track at high frequencies under multiple preloads and wheel interactions
Authors: Wu T. X. , Thompson D. J.
Published: July 2002

The track foundation is preloaded by multiple wheel loads due to the train weight and, as the pad and ballast are nonlinear, their stiffness depends upon the preload in them. Due to the influence of these resilient components of the track, the track vibration is affected by the wheel loads. It is also affected by the wheel/rail interactions. In this article the preloads in the pad and ballast are calculated by considering the nonlinear properties of the track foundation, and thus the preloaded pad and ballast stiffnesses are determined. The vibration properties are explored for the track under multiple wheel loads and multiple wheel/rail interactions by comparing the results from different track models with and without these effects. It is found that the point receptance of the track is reduced and the vibration decay rate is enhanced at low frequencies due to the wheel loads. The effects of the wheel/rail interactions are most significant for frequencies 400–2000 Hz. Because of the wheel/rail interactions, the point receptance fluctuates and the vibration decay is enhanced in the regions around the wheels.
Minimum audible angles in the horizontal and vertical planes: Effects of stimulus onset asynchrony and burst duration
Authors: Strybel Thomas Z. , Fujimoto Ken
Published: July 2002

The effects of burst duration and stimulus onset asynchrony (SOA, the onset–onset time difference) on the minimum audible angle (MAA) were measured in the horizontal and vertical planes using high-pass noise bursts. Four listeners were tested with two burst durations (10 and 50 ms) and five SOAs (25, 50, 100, 200, and 400 ms), using an adaptive paradigm. In both planes, MAAs were lowest at burst duration=50 ms, and the MAAs decreased exponentially with SOA. Although the effect of burst duration was generally larger in the vertical plane than in the horizontal plane, the plane of presentation did not affect the relationship between SOA and MAA.
Inclusion of wave steepening in a frequency-domain model of trombone sound production
Authors: Thompson Michael W. , Strong William J.
Published: July 2002

A frequency-domain model of trombone sound production that includes the effects of wave steepening is proposed. This model builds upon the work of Msallam et al. [Proceedings of the Institute of Acoustics 19(5), 419–424 (1997)] by including thermoviscous wall losses in a more realistic manner, by applying wave steepening systematically to the entire instrument, and by making quantitative comparisons to the experimentally measured output of the same trombone that the model is based on. The trombone is approximated as a set of contiguous cylindrical tubes with superposition of incoming and outgoing waves in each cylinder and with continuity of pressure and flow at each cylinder junction. The far-field radiated pressure spectrum is calculated on the basis of the spectrum of a measured pressure wave in the mouthpiece. This calculation includes the effects of wave steepening for the outgoing wave in each cylinder. The equations describing the model are given. Mouthpiece spectra are processed both with and without the effects of wave steepening. The predicted far-field spectra are compared to the corresponding measured far-field spectra. In all cases analyzed, the inclusion of wave steepening greatly reduces the error between predicted and measured spectra.
Differential degradation of antbird songs in a Neotropical rainforest:  Adaptation to perch height?
Authors: Nemeth Erwin , Winkler Hans , Dabelsteen Torben
Published: July 2002

Habitat characteristics that affect transmission and degradation of acoustical signals should influence strongly the evolution of bird songs. In this study propagation properties of songs of five antbird species were measured in a rainforest in southern Venezuela. The investigated species (Myrmothera campanisona, Thamnophilus aethiops, Thamnophilus amazonicus, Myrmotherula axillaris, and Herpsilochmus dorsimaculatus) use different song post heights at all levels of the rainforest. Because there is a height-specific pattern in degradation, it is hypothesized that their songs are adapted to species-specific transmission paths. To test this assumption, transmission parameters (excess attenuation, signal-to-noise ratio, and blur ratio) were measured for the songs at five different heights and at three different distances. In three of the five species, the results indicate a strong influence of environmental conditions on the design of the vocalizations. Degradation was minimized by the concentration of the signal to a narrower frequency range, the usage of lower frequencies, or a slower time structure for the songs near the ground. The results are discussed in relation to acoustical models of sound propagation and physiology, and it is suggested that height-dependent degradation within a forest is an important selection pressure for transmissibility in avian communication.
Time reversed reverberation focusing in a waveguide
Authors: Lingevitch J. F. , Song H. C. , Kuperman W. A.
Published: July 2002

Time reversal mirrors have been applied to focus energy at probe source locations and point scatterers in inhomogeneous media. In this paper, we investigate the application of a time reversal mirror to rough interface reverberation processing in a waveguide. The method is based on the decomposition of the time reversal operator which is computed from the transfer matrix measured on a source-receiver array [Prada et al., J. Acoust. Soc. Am. 99, 2067–2076 (1996)]. In a similar manner, reverberation data collected on a source-receiver array can be filtered through an appropriate temporal window to form a time reversal operator. The most energetic eigenvector of the time reversal operator focuses along the interface at the range corresponding to the filter delay. It is also shown that improved signal-to-noise ratio measurement of the time reversal operator can be obtained by ensonifying the water column with a set of orthogonal array beams. Since these methods do not depend upon a priori environmental information, they are applicable to complex shallow water environments. Numerical simulations with a Pekeris waveguide demonstrate this method.
A new mechanism for sonoluminescence
Authors: Prosperetti A.
Published: July 2002

It is argued that a pulsating acoustically levitated bubble cannot possibly maintain a spherical shape. A jet forms during compression, and the sound amplitude such that the jet first strikes the other side of the bubble with sufficient energy is hypothesized to be the threshold for sonoluminescence. It is proposed that the connection between jet impact and light emission is a fracturing of the liquid that cannot flow during the extremely short time scale over which pressure is applied. With this hypothesis, sonoluminescence would therefore be a manifestation of the non-Newtonian nature of water and other simple liquids when stressed with sufficient intensity and rapidity.
Automated bird songs recognition using dynamic time warping and hidden Markov models
Authors: Kogan Joseph A. , Margoliash Daniel
Published: July 2002

The performance of two well-known recognition techniques in speech adapted to the automated recognition of bird song units from continuous recordings is studied. The advantages and limitations of dynamic time warping (DTW) and hidden Markov models (HMMs) are evaluated on a large database of songs of two species: zebra finches (Taeniopygia guttata) and indigo buntings (Passerina cyanea), which have different types of vocalizations and have been recorded under different laboratory conditions. The recognition performance of these methods is also assessed with regard to song signal representation (including representations commonly used in speech recognition), model structure, and sensitivity. Depending on the quality of recordings and song complexity, the DTW-based technique gives from excellent to satisfactory results. Under more challenging conditions, such as noisy recordings or the presence in bird vocalizations of confusing transient calls, HMMs can significantly outperform DTW but requires more training examples. Even though the HMMs perform usually quite well, they often misclassify short transient calls and song units with more variable structure. To address these and other weaknesses of the studied techniques, new approaches to analyze transient and variable bird vocalizations are discussed. [Work supported in part by U.S. Army Research Office and NIH.]
The role of vocal tract filtering in identity cueing in rhesus monkey (Macaca mulatta) vocalizations
Authors: Rendall Drew , Owren Michael J. , Rodman Peter S.
Published: July 2002

The importance of individual identity and kinship has been demonstrated in the social behavior of many nonhuman primates, with some evidence suggesting that individually distinctive acoustic features are present in their vocalizations as well. In order to systematically test whether acoustic cues to identity are reliably present across the vocal repertoire of rhesus monkeys (Macaca mulatta), we examined coos, grunts, and noisy screams produced by adult females of two free-ranging groups. First, acoustic analyses were used to characterize spectral patterning, the fundamental frequency, and temporal characteristics of these three distinct call types. Vocalizations were then classified by caller identity, based on discriminant function analyses. Results showed that coos (rich, harmonically structured sounds) were markedly more distinctive by caller than were either grunts or noisy screams, and that spectral-patterning measures related to vocal tract filtering effects were the most reliable markers of individual identity. Grunts (pulsed, noisy calls) were classified at lower, but above-chance rates and spectral patterning cues were again critical in this sorting. Noisy screams (continuous, broadband noise bursts that could include a high-frequency, periodic component) could not be reliably sorted by caller. Playback experiments conducted with the screams showed no response differences when listening animals heard vocalizations produced by kin or nonkin individuals. This result was strikingly different from the corresponding outcome of a previous test with coo calls, but consistent with the acoustic analysis. Implications of these findings for vocal production mechanisms in nonhuman primates and previous studies of rhesus monkey vocalizations are discussed.
A model for transverse heat transfer in thermoacoustics
Authors: Mozurkewich George
Published: July 2002

A model for transverse heat transfer in parallel thermoacoustic pores is developed. The model is one-dimensional, in the sense that the temperatures in the gas, Tg, and in the solid walls, Tw, are assumed to be fully represented by their dependences on the pore’s axial coordinate, z. All effects of transverse variation across the cross section of the pore are subsumed into a transverse heat-transfer coefficient, h1, that couples the temperatures according to q(z)=h1[Tg(z)−Tw(z)], where q is the transverse heat transfer per unit area. First the model is applied to thermally isolated pores, and results are compared to a recent three-dimensional analysis of this case [G. Mozurkewich, J. Acoust. Soc. Am. 103, 380–388 (1998)]. Then it is extended to the case of heat-exchanger pores immediately adjacent to the end of a long stack. The heat-transfer results are cast in nondimensional form as the product of two factors. One factor depends on gas properties and the geometry of the heat exchanger, the other on the length of the stack and on a parameter related to the relative total heat pumping capacity of heat exchanger and stack. Plots of both factors are given for the special case of planar pores. The results may be applied to the design of heat exchangers for practical thermoacoustic devices.
Vibration of open cylindrical shells: A three-dimensional elasticity approach
Authors: Lim C. W. , Liew K. M. , Kitipornchai S.
Published: July 2002

The three-dimensional elastic analysis of the vibration of open cylindrical shells are presented. Transverse normal stress usually neglected in plate and shell higher-order theories has been considered. The natural frequencies and vibration mode shapes have been obtained via a three-dimensional displacement-based extremum energy principle. Excessive requirements for memory and computational effort have been overcome, without sacrificing numerical accuracy, by (i) decoupling the three-dimensional displacements into the product of a set of beam and shell shape functions; and (ii) classifying the vibration modes. The effects of subtended angle and aspect ratio have been concluded for shells with various boundary conditions. Typical vibration mode shapes demonstrating the dependence of vibration characteristics on boundary constraints are presented.
Geoacoustic inversion via local, global, and hybrid algorithms
Authors: Fallat Mark R. , Dosso Stan E.
Published: July 2002

In this paper, local, global, and hybrid inversion algorithms are developed and applied to the problem of determining geoacoustic properties by minimizing the mismatch between measured and modeled acoustic fields. Local inversion methods are sensitive to gradients in the mismatch and move effectively downhill, but generally become trapped in local minima and must be initiated from a large number of starting points. Global inversion methods use a directed random process to search the parameter space for the optimal solution. They include the ability to escape from local minima, but as no gradient information is used, the search can be relatively inefficient. Hybrid inversion methods combine local and global approaches to produce a more efficient and effective algorithm. Here, downhill simplex (local) and simulated annealing (global) methods are developed individually and combined to produce a hybrid simplex simulated annealing algorithm. The hybrid inversion is found to be faster by more than an order of magnitude for a benchmark testcase in which the form of the geoacoustic model is known. The hybrid inversion algorithm is also applied to a testcase consisting of an unknown number of layers representing a general geoacoustic profile. Since the form of the model is not known, an underparameterized approach is employed to determine a minimum-structure solution.
Wave propagation in a viscoelastic medium containing fluid-filled microspheres
Authors: Baird A. M. , Kerr F. H. , Townend D. J.
Published: July 2002

Effective medium techniques have been developed by many authors to model the acoustic propagation through layers of visco-elastic materials which contain fluid-filled or elastic cavities. This paper extends such work to the case of materials containing air-filled microspheres whose thin glassy shell separates the interior air from the surrounding polymer. Such composites have been found particularly useful in conditions of high hydrostatic loading where the presence of the reinforcing shells delays the onset of the hole collapse and the consequent degradation in the acoustic performance of the composite. In the present paper, a model is presented which includes the effect of shell wall thickness variability but excludes the depth dependency—the latter will be presented in a sequel. Theoretical predictions are compared with experimentally measured values of transmission loss for both stiff and soft polymer substrates and, in each case, good agreement with experimental data is shown.
Quantifying complex patterns of bioacoustic variation: Use of a neural network to compare killer whale (Orcinus orca) dialects
Authors: Deecke V. B. , Ford J. K. B. , Spong P.
Published: July 2002

A quantitative measure of acoustic similarity is crucial to any study comparing vocalizations of different species, social groups, or individuals. The goal of this study was to develop a method of extracting frequency contours from recordings of pulsed vocalizations and to test a nonlinear index of acoustic similarity based on the error of an artificial neural network at classifying them. Since the performance of neural networks depends on the amount of consistent variation in the training data, this technique can be used to assess such variation from samples of acoustic signals. The frequency contour extraction and the neural network index were tested on samples of one call type shared by nine social groups of killer whales. For comparison, call similarity was judged by three human subjects in pairwise classification tasks. The results showed a significant correlation between the neural network index and the similarity ratings by the subjects. Both measures of acoustic similarity were significantly correlated with the groups’ association patterns, indicating that both methods of quantifying acoustic similarity are biologically meaningful. An index based on neural network analysis therefore represents an objective and repeatable means of measuring acoustic similarity, and allows comparison of results across studies, species, and time.
Wideband reflectance tympanometry in normal adults
Authors: Margolis Robert H. , Saly George L. , Keefe Douglas H.
Published: July 2002

Acoustic impedance/reflectance measurements were made at various ear-canal pressures in 20 subjects with a clinical acoustic immittance instrument and an experimental impedance/reflectance system. Measurements were made over a frequency range of 226–2000 Hz with the clinical system and 125–11 310 Hz with the experimental system. For frequencies ⩽2.0 kHz, tympanograms obtained with the two systems are similar, with patterns that progress through the same orderly sequence with increasing frequency. Eardrum impedance measurements were also similar. There are small gender differences in middle-ear impedance. Reflectance patterns (reflectance versus frequency) at ambient ear-canal air pressure are characterized by high reflectance at low frequencies, two distict minima at 1.2 and 3.5 kHz, increasing reflectance to 8.0 kHz, and decreasing reflectance above that frequency. Ear-canal pressure increases reflectance at low frequencies, decreases reflectance in the region of the minimum, and increases reflectance slightly at high frequencies. Reflectance tympanograms (reflectance versus ear-canal pressure) progress through a sequence of three patterns. At low frequencies, reflectance tympanograms are “V” shaped, indicating that pressure increases reflectance. At frequencies near the minimum reflectance, the pattern inverts, indicating that pressure decreases reflectance. At high frequencies, the patterns are flat, indicating that ear-canal pressure has little effect. Results presented for one patient suggest that reflectance tympanometry may be useful for detecting middle-ear pathology.
Detection and intensity discrimination of Gaussian-shaped tone pulses as a function of duration
Authors: Baer Thomas , Moore Brian C. J. , Glasberg Brian R.
Published: July 2002

[J. Acoust. Soc. Am. 105, 3425–3435 (1999)] proposed that the auditory system partitions the spectro-temporal domain into frequency-time (f-t) windows and that the characteristics of these windows could be explored by measuring intensity discrimination for Gaussian-shaped tone pulses presented just above their detection threshold in noise. They reasoned that for a long-duration tone pulse, the auditory representation would be maximally compact in the frequency domain, but would spread across several f-t windows in the time domain. For a very-short-duration tone pulse, the auditory representation would be maximally compact in the time domain, but would spread across several f-t windows in the frequency domain. There should be some intermediate duration at which the auditory representation is compact in both the time and frequency domains and for which intensity-discrimination performance should worsen, due to the limited opportunity for multiple looks. Their data for signal frequencies of 1 and 4 kHz were consistent with this expectation; intensity discrimination was poorest at a duration of about 3–5 ms at 1 kHz and 1 ms at 4 kHz (durations are specified between 6.8-dB-down points on the envelope). This experiment attempted to replicate those results and to extend them to a wider range of frequencies and levels. Intensity discrimination of Gaussian-shaped tone pulses was measured at three levels: 10 dB above absolute threshold or above masked threshold in a pink noise with a spectrum level of either 15 or 40 dB at 1 kHz. The signal frequency was 0.25 kHz (durations from 2 to 320 ms), 1 kHz (durations from 0.5 to 80 ms), or 4 kHz (durations from 0.1 to 20 ms). Three normally hearing subjects were tested. At 1 and 4 kHz, performance was poorest overall for the 15-dB pink noise level, and thresholds showed a peak at intermediate durations (about 3–5 ms at 1 kHz and 1 ms at 4 kHz). Such peaks were still apparent, but smaller in the no-noise condition and were almost absent at the higher noise level. For the 0.25-kHz signal frequency, peaks were not observed consistently at any level, although two subjects showed small peaks for durations around 10 ms. An explanation is offered for the results in terms of the level and frequency dependence of basilar-membrane input–output functions.
Vowel formant discrimination: Towards more ordinary listening conditions
Authors: Kewley-Port Diane , Zheng Yijian
Published: July 2002

Thresholds for formant frequency discrimination have been established using optimal listening conditions. In normal conversation, the ability to discriminate formant frequency is probably substantially degraded. The purpose of the present study was to change the listening procedures in several substantial ways from optimal towards more ordinary listening conditions, including a higher level of stimulus uncertainty, increased levels of phonetic context, and with the addition of a sentence identification task. Four vowels synthesized from a female talker were presented in isolation, or in the phonetic context of /bVd/ syllables, three-word phrases, or nine-word sentences. In the first experiment, formant resolution was estimated under medium stimulus uncertainty for three levels of phonetic context. Some undesirable training effects were obtained and led to the design of a new protocol for the second experiment to reduce this problem and to manipulate both length of phonetic context and level of difficulty in the simultaneous sentence identification task. Similar results were obtained in both experiments. The effect of phonetic context on formant discrimination is reduced as context lengthens such that no difference was found between vowels embedded in the phrase or sentence contexts. The addition of a challenging sentence identification task to the discrimination task did not degrade performance further and a stable pattern for formant discrimination in sentences emerged. This norm for the resolution of vowel formants under these more ordinary listening conditions was shown to be nearly a constant at 0.28 barks. Analysis of vowel spaces from 16 American English talkers determined that the closest vowels, on average, were 0.56 barks apart, that is, a factor of 2 larger than the norm obtained in these vowel formant discrimination tasks.
Dynamic Mechanical Properties of Polyethylene Melts: Calculation of Relaxation Spectrum from Loss Modulus
Authors: Shroff Ramesh N.
Published: July 2002

Dynamic mechanical properties of several polyethylene melts were investigated using the Weissenberg rheogoniometer. The use of the rheogoniometer for oscillatory shear testing has been discussed. The methods of determining relaxation spectrum from loss modulus based on second-order approximation of Schwarzl and Staverman, and first- and second-order approximations of Ninomiya and Ferry were found relatively inaccurate in reproducing the original loss modulus and storage modulus data. As a result, the iterative procedure based on Roesler and Twyman's derivation and that based on Tanner's algorithm were employed and found to regenerate accurately the original experimental data. Of all the approximation methods, the one based on the second-order approximation method of Williams and Ferry was subject to least error in its ability to regenerate the original melt data.
Oscillatory Shear of Nonlinear Fluids I. Preliminary Investigation
Authors: Dodge James S. , Krieger Irvin M.
Published: July 2002

Experimental oscillatory shear stress data were compared to the nonlinear behavior predicted from steady-state viscosity versus shear rate data. Both types of experimental data were obtained using a modified Weiseenberg Rheogoniometer, while finite difference techniques predicted the oscillatory data for nonlinear purely viscous materials. For nonlinear viscous fluids whose relaxation times are short compared to the period of oscillation, the harmonic amplitudes and phases are predictable from the steady-state viscosity versus shear rate function. Thixotropic and viscoelastic fluids showed large discrepancies between experimental and predicted data, indicating significant time dependence. These results indicate the suitability of oscillatory testing procedures for investigation of time-dependent materials.
Association Between Rates of Down Syndrome Diagnosis in States With vs Without 20-Week Abortion Bans From 2011 to 2018
Authors: Chaiken Sarina R. , Mandelbaum Ava D. , Garg Bharti , Doshi Uma , Packer Claire H. , Caughey Aaron B.
Published: March 2023

Importance

Many states enacted 20-week abortion bans from 2011 to 2018. Such bans affect individuals who receive diagnoses of fetal anomalies and aneuploidy in the second trimester, preventing pregnant individuals from having the choice of whether or not to continue the pregnancy.

Objectives

To examine the trends of neonatal Down syndrome rates and assess the association between enactment of 20-week abortion bans and rates of Down syndrome diagnosis.

Design, Setting, and Participants

This population-based, historical cohort study used National Vital Statistics System data on 31 157 506 births in the US from 2011 to 2018. Statistical analysis was performed from May 2021 to February 2023.

Exposure

States were categorized as those with or without a 20-week abortion ban enacted during the study period.

Main Outcomes and Measures

Demographic characteristics between the ban and no-ban states were compared using χ2 tests and 2-sample t tests. Multivariable logistic regression evaluated the adjusted odds of Down syndrome among births in states that enacted 20-week abortion bans after the abortion ban enactment, adjusting for state, year of birth, maternal race and ethnicity, age, educational level, insurance, and number of prenatal visits.

Results

The cohort consisted of 31 157 506 births (mean [SD] maternal age, 28.4 [5.9] years) in the United States, of whom 15 951 neonates (0.05%) received a diagnosis of Down syndrome at birth. A total of 17 states enacted 20-week abortion bans during the study period, and 33 states did not enact bans. In both states with and states without bans, the birth prevalence of neonatal Down syndrome increased over time; in states with bans, rates increased from 48.0 to 58.4 per 100 000 births; in states without bans, rates increased from 47.4 to 53.3 per 100 000 births. In multivariable logistic regression assessing the interaction of time and presence of a 20-week abortion ban, the odds of Down syndrome were higher in states that enacted 20-week abortion bans after enactment of the law compared with the years prior to enactment of the ban (adjusted odds ratio, 1.22; 95% CI, 1.11-1.35).

Conclusions and Relevance

In the US from 2011 to 2018, neonatal Down syndrome diagnoses increased more in states that enacted 20-week abortion bans compared with states that did not enact bans. Because these abortion bans were enacted throughout the study period and are known to inhibit choice in patient decision-making, it is possible that the difference in the rates of diagnosis is associated with these policies.