bluuebunny/crossref_metadata_2025 huggingface dataset:
Interaction of Scorpion α-Toxins with Cardiac Sodium Channels
Authors: Chen Haijun , Heinemann Stefan H.
Published: July 2002

The effects of the scorpion α-toxins Lqh II, Lqh III, and LqhαIT on human cardiac sodium channels (hH1), which were expressed in human embryonic kidney (HEK) 293 cells, were investigated. The toxins removed fast inactivation with EC50 values of <2.5 nM (Lqh III), 12 nM (Lqh II), and 33 nM (LqhαIT). Association and dissociation rates of Lqh III were much slower than those of Lqh II and LqhαIT, such that Lqh III would not dissociate from the channel during a cardiac activation potential. The voltage dependence of toxin dissociation from hH1 channels was nearly the same for all toxins tested, but it was different from that found for skeletal muscle sodium channels (μI; Chen et al. 2000). These results indicate that the voltage dependence of toxin binding is a property of the channel protein. Toxin dissociation remained voltage dependent even at high voltages where activation and fast inactivation is saturated, indicating that the voltage dependence originates from other sources. Slow inactivation of hH1 and μI channels was significantly enhanced by Lqh II and Lqh III. The half-maximal voltage of steady-state slow inactivation was shifted to negative values, the voltage dependence was increased, and, in particular for hH1, slow inactivation at high voltages became more complete. This effect exceeded an expected augmentation of slow inactivation owing to the loss of fast inactivation and, therefore, shows that slow sodium channel inactivation may be directly modulated by scorpion α-toxins.
Cftr
Authors: Smith Stephen S. , Liu Xuehong , Zhang Zhi-Ren , Sun Fang , Kriewall Thomas E. , McCarty Nael A. , Dawson David C.
Published: July 2002

The goal of the experiments described here was to explore the possible role of fixed charges in determining the conduction properties of CFTR. We focused on transmembrane segment 6 (TM6) which contains four basic residues (R334, K335, R347, and R352) that would be predicted, on the basis of their positions in the primary structure, to span TM6 from near the extracellular (R334, K335) to near the intracellular (R347, R352) end. Cysteines substituted at positions 334 and 335 were readily accessible to thiol reagents, whereas those at positions 347 and 352 were either not accessible or lacked significant functional consequences when modified. The charge at positions 334 and 335 was an important determinant of CFTR channel function. Charge changes at position 334—brought about by covalent modification of engineered cysteine residues, pH titration of cysteine and histidine residues, and amino acid substitution—produced similar effects on macroscopic conductance and the shape of the I-V plot. The effect of charge changes at position 334 on conduction properties could be described by electrodiffusion or rate-theory models in which the charge on this residue lies in an external vestibule of the pore where it functions to increase the concentration of Cl adjacent to the rate-limiting portion of the conduction path. Covalent modification of R334C CFTR increased single-channel conductance determined in detached patches, but did not alter open probability. The results are consistent with the hypothesis that in wild-type CFTR, R334 occupies a position where its charge can influence the distribution of anions near the mouth of the pore.
On the 𝑝-divisibility of Fermat quotients
Authors: Ernvall R. , Metsänkylä T.
Published: July 2002

The authors carried out a numerical search for Fermat quotientsQa=(ap−1−1)/pQ_{a} = (a^{p-1}-1)/pvanishing modpp, for1≤a≤p−11 \le a \le p-1, up top>106p > 10^{6}. This article reports on the results and surveys the associated theoretical properties ofQaQ_{a}. The approach of fixing the primepprather than the baseaaleads to some aspects of the theory apparently not published before.
Thurston boundary of Teichmüller spaces and the commensurability modular group
Authors: Biswas Indranil , Mitra Mahan , Nag Subhashis
Published: July 2002

If

p
:
Y
→
X

p : Y \rightarrow X

is an unramified covering map between two compact oriented surfaces of genus at least two, then it is proved that the embedding map, corresponding to

p
p

, from the Teichmüller space

T

(
X
)

\mathcal {T}(X)

, for

X
X

, to

T

(
Y
)

\mathcal {T}(Y)

actually extends to an embedding between the Thurston compactification of the two Teichmüller spaces. Using this result, an inductive limit of Thurston compactified Teichmüller spaces has been constructed, where the index for the inductive limit runs over all possible finite unramified coverings of a fixed compact oriented surface of genus at least two. This inductive limit contains the inductive limit of Teichmüller spaces, constructed by I. Biswas, S. Nag and D. Sullivan, Determinant bundles, Quillen metrics and Mumford isomorphisms over the Universal Commensurability Teichmüller Space, Acta Mathematica, 176 (1996), 145–169, as a subset. The universal commensurability modular group, which was constructed in the above mentioned article, has a natural action on the inductive limit of Teichmüller spaces. It is proved here that this action of the universal commensurability modular group extends continuously to the inductive limit of Thurston compactified Teichmüller spaces.
Distinct Regulatory Proteins Control the Graded Transcriptional Response to Increasing H2O2 Levels in Fission Yeast Schizosaccharomyces pombe
Authors: Quinn Janet , Findlay Victoria J. , Dawson Keren , Millar Jonathan B.A. , Jones Nic , Morgan Brian A. , Toone W. Mark
Published: July 2002

The signaling pathways that sense adverse stimuli and communicate with the nucleus to initiate appropriate changes in gene expression are central to the cellular stress response. Herein, we have characterized the role of the Sty1 (Spc1) stress-activated mitogen-activated protein kinase pathway, and the Pap1 and Atf1 transcription factors, in regulating the response to H2O2 in the fission yeast Schizosaccharomyces pombe. We find that H2O2 activates the Sty1 pathway in a dose-dependent manner via at least two sensing mechanisms. At relatively low levels of H2O2, a two component-signaling pathway, which feeds into either of the two stress-activated mitogen-activated protein kinase kinase kinases Wak1 or Win1, regulates Sty1 phosphorylation. In contrast, at high levels of H2O2, Sty1 activation is controlled predominantly by a two-component independent mechanism and requires the function of both Wak1 and Win1. Individual transcription factors were also found to function within a limited range of H2O2 concentrations. Pap1 activates target genes primarily in response to low levels of H2O2, whereas Atf1 primarily controls the transcriptional response to high concentrations of H2O2. Our results demonstrate that S. pombe uses a combination of stress-responsive regulatory proteins to gauge and effect the appropriate transcriptional response to increasing concentrations of H2O2.
Absence of Direct Delivery for Single Transmembrane Apical Proteins or Their “Secretory” Forms in Polarized Hepatic Cells
Authors: Bastaki M. , Braiterman L. T. , Johns D. C. , Chen Y.-H. , Hubbard A. L.
Published: July 2002

The absence of a direct route to the apical plasma membrane (PM) for single transmembrane domain (TMD) proteins in polarized hepatic cells has been inferred but never directly demonstrated. The genes encoding three pairs of apical PM proteins, whose extracellular domains are targeted exclusively to the apical milieu in Madin-Darby canine kidney cells, were packaged into recombinant adenovirus and delivered to WIF-B cells in vitro and liver hepatocytes in vivo. By immunofluorescence and pulse-chase metabolic labeling, we found that the soluble constructs were overwhelmingly secreted into the basolateral milieu, which in vivo is the blood and in vitro is the culture medium. The full-length proteins were first delivered to the basolateral surface but then concentrated in the apical PM. Our results imply that hepatic cells lack trans-Golgi network (TGN)-based machinery for directly sorting single transmembrane domain apical proteins and raise interesting questions about current models of PM protein sorting in polarized and nonpolarized cells.
Checkpoint Protein BubR1 Acts Synergistically with Mad2 to Inhibit Anaphase-promoting Complex
Authors: Fang Guowei
Published: July 2002

The spindle assembly checkpoint monitors the attachment of kinetochores to the mitotic spindle and the tension exerted on kinetochores by microtubules and delays the onset of anaphase until all the chromosomes are aligned at the metaphase plate. The target of the checkpoint control is the anaphase-promoting complex (APC)/cyclosome, a ubiquitin ligase whose activation by Cdc20 is required for separation of sister chromatids. In response to activation of the checkpoint, Mad2 binds to and inhibits Cdc20-APC. I show herein that in checkpoint-arrested cells, human Cdc20 forms two separate, inactive complexes, a lower affinity complex with Mad2 and a higher affinity complex with BubR1. Purified BubR1 binds to recombinant Cdc20 and this interaction is direct. Binding of BubR1 to Cdc20 inhibits activation of APC and this inhibition is independent of its kinase activity. Quantitative analysis indicates that BubR1 is 12-fold more potent than Mad2 as an inhibitor of Cdc20. Although at high protein concentrations BubR1 and Mad2 each is sufficient to inhibit Cdc20, BubR1 and Mad2 mutually promote each other's binding to Cdc20 and function synergistically at physiological concentrations to quantitatively inhibit Cdc20-APC. Thus, BubR1 and Mad2 act cooperatively to prevent premature separation of sister chromatids by directly inhibiting APC.
SWAN: sliding window analysis of nucleotide sequence variability.
Authors: Proutski V , Holmes E
Published: July 2002

RESULTS: This paper describes a new program which reveals, analyses and graphically represents patterns of variability along nucleotide sequences. AVAILABILITY: The program, 'SWAN', is available from the WWW at http://evolve.zoo.ox.ac.uk/ or from the authors upon request. CONTACT: Vitali.Proutski@zoology.oxford.ac.uk
Zomit: biological data visualization and browsing.
Authors: Pook S , Vaysseix G , Barillot E
Published: July 2002

MOTIVATION: The problems caused by the difficulty in visualizing and browsing biological databases have become crucial. Scientists can no longer interact directly with the huge amount of available data. However, future breakthroughs in biology depend on this interaction. We propose a new metaphor for biological data visualization and browsing that allows navigation in very large databases in an intuitive way. The concepts underlying our approach are based on navigation and visualization with zooming, semantic zooming and portals; and on data transformation via magic lenses. We think that these new visualization and navigation techniques should be applied globally to a federation of biological databases. RESULTS: We have implemented a generic tool, called Zomit, that provides an application programming interface for developing servers for such navigation and visualization, and a generic architecture-independent client (Javatrade mark applet) that queries such servers. As an illustration of the capabilities of our approach, we have developed ZoomMap, a prototype browser for the HuGeMap human genome map database. AVAILABILITY: Zomit and ZoomMap are available at the URL http://www.infobiogen.fr/services/zomit.
Browsing protein families via the ‘Rich Family
Description’ format
Authors: Corpet Florence , Gouzy Jérôme , Kahn Daniel
Published: July 2002

Motivation: Multiple alignments of protein sequences are the basis of structural and functional analysis of protein families. It is however difficult even for an expert biologist to comprehend an alignment of more than 50 to 100 homologous sequences.

Results: This paper presents a browser for the analysis of multiple alignments of large numbers of protein sequences. Phylogenetic trees and consensus sequences are computed and used to summarise the alignments; these data are stored in a structure called Rich Family Description. Summary alignments and trees are displayed in HTML pages and can be developed or reduced by the user. This browser is used to display the ProDom domain families on the Web. Its zooming facilities allow extracting information from alignments of more than 1000 homologous sequences.

Availability: Programs are available free of charge on request from the authors. The ProDom database can be consulted at http://www.toulouse.inra.fr/prodom.html

Contact: fcorpet@toulouse.inra.fr
Transformation distances: a family of dissimilarity measures based on movements of segments.
Authors: Varr√© J S , Delahaye J P , Rivals E
Published: July 2002

MOTIVATION: Evolution acts in several ways on DNA: either by mutating a base, or by inserting, deleting or copying a segment of the sequence (Ruddle, 1997; Russell, 1994; Li and Grauer, 1991). Classical alignment methods deal with point mutations (Waterman, 1995), genome-level mutations are studied using genome rearrangement distances (Bafna and Pevzner, 1993, 1995; Kececioglu and Sankoff, 1994; Kececioglu and Ravi, 1995). The latter distances generally operate, not on the sequences, but on an ordered list of genes. To our knowledge, no measure of distance attempts to compare sequences using a general set of segment-based operations. RESULTS: Here we define a new family of distances, called transformation distances, which quantify the dissimilarity between two sequences in terms of segment-based events. We focus on the case where segment-copy, -reverse-copy and -insertion are allowed in our set of operations. Those events are weighted by their description length, but other sets of weights are possible when biological information is available. The transformation distance from sequence S to sequence T is then the Minimum Description Length among all possible scripts that build T knowing S with segment-based operations. The underlying idea is related to Kolmogorov complexity theory. We present an algorithm which, given two sequences S and T, computes exactly and efficiently the transformation distance from S to T. Unlike alignment methods, the method we propose does not necessarily respect the order of the residues within the compared sequences and is therefore able to account for duplications and translocations that cannot be properly described by sequence alignment. A biological application on Tnt1 tobacco retrotransposon is presented. AVAILABILITY: The algorithm and the graphical interface can be downloaded at http://www.lifl.fr/ approximately varre/TD
Shapes of river networks and leaves: are they statistically similar?
Authors: Pelletier Jon D. , Turcotte Donald L.
Published: July 2002

The structure of river networks is compared with the vein structure of leaves. The two structures are visually similar at the smaller scales. The statistics of branching and side branching are nearly identical. The branching structure of diffusion–limited aggregation clusters is also similar and can provide an explanation for the structure of river networks. The origin of the self–similar branching and side branching of the vein structure in leaves is not clear but it appears to be an optimal network in terms of transporting nutrients to all parts of the leaf with the least total resistance.
Complex SNP-Based Haplotypes in Three Human Helicases: Implications for Cancer Association Studies
Authors: Trikka Dimitra , Fang Zhe , Renwick Alex , Jones Sally H. , Chakraborty Ranajit , Kimmel Marek , Nelson David L.
Published: July 2002

We have initiated a candidate gene approach to study variation and predisposition to cancer in the four major ethnic groups that constitute the U.S. population (African Americans, Caucasians, Hispanics, and Asians). We resequenced portions of three helicase genes (BLM, WRN, and RECQL) identifying a total of 37 noncoding single nucleotide polymorphisms (SNPs). Haplotype inference predicted 50 haplotypes in BLM, 56 in WRN, and 47 in RECQL in a sample of 600 chromosomes. Approximately 10% of the predicted haplotypes were shared among all ethnic groups. Linkage disequilibrium and recombination effects showed that each locus has taken a diverse evolutionary path. Primate DNA analysis of the same loci revealed one human haplotype per gene shared with the great apes, indicating that the observed diversity occurred since the divergence of humans from the last common ancestor. In BLM, we confirmed the presence of a founder haplotype among Ashkenazi Jews homozygous for theblmAsh mutation. The cosegregating haplotype was seen in all (6/6) samples of Ashkenazi descent, whereas in the general population it has a low frequency (0.02) and was not found in African Americans. In WRN, ethnic samples were studied for their haplotype content and the presence or absence of six previously described coding SNPs (cSNPs). Hispanic individuals carrying two of these cSNPs showed a 60% increase in the frequency of a common haplotype (haplotype No. 28). In the pooled sample, no association was found. Because (1) the majority of the haplotypes are population specific and (2) the patterns of linkage disequilibrium, recombination, and haplotype diversity are markedly different between gene regions, these data show the importance of either ethnically matched controls or within-family-based disease-gene association studies.

[The sequence data described in this paper have been submitted to the GenBank data library under accession no. AC006559. Online supplemental material available at http://www.genome.org]
Impaired Conditioned Taste Aversion Learning in Spinophilin Knockout Mice
Authors: Stafstrom-Davis Carrie A. , Ouimet Charles C. , Feng Jian , Allen Patrick B. , Greengard Paul , Houpt Thomas A.
Published: July 2002

Plasticity in dendritic spines may underlie learning and memory. Spinophilin, a protein enriched in dendritic spines, has the properties of a scaffolding protein and is believed to regulate actin cytoskeletal dynamics affecting dendritic spine morphology. It also binds protein phosphatase-1 (PP-1), an enzyme that regulates dendritic spine physiology. In this study, we tested the role of spinophilin in conditioned taste aversion learning (CTA) using transgenic spinophilin knockout mice. CTA is a form of associative learning in which an animal rejects a food that has been paired previously with a toxic effect (e.g., a sucrose solution paired with a malaise-inducing injection of lithium chloride). Acquisition and extinction of CTA was tested in spinophilin knockout and wild-type mice using taste solutions (sucrose or sodium chloride) or flavors (Kool-Aid) paired with moderate or high doses of LiCl (0.15 M, 20 or 40 mL/kg). When sucrose or NaCl solutions were paired with a moderate dose of LiCl, spinophilin knockout mice were unable to learn a CTA. At the higher dose, knockout mice acquired a CTA but extinguished more rapidly than wild-type mice. A more salient flavor stimulus (taste plus odor) revealed similar CTA learning at both doses of LiCl in both knockouts and wild types. Sensory processing in the knockouts appeared normal because knockout mice and wild-type mice expressed identical unconditioned taste preferences in two-bottle tests, and identical lying-on-belly responses to acute LiCl. We conclude that spinophilin is a candidate molecule required for normal CTA learning.
Three‐dimensional reconstruction of curves from pairs of projection views in the presence of error. I. Algorithms
Authors: Bullitt E. , Liu A. , Pizer S. M.
Published: July 2002

We have previously described an approach to 3D intracerebral vascular reconstruction that uses an MRA as a reconstruction base. Additional vessels seen only by angiography are added by segmenting 2D curves from projection angiograms and reconstructing these curves into 3D, building upon the MRA. Intracerebral vascular reconstruction is difficult for at least two reasons. First, 2D curves must be associated on projection images even when the human eye cannot do so. Second, 3D curves must be reconstructed in the presence of errors such as misregistration, image distortion, and misdefinition of 2D curves. This paper is the first of two that address the specific issue of reconstruction of a 3D curve from a given pair of 2D curves in the presence of error. The method explicitly separates what can and cannot be determined from a pair of projection views. It is also capable of recognizing interruptions produced by viewplane errors, of continuing reconstruction beyond such interruptions, and of localizing and estimating the magnitude of the interruptions. These measurements can also be used to estimate the lengths of regional disparities between a pair of 2D curves, leading to a quantitative estimate of the capacity of a pair of 2D curves to combine to create a 3D object (match value). Match values can be used, in turn, as part of the strategy for automatically associating pairs of 2D curves. This paper provides methods for reconstructing a given pair of 2D curves into 3D in the presence of error and for calculating match values. Error analysis is given in the companion report.
Inverse planning incorporating organ motion
Authors: Li Jonathan G. , Xing Lei
Published: July 2002

Accurate targeting is important in intensity‐modulated radiation therapy (IMRT). The positional uncertainties of structures with respect to the external beams arise in part from random organ motion and patient setup errors. While it is important to improve immobilization and reduce the influence of organ motion, the residual effects should be included in the IMRT plan design. Current inverse planning algorithms follow the conventional approach and include uncertainties by assuming population‐based margins to the target and sensitive structures. Margin around a structure represents a “hard boundary” and the fact that a structure has a spatial probability distribution has been completely ignored. With increasing understanding of spatial uncertainties of structures and the technical capability of fine‐tuning the dose distribution on an individual beamlet level in IMRT, it seems timely and important to fully utilize the information in the planning process. This will reduce the “effective” margins of the structures and facilitate dose escalation. Instead of specifying a “hard margin,” we describe an inverse planning algorithm which takes into consideration positional uncertainty in terms of spatial probability distribution. The algorithm was demonstrated by assuming that the random organ motion can be represented by a three‐dimensional Gaussian distribution function. Other probability distributions can be dealt with similarly. In particular, the commonly used “hard margin” is a special case of the current approach with a uniform probability distribution within a specified range. The algorithm was applied to plan treatment for a prostate case and a pancreatic case. The results were compared with those obtained by adding a margin to the clinical target volume. Better sparing of the sensitive structures were obtained in both cases using the proposed method for approximately the same target coverage.
Kronig–Penney model with the tail-cancellation method
Authors: Mishra Subodha , Satpathy S.
Published: July 2002

The Kronig–Penney model of an electron moving in a periodic potential is solved by the so-called tail-cancellation method. The problem also serves as a simple illustration of the tail-cancellation method itself.
Coulomb crystals of oil droplets
Authors: Robertson Scott , Younger Richard
Published: July 2002

Coulomb crystals of charged liquid droplets have been created in a Paul trap at atmospheric pressure. The technique improves upon similar experiments with solid dust particles by having a controlled and reproducible charge-to-mass ratio. The charge-to-mass ratio of the droplets, the spatial configurations of small crystals, and the frequency of the center-of-mass mode of oscillation have been determined.
Going bananas in the radiation laboratory
Authors: Hoeling Barbara , Reed Douglas , Siegel P. B.
Published: July 2002

A simple setup for measuring the amount of potassium in foods is described. A 3-in. NaI detector is used to measure samples that are 3000 cm3 in size. With moderate shielding, the potassium content can be measured down to a detection limit of a few parts per 10 000.
Eddy currents: Contactless measurement of electrical resistivity
Authors: Kraftmakher Yaakov
Published: July 2002

A simple and inexpensive student experiment is described, consisting of determination of the effective magnetic susceptibility of a cylindrical conductor in an axial ac magnetic field and contactless measurement of electrical resistivity. The experiment shows an important application of eddy currents.
Effects of consonantal context on perceptual assimilation of American English vowels by Japanese listeners
Authors: Strange Winifred , Akahane-Yamada Reiko , Kubo Rieko , Trent Sonja A. , Nishi Kanae
Published: July 2002

This study investigated the extent to which adult Japanese listeners’ perceived phonetic similarity of American English (AE) and Japanese (J) vowels varied with consonantal context. Four AE speakers produced multiple instances of the 11 AE vowels in six syllabic contexts /b-b, b-p, d-d, d-t, g-g, g-k/ embedded in a short carrier sentence. Twenty-four native speakers of Japanese were asked to categorize each vowel utterance as most similar to one of 18 Japanese categories [five one-mora vowels, five two-mora vowels, plus/ei, ou/ and one-mora and two-mora vowels in palatalized consonant CV syllables, Cja(a), Cju(u), Cjo(o)]. They then rated the “category goodness” of the AE vowel to the selected Japanese category on a seven-point scale. None of the 11 AE vowels was assimilated unanimously to a single J response category in all context/speaker conditions; consistency in selecting a single response category ranged from 77% for /eɪ/ to only 32% for /æ/. Median ratings of category goodness for modal response categories were somewhat restricted overall, ranging from 5 to 3. Results indicated that temporal assimilation patterns (judged similarity to one-mora versus two-mora Japanese categories) differed as a function of the voicing of the final consonant, especially for the AE vowels, /i, u, ɪ, ɛ, ʌ, ʊ/. Patterns of spectral assimilation (judged similarity to the five J vowel qualities) of /ɪ, ɛ, æ, ʌ/ also varied systematically with consonantal context and speakers. On the basis of these results, it was predicted that relative difficulty in the identification and discrimination of AE vowels by Japanese speakers would vary significantly as a function of the contexts in which they were produced and presented.
The surface motion due to a line force or dislocation within an anisotropic elastic half-space
Authors: Wu Kuang-Chong
Published: July 2002

An explicit solution of the surface displacements due to a line force or a line dislocation within an anisotropic half-space is presented. The surface displacements are derived from the solution corresponding to a suddenly applied surface line force using the reciprocal theorem. The solution is in a closed form for isotropic media. For anisotropic solids, only an eigenvalue problem needs to be solved numerically for a given time and position to calculate the surface response. Numerical results are given for silicon.
Turning point filters: Analysis of sound propagation on a gyre-scale
Authors: Dzieciuch Matthew , Worcester Peter , Munk Walter
Published: July 2002

Acoustic transmissions from Pioneer Seamount off California to a vertical array near Hawaii are analyzed using a technique which we call a turning-point filter. The observables, travel time and axial inclination, are interpreted in terms of the ocean sound–speed field. The method permits a uniform treatment of the arrival pattern, from the early ray-like arrivals to the late mode-like arrivals, including peak arrivals which cannot be identified as either rays or modes. An adiabatic range dependence is assumed, and Wentzel–Kramers–Brillouin–Jeffreys formalism is applied.
Melody recognition using three types of dichotic-pitch stimulus
Authors: Akeroyd Michael A. , Moore Brian C. J. , Moore Geoffrey A.
Published: July 2002

The recognition of 10 different 16-note melodies, constructed using either dichotic-pitch stimuli or diotic pure-tone stimuli, was measured. The dichotic pitches were created by placing a frequency-dependent transition in the interaural phase of a noise burst. Three different configurations for the transition were used in order to give Huggins pitch, binaural-edge pitch, and binaural-coherence-edge pitch. Forty-nine inexperienced listeners participated. The melodies evoked by the dichotic stimuli were consistently identified well in the first block of trials, indicating that the sensation of dichotic pitch was relatively immediate and did not require prolonged listening experience. There were only small improvements across blocks of trials. The mean scores were 97% (pure tones), 93% (Huggins pitch), 89% (binaural-edge pitch), and 77% (binaural-coherence-edge pitch). All pairwise differences were statistically significant, indicating that Huggins pitch was the most salient of the dichotic pitches and binaural-coherence-edge pitch was weakest. To account for these differences in salience, a simulation of lateral inhibition was applied to the recovered spectrum generated by the modified equalization cancellation model [J. F. Culling, A. Q. Summerfield, and D. H. Marshall, J. Acoust. Soc. Am. 103, 3509–3526 (1998)]. The height of the peak in the resulting “edge-enhanced” recovered spectrum reflected the relative strength of the different dichotic pitches.
The high-frequency backscattering angular response of gassy sediments: Model/data comparison from the Eel River Margin, California
Authors: Fonseca Luciano , Mayer Larry , Orange Dan , Driscoll Neal
Published: July 2002

A model for the high-frequency backscatter angular response of gassy sediments is proposed. For the interface backscatter contribution we adopted the model developed by Jackson et al. [J. Acoust. Soc. Am. 79, 1410–1422 (1986)], but added modifications to accommodate gas bubbles. The model parameters that are affected by gas content are the density ratio, the sound speed ratio, and the loss parameter. For the volume backscatter contribution we developed a model based on the presence and distribution of gas in the sediment. We treat the bubbles as individual discrete scatterers that sum to the total bubble contribution. This total bubble contribution is then added to the volume contribution of other scatters. The presence of gas affects both the interface and the volume contribution of the backscatter angular response in a complex way that is dependent on both grain size and water depth. The backscatter response of fine-grained gassy sediments is dominated by the volume contribution while that of coarser-grained gassy sediments is affected by both volume and interface contributions. In deep water the interface backscatter is only slightly affected by the presence of gas while the volume scattering is strongly affected. In shallow water the interface backscatter is severely reduced in the presence of gas while the volume backscatter is only slightly increased. Multibeam data acquired offshore northern California at 95 kHz provides raw measurements for the backscatter as a function of grazing angle. These raw backscatter measurements are then reduced to scattering strength for comparison with the results of the proposed model. The analysis of core samples at various locations provides local measurements of physical properties and gas content in the sediments that, when compared to the model, show general agreement.
Shape of the acoustic slowness surface of anisotropic solids near points of conical degeneracy
Authors: Shuvalov A. L. , Every A. G.
Published: July 2002

Phase-speed degeneracy results in striking distortions in the shape of the acoustic slowness surface of anisotropic solids. It is shown here that in the general case of conical degeneracy, there can be up to three pairs of lines of zero Gaussian curvature passing between the two adjacent slowness sheets through the point of degeneracy.
Is loudness simply proportional to the auditory nerve spike count?
Authors: Relkin Evan M. , Doucet John R.
Published: July 2002

It is often asserted that the physiological correlate of loudness is the simple sum of the spike activity produced by all neurons in the auditory nerve (the auditory nerve spike count). We will refer to this hypothesis as the spike count hypothesis. The spike count hypothesis has been tested in the past using models of the auditory periphery and in almost all cases, the hypothesis has been supported. Our new technique for recording a compound potential from the chinchilla auditory nerve, the perstimulus compound action potential (PCAP), makes possible the measurement of the growth of the auditory nerve spike count, thus providing data that can be used to test the spike count hypothesis empirically. It was observed that the growth of the auditory nerve spike count in response to a 1-kHz pure tone (in dB/dB) is 33% shallower than the growth of loudness for a 1-kHz tone, and this discrepancy increases to 66% for an 8-kHz tone. In addition, “equal-count” contours were constructed in a manner analogous to equal-loudness contours. It was found that as reference intensity increases, equal-count contours become sharply curved upward at high frequencies whereas equal-loudness contours become increasingly flat. These differences are unlikely to be the result of the cross-species comparison, since the discrepancies are mostly attributable to the skewed pattern of spread of excitation along the basilar membrane, a property shared by humans and chinchillas. Therefore, we conclude that the simple sum of the spike activity in the auditory nerve cannot be the physiological correlate of loudness.
Space-time array processing: The model-based approach
Authors: Sullivan E. J. , Candy J. V.
Published: July 2002

A method of space–time array processing is introduced that is based on the model-based approach. The signal and measurement systems are placed into state-space form, thereby allowing the unknown parameters of the model, such as signal bearings, to be estimated by an extended Kalman filter. A major advantage of the model-based approach is that there is no inherent limitation to the degree of sophistication of the models used, and therefore it can deal with other than plane-wave models, such as cylindrically or spherically spreading propagation models, as well as more sophisticated representations such as the normal mode and the parabolic equation propagation models. Since the processor treats the parameters of interest as unknown parameters to be estimated, there is no explicit beamformer structure, and therefore no accuracy limitations such as fixed beam bin sizes and predetermined number of preformed beams. After a theoretical exposition of the underlying theory, the performance of the processor is evaluated with synthesized data sets. The results indicate that the method is a highly effective approach that is capable of significantly outperforming conventional array processors.
Shallow-water tomography: Acoustic maps of the New England shelfbreak front
Authors: Chiu Ching-Sang , Lynch James F. , Gawarkiewicz Glen
Published: July 2002

In the summer of 1996, an integrated acoustic-oceanographic experiment was carried out in the Middle Atlantic Bight to study the dynamics of the shelfbreak front and the effects of the frontal variability on sound propagation. The experiment employed a suite of acoustic and oceanographic sensors, including several sources and two vertical hydrophone arrays (VLAs) straddling the shelfbreak front and a SeaSoar that provided several high-resolution, three-dimensional surveys of the frontal region. In this presentation, the results of an acoustic tomographic analysis of the frontal variability are reported. In deriving the tomographic maps, an adaptive beamformer was first used to detect, resolve, and track individual acoustic ray and modal arrivals from a 224- and a 400-Hz source on the slope to a vertical array on the shelf. A hybrid ray-mode inverse technique was then applied to the resolved arrivals to produce a time series of cross-frontal images of ocean temperature. The tomographic observations are interpreted together with the SeaSoar, ADCP, and thermistor data. [Work supported by ONR.]
Elastic wave propagation and scattering in heterogeneous, anisotropic media: Textured polycrystalline materials
Authors: Turner Joseph A.
Published: July 2002

The propagation of elastic waves through heterogeneous anisotropic media is considered. Appropriate ensemble averaging of the elastic wave equation leads to the Dyson equation which governs the mean response of the field. The Dyson equation is given here in terms of anisotropic elastic Green’s dyads for the medium with and without heterogeneities. The solution of the Dyson equation for the mean response is given for heterogeneities that are weak. The formalism is further specified for the case of equiaxed cubic polycrystalline metals with a single aligned axis. The Green’s dyads in this case are those for a transversely isotropic medium. Simple expressions for the attenuations of the shear horizontal, quasicompressional, and quasishear waves are given in terms of integrations on the unit circle. The derived expressions are limited to frequencies below the geometric optics limit, but give the attenuations in a direct manner. Comparisons with previous results are also discussed. It is anticipated that a similar approach is necessary for the study of wave propagation in complex anisotropic materials such as fiber-reinforced composites. In addition, the results are applicable to diffuse ultrasonic inspection of textured polycrystalline media.
A finite element analysis of an interferometric optical fiber hydrophone with a concentric composite mandrel including a foaming layer
Authors: Im Jong-in , Roh Yongrae
Published: July 2002

This paper outlines the design of an optical fiber hydrophone with a concentric composite mandrel that has a fundamental resonance frequency over 15 kHz and which demonstrates a good sensitivity in underwater conditions over 200 m. The composite mandrel consists of double layers (a thin foaming layer on top of a base layer) and a center hole. The foaming layer is coated on top of the base layer, made of a common material (aluminum), so as to radically improve the sensitivity of the sensor through its superior compliance. The optimal structure of the composite mandrel was determined using the finite element method (FEM) to analyze the influence of both the material properties of the foaming layer and the geometry of the composite mandrel on the performance of the hydrophone. The geometrical parameters included the thickness of the foaming layer, the inner and outer diameters, and the length of the mandrel. The analysis results indicated that for a higher sensitivity, a hydrophone needed as thick a foaming layer as possible, made from a material with a relatively low Young’s modulus, if possible, less than 1 GPa. The sensitivity also increased with a smaller outer diameter and longer mandrel, and additional sensitivity was achieved by decreasing the ratio of the inner diameter to the outer diameter. The sensitivity of the optimal structure Al composite mandrel was about −82 dB in relation to 1 rad/μPa. This result is 14 dB higher than that of a simple concentric Al mandrel-type hydrophone of the same dimensions, which verifies the effectiveness of the foaming layer.
Matched-field replica model optimization and bottom property inversion in shallow water
Authors: Baxley Paul A. , Booth Newell O. , Hodgkiss William S.
Published: July 2002

Matched-field replica models based on an inaccurate knowledge of geoacoustic parameters such as bottom attenuation, shear, and interfacial sound-speed discontinuities, can predict an incorrect number of propagating modes for a shallow-water channel. The resulting degradation in the matched-field ambiguity surface can be substantially reduced by obtaining optimal replica models via modal-sum-limit optimization or bottom-property inversion. The use of these techniques for multi-tone (70, 95, 145, and 195 Hz) source-tow data recorded near San Diego during the first Shallow-Water Evaluation Cell Experiment (SWellEX-1) significantly increased matched-field correlation levels and improved source localization relative to results obtained with a previous nonoptimized model. The predicted number of propagating modes was also reduced substantially. The inversion for bottom properties (attenuation, interfacial sound-speed discontinuities, no shear) provided sediment attenuation estimates which agree well with Hamilton’s models and were an order-of-magnitude greater than that used in the nonoptimized model, which accounts for the reduction in the number of modes. A simulated modal decomposition using the inverted optimal replica model verifies the number of modes predicted by the modal-sum-limit optimization.
Sidelobe reduction of limited diffraction beams with Chebyshev aperture apodization
Authors: He Shiping , Lu Jian-yu
Published: July 2002

A limited diffraction beams (LDB) imaging system with Chebyshev weighting is presented. The objective of the paper is to reduce the sidelobes of the LDB without impacting on main-lobe performance and increase the contrast-resolution of the imaging system. The Chebyshev weighting is applied to the LDB and an analytic description and the simulation results are obtained. Theoretical analysis and simulation results show that the LDB with Chebyshev weighting can reduce sidelobes, and improve imaging system performances.
Molecular weight distribution from viscoelastic data: The importance of tube renewal and Rouse modes
Authors: Léonardi Frédéric , Allal Ahmed , Marin Gérard
Published: July 2002

Rheological models based on molecular dynamics (as opposite to empirical relationships) are now preferred to link the molecular weight distribution (MWD) of linear polymers to their rheological properties. These models incorporate the double reptation concept, which represents the relaxation modulus as an integral over the molecular weight distribution. We propose a method that incorporates a detailed modeling of all the relevant relaxation processes, including Rouse fast and longitudinal modes and glassy relaxation. In addition, we take into account the effect of polydispersity on the relaxation times for reptation, i.e., “tube renewal.” In order to demonstrate the importance of these features of our technique, we compare it with one involving the direct inversion of the double reptation integral without accounting for tube renewal and additional relaxation processes. To invert the relaxation modulus in terms of the molecular weight distribution, one must either solve the ill-posed problem using an efficient numerical algorithm or postulate a function to describe the MWD. The second approach is more robust and less sensitive to noisy data, but one must assume the form of the MWD a priori. We present a procedure for selecting this function and use it to compare the two approaches to inverting a G(t) model. Data for several binary blends and commercial polymers are analyzed using both approaches. We conclude that the more detailed technique is necessary when the MWD is broad or when there is a significant amount of low-molecular weight material present.
Viscoelastic properties of concentrated cellulose acetate solutions
Authors: Wang C. S. , Fried J. R.
Published: July 2002

Steady-shear and dynamic viscoelastic properties of cellulose acetate (CA) solutions were measured for concentrations up to 20 wt. % in dimethyl formamide, dimethyl sulfoxide, N-methyl-2-pyrrolidinone, and triethyl phosphate. For each solvent system, the specific viscosity showed a transition in concentration dependence from approximately c1 to c5 at about 3.4 g/dl while the steady-state compliance of the solutions was inversely dependent on concentration for CA content above 10 wt. %. Master curves of the concentration-reduced viscoelastic parameters were obtained by using a concentration-dependent function equal to c. Over the entire experimental frequency range, the dynamic storage and loss moduli of the 20 wt. % solutions did not exhibit any rubbery plateaus. Results suggest that the observed transition in concentration dependence of the specific viscosity was due to the chain rigidity of CA rather than the typical polymer chain entanglement effect. The solvent nature strongly influenced the specific viscosity but not the steady-state compliance. Negative primary normal forces, due to inertia, were observed for relatively dilute CA solutions at high shear rates.
The crystal structure of La0.7Pr0.3Ba2Cu3Od ceramic compound
Authors: Wu X. S. , Sha H. , Tan W. S. , Yu Tao , Hu A. , Jiang S. S. , Wang J. , Ding Y. F.
Published: July 2002

The structure of new La0.7Pr0.3Ba2Cu3Oy (LPBCO) compound was obtained at room temperature from synchrotron radiation X-ray powder diffraction data and refined by Rietveld technique. LPBCO has an isotypical structure with YBa2Cu3Oy (YBCO). The crystal data are: La0.7Pr0.3Ba2Cu3O6.96, Mr=716.16, orthorhombic system, space group Pmmm, a=3.9147(1) Å, b=3.8672(1) Å, c=11.7033(2) Å, V=177.177(6) Å3, Z=1, Dx=6.714 g/cm3; the structure was refined with 35 parameters to Rwp=7.41%, Rp=5.32%, and Rexp=3.07% for 5001 step intensities. Moreover, the total content of oxygen in a unit cell is refined as 6.96, which is less than that of the calculated one. We attribute the superconductivity-depression to the increase of the valence of copper.
Participatory design of a sleep intervention with correctional supervisors using a root causes approach
Authors: Namazi Sara , Dugan Alicia G. , Cavallari Jennifer M. , Rinker Robert D. , Preston Julius C. , Steele Vincent L. , El Ghaziri Mazen , Cherniack Martin G.
Published: December 2022

Background

After a Design Team (DT) conducted a workforce health assessment of correctional supervisors, they selected sleep as an intervention priority, given its numerous health and work consequences. Existing workplace sleep interventions are designed with little worker input, but participatory solutions that incorporate workers' lived experiences and root causes of poor sleep may be more relevant, appropriate, and acceptable to end‐users, resulting in better uptake.

Methods

The DT met bi‐monthly to complete the Intervention Design and Analysis Scorecard (IDEAS) tool to brainstorm interventions that address root causes of poor sleep, and evaluate, rank, and select interventions for implementation. We conducted a qualitative review of meeting notes and worksheets from each IDEAS step, and present our findings on root causes and prioritized solutions.

Results

The DT consisted of two university researchers and seven members of a correctional supervisors' union, with 5–9 participants attending each meeting. IDEAS Steps 1–5 were completed in eight meetings over six months. Root causes of poor sleep included mind/body and environmental disruptions, and insufficient time. Three solutions were proposed: training on sleep hygiene, meditation, and sleep debt management; a sleep‐tracking smartphone app; and a shared overtime policy based on splitting one 8‐hour shift between two supervisors.

Conclusions

This is the first known application of IDEAS to address sleep, and targeting root causes may result in more efficacious interventions for sleep improvement. Moreover, because IDEAS guides DTs in selecting solutions with the greatest perceived health benefits, reach, cost‐effectiveness, and feasibility, it may result in more successful implementation.