bluuebunny/crossref_metadata_2025 huggingface dataset:
The Muscle Chloride Channel ClC-1 Has a Double-Barreled Appearance that Is Differentially Affected in Dominant and Recessive Myotonia
Authors: Saviane Chiara , Conti Franco , Pusch Michael
Published: July 2002

Single-channel recordings of the currents mediated by the muscle Cl− channel, ClC-1, expressed in Xenopus oocytes, provide the first direct evidence that this channel has two equidistant open conductance levels like the Torpedo ClC-0 prototype. As for the case of ClC-0, the probabilities and dwell times of the closed and conducting states are consistent with the presence of two independently gated pathways with ≈ 1.2 pS conductance enabled in parallel via a common gate. However, the voltage dependence of the common gate is different and the kinetics are much faster than for ClC-0. Estimates of single-channel parameters from the analysis of macroscopic current fluctuations agree with those from single-channel recordings. Fluctuation analysis was used to characterize changes in the apparent double-gate behavior of the ClC-1 mutations I290M and I556N causing, respectively, a dominant and a recessive form of myotonia. We find that both mutations reduce about equally the open probability of single protopores and that mutation I290M yields a stronger reduction of the common gate open probability than mutation I556N. Our results suggest that the mammalian ClC-homologues have the same structure and mechanism proposed for the Torpedo channel ClC-0. Differential effects on the two gates that appear to modulate the activation of ClC-1 channels may be important determinants for the different patterns of inheritance of dominant and recessive ClC-1 mutations.
Divalent Cation Interactions with Light-Dependent K Channels
Authors: Nasi Enrico , del Pilar Gomez Maria
Published: July 2002

The light-dependent K conductance of hyperpolarizing Pecten photoreceptors exhibits a pronounced outward rectification that is eliminated by removal of extracellular divalent cations. The voltage-dependent block by Ca2+ and Mg2+ that underlies such nonlinearity was investigated. Both divalents reduce the photocurrent amplitude, the potency being significantly higher for Ca2+ than Mg2+ (K1/2 ≈ 16 and 61 mM, respectively, at Vm = −30 mV). Neither cation is measurably permeant. Manipulating the concentration of permeant K ions affects the blockade, suggesting that the mechanism entails occlusion of the permeation pathway. The voltage dependency of Ca2+ block is consistent with a single binding site located at an electrical distance of δ ≈ 0.6 from the outside. Resolution of light-dependent single-channel currents under physiological conditions indicates that blockade must be slow, which prompted the use of perturbation/relaxation methods to analyze its kinetics. Voltage steps during illumination produce a distinct relaxation in the photocurrent (τ = 5–20 ms) that disappears on removal of Ca2+ and Mg2+ and thus reflects enhancement or relief of blockade, depending on the polarity of the stimulus. The equilibration kinetics are significantly faster with Ca2+ than with Mg2+, suggesting that the process is dominated by the “on” rate, perhaps because of a step requiring dehydration of the blocking ion to access the binding site. Complementary strategies were adopted to investigate the interaction between blockade and channel gating: the photocurrent decay accelerates with hyperpolarization, but the effect requires extracellular divalents. Moreover, conditioning voltage steps terminated immediately before light stimulation failed to affect the photocurrent. These observations suggest that equilibration of block at different voltages requires an open pore. Inducing channels to close during a conditioning hyperpolarization resulted in a slight delay in the rising phase of a subsequent light response; this effect can be interpreted as closure of the channel with a divalent ion trapped inside.
Volume-Sensitive K+/Cl− Cotransport in Rabbit Erythrocytes
Authors: Jennings Michael L.
Published: July 2002

The kinetics of activation and inactivation of K+/Cl− cotransport (KCC) have been measured in rabbit red blood cells for the purpose of determining the individual rate constants for the rate-limiting activation and inactivation events. Four different interventions (cell swelling, N-ethylmaleimide [NEM], low intracellular pH, and low intracellular Mg2+) all activate KCC with a single exponential time course; the kinetics are consistent with the idea that there is a single rate-limiting event in the activation of transport by all four interventions. In contrast to LK sheep red cells, the KCC flux in Mg2+-depleted rabbit red cells is not affected by cell volume. KCC activation kinetics were examined in cells pretreated with NEM at 0°C, washed, and then incubated at higher temperatures. The forward rate constant for activation has a very high temperature dependence (Ea ∼ 32 kCal/mol), but is not affected measurably by cell volume. Inactivation kinetics were examined by swelling cells at 37°C to activate KCC, and then resuspending at various osmolalities and temperatures to inactivate most of the transporters. The rate of transport inactivation increases steeply as cell volume decreases, even in a range of volumes where nearly all the transporters are inactive in the steady state. This finding indicates that the rate-limiting inactivation event is strongly affected by cell volume over the entire range of cell volumes studied, including normal cell volume. The rate-limiting inactivation event may be mediated by a protein kinase that is inhibited, either directly or indirectly, by cell swelling, low Mg2+, acid pH, and NEM.
Single-Channel Properties in Endoplasmic Reticulum Membrane of Recombinant Type 3 Inositol Trisphosphate Receptor
Authors: Mak Don-On Daniel , McBride Sean , Raghuram Viswanathan , Yue Yun , Joseph Suresh K. , Foskett J. Kevin
Published: July 2002

The inositol 1,4,5-trisphosphate receptor (InsP3R) is an intracellular Ca2+-release channel localized in endoplasmic reticulum (ER) with a central role in complex Ca2+ signaling in most cell types. A family of InsP3Rs encoded by several genes has been identified with different primary sequences, subcellular locations, variable ratios of expression, and heteromultimer formation. This diversity suggests that cells require distinct InsP3Rs, but the functional correlates of this diversity are largely unknown. Lacking are single-channel recordings of the recombinant type 3 receptor (InsP3R-3), a widely expressed isoform also implicated in plasma membrane Ca2+ influx and apoptosis. Here, we describe functional expression and single-channel recording of recombinant rat InsP3R-3 in its native membrane environment. The approach we describe suggests a novel strategy for expression and recording of recombinant ER-localized ion channels in the ER membrane. Ion permeation and channel gating properties of the rat InsP3R-3 are strikingly similar to those of Xenopus type 1 InsP3R in the same membrane. Using two different two-electrode voltage clamp protocols to examine calcium store-operated calcium influx, no difference in the magnitude of calcium influx was observed in oocytes injected with rat InsP3R-3 cRNA compared with control oocytes. Our results suggest that if cellular expression of multiple InsP3R isoforms is a mechanism to modify the temporal and spatial features of [Ca2+]i signals, then it must be achieved by isoform-specific regulation or localization of various types of InsP3Rs that have relatively similar Ca2+ permeation properties.
Inactivation of Bk Channels Mediated by the Nh2 Terminus of the β3b Auxiliary Subunit Involves a Two-Step Mechanism
Authors: Lingle Christopher J. , Zeng Xu-Hui , Ding J.-P. , Xia Xiao-Ming
Published: July 2002

A family of auxiliary β subunits coassemble with Slo α subunit to form Ca2+-regulated, voltage-activated BK-type K+ channels. The β subunits play an important role in regulating the functional properties of the resulting channel protein, including apparent Ca2+ dependence and inactivation. The β3b auxiliary subunit, when coexpressed with the Slo α subunit, results in a particularly rapid (∼1 ms), but incomplete inactivation, mediated by the cytosolic NH2 terminus of the β3b subunit (Xia et al. 2000). Here, we evaluate whether a simple block of the open channel by the NH2-terminal domain accounts for the inactivation mechanism. Analysis of the onset of block, recovery from block, time-dependent changes in the shape of instantaneous current-voltage curves, and properties of deactivation tails suggest that a simple, one step blocking reaction is insufficient to explain the observed currents. Rather, blockade can be largely accounted for by a two-step blocking mechanism () in which preblocked open states (O*n) precede blocked states (In). The transitions between O* and I are exceedingly rapid accounting for an almost instantaneous block or unblock of open channels observed with changes in potential. However, the macroscopic current relaxations are determined primarily by slower transitions between O and O*. We propose that the O to O* transition corresponds to binding of the NH2-terminal inactivation domain to a receptor site. Blockade of current subsequently reflects either additional movement of the NH2-terminal domain into a position that hinders ion permeation or a gating transition to a closed state induced by binding of the NH2 terminus.
Cftr
Authors: Liu Xuehong , Smith Stephen S. , Sun Fang , Dawson David C.
Published: July 2002

Some studies of CFTR imply that channel activation can be explained by an increase in open probability (Po), whereas others suggest that activation involves an increase in the number of CFTR channels (N) in the plasma membrane. Using two-electrode voltage clamp, we tested for changes in N associated with activation of CFTR in Xenopus oocytes using a cysteine-substituted construct (R334C CFTR) that can be modified by externally applied, impermeant thiol reagents like [2-(trimethylammonium)ethyl] methanethiosulfonate bromide (MTSET+). Covalent modification of R334C CFTR with MTSET+ doubled the conductance and changed the I-V relation from inward rectifying to linear and was completely reversed by 2-mercaptoethanol (2-ME). Thus, labeled and unlabeled channels could be differentiated by noting the percent decrease in conductance brought about by exposure to 2-ME. When oocytes were briefly (20 s) exposed to MTSET+ before CFTR activation, the subsequently activated conductance was characteristic of labeled R334C CFTR, indicating that the entire pool of CFTR channels activated by cAMP was accessible to MTSET+. The addition of unlabeled, newly synthesized channels to the plasma membrane could be monitored on-line during the time when the rate of addition was most rapid after cRNA injection. The addition of new channels could be detected as early as 5 h after cRNA injection, occurred with a half time of ∼24–48 h, and was disrupted by exposing oocytes to Brefeldin A, whereas activation of R334C CFTR by cAMP occurred with a half time of tens of minutes, and did not appear to involve the addition of new channels to the plasma membrane. These findings demonstrate that in Xenopus oocytes, the major mechanism of CFTR activation by cAMP is by means of an increase in the open probability of CFTR channels.
Quotient divisible abelian groups
Authors: Fomin A. , Wickless W.
Published: July 2002

An abelian group

G
G

is called quotient divisible if

G
G

is of finite torsion-free rank and there exists a free subgroup

F
⊂
G

F\subset G

such that

G

/

F

G/F

is divisible. The class of quotient divisible groups contains the torsion-free finite rank quotient divisible groups introduced by Beaumont and Pierce and essentially contains the class

G

\mathcal {G}

of self-small mixed groups which has recently been investigated by several authors. We construct a duality from the category of quotient divisible groups and quasi-homomorphisms to the category of torsion-free finite rank groups and quasi-homomorphisms. Our duality when restricted to torsion-free quotient divisible groups coincides with the duality of Arnold and when restricted to

G

\mathcal {G}

coincides with the duality previously constructed by the authors.
Comments on search procedures for primitive roots
Authors: Bach Eric
Published: July 2002

Let

p
p

be an odd prime. Assuming the Extended Riemann Hypothesis, we show how to construct

O
(

(
log
⁡
p

)

4

(
log
⁡
log
⁡
p

)

−
3

)

O( {(\log p)^{4} (\log \log p)^{-3} } )

residues modulo

p
p

, one of which must be a primitive root, in deterministic polynomial time. Granting some well-known character sum bounds, the proof is elementary, leading to an explicit algorithm.
Discrete gauge invariant approximations of a time dependent Ginzburg-Landau model of superconductivity
Authors: Du Qiang
Published: July 2002

We present here a mathematical analysis of a nonstandard difference method for the numerical solution of the time dependent Ginzburg-Landau models of superconductivity. This type of method has been widely used in numerical simulations of the behavior of superconducting materials. We also illustrate some of their nice properties such as the gauge invariance being retained in discrete approximations and the discrete order parameter having physically consistent pointwise bound.
Convergence of Newton’s method and inverse function theorem in Banach space
Authors: Xinghua Wang
Published: July 2002

Under the hypothesis that the derivative satisfies some kind of weak Lipschitz condition, a proper condition which makes Newton’s method converge, and an exact estimate for the radius of the ball of the inverse function theorem are given in a Banach space. Also, the relevant results on premises of Kantorovich and Smale types are improved in this paper.
Speeding Fermat’s factoring method
Authors: McKee James
Published: July 2002

A factoring method is presented which, heuristically, splits composite

n
n

in

O
(

n

1

/

4
+
ϵ

)

O(n^{1/4+\epsilon })

steps. There are two ideas: an integer approximation to

√
(
q

/

p
)

\surd (q/p)

provides an

O
(

n

1

/

2
+
ϵ

)

O(n^{1/2+\epsilon })

algorithm in which

n
n

is represented as the difference of two rational squares; observing that if a prime

m
m

divides a square, then

m
2

m^2

divides that square, a heuristic speed-up to

O
(

n

1

/

4
+
ϵ

)

O(n^{1/4+\epsilon })

steps is achieved. The method is well-suited for use with small computers: the storage required is negligible, and one never needs to work with numbers larger than

n
n

itself.
Probing for Membrane Domains in the Endoplasmic Reticulum: Retention and Degradation of Unassembled MHC Class I Molecules
Authors: Spiliotis Elias T. , Pentcheva Tsvetelina , Edidin Michael
Published: July 2002

Quality control of protein biosynthesis requires ER-retention and ER-associated degradation (ERAD) of unassembled/misfolded molecules. Although some evidence exists for the organization of the ER into functionally distinct membrane domains, it is unknown if such domains are involved in the retention and ERAD of unassembled proteins. Here, it is shown that unassembled MHC class I molecules are retained in the ER without accumulating at ER-exit sites or in the ERGIC of β2m−/−cells. Furthermore, these molecules did not cluster in the ER membrane and appeared to be highly mobile even when ERAD or their association with calnexin were inhibited. However, upon ATP depletion, they were reversibly segregated into an ER membrane domain, distinct from ER exit sites, which included calnexin and COPII, but not the ERGIC marker protein p58. This quality control domain was also observed upon prolonged inhibition of proteasomes. Microtubules were required for its appearance. Segregation of unfolded proteins, ER-resident chaperones, and COPII may be a temporal adaptation to cell stress.
Coordinated Traffic of Grb2 and Ras during Epidermal Growth Factor Receptor Endocytosis Visualized in Living Cells
Authors: Jiang Xuejun , Sorkin Alexander
Published: July 2002

Activation of the epidermal growth factor receptor (EGFR) triggers multiple signaling pathways and rapid endocytosis of the epidermal growth factor (EGF)–receptor complexes. To directly visualize the compartmentalization of molecules involved in the major signaling cascade, activation of Ras GTPase, we constructed fusions of Grb2, Shc, H-Ras, and K-Ras with enhanced cyan fluorescent protein (CFP) or yellow fluorescent protein (YFP), and used live-cell fluorescence imaging microscopy combined with the fluorescence resonance energy transfer (FRET) technique. Stimulation of cells by EGF resulted in the accumulation of large pools of Grb2-CFP and YFP-Shc in endosomes, where these two adaptor proteins formed a complex with EGFR. H-Ras and K-Ras fusion proteins were found at the plasma membrane, particularly in ruffles and lamellipodia, and also in endosomes independently of GTP/GDP loading and EGF stimulation. The relative amount of endosomal H-Ras was higher than that of K-Ras, whereas K-Ras predominated at the plasma membrane. On application of EGF, Grb2, and Ras converge in the same endosomes through the fusion of endosomes containing either Grb2 or Ras or through the joint internalization of two proteins from the plasma membrane. To examine the localization of the GTP-bound form of Ras, we used a FRET assay that exploits the specific interaction of GTP-bound CFP-Ras with the YFP-fused Ras binding domain of c-Raf. FRET microscopy revealed that GTP-bound Ras is located at the plasma membrane, mainly in ruffles and at the cell edges, as well as in endosomes containing EGFR. These data point to the potential for endosomes to serve as sites of generation for persistent signaling through Ras.
CONSUMERS' INFLATION EXPECTATIONS AND MONETARY POLICY IN EUROPE
Authors: Berk Jan Marc
Published: July 2002

This article analyses the effects of monetary policy decisions on inflation expectations of European consumers. Using a novel approach, I convert qualitative survey responses of consumers in various European countries into a quantitative time series of inflation expectations. I investigate the effects of unanticipated movements in interest rates and inflation on inflation expectations across European countries. I inter alia seek to explore whether the reaction differs of consumers in countries with more credible central banks than those in less credible countries.
Chemical communication during mating of the harpacticoid Tigriopus japonicus
Authors: Kelly Lisa S. , Snell Terry W. , Lonsdale Darcy J.
Published: July 2002

The importance of contact and diffusible pheromones in the reproductive biology of the harpacticoid
Tigriopus japonicus
was studied. When given a choice, males preferred developmentally advanced conspecific female partners over less mature or congeneric females. Males judged female attractiveness on a relative scale, based on the locally available females. The attractiveness of a female copepodid was reduced with non–fatal proteolytic treatment, but only if normal females were also present. To sample the available females, males repeatedly grabbed the caudal rami and terminal urosome segment of potential partners before committing themselves to guarding one female. Males occasionally dropped their copepodid partners. Releases increased in frequency in water conditioned from virgin adult females and adult males, decreased in mated–female conditioned water and were unaffected by copepodids or their treated water. The waning attractiveness of a recently mated female was tracked over 16 h. Relationships between
Tigriopus japonicus
adults appeared to involve both contact and diffusible pheromones. No evidence of a diffusible copepodid pheromone was uncovered.
Memory CD8+T cells in HIV infection
Authors: McMichael Andrew J. , Ogg Graham , Wilson Jamie , Callan Margaret , Hambleton Sophie , Appay Victor , Kelleher Tony , Rowland-Jones Sarah
Published: July 2002

Cytotoxic T lymphocytes (CTLs) play a central role in the control of persistent HIV infection in humans. The kinetics and general features of the CTL response are similar to those found during other persisting virus infections in humans. During chronic infection there are commonly between 0.1 and 1.0% of all CD8+T cells in the blood that are specific for immunodominant virus epitopes, as measured by HLA class I peptide tetramers. These figures are greatly in excess of the numbers found by limiting dilution assays; the discrepancy may arise because in the latter assay, CTLs have to divide many times to be detected and many of the HIV–specific CD8+T cells circulating in infected persons may be incapable of further division. Many tetramer–positive T cells make interferon–γ, β–chemokines and perforin, so are probably functional. It is not known how fast these T cells turn over, but in the absence of antigen they decay in number. Impairment of CTL replacement, because CD4+T helper cells are depleted by HIV infection, may play a major role in the development of AIDS.
Type III secretion: a bacterial device for close combat with cells of their eukaryotic host
Authors: Cornells Guy R.
Published: July 2002

Salmonella , Shigella , Yersinia , Pseudomonas aeruginosa, enteropathogenicEscherichia coliand several plantpathogenic Gram–negative bacteria use a new type of systems called ‘type III secretion’ to attack their host. These systems are activated by contact with a eukaryotic cell membrane and they allow bacteria to inject bacterial proteins across the two bacterial membranes and the eukaryotic cell membrane to reach a given compartment and destroy or subvert the target cell. These systems consist of a secretion apparatus made up of about 25 individual proteins and a set of proteins released by this apparatus. Some of these released proteins are ‘effectors’ that are delivered by extracellular bacteria into the cytosol of the target cell while the others are ‘translocators’ that help the ‘effectors’ to cross the membrane of the eukaryotic cell. Most of the ‘effectors’ act on the cytoskeleton or on intracellular signalling cascades. One of the proteins injected by the enteropathogenicE. coliserves as a membrane receptor for the docking of the bacterium itself at the surface of the cell.
Patterning of cell assemblies regulated by adhesion receptors of the cadherin superfamily
Authors: Takeichi Masatoshi , Nakagawa Shinichi , Aono Shinya , Usui Tadao , Uemura Tadashi
Published: July 2002

During morphogenesis, cell–cell association patterns are dynamically altered. We are interested in how cell adhesion molecules can regulate the patterning of cellular assemblies. Cadherins, a group of cell–cell adhesion receptors, are crucial for the organized assembly of many cell types, but they also regulate dynamic aspects of cell association. For example, during neural crest emigration from the neural tube, the cadherin subtypes expressed by crest cells are switched from one subtype to another. Artificial perturbation of this switch results in blocking of their escape from the neural tube. Intracellular modulations of cadherin activity also seem to play a role in regulation of cell adhesion. We identified p120ctnas a regulator of cadherin function in carcinoma cells. With such regulators, cells may make a choice as to whether they should maintain stable cell contacts or disrupt their association. Finally, we found another type of cadherin–mediated cell patterning: Flamingo, a seven–pass transmembrane cadherin, regulates planar cell polarity inDrosophilaimaginal discs. Thus, the cadherin superfamily receptors control the patterning of cell assemblies through a variety of mechanisms.
The dynamics of the cellular immune response to HIV infection: implications for vaccination
Authors: McMichael Andrew J. , Callan Margaret , Appay Victor , Hanke Tom , Ogg Graham , Rowland–Jones Sarah
Published: July 2002

Recent advances in measuring T–cell responses to viruses have led to new insights into how these T cells respond. In the acute infection there are massive CD8+T–cell responses to both Epstein–Barr virus (EBV) and to human immunodeficiency virus (HIV). Many of these T cells are effector cells and only a minority appear to be capable of maintaining immunological memory. In persistent virus infections, high levels of antigen–specific effector cells persist. If virus does not persist, the effectors fade in number but memory is maintained and is primed to react rapidly to a new challenge. A vaccine that stimulates only T–cell responses may protect when these memory cells respond rapidly enough to generate high numbers of effectors before the infecting virus becomes established.
Do mitochondria recombine in humans?
Authors: Eyre-Walker Adam
Published: July 2002

Until very recently, mitochondria were thought to be clonally inherited through the maternal line in most higher animals. However, three papers published in 2000 claimed population–genetic evidence of recombination in human mitochondrial DNA. Here I review the current state of the debate. I review the evidence for the two main pathways by which recombination might occur: through paternal leakage and via a mitochondrial DNA sequence in the nuclear genome. There is no strong evidence for either pathway, although paternal leakage seems a definite possibility. However, the population–genetic evidence, although not conclusive, is strongly suggestive of recombination in mitochondrial DNA. The implications of non–clonality for our understanding of human and mitochondrial evolution are discussed.
Mutational analysis of the interaction between albumin‐binding domain from streptococcal protein G and human serum albumin
Authors: Linhult Martin , Binz Hans Kaspar , Uhlén Mathias , Hober Sophia
Published: July 2002

Streptococcal protein G (SpG) is a bacterial cell surface receptor exhibiting affinity to both human immunoglobulin (IgG) and human serum albumin (HSA). Interestingly, the serum albumin and immunoglobulin‐binding activities have been shown to reside at functionally and structurally separated receptor domains. The binding domain of the HSA‐binding part has been shown to be a 46‐residue triple α‐helical structure, but the binding site to HSA has not yet been determined. Here, we have investigated the precise binding region of this bacterial receptor by protein engineering applying an alanine‐scanning procedure followed by binding studies by surface plasmon resonance (SPR). The secondary structure as well as the HSA binding of the resulting albumin‐binding domain (ABD) variants were analyzed using circular dichroism (CD) and affinity blotting. The analysis shows that the HSA binding involves residues mainly in the second α‐helix.
Incorporation of functional status into dose‐volume analysis
Authors: Marks Lawrence B. , Sherouse George W. , Munley Michael T. , Bentel Gunilla C. , Spencer David P.
Published: July 2002

The dose‐volume histogram (DVH) has gained wide acceptance as a mechanism for reducing the voluminous data of a three‐dimensional dose distribution into a two‐dimensional graph. These graphs are often converted to a single figure of merit. This data reduction technique is used both for clinical treatment plan evaluation and as part of proposed systems for estimating control and complication probabilities. It has long been recognized that a major shortcoming of the DVH as an analysis tool is that all spatial information is discarded. A subtler problem, which is addressed in this work, is that the DVH also implies homogeneity of biological consequence of irradiation in what may be a functionally heterogeneous volume of tissue. An extension to the DVH, the functional dose‐volume histogram, or dose‐function histogram (DFH), is proposed, that explicitly includes quantitative three‐dimensional functional information. The concept is illustrated by the use of SPECT imaging to assess the functional status of irradiated lung.
In situ estimation of sediment sound speed and critical angle
Authors: Maguer Alain , Bovio Edoardo , Fox Warren L. J. , Schmidt Henrik
Published: July 2002

Understanding the basic physics of sound penetration into ocean sediments is essential for the design of sonar systems that can detect, localize, classify, and identify buried objects. In this regard the sound speed of the sediment is a crucial parameter as the ratio of sound speed at the water-sediment interface determines the critical angle. Sediment sound speed is typically measured from core samples using high frequency (100’s of kHz) pulsed travel time measurements. Earlier experimental work on subcritical penetration into sandy sediments has suggested that the effective sound speed in the 2–20 kHz range is significantly lower than the core measurement results. Simulations using Biot theory for propagation in porous media confirmed that sandy sediments may be highly dispersive in the range 1–100 kHz for the type of sand in which the experiments were performed. Here it is shown that a direct and robust estimate of the critical angle, and therefore the sediment sound speed, at the lower frequencies can be achieved by analyzing the grazing angle dependence of the phase delays observed on a buried array. A parametric source with secondary frequencies in the 2–16 kHz range was directed toward a sandy bottom similar to the one investigated in the earlier study. An array of 14 hydrophones was used to measure penetrated field. The critical angle was estimated by analyzing the variations of signal arrival times versus frequency, burial depth, and grazing angle. Matching the results with classical transmission theory yielded a sound speed estimate in the sand of 1626 m/s in the frequency range 2–5 kHz, again significantly lower the 1720 m/s estimated from the cores at 200 kHz. However, as described here, this dispersion is consistent with the predictions of the Biot theory for this type of sand.
The effect of temperature on sound wave absorption in a sediment layer
Authors: Carbó Rafael , Molero Adriana C.
Published: July 2002

The effect of temperature on sound velocity, absorption, and reflection coefficient in the seabed sediment layer is investigated. Experimental measurements of sound speed, absorption, and the reflection coefficient in a sandy sediment layer have been carried out at several temperatures. An absorption reduction of 75 dB/m and a velocity increase of 65 m/s have been measured at a frequency of 1 MHz when the temperature increases from 5 to 25 °C. Because of the absorption temperature dependence the amplitude of the reflected wave from the back surface of the sub-bottom layer after going back and forth across the layer increases with the temperature.
Behavioral responses of humpback whales (Megaptera novaeangliae) to full-scale ATOC signals
Authors: Frankel A. S. , Clark C. W.
Published: July 2002

Loud (195 dB re 1 μPa at 1 m) 75-Hz signals were broadcast with an ATOC projector to measure ocean temperature. Respiratory and movement behaviors of humpback whales off North Kauai, Hawaii, were examined for potential changes in response to these transmissions and to vessels. Few vessel effects were observed, but there were fewer vessels operating during this study than in previous years. No overt responses to ATOC were observed for received levels of 98–109 dB re 1 μPa. An analysis of covariance, using the no-sound behavioral rate as a covariate to control for interpod variation, found that the distance and time between successive surfacings of humpbacks increased slightly with an increase in estimated received ATOC sound level. These responses are very similar to those observed in response to scaled-amplitude playbacks of ATOC signals [Frankel and Clark, Can. J. Zool. 76, 521–535 (1998)]. These similar results were obtained with different sound projectors, in different years and locations, and at different ranges creating a different sound field. The repeatability of the findings for these two different studies indicates that these effects, while small, are robust. This suggests that at least for the ATOC signal, the received sound level is a good predictor of response.
A finite-element model of vocal-fold vibration
Authors: Alipour Fariborz , Berry David A. , Titze Ingo R.
Published: July 2002

A finite-element model of the vocal fold is developed from basic laws of continuum mechanics to obtain the oscillatory characteristics of the vocal folds. The model is capable of accommodating inhomogeneous, anisotropic material properties and irregular geometry of the boundaries. It has provisions for asymmetry across the midplane, both from the geometric and tension point of view, which enables one to simulate certain kinds of voice disorders due to vocal-fold paralysis. It employs the measured viscoelastic properties of the vocal-fold tissues. The detailed construction of the matrix differential equations of motion is presented followed by the solution scheme. Finally, typical results are presented and validated using an eigenvalue method and a commercial finite-element package (ABAQUS).
The effect of the evanescent wave upon acoustic measurements in the human ear canal
Authors: Brass David , Locke Antony
Published: July 2002

When making acoustic measurements in a human ear canal, it is often necessary to monitor the output of a sound source with a microphone positioned within a few millimeters of that sound source. This microphone will not only measure the pressure due to the propagated acoustic wave, which we wish to measure, but also the pressure due to the evanescent wave. The pressure due to the evanescent wave can be viewed as a source of error in the measurement of the propagating acoustic wave. This paper attempts to quantify the magnitude of this error. Theoretical predictions are made of the relative level of the evanescent sound pressure in a number of source and microphone arrangements applicable to ear canal measurements. It is shown that these theoretical predictions represent an upper limit of evanescent sound pressure that can be measured experimentally. The maximum measurement error due to the presence of the evanescent wave in human ear canals below 10 kHz is predicted to be 3 dB in adults and 1.3 dB in 1 month old infants, when the loudspeaker and microphone ports are spaced more than 2 mm apart.
A study of temporal features and frequency characteristics in American English foreign accent
Authors: Arslan Levent M. , Hansen John H. L.
Published: July 2002

In this paper, a detailed acoustic study of foreign accent is proposed using temporal features, intonation patterns, and frequency characteristics in American English. Using a database which consists of words uttered in isolation, temporal features such as voice onset time, word-final stop closure duration, and characteristics of duration are investigated. Accent differences for native-produced versus Mandarin, German, and Turkish accented English utterances are analyzed. Of the dimensions considered, the most important accent relayer is found to be word-final stop closure duration. Mandarin accented English utterances show significant differences in terms of this feature when compared to native speaker utterances. In addition, the intonation characteristics across a set of foreign accents in American English is investigated. It is shown that Mandarin speaker utterances possess a larger negative continuative intonation slope than native speaker utterances, and German speaker utterances had a more positive intonation slope when compared to native speaker utterances. Finally, a detailed frequency analysis of foreign accented speech is conducted. It is shown that the midfrequency range (1500–2500 Hz) is the most sensitive frequency band to non-native speaker pronunciation variations. Based on this knowledge a new frequency scale for the calculation of cepstrum coefficients is formulated which is shown to outperform the Mel-scale in terms of its ability to classify accent automatically among four accent classes.
Characteristics of a pulsating jet through a small modulated orifice, with application to voice production
Authors: Mongeau Luc , Franchek Nancy , Coker Cecil H. , Kubli Robert A.
Published: July 2002

A detailed understanding of the aerodynamics of air flow in the larynx and the vocal tract is needed to refine physiological models of human voice production. This understanding can be applied in speech synthesis, voice diagnostics, and voice recognition. To date, most aeroacoustic models of phonation have been based on Bernoulli’s orifice theory, i.e., the assumption that flow phenomena within the larynx are “quasi-steady.” This assumption, however, has never been rigorously verified experimentally. In this study, detailed aerodynamic measurements were performed of a pulsating open jet through a modulated orifice with a time-varying area. Orifice geometry and characteristic Reynolds numbers and Strouhal numbers of the pulsating jet flow were representative of speech production. Simple source-filter models based on the quasi-steady flow assumption and an ideal one-dimensional monopole source model were found to yield satisfactory velocity, flow rate, and dynamic pressure predictions for most of the duty cycle. Significant deviations from quasi-steady behavior were observed only during the early part of the duty cycle, where the flow velocity in the center core rapidly reached a peak value immediately after release of the false folds. This acoustic near-field phenomenon did not affect the pressure waves generated by the pulsating jet through the orifice, propagated in the long rigid tube upstream of the orifice. The impact on this phenomenon on actual sound generation within the larynx, and wall pressures on the vocal folds, is not clear.
The acoustic emissions from single-bubble sonoluminescence
Authors: Matula Thomas J. , Hallaj Ibrahim M. , Cleveland Robin O. , Crum Lawrence A. , Moss William C. , Roy Ronald A.
Published: July 2002

Detailed measurements of the acoustic emissions from single-bubble sonoluminescence have been made utilizing both a small 200-μm aperture PVDF needle hydrophone, and a focused 10-MHz transducer. Signals obtained with the needle hydrophone show a fast (5.2 ns), probably bandlimited rise time and relatively large pulse amplitude (≈1.7 bar). Below the sonoluminescence threshold, the emissions are observable, but considerably smaller in amplitude (≈0.4 bar). Several signals are observed with the 10-MHz transducer and correspond to acoustic emissions from the bubble during the main collapse, as well as from the rebounds. Experiments reveal that the acoustic emissions occur at or near the minimum bubble radius. Calculations of the peak pressures and pulse widths are compared with experimental data.
Predicting hearing aid response in real ears
Authors: Sanborn Per-Eric
Published: July 2002

A hearing aid fitted to different ears will produce very different sound pressure spectra in the ear canal. In addition, this variation in response is different among hearing aids. A description in terms of an electrical analog model of the ear and hearing aid system is given. The applicability of this model is tested through series of measurements. The measurement and prediction procedure was first verified on a coupler (ear simulator) with good results from 300 to 8000 Hz. Three types of hearing aids were then measured and used on five different human ears. Where the measured and predicted response was compared a fairly good agreement was obtained from 300 Hz to approximately 6000 Hz. A major source of error is probe misalignment. The theoretical description given in the present work is likely to be valid from low frequencies to at least 10 kHz. Although solutions for related problems have been given for low frequencies, a solution of the hearing aid fitting problem at high frequencies has not been published earlier.
Bubble counting using an inverse acoustic scattering method
Authors: Duraiswami Ramani , Prabhukumar Sankar , Chahine Georges L.
Published: July 2002

A nuclei size measurement technique is developed, based on a dispersion relation for propagation of sound waves through a bubbly liquid. This is used to relate the attenuation and phase velocity of a sound wave to the bubble population, leading to two integral equations. These equations are ill posed, and require special treatment for solution. Algorithms based on a minimization method that imposes a number of physical constraints on the solution, rendering the equation well posed, are developed. The procedure is first tested on analytical data with varying artificial noise added, and found to be successful in recovering the bubble density function, and to perform much better than other published solution techniques. Then, bubbles were generated using electrolysis and air injection through porous tubes, and bubble populations measured. Short monochromatic bursts of sound at different frequencies were emitted and received using hydrophones. The received signals were then processed and analyzed to obtain the attenuation and phase velocity. The void fraction and known experimental errors were also obtained and were fed as constraints to the inverse problem solution procedure. This resulted in bubble populations which compare favorably to those obtained by microphotography.
Body waves recorded inside an elastic half-space by an embedded, wideband velocity sensor
Authors: Glaser Steven D. , Weiss Gregory G. , Johnson Lane R.
Published: July 2002

This paper presents a unique embeddible acoustic emission sensor. Comparison with theoretically calculated waveforms for the embedded sensor, surface step force Lamb’s problem prove the sensor to be an accurate transducer of particle velocity, with sensitivity of 2.34 V output per mm/s. Calibration as a surface sensor by the National Institute of Standards and Technology (NIST) show the sensor to be an accurate transducer of surface displacement with a sensitivity of 2.8 V/nm. The paper presents details about the design and construction of the sensor as well as calibration and verification. Unique design elements include the use of a lead-alloy backing masses, soft elastomer shear-spring isolation and mounting, and embedment. The sensor is based on the NIST conical lead zirconate-titanate (PZT) element and has a finished length of 38 mm and a diameter of 16 mm. The sensor is robust enough to work under 1 MPa of brine pressure.
Passive thermoacoustic tomography—A new kind of acoustic imaging for material testing and medicine
Authors: Passechnik Victor I. , Anosov Andrej A. , Bograchev Konstantin M.
Published: July 2002

Passive thermoacoustic tomography is a method for reconstructing temperature distributions inside objects, using the intensity of ultrasonic thermal acoustic radiation emitted from within the object. Methods for the reconstruction of 2-D and 3-D temperature distributions were analyzed by computer simulation. The standard error of reconstruction did not exceed 0.25 K (for about 300 measurements and fluctuation error of every measurement 0.1 K). The physical experiments for temperature reconstruction were carried out using a glycerin phantom with a heated area at a depth of 16 mm. The radiation was measured in one plane with angles of 0 and 45 degrees to the phantom border. The 2-D internal temperature distribution in this plane was reconstructed with a standard error of 0.4 K. The 1-D temperature transversal distribution was studied in a human hand immersed in water, the radiation being measured from both sides of the hand. The reconstructed distribution was approximated by a cubic parabola with an error of less than 0.5 K. Application of correlation properties of thermal acoustical radiation is discussed as well. [Work supported by Russian Basic Research Foundation Grant No. 98-01-00100.]
Simulation of ultrasonic pulse propagation, distortion, and attenuation in the human chest wall
Authors: Mast T. Douglas , Hinkelman Laura M. , Metlay Leon A. , Orr Michael J. , Waag Robert C.
Published: July 2002

A finite-difference time-domain model for ultrasonic pulse propagation through soft tissue has been extended to incorporate absorption effects as well as longitudinal-wave propagation in cartilage and bone. This extended model has been used to simulate ultrasonic propagation through anatomically detailed representations of chest wall structure. The inhomogeneous chest wall tissue is represented by two-dimensional maps determined by staining chest wall cross sections to distinguish between tissue types, digitally scanning the stained cross sections, and mapping each pixel of the scanned images to fat, muscle, connective tissue, cartilage, or bone. Each pixel of the tissue map is then assigned a sound speed, density, and absorption value determined from published measurements and assumed to be representative of the local tissue type. Computational results for energy level fluctuations and arrival time fluctuations show qualitative agreement with measurements performed on the same specimens, but show significantly less waveform distortion than measurements. Visualization of simulated tissue–ultrasound interactions in the chest wall shows possible mechanisms for image aberration in echocardiography, including effects associated with reflection and diffraction caused by rib structures. A comparison of distortion effects for varying pulse center frequencies shows that, for soft tissue paths through the chest wall, energy level and waveform distortion increase markedly with rising ultrasonic frequency and that arrival-time fluctuations increase to a lesser degree.
Sperm whale clicks: Directionality and source level revisited
Authors: Møhl B. , Wahlberg M. , Madsen P. T. , Miller L. A. , Surlykke A.
Published: July 2002

In sperm whales (Physeter catodon L. 1758) the nose is vastly hypertrophied, accounting for about one-third of the length or weight of an adult male. Norris and Harvey [in Animal Orientation and Navigation, NASA SP-262 (1972), pp. 397–417] ascribed a sound-generating function to this organ complex. A sound generator weighing upward of 10 tons and with a cross-section of 1 m is expected to generate high-intensity, directional sounds. This prediction from the Norris and Harvey theory is not supported by published data for sperm whale clicks (source levels of 180 dB re 1 μPa and little, if any, directionality). Either the theory is not borne out or the data is not representative for the capabilities of the sound-generating mechanism. To increase the amount of relevant data, a five-hydrophone array, suspended from three platforms separated by 1 km and linked by radio, was deployed at the slope of the continental shelf off Andenes, Norway, in the summers of 1997 and 1998. With this system, source levels up to 223 dB re 1 μPa peRMS were recorded. Also, source level differences of 35 dB for the same click at different directions were seen, which are interpreted as evidence for high directionality. This implicates sonar as a possible function of the clicks. Thus, previously published properties of sperm whale clicks underestimate the capabilities of the sound generator and therefore cannot falsify the Norris and Harvey theory.
The measurement of structural mobilities of a circular cylindrical shell
Authors: Ming Ruisen , Pan Jie , Norton Michael P.
Published: July 2002

Structural mobility is useful for the estimation of structural power flows in coupled systems. Although the methods of measuring structural mobilities are easily found for one-dimensional beam structures, few are available for cylindrical shells. In this paper, a new method is proposed for the measurement of the structural mobilities of a circular cylindrical shell. A point force excitation is used instead of circumferential modal forces which are difficult to implement in practice. This method utilizes the least squares technique to obtain the transfer function components of different circumferential modes from the measured data. Experiments were carried out on a circular cylindrical shell with different end conditions excited by a point force to verify the feasibility of this proposed method.