bluuebunny/crossref_metadata_2025 huggingface dataset:
Poncelet’s theorem in space
Authors: Previato Emma
Published: July 2002

A plane polygon

P

\mathcal {P}

inscribed in a conic

C
C

and circumscribed to a conic

D
D

can be continuously ‘rotated’, as it were. One of the many proofs consists in viewing each side of

P

\mathcal {P}

as translation by a torsion point of an elliptic curve. In the

n
n

-space version, involving torsion points of hyperelliptic Jacobians, there is a

g
=
(
n
−
1
)

g=(n-1)

-dimensional family of rotations, where

g
=
genus

g=\text {genus}

of the hyperelliptic curve; the polygon is now inscribed in one and circumscribed to

n
−
1

n-1

quadrics.
Annihilating a subspace of 𝐿₁ with the sign of a continuous function
Authors: Wulbert Daniel
Published: July 2002

Let

(
X
,
Σ
,
μ
)

(X,\Sigma , \mu )

be a

σ
\sigma

-finite, nonatomic, Baire measure space. Let

G
G

be a finite dimensional subspace of

L
1

(
X
,
Σ
,
μ
)

L_1(X,\Sigma , \mu )

. There is a bounded, continuous function,

q
q

, defined on

X
X

, such that (1)

∫
X

g
sgn
⁡
q
d
μ
=
0

\int _X g\operatorname {sgn} q d\mu =0

for all

g
∈
G

g \in G

, and (2)

|

sgn
⁡
q

|

=
1

|\operatorname {sgn} q | =1

almost everywhere.
The index of triangular operator matrices
Authors: Förster K.-H. , Nagy B.
Published: July 2002

For any triangular operator matrix acting in a direct sum of complex Banach spaces, the order of a pole of the resolvent (i.e. the index) is determined as a function of the coefficients in the Laurent series for all the (resolvents of the) operators on the diagonal and of the operators below the diagonal. This result is then applied to the case of certain nonnegative operators in Banach lattices. We show how simply these results imply the Rothblum Index Theorem (1975) for nonnegative matrices. Finally, examples for calculating the index are presented.
On the connectedness of the space of initial data for the Einstein equations
Authors: Smith Brian , Weinstein Gilbert
Published: July 2002

Is the space of initial data for the Einstein vacuum equations connected? As a partial answer to this question, we prove the following result: Let

M

\mathcal {M}

be the space of asymptotically flat metrics of non-negative scalar curvature on

R

3

\mathbb {R}^3

which admit a global foliation outside a point by

2
2

-spheres of positive mean and Gauss curvatures. Then

M

\mathcal {M}

is connected.
Fission Yeast F-box Protein Pof3 Is Required for Genome Integrity and Telomere Function
Authors: Katayama Satoshi , Kitamura Kenji , Lehmann Anna , Nikaido Osamu , Toda Takashi
Published: July 2002

The Skp1-Cullin-1/Cdc53-F-box protein (SCF) ubiquitin ligase plays an important role in various biological processes. In this enzyme complex, a variety of F-box proteins act as receptors that recruit substrates. We have identified a fission yeast gene encoding a novel F-box protein Pof3, which contains, in addition to the F-box, a tetratricopeptide repeat motif in its N terminus and a leucine-rich-repeat motif in the C terminus, two ubiquitous protein–protein interaction domains. Pof3 forms a complex with Skp1 and Pcu1 (fission yeast cullin-1), suggesting that Pof3 functions as an adaptor for specific substrates. In the absence of Pof3, cells exhibit a number of phenotypes reminiscent of genome integrity defects. These include G2 cell cycle delay, hypersensitivity to UV, appearance of lagging chromosomes, and a high rate of chromosome loss.pof3 deletion strains are viable because the DNA damage checkpoint is continuously activated in the mutant, and this leads to G2 cell cycle delay, thereby preventing the mutant from committing lethal mitosis. Pof3 localizes to the nucleus during the cell cycle. Molecular analysis reveals that in this mutant the telomere is substantially shortened and furthermore transcriptional silencing at the telomere is alleviated. The results highlight a role of the SCFPof3ubiquitin ligase in genome integrity via maintaining chromatin structures.
Role of Adaptor Complex AP-3 in Targeting Wild-Type and Mutated CD63 to Lysosomes
Authors: Rous Brian A. , Reaves Barbara J. , Ihrke Gudrun , Briggs John A.G. , Gray Sally R. , Stephens David J. , Banting George , Luzio J. Paul
Published: July 2002

CD63 is a lysosomal membrane protein that belongs to the tetraspanin family. Its carboxyterminal cytoplasmic tail sequence contains the lysosomal targeting motif GYEVM. Strong, tyrosine-dependent interaction of the wild-type carboxyterminal tail of CD63 with the AP-3 adaptor subunit μ3 was observed using a yeast two-hybrid system. The strength of interaction of mutated tail sequences with μ3 correlated with the degree of lysosomal localization of similarly mutated human CD63 molecules in stably transfected normal rat kidney cells. Mutated CD63 containing the cytosolic tail sequence GYEVI, which interacted strongly with μ3 but not at all with μ2 in the yeast two-hybrid system, localized to lysosomes in transfected normal rat kidney and NIH-3T3 cells. In contrast, it localized to the cell surface in transfected cells ofpearl and mocha mice, which have genetic defects in genes encoding subunits of AP-3, but to lysosomes in functionally rescued mocha cells expressing the δ subunit of AP-3. Thus, AP-3 is absolutely required for the delivery of this mutated CD63 to lysosomes. Using this AP-3–dependent mutant of CD63, we have shown that AP-3 functions in membrane traffic from thetrans-Golgi network to lysosomes via an intracellular route that appears to bypass early endosomes.
Crk Adapter Proteins Promote an Epithelial–Mesenchymal-like Transition and Are Required for HGF-mediated Cell Spreading and Breakdown of Epithelial Adherens Junctions
Authors: Lamorte Louie , Royal Isabelle , Naujokas Monica , Park Morag
Published: July 2002

Activation of the Met receptor tyrosine kinase through its ligand, hepatocyte growth factor (HGF), promotes an epithelial–mesenchymal transition and cell dispersal. However, little is known about the HGF-dependent signals that regulate these events. HGF stimulation of epithelial cell colonies leads to the enhanced recruitment of the CrkII and CrkL adapter proteins to Met-dependent signaling complexes. We provide evidence that signals involving CrkII and CrkL are required for the breakdown of adherens junctions, the spreading of epithelial colonies, and the formation of lamellipodia in response to HGF. The overexpression of a CrkI SH3 domain mutant blocks these HGF-dependent events. In addition, the overexpression of CrkII or CrkL promotes lamellipodia formation, loss of adherens junctions, cell spreading, and dispersal of colonies of breast cancer epithelial cells in the absence of HGF. Stable lines of epithelial cells overexpressing CrkII show enhanced activation of Rac1 and Rap1. The Crk-dependent breakdown of adherens junctions and cell spreading is inhibited by the expression of a dominant negative mutant of Rac1 but not Rap1. These findings provide evidence that Crk adapter proteins play a critical role in the breakdown of adherens junctions and the spreading of sheets of epithelial cells.
Analysis of base-pairing potentials between 16S rRNA and 5' UTR for translation initiation in various prokaryotes.
Authors: Osada Y , Saito R , Tomita M
Published: July 2002

MOTIVATION: It is well accepted that the 3' end of 16S rRNA is directly involved in prokaryotic translation initiation by pairing with the Shine-Dalgarno (SD) sequence, which is located in the ribosome-binding site of mRNA. According to Shine and Dalgarno, Escherichia coli 's 5' UTR has the pattern of 'AGGAGG' (SD sequence), which is complementary to the 3' end sequence of 16S rRNA. In this work, we systematically calculated free-energy values of the base pairing between the 3' end of 16S rRNA and the 5' UTR of mRNA, in order to analyze the base-pairing potentials in various prokaryotes. The free-energy values were then plotted over distances from the start codon to visualize the free-energy pattern of 5'UTRs. RESULTS: The average free-energy values fell sharply before the start codon in E. coli, which is consistent with the model that the 3' end of 16S rRNA base pairs with the SD sequence. Haemophilus influenzae, Bacillus subtilis and Helicobacter pylori show a similar pattern, suggesting that the organisms have basically the same mechanism of translation initiation as E. coli. Other eubacteria, such as Synechocystis PCC6803, Mycoplasma genitalium, Mycoplasma pneumoniae and Borrelia burgdorferi also show decreases in their free-energy values, although they are less evident. We also did the same analysis with a eukaryote genome as a control; no fall in free-energy values was observed between the 3' end of 18S rRNA and 5' UTRs of Saccharomyces cerevisiae, suggesting that this organism does not base pair in translation initiation. The three archaebacteria A. fulgidus, M. jannaschii and M. thermoautotrophicum show patterns similar to eubacteria, but not to S. cerevisiae, indicating that archaebacteria are closer to eubacteria than to eukaryotes with respect to the mechanism of translation initiation. From these observations, it appears that the shape of the curve produced by the algorithm can be used to predict the mechanism of translation initiation. AVAILABILITY: The C programs used in our analysis are available upon request.
The structural GDP/GTP cycle of human Arf6
Authors: Pasqualato Sebastiano , Ménétrey Julie , Franco Michel , Cherfils Jacqueline
Published: July 2002

The small GTP‐binding protein Arf6 coordinates membrane traffic at the plasma membrane with aspects of cytoskeleton organization. This function does not overlap with that of other members of the ADP‐ribosylation factor (Arf) family, although their switch regions, which are their major sites of interaction with regulators and effectors, have virtually identical sequences. Here we report the crystal structure of full‐length, non‐myristoylated human Arf6 bound to GTPγS. Unlike their GDP‐bound forms, the active forms of Arf6 and Arf1 are very similar. Thus, the switch regions are discriminatory elements between Arf isoforms in their inactive but not in their active forms, a property that may generalize to other families of small G proteins. This suggests that GTP‐bound Arfs may establish specific interactions outside the switch regions and/or be recognized in their cellular context rather than as isolated proteins. The structure also allows further insight into the lack of spontaneous GTPase activity of Arf proteins.
Genetic and molecular analysis of tomato
Cf
genes for resistance to
Cladosporium fulvum
Authors: Thomas Colwyn M. , Dixon Mark S. , Parniske Martin , Golstein Catherine , Jones Jonathan D. G.
Published: July 2002

In many plant–pathogen interactions resistance to disease is controlled by the interaction of plant–encoded resistance (
R
) genes and pathogen–encoded avirulence (
Avr
) genes. The interaction between tomato and the leaf mould pathogen
Cladosporium fulvum
is an ideal system to study the molecular basis of pathogen perception by plants. A total of four tomato genes for resistance to
C. fulvum
(
Cf–2
,
Cf–4
,
Cf–5
and
Cf–9
) have been isolated from two genetically complex chromosomal loci. Their gene products recognize specific
C. fulvum
–encoded avirulence gene products (Avr2, Avr4, Avr5 and Avr9) by an unknown molecular mechanism.
Cf
genes encode extracellular membrane–anchored glycoproteins comprised predominantly of 24 amino acid leucine–rich repeats (LRRs).
Cf
genes from the same locus encode proteins which are more than 90% identical. Most of the amino–acid sequence differences correspond to the solvent–exposed residues within a β–strand/β–turn structural motif which is highly conserved in LRR proteins. Sequence variability within this motif is predicted to affect the specificity of ligand binding. Our analysis of
Cf
gene loci at the molecular level has shown they comprise tandemly duplicated homologous genes, and suggests a molecular mechanism for the generation of sequence diversity at these loci. Our analysis provides further insight into the molecular basis of pathogen perception by plants and the organization and evolution of
R
gene loci.
Memory in the B–cell compartment: antibody affinity maturation
Authors: Neuberger Michael S. , Ehrenstein Michael R. , Rada Cristina , Sale Julian , Batista Facundo D. , Williams Gareth , Milstein Cesar
Published: July 2002

In the humoral arm of the immune system, the memory response is not only more quickly elicited and of greater magnitude than the primary response, but it is also different in quality. In the recall response to antigen, the antibodies produced are of higher affinity and of different isotype (typically immunoglobulin G rather than immunoglobulin M). This maturation rests on the antigen dependence of B–cell maturation and is effected by programmed genetic modifications of the immunoglobulin gene loci. Here we consider how the B–cell response to antigen depends on the affinity of the antigen–receptor interaction. We also compare and draw parallels between the two processes, which underpin the generation of secondaryresponse antibodies: V gene somatic hypermutation and immunoglobulin heavy–chain class switching.
Salmonellainteractions with host cells:in vitroto in vivo
Authors: Brett Finlay B. , Brumell John H.
Published: July 2002

Salmonellosis (diseases caused bySalmonellaspecies) have several clinical manifestations, ranging from gastroenteritis (food poisoning) to typhoid (enteric) fever and bacteraemia.Salmonellaspecies (especiallySalmonella typhimurium) also represent organisms that can be readily used to investigate the complex interplay that occurs between a pathogen and its host, bothin vitroand in vivo. The ease with whichS. typhimuriumcan be cultivated and genetically manipulated, in combination with the availability of tissue culture models and animal models, has madeS. typhimuriuma desirable organism for such studies. In this review, we focus onSalmonellainteractions with its host cells, both in tissue culture (in vitro) and in relevant animal models (in vivo), and compare results obtained using these different models. The recent advent of sophisticated imaging and molecular genetic tools has facilitated studying the events that occur in disease, thereby confirming tissue culture results, yet identifying new questions that need to be addressed in relevant disease settings.
Is human T–cell lymphotropic virus type I really silent?
Authors: Asquith Becca , Hanon Emmanuel , Taylor Graham P. , Bangham Charles R. M.
Published: July 2002

The role of the cellular immune response to human T–cell lymphotropic virus type I (HTLV–I) is not fully understood. The low level of HTLV–I protein expression in peripheral blood lymphocytes has led to the widely held belief that HTLV–I is transcriptionally silentin vivo. However, most HTLV–I–infected individuals mount a strong and persistently activated cytotoxic T–lymphocyte (CTL) response to the virus; this observation implies that there is abundant chronic transcription of HTLV–I genes. Here we show that HTLV–I Tax protein expression rises quickly in freshly isolated peripheral blood lymphocytes, but that expressing cells are rapidly killed by CTLs. Mathematical analysis of these results indicates that the CTL response is extremely efficient and that the half–life of a Tax–expressing cell is less than a day. We propose that HTLV–I protein expression in circulating lymphocytes is undetectable by current techniques because of the efficiency of the CTL–mediated immune surveillancein vivo.
The neuron-specific RNA-binding protein ELAV regulates neuroglian alternative splicing in neurons and binds directly to its pre-mRNA
Authors: Lisbin Michael J. , Qiu Jan , White Kalpana
Published: July 2002

Drosophila melanogaster neural-specific protein, ELAV, has been shown to regulate the neural-specific splicing of three genes:neuroglian (nrg), erect wing, andarmadillo. Alternative splicing of the nrg transcript involves alternative inclusion of a 3′-terminal exon. Here, using a minigene reporter, we show that the nrg alternatively spliced intron (nASI) has all the determinants required to recreate proper neural-specific RNA processing seen with the endogenousnrg transcript, including regulation by ELAV. An in vitro UV cross-linking assay revealed that ELAV from nuclear extracts cross-links to four distinct sites along the 3200 nucleotide longnASI; one EXS is positioned at the polypyrimidine tract of the default 3′ splice site. ELAV cross-linking sites (EXSs) have in common long tracts of (U)-rich sequence rather than a precise consensus; moreover, each tract has at least two 8/10U elements; their importance is validated by mutant transgene reporter analysis. Further, we propose criteria for ELAV target sequence recognition based on the four EXSs, sites within the nASI that are (U) rich but do not cross-link with ELAV, and predicted EXSs from a phylogenetic comparison withDrosophila virilis nASI. These results suggest that ELAV regulates nrg alternative splicing by direct interaction with the nASI.
V-SINEs: A New Superfamily of Vertebrate SINEs That Are Widespread in Vertebrate Genomes and Retain a Strongly Conserved Segment within Each Repetitive Unit
Authors: Ogiwara Ikuo , Miya Masaki , Ohshima Kazuhiko , Okada Norihiro
Published: July 2002

We have identified a new superfamily of vertebrate short interspersed repetitive elements (SINEs), designated V-SINEs, that are widespread in fishes and frogs. Each V-SINE includes a central conserved domain preceded by a 5′-end tRNA-related region and followed by a potentially recombinogenic (TG)n tract, with a 3′ tail derived from the 3′ untranslated region (UTR) of the corresponding partner long interspersed repetitive element (LINE) that encodes a functional reverse transcriptase. The central domain is strongly conserved and is even found in SINEs in the lamprey genome, suggesting that V-SINEs might be ∼550 Myr old or older in view of the timing of divergence of the lamprey lineage from the bony fish lineage. The central conserved domain might have been subject to some form of positive selection. Although the contemporary 3′ tails of V-SINEs differ from one another, it is possible that the original 3′ tail might have been replaced, via recombination, by the 3′ tails of more active partner LINEs, thereby retaining retropositional activity and the ability to survive for long periods on the evolutionary time scale. It seems plausible that V-SINEs may have some function(s) that have been maintained by the coevolution of SINEs and LINEs during the evolution of vertebrates.

[The sequences reported in this paper have been deposited in the DDBJ/GenBank database under accession nos.AB072981–AB073004. Supplemental figures are available online athttp://www.genome.org.]
Differential Effects of PACAP-38 on Synaptic Responses in Rat Hippocampal CA1 Region
Authors: Roberto Marisa , Scuri Rossana , Brunelli Marcello
Published: July 2002

Pituitary adenylate cyclase-activating polypeptide (PACAP-38) is a member of the vasointestinal polypeptide (VIP)/secretin/glucagon family of neuropeptides for which neuroregulatory functions have been postulated. PACAP-38 receptors are expressed in different brain regions, including hippocampus. In this study, we examined the dose-dependent effects of PACAP-38 on the excitatory postsynaptic field potential (fEPSP) evoked at the Schaffer collateral-CA1 synapse in rat hippocampal slices. Bath application of low dose (0.05 nM) of PACAP-38 induced long-lasting facilitation of the fEPSP. This enhancement was blocked by the cholinergic receptor antagonist atropine and partially by the NMDA receptor antagonist 2-amino-5-phosphonovalerate (APV) and therefore, shares a common mechanism with LTP. In contrast, a high dose (1 μM) of PACAP-38 induced a persistent depression of the fEPSP that was not blocked by antagonists of cholinergic receptors (i.e., atropine and mecamylamine), adenosine receptors (i.e., DCPCX), or glutamatergic NMDA receptors (APV). Intermediate doses (0.1–0.5 μM) of PACAP-38 produced an initial decrease of the fEPSP followed by an enhancement. This decrease was not blocked by atropine whereas the facilitation was. These results show that PACAP-38 modulates CA1 synaptic transmission in a dose-dependent manner and that the peptide interacts with cholinergic and glutamatergic systems.
Learning and Memory in Transgenic Mice Modeling Alzheimer's Disease
Authors: Ashe Karen Hsiao
Published: July 2002

Recent advances in behavioral analyses of transgenic mouse models of Alzheimer's disease (AD) are discussed, and their impact on our understanding of the molecular basis of cognitive impairment in AD is considered. Studies of the relationship between memory and Aß in transgenic mice expressing the amyloid precursor protein (APP) and its variants suggest that aging promotes the formation of soluble Aß assemblies mediating negative effects on memory. A significant component of memory loss in APP transgenic mice is apparently caused by soluble Aß assemblies, but whether and how much of the dementia within individuals afflicted with AD is caused by these Aß species is unclear. Future studies in composite transgenic mice developing amyloid plaques, neurofibrillary tangles, and other AD pathology may allow for the determination of the relative contribution of Aß and non-Aß components to dementia.
Fine‐tuning function: Correlation of hinge domain interactions with functional distinctions between LacI and PurR
Authors: Swint‐Kruse Liskin , Larson Christopher , Pettitt B. Montgomery , Matthews Kathleen Shive
Published: July 2002

LacI and PurR are highly homologous proteins. Their functional units are homodimers, with an N‐terminal DNA binding domain that comprises the helix‐turn‐helix (HTH), N‐linker, and hinge regions from both monomers. Hinge structural changes are known to occur upon DNA dissociation but are difficult to monitor experimentally. The initial steps of hinge unfolding were therefore examined using molecular dynamics simulations, utilizing a truncated, chimeric protein comprising the LacI HTH/N‐linker and PurR hinge. A terminal Gly‐Cys‐Gly was added to allow “dimerization” through disulfide bond formation. Simulations indicate that differences in LacI and PurR hinge primary sequence affect the quaternary structure of the hinge•hinge′ interface. However, these alternate hinge orientations would be sterically restricted by the core domain. These results prompted detailed comparison of recently available DNA‐bound structures for LacI and truncated LacI(1–62) with the PurR structure. Examination revealed that different N‐linker and hinge contacts to the core domain of the partner monomer (which binds effector molecule) affect the juxtapositions of the HTH, N‐linker, and hinge regions in the DNA binding domain. In addition, the two full‐length repressors exhibit significant differences in the interactions between the core and the C‐linker connection to the DNA binding domain. Both linkers and the hinge have been implicated in the allosteric response of these repressors. Intriguingly, one functional difference between these two proteins is that they exhibit opposite allosteric response to effector. Simulations and observed structural distinctions are correlated with mutational analysis and sequence information from the LacI/GalR family to formulate a mechanism for fine‐tuning individual repressor function.
Dosimetric effects of needle divergence in prostate seed implant using and radioactive seeds
Authors: Nath Sameer , Chen Zhe , Yue Ning , Trumpore Sharron , Peschel Richard
Published: July 2002

In prostate seed implants, radioactive seeds are implanted into the prostate through a guiding needle with the help of a template and real‐time imaging. The ideal locations of the guiding needles and the relative positions of the seeds in each needle are determined before the implantation under the assumption that the needles inserted at different locations will remain parallel. In actual implantation, the direction of the needle is subject variation. In this work, we studied how the dosimetry quality of an implant may be affected when the guiding needles deviate from its planned orientations. Needle divergence of varying degree was simulated on spherical models and actual patient implants. It was found that needle divergence degraded the dosimetric quality of an implant: The minimum target dose, the target dose coverage and therefore the tumor biological effective dose were quantitatively decreased as compared to the reference implant. The magnitude of degradation increased almost linearly with respect to the magnitude of needle divergence. For iodine‐125 implants, the average reduction in minimum target dose was about 10% and 20% for needle divergence of standard deviation of and respectively. The dose coverage in the target was reduced by about 1% and 3% for needle divergence of standard deviation of and respectively. Implants designed with palladium‐103 showed additional 5% reduction in minimum target dose while the effect on dose coverage was about the same as compared to the iodine‐125 implants. The degree of dosimetry degradation was shown to be dependent on the size of target volume, the seed spacing used, the use of seeding margin, and on the actual configuration of needle orientations in a given implant. One needs to minimize the physical causes of needle divergence in order to minimize its impact on planned dosimetry. The study suggests that the displacement between a needle image and its planned grid point at the base of prostate should be kept less than 5 mm in order to minimize the reduction in and the increase in cell‐survival (< a factor of 10) from the planned dosimetry.
Choosing and rechoosing to have or have not interference
Authors: Jordan Thomas F.
Published: July 2002

Loss and restoration of interference similar to that produced in “quantum erasure” can be demonstrated in interference of macroscopic laser beams by using polarization to distinguish light from two slits. You can choose whether to observe interference or identify the light from each slit. The choice can be reversed and repeated an unlimited number of times. It never becomes irreversible.
Resource Letter: ScL-1: Scaling laws
Authors: Wiesenfeld Kurt
Published: July 2002

This Resource Letter provides a guide to the literature on scaling laws in physics and allied fields. Journal articles and books are cited for the following topics: dimensional analysis, critical phenomena, fractals, nonlinear dynamics, and nonequilibrium physics.
How to beat the Rayleigh resolution limit: A lecture demonstration
Authors: Rueckner Wolfgang , Papaliolios Costas
Published: July 2002

An experiment is described in which the effect of instrument aperture size on resolution is easily demonstrated. Using diffraction as a tool rather than a limit to resolution, one can further demonstrate the possibility of detecting the presence of more than one object, even when the instrument cannot resolve the objects.
Resonance properties of the vocal folds: In vivo laryngoscopic investigation of the externally excited laryngeal vibrations
Authors: Švec Jan G. , Horáček Jaromı́r , Šram František , Veselý Jan
Published: July 2002

The study presents the first attempt to investigate resonance properties of the living vocal folds by means of laryngoscopy. Laryngeal vibrations were excited via a shaker placed on the neck of a male subject and observed by means of videostroboscopy and videokymography (VKG). When the vocal folds were tuned to the phonation frequency of 110 Hz and sinusoidal vibration with sweeping frequency (in the range 50–400 Hz) was delivered to the larynx, three clearly pronounced resonance peaks at frequencies around 110, 170, and 240 Hz were identified in the vocal fold tissues. Different modes of vibration of the vocal folds, observed as distinct lateral-medial oscillations with one, two, and three half-wavelengths along the glottal length, respectively, were associated with these resonance frequencies. At the external excitation frequencies below 100 Hz, vibrations of the ventricular folds, aryepiglottic folds and arytenoid cartilages were dominant in the larynx.
Localization of brief sounds: Effects of level and background noise
Authors: Macpherson Ewan A. , Middlebrooks John C.
Published: July 2002

Listeners show systematic errors in vertical-plane localization of wide-band sounds when tested with brief-duration stimuli at high intensities, but long-duration sounds at any comfortable level do not produce such errors. Improvements in high-level sound localization associated with increased stimulus duration might result from temporal integration or from adaptation that might allow reliable processing of later portions of the stimulus. Free-field localization judgments were obtained for clicks and for 3- and 100-ms noise bursts presented at sensation levels from 30 to 55 dB. For the brief (clicks and 3-ms) stimuli, listeners showed compression of elevation judgments and increased rates and unusual patterns of front/back confusion at sensation levels higher than 40–45 dB. At lower sensation levels, brief sounds were localized accurately. The localization task was repeated using 3-ms noise burst targets in a background of spatially diffuse, wide-band noise intended to pre-adapt the system prior to the target onset. For high-level targets, the addition of background noise afforded mild release from the elevation compression effect. Finally, a train of identical, high-level, 3-ms bursts was found to be localized more accurately than a single burst. These results support the adaptation hypothesis.
Optimum near-field performance of microphone arrays subject to a far-field beampattern constraint
Authors: Ryan James G. , Goubran Rafik A.
Published: July 2002

This article addresses the problem of maximizing the near-field gain of a microphone array subject to a constraint on the far-field beampattern. The problem arises when acquiring speech from a near-field talker in the presence of a strong source of interference located farther from the array. When the angles of incidence from the near-field target and the far-field interference are identical, enforcing a null constraint in the interference direction reduces array gain and robustness. This article shows how to mitigate this effect by selection of the constrained response level. A suitable selection is to force the beampattern in the interference direction to be proportional to the unconstrained beampattern. The proportionality constant can then be used to trade off interference reduction and array gain. Specific numerical examples are provided.
Estimation of broadband acoustic power due to rib forces on a reinforced panel under turbulent boundary layer-like pressure excitation. II. Applicability and validation
Authors: Rumerman M. L.
Published: July 2002

The previous paper showed that, when the attachment forces on a rib-reinforced panel subjected to turbulent boundary layer excitation can be considered to radiate independently, the rib-related acoustic power in a broad (e.g., one-third octave) frequency band can be estimated as the product of the average mean squared force, the real part of the radiation admittance of an attachment force, and the number of ribs. This paper shows that the radiation condition is always approximated when the acoustic wavelength is less than twice the rib spacing of a periodically reinforced panel, and generally applies at lower frequencies where the acoustic wavelength is less than four times the rib spacing. The procedure is used to estimate the broadband acoustic power radiated per rib of an infinite periodically reinforced membrane and plate in water, and the results are shown to agree with those of “exact” calculations.
Pole contribution to the field reflected by sand layers
Authors: Allard Jean-François , Henry Michel , Tizianel Julian , Nicolas Jean , Miki Yasushi
Published: July 2002

Measurements of the reflection coefficient at oblique incidence and for inhomogeneous waves are presented for layers of sand having a large flow resistivity and different thicknesses. The dependence of the reflection coefficient on the angle of incidence is different for layers of small thickness and semi-infinite layers, due to the influence of a pole which is related to an ordinary guided wave in the first case, and the Zenneck wave in the second case. Simulations indicate that the amplitude of the Zenneck wave can be measured for small source receiver distances, allowing a simple evaluation in situ of the surface impedance. The same method can be used with the ordinary surface wave for thin layers.
Acoustic scattering from two junctions in a rectangular waveguide
Authors: Kwon Jae Y. , Park Hyun H. , Eom Hyo J.
Published: July 2002

Acoustic scattering from two junctions in a rectangular waveguide is studied. Fourier transform and mode matching are used to represent the scattered wave and the simultaneous equations for the modal coefficients are formulated. The residue calculus is utilized to obtain a solution to the simultaneous equations in fast-converging series. Numerical evaluation shows the behaviors of transmission and reflection in terms of the junction geometry and operating frequency.
On inferring speed of sound in aquatic organisms
Authors: Ye Zhen , McClatchie Sam
Published: July 2002

A previous formula used for inferring speed of sound in marine organisms is considered and compared with the result from a wave scattering theory. Comparison indicates that there exists a difference between the two results, and the difference increases with the relative sound-speed contrast, and with the ratio between the dimension of animals and the acoustic wavelength. However, it is shown analytically that in the Rayleigh scattering regime and when the mass density difference between the target organisms and the medium is negligible that the earlier formula can be recovered by the result from the wave scattering theory, thereby providing a further physical and mathematical basis to the previous formula.
Effectiveness of intermittent and continuous acoustic stimulation in preventing noise-induced hearing and hair cell loss
Authors: White David R. , Boettcher Flint A. , Miles Lesa R. , Gratton Michael Anne
Published: July 2002

Resistance to noise-induced hearing loss (NIHL) was studied in gerbils exposed either to intermittent or continuous low-level noise prior to an intense noise. Auditory-evoked brainstem response (ABR) thresholds, distortion product otoacoustic emissions (DPOAEs), Q10 dB values from compound action potential (CAP) tuning curves, and outer hair cell (OHC) loss were measured for each group. Subjects were exposed to A-weighted noise (octave band noise centered at 2 kHz) on an intermittent (80 dB, 6 h/day) or continuous schedule (74 dB, 24 h/day) for 10 days, allowed to rest in quiet for 2 days, then exposed to intense A-weighted noise (107 dB, 24 h/day) for 2 days. A “noise-only” group was exposed only to the intense noise. Gerbils exposed in both the “intermittent” and “continuous” groups had less (15–30 dB) temporary threshold shift (TTS) than those in the noise-only group. In addition, the continuous group had less (10–15 dB) permanent threshold shift (PTS) than the other groups. These data suggest that resistance to NIHL is evident in both the intermittent and continuous groups when TTS is measured, but resistance to PTS is afforded only by the continuous paradigm. Both paradigms decreased OHC loss as compared to the noise-only group, with the continuous paradigm being most effective. However, neither paradigm conserved DPOAE amplitudes or tuning curve Q10 dB values relative to the noise-only group.
Real-time wave separation in a cylindrical pipe with applications to reflectometry and echo-cancellation
Authors: Guerard Jean , Boutillon Xavier
Published: July 2002

Precise control of the acoustical pressure all along a pipe requires that backward and forward propagating waves are separated in real time. This has been achieved by means of an array of up to five microphones, a high-precision analog calculation, and a real-time numerical post-treatment. The separation factor exceeds 40 dB over several kHz, when special attention to intercalibration issues and to the realization of the analog part is given. The theoretical limit at high frequencies has been reached experimentally. The advantage of a partial analog treatment over a fully numerical one will be discussed. One application consists in reflectometry (and consequently, impedancemetry) without use of the long pipe normally required. Associated with a real-time DSP processor (TMS 320C30), wave separation also permits one to efficiently control the wave reflected by one end. This is done with only one loudspeaker, whose transfer function has been inverted and implemented in the DSP as an IIR filter. This approach of active-control differs from adaptative procedures. Finally, a musical application of the system to a hybrid wind instrument will be presented. [Work supported in part by the French Ministry of Culture.]
Adapting to supernormal auditory localization cues. II. Constraints on adaptation of mean response
Authors: Shinn-Cunningham Barbara G. , Durlach Nathaniel I. , Held Richard M.
Published: July 2002

A series of experiments was performed in which subjects were trained to interpret auditory localization cues arising from locations different from their normal spatial positions. The exact pattern of mean response to these alterations (as a function of time) was examined in order to begin to develop a quantitative model of adaptation. Mean responses were roughly proportional to the normal position associated with the localization cues presented. As subjects adapted, the best-fit slope (relating mean response and normal position) changed roughly exponentially with time. The exponential rate and adaptation asymptote were found for each subject in each experiment, as well as the rate and asymptote of readaptation to normal cues. The rate of adaptation does not show any statistical dependence on experimental conditions; however, the asymptote of the best-fit slope varied with the strength of the transformation used in each experiment. This result is consistent with the hypothesis that subjects cannot adapt to a nonlinear transformation of auditory localization cues, but instead adapt to a linear approximation of the transformation. Over time, performance changes exponentially towards the best-fit linear approximation for the transformation used in a particular experiment, and the rate of this adaptation does not depend upon the transformation employed.
The high-frequency asymptotic description of pulses radiated by a circular normal transducer into an elastic half-space
Authors: Gridin Dmitri , Fradkin Larissa Ju.
Published: July 2002

A new method for simulating the propagation of pulses radiated by a circular normal ultrasonic transducer which is directly coupled to a homogeneous and isotropic elastic half-space is proposed. Both nonuniform and uniform high-frequency asymptotics inside geometrical regions as well as boundary layers (penumbra, an axial region, and a vicinity of the critical rays) have been used to describe the transient field by means of harmonic synthesis. The nonuniform asymptotic formulas involving elementary or well-known special functions elucidate the physics of the problem and give explicit dependence of the radiated waves upon the model parameters. The formulas are applicable in the radiating near field which is the near-field with the evanescent wave zone excluded. The code based on the uniform asymptotics has been tested in all regions against an exact numerical solution. It is orders of magnitude faster, but in many realistic cases the accuracy does not suffer. The limits of applicability of the model have been established.
An acoustical study of sound production in biphonic singing, Xöömij
Authors: Adachi Seiji , Yamada Masashi
Published: July 2002

A theory that the high melody pitch of biphonic singing, Xöömij, is produced by the pipe resonance of the rear cavity in the vocal tract is proposed. The front cavity resonance is not critical to the production of the melody pitch. This theory is derived from acoustic investigations on several three-dimensional shapes of a Xöömij singer’s vocal tract measured by magnetic resonance imaging. Four different shapes of the vocal tract are examined, with which the melody pitches of F6, G6, A6, and C7 are sung, along with the F3 drone of a specific pressed voice. The second formant frequency calculated from each tract shape is close to the melody pitch within an error of 36 cents. Sounds are synthesized by convolving a glottal source waveform provided by the Rosenberg model with transfer functions calculated from the vocal tract shapes. Two pitches are found to be successfully perceived when the synthesized sounds are listened to. In a frequency range below 2 kHz, their spectra have a strong resemblance to those of the sounds actually sung. The synthesized sounds, however, fail to replicate the harmonic clustering at 4–5 kHz observed in the actual sounds. This is speculated to originate from the glottal source specific to the “pressed” timbre of the drone.
Effect of stimulation rate on phoneme recognition by Nucleus-22 cochlear implant listeners
Authors: Fu Qian-Jie , Shannon Robert V.
Published: July 2002

This study investigated the effect of pulsatile stimulation rate on medial vowel and consonant recognition in cochlear implant listeners. Experiment 1 measured phoneme recognition as a function of stimulation rate in six Nucleus-22 cochlear implant listeners using an experimental four-channel continuous interleaved sampler (CIS) speech processing strategy. Results showed that all stimulation rates from 150 to 500 pulses/s/electrode produced equally good performance, while stimulation rates lower than 150 pulses/s/electrode produced significantly poorer performance. Experiment 2 measured phoneme recognition by implant listeners and normal-hearing listeners as a function of the low-pass cutoff frequency for envelope information. Results from both acoustic and electric hearing showed no significant difference in performance for all cutoff frequencies higher than 20 Hz. Both vowel and consonant scores dropped significantly when the cutoff frequency was reduced from 20 Hz to 2 Hz. The results of these two experiments suggest that temporal envelope information can be conveyed by relatively low stimulation rates. The pattern of results for both electrical and acoustic hearing is consistent with a simple model of temporal integration with an equivalent rectangular duration (ERD) of the temporal integrator of about 7 ms.
On reconstruction of acoustic pressure fields using the Helmholtz equation least squares method
Authors: Wu Sean F.
Published: July 2002

This paper presents analyses and implementation of the reconstruction of acoustic pressure fields radiated from a general, three-dimensional complex vibrating structure using the Helmholtz equation least-squares (HELS) method. The structure under consideration emulates a full-size four-cylinder engine. To simulate sound radiation from a vibrating structure, harmonic excitations are assumed to act on arbitrarily selected surfaces. The resulting vibration responses are solved by the commercial FEM (finite element method) software I-DEAS. Once the normal component of the surface velocity distribution is determined, the surface acoustic pressures are calculated using standard boundary element method (BEM) codes. The radiated acoustic pressures over several planar surfaces at certain distances from the source are calculated by the Helmholtz integral formulation. These field pressures are taken as the input to the HELS formulation to reconstruct acoustic pressures on the entire source surface, as well as in the field. The reconstructed acoustic pressures thus obtained are then compared with benchmark values. Numerical results demonstrate that good agreements can be obtained with relatively few expansion functions. The HELS method is shown to be very effective in the low-to-mid frequency regime, and can potentially become a powerful noise diagnostic tool.
Yield Stress Master Curves for Various Polymers below Their Glass Transition Temperatures
Authors: Lohr Jerome J.
Published: July 2002

Yield stress master curves are presented for poly(methyl methacrylate), polystyrene, polyvinyl chloride, and polyethylene terephthalate. Tensile yield stress was measured at strain rates varying from 0.003 in./in./min to 300 in./in./min and at temperatures varying from approximately 15°C above the glass transition temperature T0 to at least 100°C below T0. The resultant yield, or in the brittle temperature range, failure stress, when plotted as a function of logarithm of strain rate, has been shifted laterally to construct a yield stress master curve similar in concept to the well-known stress relaxation master curve. These master curves cover from 12 to 18 decades of shifted strain rate. The master curve for each material has a characteristic slope which leads, in each case, to a simple equation relating yield stress to strain rate and temperature and is applicable for temperatures from T0 to approximately 100°C below T0. The temperature-dependent shift factors aT of each material were determined for both yield stress and stress relaxation over the temperature range. Comparison of these aT curves shows that in both the ductile and brittle temperature ranges of each material, the shape of the yield stress and stress relaxation aT curves are very similar. However, the absolute magnitude of the change with temperature can be substantially different. Two possible explanations for this difference are offered.
The Inflation of Axially Symmetric Membranes by Linearly Varying Hydrostatic Pressure
Authors: Yu L. K. , Valanis K. C.
Published: July 2002

This investigation represents the application of the theory of large deformation of elastic membranes to the problem of the inflation of an axially symmetric membrane by a linearly varying hydrostatic pressure. The membrane considered here is made of neo-Hookean material. Under the assumption of very large deformation, it is shown that the stress resultants on the middle surface of the membrane are everywhere equal and constant. The problem is then reduced to a purely kinematic one. The governing equation is found to be nonlinear integral equation of the Volterra type. Further study of the problem shows that, irrespective of their initial configurations, axially symmetric membranes tend to deform to an identical shape under the present system of deforming forces. The exact analytical solution of the nonlinear integral equation has not been found. A computer program has therefore been developed to generate a numerical solution describing the deformed shape when the pressure is exerted by various types of fluids with different weight densities.
Construction of a Strain-Energy Function for an Isotropic Elastic Material
Authors: Fong Jeffrey T. , Penn Robert W.
Published: July 2002

Experimental data on the volume changes accompanying simple tension of peroxide vulcanizates of natural gum rubber, as first reported by Penn in Trans. Soc. Rheol., 14, 509 (1970), are further interpreted within the framework of the theory of a hyperelastic material. Motivated by the formal connection between a hyperelastic material and a nonlinear viscoelastic fluid (Trans. Soc. Rheol., 9, 27 (1965)), and a mathematical result on the decomposition of the scalar potential of that fluid (Z. Angew. Math. Phys. 23, 780 (1972)), the interpretation of Penn's data leads to an explicit construction of a strain-energy function for rubbery materials: W(I1,I2,I3)=C1(I1−3)+C2(I2−3)+H̄(I1,I2)(I3−1)+18K(I3−1)2.