bluuebunny/crossref_metadata_2025 huggingface dataset:
Nup98 Is a Mobile Nucleoporin with Transcription-dependent Dynamics
Authors: Griffis Eric R. , Altan Nihal , Lippincott-Schwartz Jennifer , Powers Maureen A.
Published: July 2002

Nucleoporin 98 (Nup98), a glycine-leucine-phenylalanine-glycine (GLFG) amino acid repeat-containing nucleoporin, plays a critical part in nuclear trafficking. Injection of antibodies to Nup98 into the nucleus blocks the export of most RNAs. Nup98 contains binding sites for several transport factors; however, the mechanism by which this nucleoporin functions has remained unclear. Multiple subcellular localizations have been suggested for Nup98. Here we show that Nup98 is indeed found both at the nuclear pore complex and within the nucleus. Inside the nucleus, Nup98 associates with a novel nuclear structure that we term the GLFG body because the GLFG domain of Nup98 is required for targeting to this structure. Photobleaching of green fluorescent protein-Nup98 in living cells reveals that Nup98 is mobile and moves between these different localizations. The rate of recovery after photobleaching indicates that Nup98 interacts with other, less mobile, components in the nucleoplasm. Strikingly, given the previous link to nuclear export, the mobility of Nup98 within the nucleus and at the pore is dependent on ongoing transcription by RNA polymerases I and II. These data give rise to a model in which Nup98 aids in direction of RNAs to the nuclear pore and provide the first potential mechanism for the role of a mobile nucleoporin.
Symplekin, a Constitutive Protein of Karyo- and Cytoplasmic Particles Involved in mRNA Biogenesis inXenopus laevisOocytes
Authors: Hofmann Ilse , Schnölzer Martina , Kaufmann Isabelle , Franke Werner W.
Published: July 2002

Symplekin is a dual location protein that has been localized to the cytoplasmic plaques of tight junctions but also occurs in the form of interchromatin particles in the karyoplasm. Here we report the identification of two novel and major symplekin-containing protein complexes in both the karyo- and the cytoplasm of Xenopus laevis oocytes. Buffer-extractable fractions from the karyoplasm of stage IV–VI oocytes contain an 11S particle, prepared by immunoselection and sucrose gradient centrifugation, in which symplekin is associated with the subunits of the cleavage and polyadenylation specificity factor (CPSF). Moreover, in immunofluorescence microscopy nuclear symplekin colocalizes with protein CPSF-100 in the “Cajal bodies.” However, symplekin is also found in cytoplasmic extracts of enucleated oocytes and egg extracts, where it occurs in 11S as well as in ca. 65S particles, again in association with CPSF-100. This suggests that, in X. laevis oocytes, symplekin is possibly involved in both processes, 3′-end processing of pre-mRNA in the nucleus and regulated polyadenylation in the cytoplasm. We discuss the possible occurrence of similar symplekin-containing particles involved in mRNA metabolism in the nucleus and cytoplasm of other kinds of cells, also in comparison with the nuclear forms of other dual location proteins in nuclei and cell junctions.
Measurement of the effectiveness of transitive sequence comparison, through a third 'intermediate' sequence.
Authors: Gerstein M
Published: July 2002

MOTIVATION: Transitive sequence matching expands the scope of sequence comparison by re-running the results of a given query against the databank as a new query. This sometimes results in the initial query sequence (Q) being related to a final match (M) indirectly, through a third, 'intermediate' sequence (Q --> I --> M ). This approach has often been suggested as providing greater sensitivity in sequence comparison; however, it has not yet been possible to gauge its improvement precisely. RESULTS: Here, this improvement is comprehensively measured by seeing what fraction of the known structural relationships transitive sequence matching can uncover beyond that found by normal pairwise comparison (i.e. direct linkage). The structural relationships are taken from a well-characterized test set, the scop classification of protein structure. Specifically, 2055 known structural similarities (called 'pairs') between distantly related proteins constitute the basic test set. To make the measurement of transitive matching properly, special data sets, called 'baseline sets', are derived from this. They consist of pairs of sequences that have a clear structural relationship that cannot be found by normal sequence comparison (i.e. they cannot be directly linked). Specifically, using standard sequence comparison protocols (FASTA with an e-value cut-off of 0. 001), it is found that the baseline set consists of 1742 pairs. A third intermediate sequence can link 86 of these indirectly (5%), where this third sequence is drawn from the entire, current universe of protein sequences. The number of false positives is minimal. Furthermore, when one considers only the relationships within the test set that correspond to a close structural alignment, the coverage increases considerably. In particular, 862 of the baseline set pairs fit to better than 2.6 A RMS, and transitive matching can find 62 of these (9%). AVAILABILITY: All the test data, including precise similarity values calculated from structural alignment, are available in tabular format over the Web from http://bioinfo.mbb. yale.edu/align. CONTACT: Mark.Gerstein@yale.edu
Bayesian inference on biopolymer models.
Authors: Liu J S , Lawrence C E
Published: July 2002

MOTIVATION: Most existing bioinformatics methods are limited to making point estimates of one variable, e.g. the optimal alignment, with fixed input values for all other variables, e.g. gap penalties and scoring matrices. While the requirement to specify parameters remains one of the more vexing issues in bioinformatics, it is a reflection of a larger issue: the need to broaden the view on statistical inference in bioinformatics. RESULTS: The assignment of probabilities for all possible values of all unknown variables in a problem in the form of a posterior distribution is the goal of Bayesian inference. Here we show how this goal can be achieved for most bioinformatics methods that use dynamic programming. Specifically, a tutorial style description of a Bayesian inference procedure for segmentation of a sequence based on the heterogeneity in its composition is given. In addition, full Bayesian inference algorithms for sequence alignment are described. AVAILABILITY: Software and a set of transparencies for a tutorial describing these ideas are available at http://www.wadsworth.org/res&res/bioinfo/
Pharmacokinetics of the 8-methoxyquinolone, moxifloxacin: tissue distribution in male rats
Authors: Siefert H. M. , Kohlsdorfer C. , Steinke W. , Witt A.
Published: July 2002

BAY 12-8039 (moxifloxacin-HCl) and 14C-labelled BAY 12-8039 were administered to male rats as single iv and oral doses of 4.6 and 5.0 mg/kg bodyweight respectively. The distribution of substance-associated radioactivity in the body was investigated by whole-body autoradiography. The concentrations of the unchanged compound in plasma, skin suction blister fluid and lung tissue were determined by HPLC. Whole-body autoradiography revealed distinctly higher concentrations of radioactivity in the gastrointestinal tract, urinary bladder and in most organs and tissues (e.g. kidneys, liver, spleen, lungs, various glands, cartilaginous tissues and in melanin-containing structures located in the eye, meninges and hair follicles of pigmented skin) than in blood. Radioactivity crossed the blood- brain barrier only to a small extent. The results show a high tissue affinity and a rapid and homogeneous distribution of radioactivity from blood to organs or tissues. No relevant difference in the distribution of radioactivity was found following iv and oral administration. After iv and oral dosing similar concentrations of the unchanged compound were determined in skin suction blister fluid and plasma. The concentrations of the unchanged compound in lung tissue were about three times higher than those in plasma following both iv and oral administration. The concentration–time courses for moxifloxacin in plasma and lung tissue were parallel.
Magma Mixing and Crustal Recycling Recorded in Ternary Feldspar from Compositionally Zoned Peralkaline Ignimbrite ‘A’, Gran Canaria, Canary Islands
Authors: TROLL VALENTIN R. , SCHMINCKE HANS-ULRICH
Published: July 2002

Miocene Ignimbrite ‘A’ on Gran Canaria contains three compositional endmember fiamme types(two rhyolites and one trachyte) each of which crystallized distinct feldspar. Various textural and compositional criteria are interpreted as reflecting a complex scenario within the magma chamber in which the crystals formed. About 25–30% of the feldspar phenocrysts contain evidence for magma mixing in the form of (1) partial to severe dissolution–resorption rims, (2) distinct zones of drastically different compositions and (3) overgrowth textures on formerly resorbed crystals. Four major types of zoning in the oligoclase to anorthoclase feldspars of ignimbrite ‘A’ include a normal and a reversely zoned type and two complexly zoned types. The feldspars with normal and reverse zonation show only minor compositional amplitudes between individual zones (ΔAb, Or ∼4%), whereas the complexly zoned types show compositional differences between zones of up to 18 mol % Ab and 20 mol % Or and are commonly associated with an internal dissolution surface. Complex zoning with large compositional amplitudes and dissolution textures is taken as evidence of crystal movements within the magma and across compositional boundaries between magma batches. A multiple ‘step-cycle’ model, involving growth and transport of a crystal into another magma batch and its return to the original host magma, is suggested by the data. Moreover, feldspars from one rhyolite compositional group are found to be substantially elevated in δ18O, suggesting an input of a high δ18O component to this rhyolite. The other endmember rhyolite appears to be related to the endmember trachyte by mainly crystal fractionation of anorthoclase feldspar. This observation is consistent with trace element and rare earth element concentrations for the magma endmembers and their feldspars, where contamination led to a depletion in incompatible trace elements and light rare earth elements in the contaminated rhyolite and its feldspar phenocrysts. We suggest that the combination of textural and compositional variation in ternary feldspar of peralkaline rhyolitic systems is well suited to reconstruct dynamic processes such as magma mixing and contamination in evolving rhyolitic magma chambers.
Thirty–six views of T–cell recognition
Authors: Krummel Matthew , Wülfing Christoph , Sumen Cenk , Davis Mark M.
Published: July 2002

While much is known about the signalling pathways within lymphocytes that are triggered during activation, much less is known about how the various cell surface molecules on T cells initiate these events. To address this, we have focused on the primary interaction that drives T–cell activation, namely the binding of a particular T–cell receptor (TCR) to peptide–MHC ligands, and find a close correlation between biological activity and off–rate; that is, the most stimulatory TCR ligands have the slowest dissociation rates. In general, TCRs from multiple histocompatibility complex (MHC) class–II–restricted T cells have half–lives of 1–11s at 25°C, a much narrower range than found with antibodies and suggesting a strong selection for an optimum dissociation rate. TCR ligands with even faster dissociation rates tend to be antagonists. To observe the effects of these different ligands in their physiological setting, we made gene fusions of various molecules with green fluorescent protein (GFP), transfected them into the relevant lymphocytes, and observed their movements during T–cell recognition using multicolour video microscopy. We find that clustering of CD3ζ–GFP and CD4–GFP on the T cell occurs concomitantly or slightly before the first rise in calcium by the T cell, and that various GFP–labelled molecules on the B–cell side cluster shortly thereafter (ICAM–1, class II MHC, CD48), apparently driven by T–cell molecules. Most of this movement towards the interface is mediated by signals through the co–stimulatory receptors, CD28 and LFA–1, and involves myosin motors and the cortical actin cytoskeleton. Thus, we have proposed that the principal mechanism by which co–stimulation enhances T–cell responsiveness is by increasing the local density of T–cell activation molecules, their ligands and their attendant signalling apparatus. In collaboration with Michael Dustin and colleagues, we have also found that the formation and stability of the TCR–peptide–MHC cluster at the centre of the interaction cap between T and B cells is highly dependent on the dissociation rate of the TCR and its ligand. Thus, we are able to link this kinetic parameter to the formation of a cell surface structure that is linked to and probably causal with respect to T–cell activation.
Mouse BAC Ends Quality Assessment and Sequence Analyses
Authors: Zhao Shaying , Shatsman Sofiya , Ayodeji Bola , Geer Keita , Tsegaye Getahun , Krol Margaret , Gebregeorgis Elizabeth , Shvartsbeyn Alla , Russell Daniel , Overton Larry , Jiang Lingxia , Dimitrov George , Tran Kevin , Shetty Jyoti , Malek Joel A. , Feldblyum Tamara , Nierman William C. , Fraser Claire M.
Published: July 2002

A large-scale BAC end-sequencing project at The Institute for Genomic Research (TIGR) has generated one of the most extensive sets of sequence markers for the mouse genome to date. With a sequencing success rate of >80%, an average read length of 485 bp, and ABI3700 capillary sequencers, we have generated 449,234 nonredundant mouse BAC end sequences (mBESs) with 218 Mb total from 257,318 clones from libraries RPCI-23 and RPCI-24, representing 15× clone coverage, 7% sequence coverage, and a marker every 7 kb across the genome. A total of 191,916 BACs have sequences from both ends providing 12× genome coverage. The average Q20 length is 406 bp and 84% of the bases havephred quality scores ≥ 20. RPCI-24 mBESs have more Q20 bases and longer reads on average than RPCI-23 sequences. ABI3700 sequencers and the sample tracking system ensure that > 95% of mBESs are associated with the right clone identifiers. We have found that a significant fraction of mBESs contains L1 repeats and ∼48% of the clones have both ends with ≥ 100 bp contiguous unique Q20 bases. About 3% mBESs match ESTs and > 70% of matches were conserved between the mouse and the human or the rat. Approximately 0.1% mBESs contain STSs. About 0.2% mBESs match human finished sequences and > 70% of these sequences have EST hits. The analyses indicate that our high-quality mouse BAC end sequences will be a valuable resource to the community.
Measurement of half‐value layer in x‐ray CT: A comparison of two noninvasive techniques
Authors: Kruger Randell L. , McCollough Cynthia H. , Zink Frank E.
Published: July 2002

The purpose of this paper is to determine the accuracy and reproducibility of two noninvasive methods of measuring half‐value layer (HVL), ring and localization, compared with an invasive technique (suspending tube rotation). The ring method uses concentric aluminum rings about a CTDI ionization chamber at isocenter. Data were acquired using axial CT protocols (rotating x‐ray tube, stationary patient table). The localization technique uses square aluminum sheets secured to the gantry shroud to filter the radiation beam, and a CTDI chamber suspended externally at isocenter. Data were acquired using localization image protocols (stationary x‐ray tube, moving patient table). The invasive technique was similar to the localization technique except that the ion chamber was placed on the patient table and the tube rotation disabled using service software. Data for all techniques were collected on the same CT system. Independent data sets were collected to determine reproducibility. Sensitivity to ionization chamber lateral displacement from isocenter was investigated. Measured HVLs (mm aluminum, mean±std, were 7.19±0.03 (ring); 7.17±0.04 (localization); and 7.24±0.02 (service mode), which were not significantly different Displacing the chamber from isocenter changes the HVL, depending on the bow‐tie filter, by as much as 5 mm aluminum. Aluminum filter to ion chamber distances of 25–35 cm provided accurate results. Both noninvasive techniques were accurate and reproducible at isocenter. However, the measured HVL was dependent upon the bow‐tie filter and the lateral displacement of the ionization chamber with respect to isocenter. Greater than 2 cm off of isocenter, the ring technique did not provide accurate HVL measurements.
The skeletal calcium/phosphorus ratio: A new in vivo method of determination
Authors: Fountos George , Yasumura Seiichi , Glaros Dimitris
Published: July 2002

We describe a new method for assessing the Ca/P ratio of bone in vivo using γ‐ray photon absorptiometry. The theoretical approach of the method and the estimation of the variance are presented. Two radiation sources, Gd‐153 (100 keV), and I‐125 (27.5 keV), and a germanium detector were used to determine this ratio. Measurements were made on bone phantoms with different Ca/P ratios; also, the ratio was measured on lamb and sheep tibias, rabbit tibias, and human fingers. Since the accuracy of the method is affected by the amount of fat and collagen in the measurement field, the effect of collagen and fat on the measurements also was investigated. In all cases, the precision of the method, expressed as the coefficient of variation (CV): was near to the theoretical one, ranging from 1.8% to 3.2%. For human fingers, the CV was 3.2%, a value near to the theoretical 2.9% with a dose to the skin ranging from 0.044 to 0.066 mGy, depending on the width of the finger.
A schema for estimating absorbed dose to organs following the administration of radionuclides with multiple unstable daughters: A matrix approach
Authors: Hamacher K. A. , Sgouros G.
Published: July 2002

The dosimetry of alpha particle emitters requires that all decays, including those of unstable intermediates be included in the calculation. Such calculations are complicated by the potential differential biologic distribution of each of the intermediates. In this work we present a formalism which will account for the known biodistribution factors of the daughters and the resulting effective biodistribution which will depend upon the site at which the parent radionuclide decays. The number of decays or cumulated activity of a daughter radionuclide present in a particular tissue is estimated using a probability matrix which describes the likelihood of daughter decay in a particular tissue as a function of the decay site of the parent. An example of three initial compartments is provided to illustrate the use of this formalism. Such modeling may be used to evaluate the feasibility of using radionuclides whose decay includes alpha‐emitting intermediates. Model validation and refinement will require an assessment of the fate of free, alpha‐emitting intermediates in various biological milieus.
Mirage mirror on the wall
Authors: Kosa T. , Palffy-Muhoray P.
Published: July 2002

We discuss mirages formed near a sun-heated wall, and consider the underlying physics. The temperature and refractive index variations in air near the wall are estimated, and a simple approximate picture of ray propagation is presented. Estimates of the thermal decay length and ray curvature are compared with experimental observations.
The role of the mora in the timing of spontaneous Japanese speech
Authors: Warner Natasha , Arai Takayuki
Published: July 2002

This study investigates whether the mora is used in controlling timing in Japanese speech, or is instead a structural unit in the language not involved in timing. Unlike most previous studies of mora-timing in Japanese, this article investigates timing in spontaneous speech. Predictability of word duration from number of moras is found to be much weaker than in careful speech. Furthermore, the number of moras predicts word duration only slightly better than number of segments. Syllable structure also has a significant effect on word duration. Finally, comparison of the predictability of whole words and arbitrarily truncated words shows better predictability for truncated words, which would not be possible if the truncated portion were compensating for remaining moras. The results support an accumulative model of variance with a final lengthening effect, and do not indicate the presence of any compensation related to mora-timing. It is suggested that the rhythm of Japanese derives from several factors about the structure of the language, not from durational compensation.
Generation of articulatory movements by using a kinematic triphone model
Authors: Okadome Takeshi , Honda Masaaki
Published: July 2002

The method described here predicts the trajectories of articulatory movements for continuous speech by using a kinematic triphone model and the minimum-acceleration model. The kinematic triphone model, which is constructed from articulatory data obtained from experiments using an electro-magnetic articulographic system, is characterized by three kinematic features of a triphone and by the intervals between two successive phonemes in the triphone. After a kinematic feature of a phoneme in a given sentence is extracted, the minimum-acceleration trajectory that coincides with the extremum of the time integral of the squared magnitude of the articulator acceleration is formulated. The calculation of the minimum acceleration requires only linear computation. The method predicts both the qualitative features and the quantitative details of experimentally observed articulation.
Kinematics of normal lingual diadokokinesis
Authors: Flanagan Kevin P. , Dembowski James S.
Published: July 2002

Speech-language clinicians use diadochokinetic (DDK) tasks as a behavioral measure of the status of the speech production system. The articulator kinematics of these repetitive syllable productions has been relatively little studied (most studies of speech DDK have been acoustic). As a result, many clinicians misunderstand the relationship between syllable rate and movement parameters, such as rate of articulator movement and range of articulator movement. For example, clinicians assume that because ‘‘kuh’’ syllable repetitions are relatively slow, tongue dorsum movements must be slow. However, Westbury and Dembowski [Ann. Bull. RILP No. 27 (1993)] showed that the tongue dorsum may produce larger and faster movements than other tongue points (such as the tongue tip). Therefore, syllable repetition rates may not reflect movement speeds for individual articulator points. This study replicates and extends these findings, using a larger speaker sample encompassing a wider age range. The goal of this study is to further clarify the relationship between articulator speed, range of articulator motion, and syllable rate. That is, it seeks to examine whether syllable rate is related to how quickly the tongue moves or how far the tongue moves. Data are derived from the University of Wisconsin X-ray Microbeam Database.
Acoustic propagation through a low Mach number, stratified flow
Authors: Elisseeff Pierre , Schmidt Henrik
Published: July 2002

Propagation of sound in an oceanic waveguide in the presence of a low Mach number, stratified flow is investigated. Equations for the wave-number integration (WI) and normal-mode (NM) approaches are simultaneously derived in a consistent formulation. At low Mach numbers acoustic azimuthal coupling is negligible and the effect of current can be accounted for by a simple modification of existing WI and NM, codes. Numerical results for low- and high-frequency sources in a simple waveguide show a high degree of agreement between modified versions of OASES and KRAKEN, and confirm previous theoretical results. An approximate modal closed-form solution based on the medium-at-rest mode set is then derived assuming adiabatic propagation (no current-induced mode coupling). Comparison with the modified versions of KRAKEN and OASES shows this assumption breaks down if there is bottom penetration or if the current profile exhibits somewhat sharp variations with respect to depth. An application to matched-field current tomography is eventually presented. Assuming accurate knowledge of the acoustic waveguide, a current velocity of 1.5 m/s can be measured at a range of 2 km with a resolution of 0.2 m/s using a multitone cw signal spanning 200–250 Hz.
The application of a FEM–BEM model to predict acoustic silencer performance and the BEM model to predict vented earmold dynamics
Authors: Choi Chang-Hwan , Royster Larry H. , Ciskowski Robert D.
Published: July 2002

A directly coupled boundary element and finite element model has been applied to the dynamics of acoustic silencers exhibiting flexible surfaces. In this coupled BEM–FEM formulation, the BEM model used a three-node isoparametric triangular linear continuous element to discretize the acoustic cavity. The BEM model was coupled to a flat shell FEM model. The formulated model was then used to predict the performance of various silencer configurations. In a parallel study, the BEM model was used to study the various parameters affecting the performance of vented earmolds coupled to a headset driver and the ear canal. The preliminary findings from this effort will be presented. [See NOISE-CON Proceedings for full paper.]
Measurements of thermoacoustic functions for single uniform pores
Authors: Wilen Larry A.
Published: July 2002

In previous work, a technique to measure the thermoacoustic properties of single pores was described [L. Wilen, J. Acoust. Soc. Am. 101, 1388–1397 (1997)]. By modulating the volume of a pore and measuring the resultant pressure response, the complex compressibility is measured as a function of frequency. Measurements of different lengths of a given pore allow the end effects to be subtracted out. By working down to very low frequencies, a wide range of values for the ratio of the thermal penetration depth to pore size are accessible. This technique will be briefly reviewed, and recent experimental results for pores of various geometries will be compared to the known theory. Experimental results will also be shown for pores not easily treated by analytic theory. Finally, possible applications to full tests of thermoacoustics in a single pore will be discussed. [Work supported by ONR and NSF.]
Numerical study of the performance of an idealized thermoacoustic stack
Authors: Worlikar Aniruddha S. , Knio Omar M. , Klein Rupert
Published: July 2002

The unsteady, thermally stratified flow in the neighborhood of an idealized stack is simulated using a nonlinear two-dimensional model. The model relies on a vorticity-based formulation of the compressible conservation equations in the low-Mach-number and short-stack limits. The action of the acoustic standing wave is represented in terms of oscillating velocity conditions, and heat exchangers are modeled by maintaining the temperature at the cold and hot ends of the stack at fixed, constant values. Simulations are used to visualize the unsteady velocity and temperature fields, and to analyze the dependence of the ‘‘steady-state’’ cooling load on the drive ratio and the length of the heat exchangers. [Work of ASW and OMK supported by the Office of Naval Research. RK is partially supported by Deutsche Forschungsgemeinschaft (DFG).]
Prognostics: What does it mean in condition-based maintenance?
Authors: Nickerson G. W.
Published: July 2002

The machinery condition monitoring community continues its search for the ‘‘Holy Grail’’ of prognostics. The problem is that there is no common agreement on two questions: ‘‘What does the term prognostics mean in this context’’? and ‘‘What must be done to achieve it’’? This paper differentiates ‘‘predictive maintenance’’ (in its generally accepted form) from ‘‘condition-based maintenance’’ (which requires prognostics). A justification for development and implementation of the more advanced and cost-effective condition-based maintenance is presented. A working definition of prognostics for the condition-based maintenance community is proposed. Further, a methodology for setting acceptable false alarm rates for both diagnostics and prognostics is presented to frame the problem for the research community in terms of the application environment, particularly for mission critical equipment. [See NOISE-CON Proceedings for full paper.]
Prognostics for a reciprocating air compressor
Authors: McCarthy Daniel J.
Published: July 2002

The health of a reciprocating air compressor can affect the time of occurrence of valve impacts within the compressor. A computer simulation reveals useful insight into the nature of the timing changes, which provides a basis for automated prognosis of the machine health. As an example, consider that the opening impact of a leaky discharge valve is delayed by an amount proportional to the size of the leak. The effect that the leak has on the efficiency of the compressor can be determined using the simulation, and a threshold for lost efficiency can be tied to the time of occurrence of the valve impact. Using the computer simulation as an aid, the vibration transients generated by the impacts can be clearly identified in the vibration signal measured on the exterior of the compressor. The time of occurrence of the impacts can then be accurately determined from the measured vibration using minimum-phase processing, a sliding exponential window, and statistical curve fitting. [See NOISE-CON Proceedings for full paper.]
Broadband acoustic imaging of breaking waves
Authors: Andrew Rex K. , Farmer David M. , Kirlin R. Lynn
Published: July 2002

An acoustic array was deployed in the near-surface layer in Saanich Inlet, BC, to image breaking waves using only the naturally occurring acoustical radiation in the band (160 and 2000 Hz) from the breaking region. The 15-element array was configured as a horizontal cross with an 8-m aperture, bottom-moored, and positioned nominally 3 m beneath the surface. A novel broadband scheme combined information at six independent frequencies above about 400 Hz to yield unambiguous resolved images. A parametric image analysis shows that the images align closely with the wind and can be observed moving downwind with a speed roughly equal to the dominant phase speed of the wind waves. Absolute power levels are found to be consistent with previously published results. The data also provide inferences regarding the sound generation mechanism at ‘‘collective oscillation’’ frequencies below about 400 Hz. [Work supported by ONR.]
The shelfbreak front PRIMER experiment
Authors: Gawarkiewicz Glen , Pickart Robert , Lynch James F. , Chiu Ching-Sang , Smith Kevin , Miller James H.
Published: July 2002

In July and August 1996, a combined physical oceanography and acoustics experiment was performed in the Mid-Atlantic Bight south of Nantucket Shoals. The purpose of this experiment was to examine coastal frontal variability and its impact on acoustic propagation and imaging. Extensive oceanographic measurements of the experimental region were made. These measurements included: (1) SeaSoar hydrography; (2) moored T, S, and current meter sensors; and (3) satellite infrared imaging of the sea surface temperature. These measurements provided what is believed to be the highest resolution imaging of a shelfbreak frontal region yet obtained. Acoustic measurements in the experimental region included: (1) a three-dimensional tomographic imaging array; and (2) aircraft deployed SUS drop fields. Observations revealed the presence of a strong jet associated with sharp thermal gradients. During this time period, the front was contorted by the presence of a streamer of shelf water moving offshore, which resulted in large thermal gradients in both along the shelf and across the shelf direction. The oceanographic activity produced significant mode coupling in the acoustic signals, leading to large time spreading of the source pulses.
Analysis of internal wave and bottom effects on the acoustic field generated by a towed source during the SWARM95 experiment
Authors: Turgut Altan , Pasewark Bruce H. , Wolf Stephen N. , Orr Marshall , Lynch James F.
Published: July 2002

Thirty-second duration 250- to 375-Hz LFM pulses were transmitted from a towed acoustic transducer to study the effects of internal waves and the sea bottom on an acoustic signal propagating along a 30-km transmission path. The data were taken on the New Jersey continental shelf as a part of the multi-institutional SWARM95 experiment. Environmental data were collected by using CTDs, thermistor strings, a high-frequency acoustic flow visualization system, and a chirp sonar system. Geoacoustic properties of the bottom were inverted from the chirp sonar data with a 1.5-m vertical resolution and 40-m penetration. A deterministic sound speed field in the water column was constructed by imposing the high-frequency visualization measurements on both CTD and thermistor string data. Environmental data indicated that two distinct geological provinces and two major internal wave packets were crossed during the 30-km towed transmission. Using a full-wave broadband PE model, vertical structures of sound field were calculated for comparison to data obtained by a 32-element vertical line receiver array. Preliminary model/data comparisons indicate the dominance of water column effects over the bottom effects. [Work supported by ONR.]
Broadband propagation and azimuthal dependence through internal waves
Authors: Badiey M. , Lynch J. , Orr M. , Tang X. , Wolf S.
Published: July 2002

During the SWARM 95 experiments the out-of-plane broadband acoustic propagations were used to examine the effect of azimuth as well as the frequency dependence on the propagation of an acoustic pulse through internal waves. A highly repeatable source (a 40-in. airgun with center frequency of 75 Hz and bandwidth of 50 Hz) was used at different water depths. The environmental data were measured at the source and at the two receiver arrays located approximately 25–30 km away perpendicular to the main propagation track. It is shown that the dominant energy of the propagation is distributed between the first and the second modes. The transfer of energy among the modes as well as the fluctuations of the field are depth dependent as well as time dependent, which can be related to the internal wave characteristics. The coherence of the field in cross range due to the same source signature is also examined.
Room noise criteria—A new approach at low frequencies
Authors: Hellweg Robert D. , Pei Hsien-sheng (Jason)
Published: July 2002

ANSI S12.2-1995, ‘‘Criteria for Evaluating Room Noise,’’ permits two different sets of criterion curves for evaluating room noise—room criterion (RC) and balanced noise criterion (NCB)—with little guidance as to the selection. These different procedures can have significant impacts on the cost of designs, especially in the low-frequency regions, since the difference in the criteria is more than 10 dB in the 16- and 31-Hz octave bands at lower levels. The authors suggest there are sufficient data to support a modification to ANSI S12.2, resulting in a single evaluation procedure based on the strengths of each of the two existing procedures. The authors suggest establishing room criterion curves for steady noise without abnormal temporal or spectral characteristics, with correction factors for noises with abnormal features. The suggested criteria for steady noise are the NCB curves based on time-average octave band sound pressure levels, and as a starting point, the correction factors for low-frequency tones and fluctuation differences between the NCB and RC curves. Analyses of currently funded research and re-examination of existing cases can determine the exact correction factors and measurement techniques to quantify these abnormal characteristics. A revised ANSI S12.2 could have basic criterion curves for steady, continuous, and broadband room noises, which could be used for design with correction factors to these basic criterion curves for sounds with abnormal characteristics. [See NOISE-CON Proceedings for full paper.]
Issues in design of combustion turbine silencers
Authors: Cummins Jim R.
Published: July 2002

Many power plants now use combustion turbines as their primary power source. Among the major noise sources on combustion turbines are the intake and exhaust. Each of these sources has unique characteristics but a common feature is an in-line silencer to control the noise. In this paper the issues affecting the design and application of silencers on combustion turbines is considered. The primary issues presented are acoustical and include lack of confidence in sound power levels, uncertainties in the application of predicted silencer performance, and the effects of size, geometry, temperature, and flow. While the primary focus is on the exhaust system, some topics related to the inlet are also presented. Other issues and trade-offs concerning pressure drop performance, mechanical survivability, and thermal performance are also presented. Some suggestions for ways to overcome the issues are also presented. [See NOISE-CON Proceedings for full paper.]
Scattering from elastic axi-symmetric objects in a range-dependent waveguide near ocean surfaces
Authors: Werby M. F. , Sidorovskaia N. A.
Published: July 2002

The correct formulation for scattering from objects near an interface is described. The method used to couple the related scattered solution to a range-dependent waveguide is then shown. Calculations for elongated elastic objects such as elastic spheroidal solids and shells are then incorporated into the formulation, and the effect of the imbedding of objects in the waveguide are illustrated, particularly in the vicinity of an ocean surface. [Work sponsored by ONR, the Naval Res. Lab., and the Univ. of New Orleans.]
Vibrations of a two-level underground station
Authors: Kostarev S. A.
Published: July 2002

A method of vibration calculations of a two-level underground station and its transmission to the ground surface is derived and the algorithm is realized as a part of an integrated package UNSONIC 2.1. A two-level station is constructed with typical sizes significantly exceeding the length of bending waves in the separate constructive elements. The lower level in the considered model is on the ground and the base of the upper floor is suspended on the walls of the station. Forces from the moving trains are localized on four railways of both levels. The package of programs developed in the Acoustics Laboratory of the Tunneling Association (Moscow) permits the calculation of all the vibration levels inside the station and tunnels, and on the ground surface in the adjacent area.
Three-dimensional matched-field tracking in shallow water using SWellEx-96 Data
Authors: Orris Gregory J. , Fialkowski Laurie T. , Nicholas Michael , Perkins John S.
Published: July 2002

A three-dimensional version of matched-field tracking (MFT), a generalization of matched-field processing (MFP), is used to locate and track a towed source using a vertical array during SWellEx-96—an experiment conducted off the San Diego coast in May 1996. Archival and in situ environmental data are used as input into a forward propagating adiabatic normal mode (ANM) model and a reciprocal propagating parabolic equation (PE) model to create the three-dimensional replica fields used to compute ambiguity volumes (the three-dimensional generalization of the ubiquitous two-dimensional ambiguity surface). Interaction with variable bathymetry caused by a downward refracting sound-speed profile and shallow water is not sufficient to provide uniqueness of the data and replica fields, thus creating many ambiguities for any given data within the fiducial volume. These ambiguities can be minimized via MFT, which uses source motion to reduce the number and relative magnitude of false ambiguities by averaging the ambiguity functions corresponding to trial source tracks defined by an initial position and velocity vector. As increasing numbers of ambiguity functions are averaged, steady movement within a fluctuating background can be detected.
The acoustics of snapping shrimps
Authors: Au Whitlow W. L. , Banks Kiara
Published: July 2002

With an increased interest in acoustic daylight, the contribution of snapping shrimp noise has drawn considerable attention. These crustaceans are among the major contributors of biological noise in shallow waters of temperate and tropical regions. The shrimp produce sounds by rapidly closing one of their frontal claws, snapping the ends together to generate a loud click. The acoustics of the species Synalpheus paraneomeris was studied by measuring the sound produced by individual shrimp housed in a small cage located 1 m from an H-52 hydrophone. Ten clicks each from 40 specimens were digitized at a 1-MHz sample rate. A low-frequency precursor signature (never reported before), which may be associated with the plunger on one of the claws that directs a water jet forward, was observed. The peak-to-peak source level varied linearly with claw size and body length and had values from 183 to 189 dB re: 1 μPa. The acoustic power produced by a typical snap was calculated to be about 3 W. A typical spectrum was very broad with only a 20-dB difference between the peak at 2–5 kHz and components out to 200 kHz.
Photoacoustic signals from small gas leaks
Authors: Yönak Serdar H. , Dowling David R.
Published: July 2002

In the manufacture of heat exchangers or other devices filled with compressed gases or liquids, efficient detection of leaks is a critical process. Photoacoustics has been used to quickly detect these leaks in an industrial environment. Although this technology can detect leaks as small as 10−6 standard cc/s, it has not been extended to localization or quantification of these leaks. This work aims to resolve these issues. An acoustic source strength based on the Beer-Lambert law and gas diffusion from a point source is developed and used to predict photoacoustic signals. The relationship between photoacoustic signals and leak test parameters, specifically leak rate, modulation frequency, and laser power, are presented. An effective strategy for illuminating the suspected leak area is shown, and leak detection using multiple microphones is discussed. A carbon dioxide laser tuned to 10.6 microns is used as the radiation source with sulfur hexaflouride as the tracer gas. Comparisons are made between theoretical predictions and experimental results. [Work sponsored by Ford Motor Company.]
Holographic analysis of standing sound waves in a resonance tube
Authors: Hughes Russell S. , Russell Daniel A. , Parker David E.
Published: July 2002

Optical holographic interferometry was used to observe standing sound waves in air inside a resonance tube. The resonance tube had a rectangular cross section and was driven by a small loudspeaker at one end. The front face of the resonance tube was constructed of Plexiglas, allowing optical interrogation of the interior of the tube. The object beam of the holographic setup was directed through the Plexiglas and reflected off the back wall. When driven at resonance, the fluctuation in air density at antinodes altered the index of refraction in the tube, causing interference patterns on the resulting hologram. Both real-time and time-averaged holograms were made of the first 15 longitudinal standing wave modes. The first eight modes agree very well with predictions for a closed-closed tube. This talk will focus on the holographic experiment and will demonstrate the visualization of standing sound waves.
New automated microphone reciprocity calibration system and results obtained
Authors: Frederiksen Erling , Christensen Joergen I.
Published: July 2002

Microphone calibration by the reciprocity technique is performed by national and other high-level acoustic calibration laboratories. In the past, the electrical transfer function of coupled pairs of microphones was determined by manual measurements. As such measurements were very time-consuming, only a few calibrations were performed at a rather limited number of frequencies. A new automated measurement system has been developed. This has significantly increased the efficiency of transfer function measurements and extended the practical applications of the reciprocity technique. The uncertainty of voltage ratio measurements is less than 0.02 dB (k=2) between 40 Hz and 30 kHz, while the repeatability is about two times better. These numbers are so low that they have only a minor influence on the resulting uncertainty of laboratory standard microphone calibrations. Today, pressure response calibrations (according to IEC1094-2) can be performed with an uncertainty of 0.02 to 0.04 dB. The probe for measurement of electrical current through the transmitter and the preamplifier for the receiver microphones are both connected via cables. This makes it possible to place the microphones remotely from the main instrument, as required with environmental testing (pressure, temperature) and free-field calibrations. Calibration results obtained with the new system will be presented.
A study of noise and vibration measurements in an engine dynamometer cell using intensity methods
Authors: Padiyar Satish
Published: July 2002

In automobile engine development, the use of dynamometer cell tests has been established as often-times, a reliable and efficient alternative to in-vehicle tests. Engine noise, vibration, and harshness (NVH) characterization involves studying the relationship between the engine dynamics and NVH parameters of interest. In dynamometer cells that have been designed to be fully or partially anechoic in a given frequency range, noise measurements can be made reliably in the designated frequency range, without concern for the effects of reflections from the cell walls. For NVH measurements in dynamometer cells outside the designated anechoic frequency range, engineers and researchers often resort to expensive anechoic enclosures around the engine alone. This paper will discuss the results of the use of intensity techniques for noise measurements, in an attempt to increase the usable frequency range of an engine dynamometer cell for automobile NVH characterization.
Further observations on NCB and RC rumble and hiss criteria for predicting response to sound in rooms
Authors: Tocci Gregory C.
Published: July 2002

At NOISE-CON96 in Seattle, this author presented a paper comparing assessments of 238 actual measured room octave band sound spectra using NC (tangency), NCB, and RC methods. Also determined for these spectra were the presence of excessive rumble and hiss characteristics using the NCB and RC definitions. This paper goes one step further by presenting observations on how well building owner/user subjective judgments correlate with determinations of rumble and hiss using the NCB and RC definitions. [See NOISE-CON Proceedings for full paper.]
Experimental observation of sound propagation through thermal turbulence near a boundary
Authors: Wasier J. , Blanc-Benon Ph. , Juvé D.
Published: July 2002

The statistical properties of an ultrasonic wave that traverses a medium exhibiting temperature fluctuations are investigated under well-controlled laboratory conditions. A heated grid in air is placed horizontally in a large anechoic room and the mixing of the free convection plumes above the grid generates a homogeneous isotropic random thermal field. The spectrum of refractrive index fluctuations is accurately described by a modified von Karman model which takes into account the entire spectrum of turbulence. Experimental data are obtained by varying both the frequency of the acoustic source and the distance of propagation. Measurements will be presented for a rigid boundary and for a finite impedance boundary. In this paper, attention is concentrated on the mean sound pressure levels and the intensity fluctuations. Experimental values will be compared with results of numerical simulations based on a wide angle parabolic code. [P. Chevret et al., J. Acoust. Soc. Am. 100, 3587–3599 (1996)]. [Work supported by DGA-DRET under Contract No. 94-083.]