bluuebunny/crossref_metadata_2025 huggingface dataset:
Treatment of influenza with neuraminidase inhibitors: virological implications
Authors: Roberts Noel A.
Published: July 2002

Evaluation of the emergence of influenza virus resistance to neuraminidase inhibitors (NAIs) is now demanded following experience with amantadinamines. Preliminary data have indicated that NAI–resistant virus is unlikely to emerge readily in the clinic and this is consistent with the difficulty experienced in selecting resistant virus
in vitro
. Resistance mutations can occur in both neuraminidase and haemagglutinin genes. The neuraminidase mutations are viral subtype specific and, therefore, clinically relevant subtypes must be employed for
in vitro
studies if pre–clinical data are to have predictive value. Haemagglutinin mutations generated
in vitro
are probably both subtype and cell culture system specific and, therefore, may not be predictive of clinical findings. Analysis of influenza–positive samples from NAI–treated patients in the clinical setting must include samples from late treatment time–points (day 4 and later) in order for resistant virus to be detected as
in vitro
studies and current clinical experience have indicated that resistant virus is slow to emerge and is transient.
FLOOZY of petunia is a flavin mono-oxygenase-like protein required for the specification of leaf and flower architecture
Authors: Tobeña-Santamaria Rafael , Bliek Mattijs , Ljung Karin , Sandberg Göran , Mol Joseph N.M. , Souer Erik , Koes Ronald
Published: July 2002

The mechanisms that determine the relative positions of floral organs, and thereby their numbers, is a poorly understood aspect of flower development. We isolated a petunia mutant, floozy(fzy), in which the formation of floral organ primordia in the outermost three floral whorls and one of the two bracts at the base of the flower is blocked at an early stage. In addition, fzymutants fail to generate secondary veins in leaves and bracts and display a decreased apical dominance in the inflorescence. FZYencodes an enzyme with homology to flavin mono-oxygenases and appears to be the ortholog of YUCCA genes of Arabidopsis. FZY is expressed in young leafs and bracts and in developing flowers. In young floral meristems FZY is expressed in the center of the meristem dome and, later, expression becomes localized on the flanks of the initiating petal and stamen primordia and at several sites in maturing anthers and carpels. These findings indicate that FZY is involved in synthesizing a signaling compound that is required for floral organ initiation and specification of the vascularization pattern in leaves. Although fzy mutants contain normal auxin levels, ectopic expression of FZY results in excessive auxin accumulation, suggesting that the signaling compound is auxin.
Different phosphorylated forms of RNA polymerase II and associated mRNA processing factors during transcription
Authors: Komarnitsky Philip , Cho Eun-Jung , Buratowski Stephen
Published: July 2002

The activities of several mRNA processing factors are coupled to transcription through binding to RNA polymerase II (Pol II). The largest subunit of Pol II contains a repetitive carboxy-terminal domain (CTD) that becomes highly phosphorylated during transcription. mRNA-capping enzyme binds only to phosphorylated CTD, whereas other processing factors may bind to both phosphorylated and unphosphorylated forms. Capping occurs soon after transcription initiation and before other processing events, raising the question of whether capping components remain associated with the transcription complex after they have modified the 5′ end of the mRNA. Chromatin immunoprecipitation in Saccharomyces cerevisiae shows that capping enzyme cross-links to promoters but not coding regions. In contrast, the mRNA cap methyltransferase and the Hrp1/CFIB polyadenylation factor cross-link to both promoter and coding regions. Remarkably, the phosphorylation pattern of the CTD changes during transcription. Ser 5 phosphorylation is detected primarily at promoter regions dependent on TFIIH. In contrast, Ser 2 phosphorylation is seen only in coding regions. These results suggest a dynamic association of mRNA processing factors with differently modified forms of the polymerase throughout the transcription cycle.
Bayesian Analysis of Haplotypes for Linkage Disequilibrium Mapping
Authors: Liu Jun S. , Sabatti Chiara , Teng Jun , Keats Bronya J.B. , Risch Neil
Published: July 2002

Haplotype analysis of disease chromosomes can help identify probable historical recombination events and localize disease mutations. Most available analyses use only marginal and pairwise allele frequency information. We have developed a Bayesian framework that utilizes full haplotype information to overcome various complications such as multiple founders, unphased chromosomes, data contamination, and incomplete marker data. A stochastic model is used to describe the dependence structure among several variables characterizing the observed haplotypes, for example, the ancestral haplotypes and their ages, mutation rate, recombination events, and the location of the disease mutation. An efficient Markov chain Monte Carlo algorithm was developed for computing the estimates of the quantities of interest. The method is shown to perform well in both real data sets (cystic fibrosis data and Friedreich ataxia data) and simulated data sets. The program that implements the proposed method, BLADE, as well as the two real datasets, can be obtained fromhttp://www.fas.harvard.edu/∼junliu/TechRept/01folder/diseq_prog.tar.gz.
Twin Priming: A Proposed Mechanism for the Creation of Inversions in L1 Retrotransposition
Authors: Ostertag Eric M. , Kazazian Haig H.
Published: July 2002

L1 retrotransposons are pervasive in the human genome. Approximately 25% of recent L1 insertions in the genome are inverted and truncated at the 5′ end of the element, but the mechanism of L1 inversion has been a complete mystery. We analyzed recent L1 inversions from the genomic database and discovered several findings that suggested a mechanism for the creation of L1 inversions, which we call twin priming. Twin priming is a consequence of target primed reverse transcription (TPRT), a coupled reverse transcription/integration reaction that L1 elements are thought to use during their retrotransposition. In TPRT, the L1 endonuclease cleaves DNA at its target site to produce a double-strand break with two single-strand overhangs. During twin priming, one of the overhangs anneals to the poly(A) tail of the L1 RNA, and the other overhang anneals internally on the RNA. The overhangs then serve as primers for reverse transcription. The data further indicate that a process identical to microhomology-driven single-strand annealing resolves L1 inversion intermediates.
Impaired Auditory Recognition Memory in Amnesic Patients with Medial Temporal Lobe Lesions
Authors: Squire Larry R. , Schmolck Heike , Stark Shauna M.
Published: July 2002

Two tests of auditory recognition memory were given to four patients with bilateral hippocampal damage (H+) and three patients with large medial temporal lobe lesions and additional variable damage to lateral temporal cortex (MTL+). When single stimuli were presented, performance was normal across delays as long as 30 sec, presumably because information could be maintained in working memory through rehearsal. When lists of 10 stimuli were presented, performance was impaired after a 5-min delay. Patients with MTL+ lesions performed marginally worse than patients with H+ lesions, consistent with findings for recognition memory in other modalities. The findings show that auditory recognition, like recognition memory in other sensory modalities, is dependent on the medial temporal lobe.
Ion recombination and polarity effect of ionization chambers in kilovoltage x‐ray exposure measurements
Authors: Das Indra J. , Akber Syed F.
Published: July 2002

Exposure measurements with ionization chambers are dependent on the correction factors related to the beam energy temperature and pressure ionization recombination and polarity effects. In this work, six different chambers commonly used in diagnostic radiology were investigated for the and at various exposure rates by changing the tube voltage, beam current, exposure time, and distance. A special triaxial connector was used to connect chambers to an electrometer capable of measuring positive and negative polarity and 150 V and 300 V electrode potentials to measure the and respectively. A mammography unit (24–35 kVp) and a diagnostic x‐ray unit (60–125 kVp) were used. Results indicate that the magnitude of the is linearly dependent on kVp for large volume (>150 cm3) chambers and independent for small volume (⩽150 cm3) chambers. In general, is higher at higher exposures (increasing kVp, mAs, and decreasing distance); however, is independent of exposure rate and kVp, but strongly depends on the sensitive volume of an ion chamber. and vary between 1–48% and 1–16%, respectively, among various chambers and exposure conditions. Chambers with larger volumes have higher values of and The desired accuracy of ±5% in exposure measurements might not be feasible unless both the polarity and recombination effects are known and accounted accurately.
In‐vivo rectal dose measurements with diodes to avoid misadministrations during intracavitary high dose rate brachytherapy for carcinoma of the cervix
Authors: Alecu Rodica , Alecu Marius
Published: July 2002

Our purpose in this paper is to present an in vivo dosimetry program designed both for measuring the rectal dose and for avoiding misadministrations in gynecological intracavitary implants. A device containing an energy compensated diode was specially designed for these measurements. Our calibration procedure as well as the clinical protocol is described. Measurements have been performed for 50 treatments delivered with a Fletcher Suit Delclos applicator. The calculated and in vivo measured values for the “20% reading,” i.e., the dose delivered to the diode by the initial 20% of the total dwell time, agreed to within 15%.
Cone‐beam computed tomography with a flat‐panel imager: Effects of image lag
Authors: Siewerdsen J. H. , Jaffray D. A.
Published: July 2002

A system for cone‐beam computed tomography (CBCT) has been developed based upon the technology of active matrix flat‐panel imagers (FPIs), and the system has demonstrated the potential for fully three‐dimensional volumetric imaging with high spatial and contrast resolution. This paper investigates the effects of image lag (arising from charge trapping and release in the FPI pixels) upon CBCT reconstructions. Hypotheses were derived based upon a simple, geometrical/physical model, suggesting that image lag in the projection data results primarily in two artifacts: a spatial blurring artifact in the direction opposite to the direction of rotation (called a “comet”) and a line artifact along the direction of the first few projections (called a “streak”). The hypotheses were tested by means of computer simulations and experimental measurements that yielded CBCT images of a simple cylindrical water phantom containing an attenuating rod of varying size and composition. The computer simulations generated projection images based upon analysis of the system geometry and a simple model of the FPI that allowed free adjustment of the image lag. Experimental measurements involved CBCT scans of the phantom under various conditions and modes of acquisition followed by examination of the resulting CBCT axial slices for lag artifacts. Measurements were performed as a function of exposure level, position and contrast of the rod, and for three modes of acquisition designed to isolate and/or minimize the two hypothesized artifacts. The results clearly illustrate the comet and streak artifacts, particularly in relation to high‐contrast objects imaged at high exposure levels. The significance of such artifacts under clinical conditions is expected to be small, considering the magnitude of the effect relative to the morphology and composition of typical anatomy. The artifacts may become appreciable, however, in the presence of high‐contrast objects, such as marker BBs, dental fillings, and metal prosthetics. A procedural method of reducing lag artifacts is demonstrated.
Cone‐beam computed tomography with a flat‐panel imager: Initial performance characterization
Authors: Jaffray D. A. , Siewerdsen J. H.
Published: July 2002

The development and performance of a system for x‐ray cone‐beam computed tomography (CBCT) using an indirect‐detection flat‐panel imager (FPI) is presented. Developed as a bench‐top prototype for initial investigation of FPI‐based CBCT for bone and soft‐tissue localization in radiotherapy, the system provides fully three‐dimensional volumetric image data from projections acquired during a single rotation. The system employs a 512×512 active matrix of thin‐film transistors and photodiodes in combination with a luminescent phosphor. Tomographic imaging performance is quantified in terms of response uniformity, response linearity, voxel noise, noise‐power spectrum (NPS), and modulation transfer function (MTF), each in comparison to the performance measured on a conventional CT scanner. For the geometry employed and the objects considered, response is uniform to within 2% and linear within 1%. Voxel noise, at a level of ∼20 HU, is comparable to the conventional CT scanner. NPS and MTF results highlight the frequency‐dependent transfer characteristics, confirming that the CBCT system can provide high spatial resolution and does not suffer greatly from additive noise levels. For larger objects and/or low exposures, additive noise levels must be reduced to maintain high performance. Imaging studies of a low‐contrast phantom and a small animal (a euthanized rat) qualitatively demonstrate excellent soft‐tissue visibility and high spatial resolution. Image quality appears comparable or superior to that of the conventional scanner. These quantitative and qualitative results clearly demonstrate the potential of CBCT systems based upon flat‐panel imagers. Advances in FPI technology (e.g., improved x‐ray converters and enhanced electronics) are anticipated to allow high‐performance FPI‐based CBCT for medical imaging. General and specific requirements of kilovoltage CBCT systems are discussed, and the applicability of FPI‐based CBCT systems to tomographic localization and image‐guidance for radiotherapy is considered.
Using great circles to understand motion on a rotating sphere
Authors: McIntyre D. H.
Published: July 2002

Motion observed in a rotating frame of reference is generally explained by invoking inertial forces. While this approach simplifies some problems, there is often little physical insight into the motion, in particular into the effects of the Coriolis force. To aid in the understanding of three-dimensional inertial forces, motion on a rotating sphere is considered from the points of view of an inertial observer and of an observer fixed on the sphere. The inertial observer observes the motion to be along a great circle fixed in the inertial frame, in analogy with simple straight-line motion in the two-dimensional case. This simple “straight-line” viewpoint of the inertial observer is reconciled qualitatively and quantitatively with the view of the rotating observer that requires inertial forces in order to account for the motion. Through a succession of simple examples, the Coriolis and centrifugal effects are isolated and illustrated, as well as effects due to the curvilinear nature of motion on a sphere.
From Schrödinger’s equation to the quantum search algorithm
Authors: Grover Lov K.
Published: July 2002

The quantum search algorithm is a technique for searching N possibilities in only O(N) steps. Although the algorithm itself is widely known, not so well known is the series of steps that first led to it; these are quite different from any of the generally known forms of the algorithm. This paper describes these steps, which start by discretizing Schrödinger’s equation. This paper also provides a self-contained introduction to quantum computing algorithms from a new perspective.
Electromagnetic induction and damping: Quantitative experiments using a PC interface
Authors: Singh Avinash , Mohapatra Y. N. , Kumar Satyendra
Published: July 2002

A bar magnet, attached to an oscillating system, passes through a coil periodically, generating a series of electromotive force pulses. A novel method for the quantitative verification of Faraday’s law is described which eliminates all errors associated with angular measurements, thereby revealing subtle features of the underlying mechanics. When electromagnetic damping is activated by short-circuiting the coil, a distinctly linear decay of the oscillation amplitude is observed. A quantitative analysis reveals an interesting interplay of the electromagnetic and mechanical time scales.
Equilibrium time correlation functions and the dynamics of fluctuations
Authors: Luban Marshall , Luscombe James H.
Published: July 2002

Equilibrium time correlation functions are of great importance because they probe the equilibrium dynamical response to external perturbations. We discuss the properties of time correlation functions for several systems that are simple enough to illustrate the calculational steps involved. The discussion underscores the need for avoiding language which misleadingly suggests that thermal equilibrium is associated with a quiescent or moribund state of the system.
Free fall and angular momentum
Authors: Mohazzabi Pirooz
Published: July 2002

The problem of free fall (rising or falling) of an object near the surface of the rotating earth is revisited. Expressions for the eastward and westward deflections of the object, which are normally explained by Coriolis force, are derived directly from conservation of angular momentum of the object with respect to the center of the earth. Launching conditions for zero lateral (east–west) deflections are also discussed. The treatment is simple enough, both conceptually and mathematically, to be presented in an introductory physics course.
Expansion method for stationary states of quantum billiards
Authors: Kaufman David L. , Kosztin Ioan , Schulten Klaus
Published: July 2002

A simple expansion method for numerically calculating the energy levels and the corresponding wave functions of a quantum particle in a two-dimensional infinite potential well with arbitrary shape (quantum billiard) is presented. The method permits the study of quantum billiards in an introductory quantum mechanics course. According to the method, wave functions inside the billiard are expressed in terms of an expansion of a complete set of orthonormal functions defined in a surrounding rectangle for which the Dirichlet boundary conditions apply, while approximating the billiard boundary by a potential energy step of a sufficiently large size. Numerical implementations of the method are described and applied to determine the energies and wave functions for quarter-circle, circle, and triangle billiards. Finally, the expansion method is applied to investigate the quantum signatures of chaos in a classically chaotic generic-triangle billiard.
Structural-acoustic coupling in a partially opened plate-cavity system: Experimental observation by using nearfield acoustic holography
Authors: Kim Sea-Moon , Kim Yang-Hann
Published: July 2002

In order to understand the cause and effect relation between a structure and a fluid, many studies on structural-acoustic coupling have been done. However, the studies were restricted to the interaction between only a structure and a fluid located on one or the other side of the structure. It is our aim to understand the coupling mechanism of a generally coupled system that has direct interaction between a finite interior fluid and a semi-infinite exterior one. We believe that this configuration allows the structure to interact with the fluid of the finite volume and that of the infinite one, thus providing a more general structure-fluid coupling (or structural-acoustic coupling) mechanism. For this purpose, we selected a partially opened plate-cavity system which has two different modally reacting boundary conditions: a plate and a hole. In order to understand the physical coupling phenomena of the selected system, visualization of the sound fields was performed experimentally. We used near field acoustic holography to estimate sound field variables, such as pressures and intensities. Examining the acoustic variables, we found that there are two types of coupling mechanisms depending on frequency and associated wavelength. One is where the plate and the cavity are so strongly coupled that the plate can be considered as a source. In this case, the system radiates acoustic energy effectively through the plate. The other is where the coupling interaction behavior decreases the radiation efficiency. The frequencies that determine whether the plate is a good or bad radiator are found to be around the natural frequencies of the plate.
Spatio-temporal analysis of irregular vocal fold oscillations: Biphonation due to desynchronization of spatial modes
Authors: Neubauer Jürgen , Mergell Patrick , Eysholdt Ulrich , Herzel Hanspeter
Published: July 2002

This report is on direct observation and modal analysis of irregular spatio-temporal vibration patterns of vocal fold pathologies in vivo. The observed oscillation patterns are described quantitatively with multiline kymograms, spectral analysis, and spatio-temporal plots. The complex spatio-temporal vibration patterns are decomposed by empirical orthogonal functions into independent vibratory modes. It is shown quantitatively that biphonation can be induced either by left–right asymmetry or by desynchronized anterior–posterior vibratory modes, and the term “AP (anterior–posterior) biphonation” is introduced. The presented phonation examples show that for normal phonation the first two modes sufficiently explain the glottal dynamics. The spatio-temporal oscillation pattern associated with biphonation due to left–right asymmetry can be explained by the first three modes. Higher-order modes are required to describe the pattern for biphonation induced by anterior–posterior vibrations. Spatial irregularity is quantified by an entropy measure, which is significantly higher for irregular phonation than for normal phonation. Two asymmetry measures are introduced: the left–right asymmetry and the anterior–posterior asymmetry, as the ratios of the fundamental frequencies of left and right vocal fold and of anterior–posterior modes, respectively. These quantities clearly differentiate between left–right biphonation and anterior–posterior biphonation. This paper proposes methods to analyze quantitatively irregular vocal fold contour patterns in vivo and complements previous findings of desynchronization of vibration modes in computer modes and in in vitro experiments.
The role of Biot slow waves in electroseismic wave phenomena
Authors: Pride Steven R. , Garambois Stéphane
Published: July 2002

The electromagnetic fields that are generated as a spherical seismic wave (either P or S) traverses an interface separating two porous materials are numerically modeled both with and without the generation of Biot slow waves at the interface. In the case of an incident fast-P wave, the predicted electric-field amplitudes when slow waves are neglected can easily be off by as much as an order of magnitude. In the case of an incident S wave, the error is much smaller (typically on the order of 10% or less) because not much S-wave energy gets converted into slow waves. In neglecting the slow waves, only six plane waves (reflected and transmitted fast-P, S, and EM waves) are available with which to match the eight continuity conditions that hold at each interface. This overdetermined problem is solved by placing weights on the eight continuity conditions so that those conditions that are most important for obtaining the proper response are emphasized. It is demonstrated that when slow waves are neglected, it is best to also neglect the continuity of the Darcy flow and fluid pressure across an interface. The principal conclusion of this work is that to properly model the electromagnetic (EM) fields generated at an interface by an incident seismic wave, the full Biot theory that allows for generation of slow waves must be employed.
Effect of phase on discomfort caused by vertical whole-body vibration and shock—Experimental investigation
Authors: Matsumoto Yasunao , Griffin Michael J.
Published: July 2002

An experimental study has investigated the effect of “phase” on the subjective responses of human subjects exposed to vertical whole-body vibration and shock. The stimuli were formed from two frequency components: 3 and 9 Hz for continuous vibrations and 3 and 12 Hz for shocks. The two frequency components, each having 1.0 ms−2 peak acceleration, were combined to form various waveforms. The effects of the vibration magnitude on the discomfort caused by the input stimuli were also investigated with both the continuous vibrations and the shocks. Various objective measurements of acceleration and force at the seat surface, the effects of different frequency weightings and second and fourth power evaluations were compared with judgments of the discomfort of the stimuli. It was found that a 6% to 12% increase in magnitude produced a statistically significant increase in discomfort with both the continuous vibrations and the shocks. Judgments of discomfort caused by changes in vibration magnitude were highly correlated with all of the objective measurements used in the study. The effects on discomfort of the phase between components in the continuous vibrations were not statistically significant, as predicted using evaluation methods with a power of 2. However, small changes in discomfort were correlated with the vibration dose value (VDV) of the Wb frequency-weighted acceleration. The effect of phase between frequency components within the shocks was statistically significant, although no objective measurement method used in the study was correlated with the subjective judgments.
Response to “Articulation index predictions for hearing-impaired listeners with and without cochlear dead regions” [J. Acoust. Soc. Am. 111, 2545–2548 (2002)]
Authors: Moore Brian C. J.
Published: July 2002

Rankovic [J. Acoust. Soc. Am. 111, 2545–2548 (2002)] argues that the AI, calculated according to Fletcher’s method, gives good predictions of speech intelligibility for subjects with high-frequency hearing loss listening to amplified speech, regardless of the presence or absence of dead regions. She suggests further that “…it seems premature to introduce a clinical test for identifying dead regions because it is not clear what information is gained beyond what is obtainable by calculating the AI.” I argue that, in fact, the AI is not accurate in predicting the incremental benefit of amplifying frequencies well above the estimated edge frequency (Fe) of a dead region. For five out of nine cases, application of the AI leads to the prediction that amplification of frequencies well above Fe would improve speech scores by 10%–15%; in fact, the largest improvement was 7%.
Labiovelar compensation in back vowels
Authors: de Jong Kenneth J.
Published: July 2002

Various studies have revealed apparent motoric compensation between articulatory structures such as the jaw and lips which contribute to articulatory goals of vocal tract constriction. The present study, like Perkell et al. [J. Acoust. Soc. Am. 93, 2948–2961 (1993)] and Savariaux et al. [J. Acoust. Soc. Am. 98, 2428–2442 (1995)], investigates the possibility of compensation between labial protrusion and constriction and dorsovelar constriction—a relationship based on the similarity of the acoustic effects of such articulatory goals. The present study differs from these earlier studies in that it assumes an articulatory model of gestures, and it examines nonperipheral back vowels. X-ray microbeam records of American English speakers producing back vowels under various stress conditions were investigated. Results reveal systematic speaker differences in the direction of correlation between measures of labial and dorsal position. These results show that speakers differ as to whether they exhibit coupling between labial and dorsal activity in the lowering of back vowel timbre.
Active control of finite amplitude acoustic waves in a confined geometry
Authors: Huang Pai-Tsung , Brisson J. G.
Published: July 2002

An active control approach was developed to observe and control nonlinear effects for high-amplitude acoustic waves in a cavity. The acoustic medium was air at ambient pressure and temperature. A harmonic cavity was driven using a multi-frequency drive to selectively drive the fundamental mode and suppress nonlinear interactions between the fundamental and other modes. A semi-empirical model was developed using effective quadratic and cubic nonlinear coupling coefficients to predict resonator response. The cavity was also shown to act as an acoustic mixer. Typical acoustic pressure amplitudes were 1000 Pa (SPL 154 dB re: 20 μPa).
A numerical and experimental investigation of the performance of sound intensity probes at high frequencies
Authors: Jacobsen Finn , Cutanda Vicente , Juhl Peter M.
Published: July 2002

The influence of scattering and diffraction on the performance of sound intensity probes has been examined using a boundary element model of an axisymmetric two-microphone probe with the microphones in the usual face-to-face arrangement. On the basis of calculations for a variety of sound field conditions and probe geometries it is concluded that the optimum length of the spacer between the microphones is about one microphone diameter; with this geometry the effect of diffraction and the finite difference error almost counterbalance each other up to about an octave above the frequency limit determined by the finite difference approximation. This seems to be valid under virtually any sound field condition that could be of practical importance in sound power determination. The upper frequency limit corresponds to about 10 kHz for an intensity probe with 12-in. microphones, which means that it should be possible to cover most of the audible frequency range, say, from 50 Hz to 10 kHz, with a single probe configuration. The numerical results have been confirmed by a series of experiments.
Low-frequency acoustic scattering by gas-filled prolate spheroids in liquids. II. Comparison with the exact solution
Authors: Ye Zhen , Hoskinson Emile
Published: July 2002

This sequential paper describes a comparison between the simple closed solution proposed in a previous paper [, J. Acoust. Soc. Am. 101, 1945–1952 (1997)] with the exact solution for scattering of acoustic waves by gas-filled prolate spheroids at low frequencies. The analysis and comparison show that the low-frequency acoustic scattering by prolate spheroid gas bubbles has resonance features, and can be rather accurately described by the proposed simple formula. It is shown that the results from the simple analytic solution agree remarkably well with those obtained by the exact solution.
Coherence analysis of multimegameter range ocean acoustic signals
Authors: Dzieciuch Matthew ,   ATOC Consortium
Published: July 2002

The quality of acoustic travel time measurements depends on the coherence of the signal as well as the bandwidth. Ocean acoustic signals exhibit coherence properties in four ways: in time, in bandwidth, and in vertical and horizontal extent. (These are conjugate to Doppler broadening, pulse time spread, and rms vertical and horizontal arrival angle.) These properties have recently been measured and can be compared for several different ranges (80–5000 km), center frequencies (28–250 Hz), and geometries ( source on-bottom versus off-bottom). For signals of less than perfect coherence, techniques from communications theory can be used to improve the quality of travel time measurements by relaxing the resolution requirement. For instance, if the coherence bandwidth is less than the signal bandwidth, it is possible to consider subbands of the signal as separate measurements. How to best combine these measurements then depends crucially on the SNR. While acoustic thermometry has relied on electronically controlled sources, by allowing for the coherence structure of stochastic sources (such as T-phases, explosives, or marine mammals) an improved signal processing strategy may result. a)The ATOC Consortium: A. B. Baggeroer (MIT), T. G. Birdsall (U. Michigan), C. Clark (Cornell), J. A. Colosi (WHOI), B. D. Cornuelle (SIO), D. Costa (UCSC), B. D. Dushaw (U. Washington), M. Dzieciuch (SIO), A. M. G. Forbes (CSIRO, Hobart), C. Hill (MIT), B. M. Howe (U. Washington), J. Marshall (MIT), D. Menemenlis (MIT), J. A. Mercer (U. Washington), K. Metzger (U. Michigan), W. Munk (SIO), R. C. Spindel (U. Washington), D. Stammer (MIT), P. F. Worcester (SIO), and C. Wunsch (MIT).
Wind tunnel noise measurements on full-scale pantograph models
Authors: Lölgen Thomas
Published: July 2002

Noise reduction of pantographs is of special importance for the operation of high-speed trains, since the pantograph noise cannot be treated with passive counter measures like sound barriers. Therefore the noise emission of pantographs was investigated in an acoustically treated wind tunnel for air speeds up to 400 km/h. The aims were to determine the noise reduction potential of pantographs, to investigate their aerodynamic behavior, to validate existing theoretical models, and to compare measurement techniques and wind tunnels. The acoustic measurements were carried out using a microphone array system, a parabolic antenna as well as normal microphones. Two pantographs, which are in service today in Germany and Japan, were used as references. Two full-scale models of high-speed pantographs were tested in several configurations. The achieved noise reduction of the models compared to the reference pantographs confirmed the theoretical results.
AMOC: Acoustic monitoring of the ocean climate of the Arctic
Authors: Johannessen Ola M. ,   AMOC Group
Published: July 2002

The overall objective of AMOC is to develop and design an acoustic system for long-term monitoring of the ocean temperature and ice thickness in the Arctic Ocean, including the Fram Strait, for climate variability studies and global warming detection. The unique combination of the underwater acoustic remote sensing with satellite remote sensing of the ice cover including modeling and data assimilation, in the predicted sensitive climate region of the Arctic Ocean, is perhaps the key solution to monitor global climate changes and early detection of global warming. AMOC has the following specific objectives: (i) Compilation and analysis of existing ocean and ice data from the Arctic Ocean. (ii) Simulation of present and future Arctic Ocean environment to be used as input to acoustic modeling. (iii) Simulation of present and future basin-wide acoustic propagation using natural variability and global warming scenarios to investigate the sensitivity of acoustic methods for global warming detection. (iv) Simulation of present and future acoustic propagation in the Fram Strait to investigate the sensitivity of acoustic methods for monitoring heat and volume fluxes in an area of strong mesoscale eddy activity. (v) Design of an optimal acoustic monitoring system for climate change detection in the Arctic.
An alternative stack arrangement for thermoacoustic heat pumps and refrigerators
Authors: Bösel J. , Trepp Ch. , Fourie J. G.
Published: July 2002

One major setback of thermoacoustic engines—when comparing them with “conventional” heat-engines or refrigerators—is their low power density. In this work a new attempt for achieving higher power densities was undertaken. The stack of a thermoacoustic engine, which usually consists of parallel plates much longer than the acoustic displacement amplitude, was substituted by parallel-plate segments, which were only a fraction of the displacement amplitude long and randomly orientated to each other. This alternative stack arrangement was expected to benefit from improved heat transfer characteristics and an anisotropic thermal conductivity. A simplified numerical model confirmed these expectations. Experiments with a thermoacoustic heat pump were carried out. The experimental results qualitatively agreed with the numerical model. At most, the power density was raised by approximately 50%. The coefficient of performance—defined as useful heat output divided by work input—increased by approximately one-third.
Separate mechanisms govern the selection of spectral components for perceptual fusion and for the computation of global pitch
Authors: Brunstrom Jeffrey M. , Roberts Brian
Published: July 2002

The perceptual fusion of harmonics is often assumed to result from the operation of a template mechanism that is also responsible for computing global pitch. This dual-role hypothesis was tested using frequency-shifted complexes. These sounds are inharmonic, but preserve a regular pattern of equal component spacing. The stimuli had a nominal fundamental (F0) frequency of 200 Hz (±20%), and were frequency shifted either by 25.0% or 37.5% of F0. Three consecutive components (6–8) were removed and replaced with a sinusoidal probe, located at one of a set of positions spanning the gap. On any trial, subjects heard a complex tone followed by an adjustable pure tone in a continuous loop. Subjects were well able to match the pitch of the probe unless it corresponded with a position predicted by the spectral pattern of the complex. Peripheral factors could not account for this finding. In contrast, hit rates were not depressed for probes positioned at integer multiples of the F0(s) corresponding to the global pitch(es) of the complex, predicted from previous data [Patterson, J. Acoust. Soc. Am. 53, 1565–1572 ]. These findings suggest that separate central mechanisms are responsible for computing global pitch and for the perceptual grouping of partials.
A comparison of acoustic thermometry, XBT, TOPEX, and HOT observations of ocean temperature in the northeast Pacific
Authors: Dushaw Brian D. ,   ATOC Group
Published: July 2002

Time series of temperature have been measured acoustically in the northeast Pacific as part of the Acoustic Thermometry of Ocean Climate (ATOC) project. These time series are compared with other available data types. The acoustic time series of transmissions from the California and Kauai acoustic sources were obtained during 1996–1999. As a result of marine mammal protocols, the time series are intermittent; the California source was turned off in Fall 1998. Assuming that variations in sea-surface height observed by TOPEX/POSEIDON are caused by thermal expansion, the amplitude of the annual cycle of heat content derived from altimetry is larger than that found by the acoustic data, Levitus climatology, and monthly maps of ocean temperature from XBTs of opportunity. The heat content ‘‘anomalies’’ determined by the XBT maps are comparable in size to the differences between the XBT and acoustically derived heat content. A variety of problems with the XBT sampling may account for these differences. The 12-year time series of temperature derived from the Hawaiian Ocean Time series (HOT) data highlights the mesoscale noise in single-point sampling. However, thermal variability at 100-day time scales is observed in the acoustic data obtained between Hawaii and California using the Kauai source. Acoustic thermometry is complementary to altimetry and hydrography.
Non-Linear Behavior of Viscoelastic Materials. I. Disperse Systems of Polystyrene Solution and Carbon Black
Authors: Onogi Shigeharu , Masuda Toshiro , Matsumoto Takayoshi
Published: July 2002

To determine non-linear viscoelasticity parameters for disperse and high-polymeric systems, some fundamental relations have been derived between these parameters and the experimental quantities by viscoelastometry, particularly with a torsionally oscillating rheometer, on the basis of the general theory presented by Green and Rivlin. The non-linear viscoelasticity of several disperse systems consisting of polystyrene solutions and carbon black has been measured by means of the torsionally oscillating rheometer at various temperatures ranging from 100 to 170°C, and in a frequency range from 2×10−3 to 0.5 cycle per sec. As a result of harmonic analysis of the experimental results, it has been revealed that the resultant torque consists of the fundamental component and odd harmonics, and that the energy dissipated during one cycle is the same as that calculated from the fundamental component alone. Frequency dependence curves at various temperatures for G1′ and G1″, which correspond to G′ and G″ for linear viscoelastic materials, can be superposed into master curves by horizontal and vertical shifts. The master curves manifest a plateau lower than the ordinary rubbery plateau on the low frequency side.
Profilin upregulation induces autophagy through stabilization of AMP‐activated protein kinase
Authors: Saurav Shashank , Manna Sunil Kumar
Published: May 2022

Profilin regulates actin polymerization, and its balanced expression is required for cellular growth and development. Most tumours have compromised profilin expression, and its overexpression in MDA MB‐231 breast cancer cells has been reported to activate AMP‐activated protein kinase α (AMPKα), an energy‐sensing molecule that affects various cellular processes including autophagy. This study aims to explore the role of profilin in autophagy induction. We employed all‐trans retinoic acid (ATRA) as an inducer of profilin expression and showed that profilin induces autophagy through mTOR inhibition, autophagy‐activating kinase ULK1 upregulation, and AMPK stabilization as well as its activation. Furthermore, evidence from our study indicates physical interaction between profilin and AMPK, which results in AMPK stabilization and induction of prolonged autophagy, thereby leading to apoptosis. This study uncovers a novel mechanism that induces autophagy in triple‐negative breast cancer cells.
The NSF Convergence Accelerator program
Authors: Baru Chaitanya , Campbell Lara , Dade Aurali , Fulay Pradeep , Loewi Alex , Maughan Douglas , Mohedas Ibrahim , Molnar Linda , Pozmantier Michael , Reksulak Michael , Smith Shelby , Tehrani Nicole
Published: May 2022

The National Science Foundation's Convergence Accelerator is a unique program offering researchers and innovators the opportunity to translate research results into tangible solutions that make a difference for society. Through an intense innovation curriculum and a mentorship program, researchers gain skills and experiences that are of use not only during this program but throughout their careers. This article describes the NSF Convergence Accelerator program and its initial funded convergence research topics—or “tracks”—funded in 2019 and 2020. In almost every track and NSF‐funded project, artificial intelligence and machine learning (AI/ML) approaches and methods are playing an essential role.
Knowledge graphs to support real‐time flood impact evaluation
Authors: Johnson J. Michael , Narock Tom , Singh‐Mohudpur Justin , Fils Doug , Clarke Keith C. , Saksena Siddharth , Shepherd Adam , Arumugam Sankar , Yeghiazarian Lilit
Published: May 2022

A digital map of the built environment is useful for a range of economic, emergency response, and urban planning exercises such as helping find places in app driven interfaces, helping emergency managers know what locations might be impacted by a flood or fire, and helping city planners proactively identify vulnerabilities and plan for how a city is growing. Since its inception in 2004, OpenStreetMap (OSM) sets the benchmark for open geospatial data and has become a key player in the public, research, and corporate realms. Following the foundations laid by OSM, several open geospatial products describing the built environment have blossomed including the Microsoft USA building footprint layer and the OpenAddress project. Each of these products use different data collection methods ranging from public contributions to artificial intelligence, and if taken together, could provide a comprehensive description of the built environment. Yet, these projects are still siloed, and their variety makes integration and interoperability a major challenge. Here, we document an approach for merging data from these three major open building datasets and outline a workflow that is scalable to the continental United States (CONUS). We show how the results can be structured as a knowledge graph over which machine learning models are built. These models can help propagate and complete unknown quantities that can then be leveraged in disaster management.
Isolations of the Spring Viremia of Carp Virus in the Upper Mississippi River (USA), Including a New Host, the Quillback
Authors: Katona Ryan , Standish Isaac , McCann Rebekah , Dziki Sara , Bailey Jennifer , Puzach Corey , Warg Janet , Leis Eric , Phillips Kenneth
Published: May 2022

In July of 2018 and 2019, wild fish health surveys were conducted along the Wisconsin and Minnesota portions of the upper Mississippi River. Spring viremia of carp virus (SVCV) was isolated from Common Carp Cyprinus carpio as well as a newly identified host species, the Quillback Carpiodes cyprinus. Sanger sequencing of the gene encoding for the G protein revealed a high similarity of the Quillback isolate to various SVCV isolates identified from Common Carp that were collected during earlier wild fish health surveys and mortality events in the USA. Despite annual monitoring, this virus has been infrequently identified. The speculative role of native fish and invertebrates in allowing the virus to persist for long periods without detection is discussed.
Nitrogen‐Doped Bimetallic Carbide‐Graphite Composite as Highly Active and Extremely Stable Electrocatalyst for Oxygen Reduction Reaction in Alkaline Media
Authors: Yan Zaoxue , Zhang Yanqi , Jiang Zhifeng , Jiang Deli , Wei Wei , Hu Zhuofeng
Published: May 2022

It is demonstrated that nitrogen‐doped bimetallic carbide‐graphite composite (N‐Fe2MoC‐GC) has much superior oxygen reduction reaction (ORR) activity to commercial Pt/C with ultrahigh stability, and excellent anti‐methanol and anti‐CO performances. The N‐Fe2MoC‐GC has a high initial half‐wave potential of 0.887 V (versus RHE); its mass activity (83 mA mgcat.−1 at 0.9 V versus RHE) is 2.2 times that of Pt/C (40 wt%, 39 mA mgcat.−1). In H2/O2 alkaline fuel cell, the N‐Fe2MoC‐GC keeps 92.9% of the initial power density (1.12 W cm−2) within 70 000 cycles, ranking it as one of the most active and stable noble metal‐free catalysts reported to date. Moreover, the N‐Fe2MoC‐GC keeps high power density even under low relative humidity or at high operation temperature. The positive charge on Fe and Mo atoms caused by electron transfer from Fe2MoC to N is believed to lead to the excellent ORR activity. The inherent electrochemical stability of the Fe2MoC and graphite matrix, as well as the strong interaction between components of catalyst caused by electron transfer, accounts for the ultrahigh stability.
A Biomaterial‐Based Porous Core–Shell Sorbent for Practical and Efficient Marine Oil Spill Recovery
Authors: Raju Cijil , Mathew Liby Ann , Sureshan Kana M.
Published: May 2022

A core–shell sorbent is developed using natural fibers for marine oil spill recovery. The core of the sorbent is made using coir fibers, which is then covered with a thin layer of shell made from cotton impregnated with a phase selective oleogelator, 12‐hydroxystearic acid. The pore volume that is available for oil uptake amounts to 85–90% of the total volume of the sorbent. When it is introduced to a crude oil–water mixture, the sorbent selectively absorbs the oil instantaneously. The gelator in the shell congeals the oil in the shell matrix, forming a rigid enclosure for the absorbed oil and this allows the collection of the oil‐absorbed sorbents without dripping. The absorbed oil can be recovered quantitatively by simple pressing. The method is general and works with all kinds of crude oils. The cheaply available natural raw materials and easy preparation make this method attractive in terms of economy, reliability, scalability, practicability, and greenness.