bluuebunny/crossref_metadata_2025 huggingface dataset:
BetaTPred: prediction of β-TURNS in a protein
using statistical algorithms
Authors: Kaur Harpreet , Raghava G. P. S.
Published: July 2002

Motivation: β-turns play an important role from a structural and functional point of view. β-turns are the most common type of non-repetitive structures in proteins and comprise on average, 25% of the residues. In the past numerous methods have been developed to predict β-turns in a protein. Most of these prediction methods are based on statistical approaches. In order to utilize the full potential of these methods, there is a need to develop a web server.

Results: This paper describes a web server called BetaTPred, developed for predicting β-TURNS in a protein from its amino acid sequence. BetaTPred allows the user to predict turns in a protein using existing statistical algorithms. It also allows to predict different types of β-TURNS e.g. type I, I′, II, II′, VI, VIII and non-specific. This server assists the users in predicting the consensus β-TURNS in a protein.

Availability: The server is accessible from http://imtech.res.in/raghava/betatpred/

Contact: raghava@imtech.res.in

Supplementary information: http://imtech.res.in/raghava/betatpred/intro.html

* To whom correspondence should be addressed.
Construction of optimal quality control for oligo arrays
Authors: Colbourn Charles J. , Ling Alan C. H. , Tompa Martin
Published: July 2002

Motivation: Oligo arrays are important experimental tools for the high throughput measurement of gene expression levels. During production of oligo arrays, it is important to identify any faulty manufacturing step.

Results: We describe a practical algorithm for the construction of optimal quality control designs that identify any faulty manufacturing step. The algorithm uses hillclimbing, a search technique from combinatorial optimization. We also present the results of using this algorithm on all practical quality control design sizes.

Availability: On request from the authors.

Contact: tompa@cs.washington.edu

* To whom correspondence should be addressed.
TranScout: prediction of gene expression regulatory proteins
from their sequences
Authors: Aguilar Daniel , Oliva Baldomero , Aviles Francesc X. , Querol Enrique
Published: July 2002

Motivation: The advent of genomics yields thousands of reading frames in search of function. Identification of conserved functional motifs in protein sequences can be helpful for function prediction.

Results: A database and a classification of reported DNA-binding protein motifs has been designed. A program (‘TranScout’) has been developed for the detection and evaluation of conserved motifs in prokaryotic and eukaryotic sequences of proteins with a gene regulatory function. The efficiency of the program is shown in a benchmark against a database obtained from SWISS-PROT without the protein sequences used to train the program. All motifs were detected with a mean average sensitivity of 0.98 and a mean average specificity of 0.92.

Availability: The program is freely available for use on the internet at http://luz.uab.es/transcout/. The user can find additional information at this site.

Contact: Enric.Querol@uab.es; boliva@imim.es

* To whom correspondence should be addressed.

2 Present address: Laboratorio de Biologı́a Estructural Computacional (GRIB), Universitat Pompeu Fabra, C/Doctor Aiguader, Barcelona 08003, Spain.
PATH: a task for the inference of phylogenies
Authors: del Val Coral , Ernst Peter , Bräuning Rüdiger , Glatting Karl-Heinz , Suhai Sandor
Published: July 2002

Summary: Phylogenetic Analysis Task in Husar (PATH) is a task for the inference of phylogenies. It executes three phylogenetic methods and automatically chooses the evolutionary model for each set of data. The output of the tasks shows the consensus trees together with full results obtained from all executed methods.

Availability: PATH is available at the German EMBnet node after registration via www at http://genome.dkfz-heidelberg.de

Contact: genome@dkfz.de
THE DEMAND FOR VANITY (PLATES): ELASTICITIES, NET REVENUE MAXIMIZATION, AND DEADWEIGHT LOSS
Authors: Craft Erik D.
Published: July 2002

States raise revenue and provide a service when offering to personalize license plates. To determine the revenuE‐maximizing price and the marginal deadweight loss per dollar of net revenue, one must estimate both the slope and shift factors of the demand for vanity license plates. Shift factors include the percentage of special background plates sales (price of a complement), the requirement of front and back license plates (preferences), the age distribution (population), and income. Each $1 increase in the annual cost of owning a vanity plate reduces the final percentage of all plates personalized by 0.08%. At least ten states continue to charge a price exceeding the revenuE‐maximizing level. Many other states raise funds whose marginal social cost exceeds marginal net revenue by over 100%.
Genetic evidence for an equilibrium between docked and undocked vesicles
Authors: Li Jing , Schwarz Thomas L.
Published: July 2002

By using the
shibire
mutation to block endocytosis in a temperature–dependent fashion, we have manipulated the number of synaptic vesicles in a nerve terminal and have observed a remarkable proportionality of the number of quanta released to the size of the total vesicle pool. In the experiments described below we determine that approximately 0.3% of the vesicle pool is released per stimulus. The data suggest that the pool of readily releasable docked vesicles does not represent the saturation of a limiting number of release sites, but instead represents a subset of vesicles that is in equilibrium with the larger pool of vesicles. Before presenting this data and the significance of the finding for the regulation of neurotransmission, we will briefly review the use of
Drosophila
genetics as a tool for dissecting synaptic transmission.
Identification and analysis of bacterial virulence genesin vivo
Authors: Unsworth Kate E. , Holden David W.
Published: July 2002

Signature–tagged mutagenesis is a mutation–based screening method for the identification of virulence genes of microbial pathogens. Genes isolated by this approach fall into three classes: those with known biochemical function, those of suspected function and some whose functions cannot be predicted from database searches. A variety ofin vitroand in vivo methods are available to elucidate the function of genes of the second and third classes. We describe the use of some of these approaches to study the function of theSalmonellapathogenicity island 2 type III secretion system ofSalmonella typhimurium. This virulence determinant is required for intracellular survival. Secretion by this system is induced by an acidic pH, and its function may be to alter trafficking of theSalmonella–containing vacuole. Use of a temperature–sensitive non–replicating plasmid and competitive index tests with other genes show that in vivo phenotypes do not always correspond to those predicted fromin vitrostudies.
Components of episodic memory: the contribution of recollection and familiarity
Authors: Yonelinas Andrew P.
Published: July 2002

The examination of recognition memory confidence judgements indicates that there are two separate components or processes underlying episodic memory. A model that accounts for these results is described in which a recollection process and a familiarity process are assumed to contribute to recognition memory performance. Recollection is assumed to reflect a threshold process whereby qualitative information about the study event is retrieved, whereas familiarity reflects a classical signal–detection process whereby items exceeding a familiarity response criterion are accepted as having been studied. Evidence from cognitive, neuropsychological and neuroimaging studies indicate that the model is in agreement with the existing recognition results, and indicate that recollection and familiarity are behaviourally, neurally and phenomenologically distinct memory retrieval processes.
The haemagglutinin gene, but not the neuraminidase gene, of ‘Spanish flu’ was a recombinant
Authors: Gibbs Mark J. , Armstrong John S. , Gibbs Adrian J.
Published: July 2002

Published analyses of the sequences of three genes from the 1918 Spanish influenza virus have cast doubt on the theory that it came from birds immediately before the pandemic. They showed that the virus was of the H1N1 subtype lineage but more closely related to mammal–infecting strains than any known bird–infecting strain. They provided no evidence that the virus originated by gene reassortment nor that the virus was the direct ancestor of the two lineages of H1N1 viruses currently found in mammals; one that mostly infects human beings, the other pigs. The unusual virulence of the virus and why it produced a pandemic have remained unsolved. We have reanalysed the sequences of the three 1918 genes and found conflicting patterns of relatedness in all three. Various tests showed that the patterns in its haemagglutinin (HA) gene were produced by true recombination between two different parental HA H1 subtype genes, but that the conflicting patterns in its neuraminidase and non–structural–nuclear export proteins genes resulted from selection. The recombination event that produced the 1918 HA gene probably coincided with the start of the pandemic, and may have triggered it.
Pollen tube development and competitive ability are impaired by disruption of a Shaker K+ channel in Arabidopsis
Authors: Mouline Karine , Véry Anne-Aliénor , Gaymard Frédéric , Boucherez Jossia , Pilot Guillaume , Devic Martine , Bouchez David , Thibaud Jean-Baptiste , Sentenac Hervé
Published: July 2002

Sexual reproduction in plants requires elongation of the pollen tube through the transmitting tissues toward the ovary. Tube growth rate is a major determinant of pollen competitive ability. We report that a K+ channel of the Shaker family in Arabidopsis, SPIK, plays an important role in pollen tube development. SPIK was found to be specifically expressed in pollen. When SPIK was heterologously expressed in COS cells, its product formed hyperpolarization-activated K+ channels. Disruption (T-DNA insertion) of the SPIK coding sequence strongly affected inwardly rectifying K+-channel activity in the pollen-grain plasma membrane. Measurements of membrane potential in growing pollen tubes yielded data compatible with a contribution of SPIK to K+ influx. In vitro pollen germination assays were performed, revealing that the disruption results in impaired pollen tube growth. Analysis of the transmission rate of the disrupted allele in the progeny of heterozygous plants revealed a decrease in pollen competitive ability, the probability of fertilization by mutant pollen being ∼1.6 times lower than that by wild-type pollen. The whole set of data supports the hypothesis that functional expression ofSPIK plays a role in K+ uptake in the growing pollen tube, and thereby in tube development and pollen competitive ability.
Magnetic resonance elastography using 3D gradient echo measurements of steady‐state motion
Authors: Weaver John B. , Van Houten Elijah E. W. , Miga Michael I. , Kennedy Francis E. , Paulsen Keith D.
Published: July 2002

Magnetic resonance elastography (MRE) is an important new method used to measure the elasticity or stiffness of tissues in vivo. While there are many possible applications of MRE, breast cancer detection and classification is currently the most common. Several groups have been developing methods based on MR and ultrasound (US). MR or US is used to estimate the displacements produced by either quasi‐static compression or dynamic vibration of the tissue. An important advantage of MRE is the possibility of measuring displacements accurately in all three directions. The central problem in most versions of MRE is recovering elasticity information from the measured displacements. In previous work, we have presented simulation results in two and three dimensions that were promising. In this article, accurate reconstructions of elasticity images from 3D, steady‐state experimental data are reported. These results are significant because they demonstrate that the process is truly three‐dimensional even for relatively simple geometries and phantoms. Further, they show that the integration of displacement data acquisition and elastic property reconstruction has been successfully achieved in the experimental setting. This process involves acquiring volumetric MR phase images with prescribed phase offsets between the induced mechanical motion and the motion‐encoding gradients, converting this information into a corresponding 3D displacement field and estimating the concomitant 3D elastic property distribution through model‐based image reconstruction. Fully 3D displacement fields and resulting elasticity images are presented for single and multiple inclusion gel phantoms.
Off‐axis x‐ray spectra: A comparison of Monte Carlo simulated and computed x‐ray spectra with measured spectra
Authors: Bhat Madhava , Pattison John , Bibbo Giovanni , Caon Martin
Published: July 2002

The off‐axis x‐ray spectra from a constant potential x‐ray generator were measured with a high purity germanium spectrometer cooled to liquid nitrogen temperature. The measured spectra were compared with off‐axis x‐ray spectra calculated using a code based on the semiempirical model developed by Tucker et al. and Monte Carlo simulated x‐ray spectra using the EGS4 code system. In this study, both the Tucker model, and the EGS4 code system, were found to produce off‐axis bremsstrahlung x‐ray spectra which agreed well with the spectra measured at three emerging angles. In the measured and the EGS4 generated spectra the total K‐characteristic peaks were in increasing order, as observed in the anode to cathode direction, whereas the Tucker model produced maximum total K‐characteristic peaks at the 6° anode side, and lesser amounts at the central axis and the 6° cathode side. Large differences in the total K‐characteristic lines is seen among the three different methods. The EGS4 code system was able to produce x‐ray spectra for a combination of target materials.
Some paradoxes, errors, and resolutions concerning the spectral optimization of human vision
Authors: Soffer Bernard H. , Lynch David K.
Published: July 2002

The peak brightness of the solar spectrum is in the green when plotted in wavelength units. It peaks in the near-infrared when plotted in frequency units. Therefore the oft-quoted notion that evolution led to an optimized eye whose sensitivity peaks where there is most available sunlight is misleading and erroneous. The confusion arises when density distribution functions like the spectral radiance are compared with ordinary functions like the sensitivity of the eye. Spectral radiance functions, excepting very narrow ones, can change peak positions greatly when transformed from wavelength to frequency units, but sensitivity functions do not. Expressing the spectral radiance in terms of photons per second, rather than power, also causes a change in the shape and peak of the distribution, even keeping the choice of bandwidth units fixed. The confusion arising from comparing simple functions to distribution functions occurs in many parts of the scientific and engineering literature aside from vision, and some examples are given. The eye does not appear to be optimized for detection of the available sunlight, including the surprisingly large amount of infrared radiation in the environment. The color sensitivity of the eye is discussed in terms of the spectral properties and the photo and chemical stability of available biological materials. It is likely that we are viewing the world with a souvenir of the human evolutionary voyage.
Effects of the speed of moving noise sources on the sound visualization by means of moving frame acoustic holography
Authors: Park Soon-Hong , Kim Yang-Hann
Published: July 2002

The moving frame acoustic holography (MFAH) method [H.-S. Kwon and Y.-H. Kim, J. Acoust. Soc. Am. 103, 1734–1742 (1998)] enables the visualization of noise generated by moving noise sources, e.g., moving vehicles, by using a line array of microphones affixed to the ground. However, the sound field of a moving noise source has a moving effect, which produces the wavefront distribution different from what would be generated by the source if it were not moving. The moving effect causes errors on the reconstructed hologram by means of MFAH. This paper studies this effect with regard to the speed of noise sources. A formula, which can show the effect, was derived. This enables the analysis of the effect not only on the hologram plane but also on a prediction plane. It was shown that the phase error is more undesirable than that of magnitude. The phase error, which is proportional to the speed of a noise source, shifts the position of noise sources and distorts radiation pattern. A theoretical investigation explicitly showed that the error is negligible for low Mach number (M<0.1). Furthermore, the phase error can be reduced by introducing a correction factor. Several numerical examples illustrate the feasibility of the proposed correction method for low Mach number.
Model experiment to study sonic boom propagation through turbulence. Part III: Validation of sonic boom propagation models
Authors: Lipkens Bart
Published: July 2002

In previous papers, we have shown that model experiments are successful in simulating the propagation of sonic booms through the atmospheric turbulent boundary layer. The results from the model experiment, pressure wave forms of spark-produced N waves and turbulence characteristics of the plane jet, are used to test various sonic boom models for propagation through turbulence. Both wave form distortion models and rise time prediction models are tested. Pierce’s model [A. D. Pierce, “Statistical theory of atmospheric turbulence effects on sonic boom rise times,” J. Acoust. Soc. Am. 49, 906–924 (1971)] based on the wave front folding mechanism at a caustic yields an accurate prediction for the rise time of the mean wave form after propagation through the turbulence.
Multifrequency acoustic measurement of concentration and grain size of suspended sand in water
Authors: Schat Jan
Published: July 2002

The paper describes an ultrasonic backscatter device for measuring vertical profiles of the concentration of suspended sand in water in the presence of air bubbles. The use of six frequencies permits a simultaneous measurement of the concentration of suspended sand, the grain size, and the concentration of air bubbles. For measuring in the near field of a transducer, the sensitivity of an ideal piston-like transducer in the near field is calculated and compared with measurements. A simple, but fast and efficient inversion algorithm to convert the backscattered intensities into sediment concentration and grain size is described. Measurements of known suspensions with concentration and grain size are presented, they exhibit a low error (20% rms) over a grain radius from 40 to 300 μm. In-situ measurements of the concentration of suspended sediment in the surf zone are compared with the results of two optical backscattering sensors (OBS).
Sound-power collection by the auditory periphery of the Mongolian gerbil Meriones unguiculatus: III. Effect of variations in middle-ear volume
Authors: Ravicz Michael E. , Rosowski John J.
Published: July 2002

The effects of variations in middle-ear cavity size on hearing sensitivity in the Mongolian gerbil are predicted by computing the effect on acoustic power input to the middle ear. Acoustic power collection from a diffuse sound field was computed from measurements of the middle-ear input impedance and external-ear radiation impedance and mathematical models of the middle and external ear presented in the first two papers of this series [J. Acoust. Soc. Am. 92, 157–177 (1992); J. Acoust. Soc. Am. 99, 3044–3063 (1996)]. A reduction in middle-ear cavity volume to 14 its normal value is predicted to cause a frequency-selective elevation in auditory threshold of as much as 12 dB, with the largest elevation occuring in the 1–2 kHz range. Greater reductions produce larger threshold elevations. Increases in cavity volume cause decreases in the predicted threshold of at most 12 dB. Threshold predictions for volumes equal to those of the smaller hamster and the larger kangaroo-rat middle-ear cavity volumes resemble threshold functions measured in those animals. Results are consistent with the idea that large middle-ear cavities evolved in gerbil to improve hearing sensitivity below 3 kHz and thereby improve the animal’s chances for survival.
Elastic guided waves in plates with surface roughness. I. Model calculation
Authors: Lobkis O. I. , Chimenti D. E.
Published: July 2002

This paper reports analytical research on the effect of surface roughness on ultrasonic guided waves in plates. The theoretical model is constructed by exploiting the phase-screen assumption that takes advantage of the Kirchhoff approximation, where, on a local scale, the roughness degrades only the signal phase. The effect of the rough surface on the guided wave is treated by decomposing the wave modes into their constituent partial waves and considering individually the effect of the roughness on the partial wave components as they reflect from the plate surfaces. An approximate dispersion relation is derived for the traction-free rough waveguide that is formally identical to the conventional Lamb wave equation, but incorporating the roughness parameter as a complex plate thickness. A more accurate version of the model calculation is generalized to fluid-immersed plates having only a single rough surface either on the same, or opposite, side of the plate as the incident ultrasonic field. Calculations of the reflection coefficients in the presence of roughness serve to illustrate the phenomena for the case of the guided waves.
Attenuation in suspensions of irregularly shaped sediment particles: A two-parameter equivalent spherical scatterer model
Authors: Schaafsma Arjen S. , Hay Alex E.
Published: July 2002

Results are presented from an acoustic attenuation spectroscopy study of suspensions of irregularly shaped sediment particles and of nominally spherical lead-glass beads. The measured spectra cover a wide frequency band of 1–100 MHz. It is shown that the spectra can be brought into close agreement with the rigid movable sphere model using two equivalent sphere size parameters. One parameter is the diameter dG of an equal cross-sectional area sphere, and is used to scale the frequency to obtain the nondimensional size/frequency parameter ka. The other parameter is the diameter dp of an equal volume sphere, and is used to scale the particle volume to obtain the particle number density N. It was observed that for the irregular particles the attenuation for ka>1 is enhanced with respect to the sphere case. The observed enhancement factors are considerable: up to 1.6 for natural sand particles and 1.8 for the most irregular particles studied (ground quartz). In terms of the two-parameter model the enhancement factor is equal to a shape parameter b0=(dG/dp)3 and can indeed be explained as a shape effect. The implications of this result for the acoustic detection of suspended sediments in aqueous environments are discussed.
The perception of frequency peaks and troughs in wide frequency modulations. IV. Effects of modulation waveform
Authors: Demany Laurent , Clément Sylvain
Published: July 2002

This work extends previous studies on the perceptual asymmetry between the local maxima and minima of wide frequency modulations (FMs) [L. Demany and K. I. McAnally, J. Acoust. Soc. Am. 96, 706–715 (1994); L. Demany and S. Clément, J. Acoust. Soc. Am. 97, 2454–2459 (1995); L. Demany and S. Clément, J. Acoust. Soc. Am. 98, 2515–2523 (1995)]. In experiment 1, subjects had to discriminate frequency shifts in the temporally central vertex of V- and Λ-shaped FMs imposed on 200-ms sinusoidal tone bursts. The precise shapes of these FMs varied in eight steps from quasi-triangles (with a durationless central vertex) to quasi-squares (with a long-duration central vertex). The central vertex was either a minimum or a maximum, but in each case the corresponding frequency was near 1000 Hz and the FM span was about 0.5 oct. For each FM shape, the discrimination threshold was lower when the vertex was a maximum than when it was a minimum, but (in four subjects out of five) this difference decreased monotonically as the FM became less and less triangular. FM shape had a remarkably small effect on the discrimination of the maxima, and the thresholds measured for the sharpest maxima were unexpectedly low. In subsequent experiments, subjects had to discriminate frequency shifts in the starting point or the final point of unidirectional FMs (tone glides) that spanned about 0.5 oct in 100 ms. The relevant frequency extremum was near 1000 Hz in each condition. At the final point of the glides, discrimination was better for rising glides than for falling glides. At the starting point of the glides, discrimination was better for falling glides than for rising glides. Thus discrimination was always better when the relevant frequency extremum was a maximum than when it was a minimum, and this effect was produced both “forward” and “backward.” The latter fact suggests that the perceptual asymmetry of FM originates at least partly from central factors.
Predicted scattering of sound by diffuse hydrothermal vent plumes at mid-ocean ridges
Authors: Duda Timothy F. , Trivett D. Andrew
Published: July 2002

Amplitude and phase fluctuations of monochromatic acoustic signals traveling through diffuse mid-ocean ridge hydrothermal vent plumes are modeled using existing theory in an attempt to find suitable frequencies and path lengths for plume monitoring. Weak-scattering solutions are evaluated numerically, with model parameters adjusted to match observed plume characteristics. Constraints required for weak-scattering solutions to be valid can be met for transmission ranges of 500–2000 m and frequencies of 20–80 kHz. Therefore, because fluid structure and scattering strength are more closely linked for weak scattering than for stronger scattering, inversion for fluid statistical properties may be possible, enabling diffuse vent monitoring. Such monitoring would be subject to geometric assumptions such as transmission entirely within a statistically homogeneous plume. Performance-limiting phase fluctuations have also been computed for a 13–17 kHz geodetic survey system.
Analysis of the micropipet experiment with the anisotropic outer hair cell wall
Authors: Spector Alexander A. , Brownell William E. , Popel Aleksander S.
Published: July 2002

The in-plane and bending stiffnesses of the outer hair cell wall are characteristics crucial to the understanding of force and energy transmission between cochlear elements. A mathematical interpretation is given of the micropipet experiment directed at determining the outer hair cell wall stiffness. On the basis of the microstructural observation of the wall showing that it comprises protein networks with different elastic properties, the model of an orthotropic cylindrical shell is used. The boundary-value problem is analyzed corresponding to the stress–strain state of the wall (shell) caused by the action of the micropipet. The solution is given in terms of Fourier series with respect to the circumferential coordinate. An asymptotic analysis of the solution is developed and an approximate formula for the length of the tongue aspirated within the pipet is derived. This leads to an analytical expression for the stiffness parameter measured in the micropipet experiment in terms of Young’s moduli and Poisson’s ratios of the wall. This expression is an important part of the estimation of the elastic constants of the wall.
Lattice Boltzmann methods in acoustics
Authors: Buick James M. , Campbell D. Murray , Greated Clive A.
Published: July 2002

The lattice Boltzmann model is a recently developed technique for the numerical simulation of fluid motion. It has been successfully applied to a variety of incompressible fluid phenomena and has been shown to be an efficient simulation tool which is ideally suited for implementation on massively parallel computers. Here the application of the lattice Boltzmann model is considered to simulate acoustical processes in which the fluid can, to a first approximation, be considered to be incompressible. The validity and limitations of this approach are considered and the results of simulations performed on the Cray T3D at Edinburgh University are presented. These include sound propagation in tubes, modeling of air flow in the mouthpiece of brass instruments, and the simulation of acoustic streaming in tubes and around cylinders. In each case the fluid velocity, density, and pressure are found at each grid point and each time-step of the simulation, allowing flow patterns and density changes to be observed. The results of the simulations are compared to the predictions of theory and/or experimental observations and suggest that the lattice Boltzmann method can be used as a numerical tool to give insight into complex acoustical situations.
Dispersion of nonlinearity, nonlinear dispersion, and absorption of sound in micro-inhomogeneous materials
Authors: Gusev Vitalyi E. , Lauriks Walter , Thoen Jan
Published: July 2002

New evolution equations for nonlinear acoustic waves in micro-inhomogeneous media, which take into account relaxation processes, are derived. The proposed theory provides the description of such physical effects as frequency-dependent nonlinear absorption of sound, nonlinearity of its velocity dispersion, and dispersion of the nonlinear acoustic parameters of micro-inhomogeneous materials. The theory predicts that, depending on the ratio of the characteristic relaxation time to the wave period, nonlinearity can grow or diminish with increasing frequency, while an increase in wave amplitude can lead to a rise or fall of the propagation velocity. In the limiting cases where the relaxation processes are instantaneous or quasi-frozen, analytical solutions of the nonlinear equations are found and analyzed.
Active control of sound transmission through a double-leaf partition by volume velocity cancellation
Authors: Pan X. , Sutton T. J. , Elliott S. J.
Published: July 2002

The paper considers the active control of harmonic sound transmitted through a double-leaf partition by cancelling the volume velocity of the radiating panel. The double-leaf partition consists of a pair of small plates, 300×380 mm, separated by a 100-mm air-gap. The panel volume velocity can be sensed by a single shaped film of piezoelectric PVDF material attached to the plate. Cancellation of volume velocity using a single point force is compared with the result using a matched, distributed actuator which applies a uniform force to the plate and does not give rise to control spillover. Comparison with earlier work in which the volume velocity of a single plate was cancelled [Johnson and Elliott, J. Acoust. Soc. Am. 98, 2174–2186 (1995)] shows that substantial reductions in the transmitted sound power are only possible up to around 350 Hz, as opposed to 600 Hz in the single panel case. A radiation mode analysis of the panels shows that the double-leaf construction provides good passive attenuation of the first radiation mode at high frequencies, so that inefficiently radiating even modes of the radiating panel make a dominant contribution to the radiated sound power. Thus there is no advantage in controlling volume velocity in this frequency range.
Highly resolved detection and selective focusing in a waveguide using the D.O.R.T. method
Authors: Mordant Nicolas , Prada Claire , Fink Mathias
Published: July 2002

The D.O.R.T. method (French acronym for Decomposition of the Time Reversal Operator) is a scattering analysis technique using an array of transducers. The method is effective to achieve detection and selective focusing on pointlike scatterers through inhomogeneous media [J. Acoust. Soc. Am. 99, 2067–2076 (1996)]. Laboratory measurements in a water waveguide are presented. Taking advantage of the multiple reflections at the interfaces of the guide, high resolution is achieved with the D.O.R.T. method. The separation of two scatterers and the selective focusing are obtained with a transverse resolution at least nine times better than the free-space limit prediction. The detection of a scatterer from the water/air interface of the guide is also achieved with high resolution (1/20 of the free space diffraction spot). The effect on the D.O.R.T. method of surface waves produced at one interface of the guide is measured. Finally, the impulse response function of each scatterer to the array is computed as a combination of the eigenvectors of the time-reversal operator obtained at each frequency. Using these impulse Green’s functions, selective focusing with high temporal and spatial compression is performed.
Experimental study of a radial mode thermoacoustic prime mover
Authors: Lightfoot Jay A. , Arnott W. Patrick , Bass Henry E. , Raspet Richard
Published: July 2002

The purpose of this research is to branch out from thermoacoustics in the plane wave geometry to study radial wave thermoacoustic engines. The radial wave prime mover is described. Experimental results for the temperature difference at which oscillations begin are compared with theoretical predictions. Predictive models often assume a uniform pore size and temperature continuity between the stack and heat exchangers; however, stacks of nonuniform pore size and temperature discontinuities between the stack and heat exchangers are common imperfections in experimental devices. The radial engine results are explained using a theoretical model which takes into account these prevalent construction flaws. Theory and experiment are shown to be in agreement after the complications are included. Spectral measurements show that an additional feature of the radial geometry is the anharmonicity of the resonant modes which significantly reduces nonlinear harmonic generation.
Errors due to sensor and position mismatch in planar acoustic holography
Authors: Nam Kyoung-Uk , Kim Yang-Hann
Published: July 2002

There are many sources of measurement errors when one attempts to construct a hologram of near-field acoustic holography. These errors are amplified when predicting pressure at a point which is located near an acoustic source. Errors due to a sensor mismatch and an inaccurate measurement location, or position mismatch, are the main interests of this study. We theoretically measure the errors in terms of their probabilities, bias, and random error. Analysis in a wave number domain shows that the bias error can be regarded as negligible, but the random error is significant in a backward prediction. The random error is suggested to be measured in terms of random error energy. Then, the amplification ratio of the random error energy is related to measurement spacing on a hologram plane, prediction spacing on a prediction plane, and the distance between the hologram and prediction plane.
X-ray powder diffraction studies of a new compound: Th13Te24O74
Authors: Tripathi S. N. , Achary S. N. , Namboodiri P. N.
Published: July 2002

The compound Th13Te24O74 was prepared by three independent methods, namely, thermal decomposition of ThTe2O6 in oxygen and argon and direct solid-state reaction of ThO2 and TeO2. The X-ray powder diffraction patterns of the three products, by and large, are similar, except for some differences in intensities and extra diffraction lines. The thermal decomposition of ThTe2O6 was carried out in the streams of oxygen and argon by thermogravimetry at a heating rate of 5 K/min in the temperature range of 725–840 °C. The solid-state reaction of ThO2 and TeO2 (13:24) was carried out in a sealed ampoule at 700 °C. The measured density of this compound is 8.23 g/cm3. An orthorhombic lattice with unit cell parameters, a=11.310±0.005 Å, b=14.064±0.006 Å, c=9.056±0.004 Å, and volume of 1440.419±1.088 (Å)3 was determined for this compound.
Recyclable 2D Colloid Surfactants with High Catalytic Activities at Pickering Emulsion Interfaces
Authors: Seo Bokgi , Sung Minchul , Park Bum Jun , Kim Jin Woong
Published: February 2022

This study introduces a novel 2D colloid surfactant system that exhibits catalytic activity at the interface of a reactant‐containing water‐in‐oil Pickering emulsion microreactor. To this end, amphiphilic nanoplatelets (ANPLs) are fabricated with hydrophobic poly (n‐butyl methacrylate) brushes on one face, and hydrophilic poly (2‐aminoethyl methacrylate) brushes on the other face via surface‐induced activators regenerated by electron transfer atom transfer radical polymerization (SI‐ARGET ATRP) on zirconium hydrogen phosphate (ZrHP) nanoplatelets. Subsequently, in situ reduction of metal precursors on the primary amine reaction sites on the hydrophilic face of ANPLs is conducted, thus enabling the production of ANPL catalysts (ANPLcat): ANPLAg, ANPLPd, and ANPLAu. Owing to the platelet geometry and catalytic functionalization, the ANPLcat demonstrates excellent ability to stabilize the Pickering emulsion reactant drops, while exhibiting its own catalytic activity at the interface. It is demonstrated that this ANPLcat system has a high catalytic activity that requires a short reduction reaction time with the speed of which is 750% higher compared with the spherical colloidal surfactant catalyst. In addition, ANPLcat is easily recoverable and recyclable. These results highlight that the ANPLcat‐based emulsion microreactor system is expected to be widely applied as a high‐performance catalyst for various organic chemical reactions.
A “Closed‐Loop” Therapeutic Strategy Based on Mutually Reinforced Ferroptosis and Immunotherapy
Authors: Du Yaqian , Zhang Rui , Yang Jiani , Liu Shikai , Zhou Jialing , Zhao Ruoxi , He Fei , Zhang Yanqiao , Yang Piaoping , Lin Jun
Published: February 2022

The immunosuppression and immune escape of current immunotherapy result in low efficacy, and ferroptosis is greatly restricted by the low reactive oxygen species (ROS) production efficiency. Here, for the first time a “closed‐loop” therapy based on photothermal enhancement of ferroptosis and immunotherapy stimulated by each other on a multifunctional nanoplatform is reported. This platform is composed of copper silicate and iron silicate mesoporous hollow nanospheres, followed by in situ growth of Au nanoparticles and loading of an immune adjuvant resiquimod R848. The laser irradiation‐mediated heat and the introduction of copper ions significantly enhance ROS generation, leading to the simultaneous depletion of glutathione peroxidase 4 (GPX4) and glutathione (GSH). The onset of ferroptosis in tumor cells is thus enhanced and an immune response with immunogenic cell death (ICD) is triggered, promoting the dendritic cells (DCs) maturation and T cell infiltration. Interferon γ (IFN‐γ) released from CD8+ T cells downregulates the expression of SLC7A11 and GPX4, which in turn enhances ferroptosis expression, thus constituting a “closed‐Loop” therapy. Importantly, this system is effective in both killing the primary tumor and inhibiting tumor metastasis. The proposed “closed‐loop” therapeutic strategy may provide a guidance for the design of future antitumor nanoplatforms.
Band Alignment at Heterointerface with Rapid Charge Transfer Supporting Excellent Photocatalytic Degradation of Methylene Blue under Sunlight
Authors: Talukdar Meenakshi , Behera Sushant Kumar , Jana Subrata , Samal Prasanjit , Deb Pritam
Published: February 2022

Engineering 2D heterostructure using proximitized interfaces is an effective approach to attain high efficiency photocatalytic performance toward dye degradation. Strong interfacial interaction and abundant coupled interfaces and 2D/2D face‐to‐face contact heterostructure facilitate efficient charge separation contributing to high photocatalytic activity. In this aspect, for the first time the authors have analyzed the band alignment of the 2D/2D heterojunction, using Perdew–Burke–Ernzerhof semilocal meta‐generalized‐gradient approximation case and Heyd–Scuseria–Ernzerhof hybrid functional approach in density functional theory stimulation. Close proximity of CuSe nanoflakes with carbon nitride sheets facilitate electron transfer process leading to more proficient photocatalytic degradation, which is confirmed from the inverse participation ratio of individual atoms on the proximitized hetero interface and electrostatic potential line‐ups. The results demonstrate that this 2D/2D heterostructure has desired type‐II band alignment, which is facilitating rapid separation of photogenerated carriers in support of experimental findings. The face‐to‐face contact heterostructure with effective separation and low recombination rate of photogenerated electron–hole pairs helps in complete degradation of dye within 15 min. Further, the brilliance in photocatalytic performance of the developed type II heterostructure correlating with experimental results has introduced this system as a new class of material for wastewater treatment.
Microporous‐Ceria‐Wrapped Gold Nanoparticles for Conductometric and SERS Dual Monitoring of Hazardous Gases at Room Temperature
Authors: Bao Haoming , Guo Yujing , Zhang Tao , Fu Hao , Zhu Shuyi , Zhou Le , Zhang Hongwen , Li Yue , Cai Weiping
Published: February 2022

This work proposes a novel and simple synthesis method for microporous‐ceria‐wrapped gold (Au@mp‐CeO2) nanoparticles (NPs) based on linker molecule‐induced stacking of ultrafine CeO2 particles (or beads) on the surface of pre‐prepared gold NPs. The resulting NPs have a uniform size and microporous CeO2 shells with a mean thickness of 28 nm and porosity of 42%. The shell is highly tunable from about 4 to 30 nm thick. This method is universal and suitable for other metal@mp‐oxide nanoarchitectures (such as Au@mp‐CuO NPs, Au@mp‐Cr2O3 NPs, Ag@mp‐CeO2 NPs, and Ag@mp‐CeO2 nanowires) simply via changing the pre‐prepared metal cores or shell precursors. Most significantly, the as‐prepared Au@mp‐CeO2 NPs can be used for accurate monitoring of toluene vapor (10 ppm level) at room temperature based on their conductometric and surface‐enhanced Raman spectroscopy (SERS) dual response. Moreover, these NPs can be also used for other hazardous gases, such as chlorobenzene, hydrogen sulfide, and 1‐dodecanethiol. This excellent performance benefits from the micropore‐enhanced interaction between CeO2 and gas molecules. This work not only provides new and controllable preparation for metal@mp‐oxide nanoarchitectures, but also demonstrates the great potential applications of these materials in real‐time and identifiable monitoring of hazardous gases.
Resonance Frequency Tuning of a 200 GHz Band Absorber by an External Magnetic Field
Authors: Tsukamoto Seiya , Oki Yurie , Imoto Kenta , Namai Asuka , Yoshikiyo Marie , Ohkoshi Shin-ichi
Published: February 2022

The effect of the external magnetic field on the millimeter‐wave absorption of rhodium‐substituted epsilon iron oxide, ε‐Rh0.13Fe1.87O3 (1) and ε‐Rh0.19Fe1.81O3 (2) nanomagnets, is investigated. Terahertz time‐domain spectroscopy (THz‐TDS) shows that 1 and 2 display a zero‐field ferromagnetic resonance (the so‐called natural resonance) at 201 GHz with a linewidth of 20 GHz and at 210 GHz with a linewidth of 30 GHz, respectively. The ferromagnetic resonance is measured under an external magnetic field (H
ex). Applying +3.5 kOe parallel to the remnant magnetization and −3.5 kOe antiparallel to the remnant magnetization shifts the resonance frequency at 201 GHz in 1 by +6 and −4 GHz and that in 2 by +4 and −4 GHz, respectively. Simulations of the ferromagnetic resonance using the Landau−Lifshitz−Gilbert model reproduce the magnetic field‐induced shifts of the resonance frequencies. The 220 GHz band millimeter wave is the highest frequency with a high transparency for “atmospheric windows” and is expected to be a carrier frequency for sixth‐generation mobile communication systems (6 G) or 7 G. This study may help realize applications for millimeter‐wave isolators, circulators, or shutters.
Resonant Magnetooptical Effects in Encapsulated 1D Plasmonic Crystals
Authors: Pomozov Alexander R. , Maydykovskiy Anton I. , Ketsko Valerii A. , Stognij Alexander I. , Murzina Tatiana V.
Published: February 2022

New approaches for the composition of efficient robust plasmonic crystals are very desired for practical applications as well as for the observation of new exciting effects at the nanoscale. Herein, both experimentally and theoretically resonant optical effects in encapsulated magnetoplasmonic crystals composed of a 1D gold grating sandwiched between two layers of iron garnet with slightly different dielectric properties are studied. It is demonstrated that depending on the geometry of the magnetic field application, various mechanisms provide resonant enhancement of the magnetooptical (MO) response of the structure; the strongest MO effect is attained for the case of waveguide modes propagating in iron garnet dielectric layer along the longitudinal magnetic field, when the magnetization‐induced rotation of the polarization plane up to a few degrees is observed. The obtained results demonstrate high potential of magnetoplasmonic waveguides as stable and efficient plasmonic devices.
Probing the functional consequence and clinical relevance of CD320 p.E88del, a variant in the transcobalamin receptor gene
Authors: Pangilinan Faith , Watkins David , Bernard David , Chen Yue , Dong Ningzheng , Wu Qingyu , Ozel‐Abaan Hatice , Kaur Manjit , Caggana Michele , Morrissey Mark , Browne Marilyn L. , Mills James L. , Van Ryzin Carol , Shchelochkov Oleg , Sloan Jennifer , Venditti Charles P. , Sarafoglou Kyriakie , Rosenblatt David S. , Kay Denise M. , Brody Lawrence C.
Published: February 2022

The biological and clinical significance of the p.E88del variant in the transcobalamin receptor, CD320, is unknown. This allele is annotated in ClinVar as likely benign, pathogenic, and of uncertain significance. To determine functional consequence and clinical relevance of this allele, we employed cell culture and genetic association studies. Fibroblasts from 16 CD320 p.E88del homozygotes exhibited reduced binding and uptake of cobalamin. Complete ascertainment of newborns with transiently elevated C3 (propionylcarnitine) in New York State demonstrated that homozygosity for CD320 p.E88del was over‐represented (7/348, p < 6 × 10−5). Using population data, we estimate that ~85% of the p.E88del homozygotes born in the same period did not have elevated C3, suggesting that cobalamin metabolism in the majority of these infants with this genotype is unaffected. Clinical follow‐up of 4/9 homozygous individuals uncovered neuropsychological findings, mostly in speech and language development. None of these nine individuals exhibited perturbation of cobalamin metabolism beyond the newborn stage even during periods of acute illness. Newborns homozygous for this allele in the absence of other factors are at low risk of requiring clinical intervention, although more studies are required to clarify the natural history of various CD320 variants across patient populations.
Drastic Events and Gradual Change Define the Structure of an Active Copper‐Zinc‐Alumina Catalyst for Methanol Synthesis
Authors: Beck Arik , Newton Mark A. , Zabilskiy Maxim , Rzepka Przemyslaw , Willinger Marc G. , van Bokhoven Jeroen A.
Published: February 2022

The copper‐zinc‐alumina (CZA) catalyst is one of the most important catalysts. Nevertheless, understanding of the complex CZA structure is still limited and hampers further optimization. Critical to the production of a highly active and stable catalyst are optimal start‐up procedures in hydrogen. Here, by employing operando X‐ray absorption spectroscopy and X‐ray diffraction, we follow how the industrial CZA precursor evolves into the working catalyst. Two major events in the activation drastically alter the copper‐ and zinc‐containing components in the CZA catalyst and define the final working catalyst structure: the reduction of the starting copper(II) oxide, and the ripening and re‐oxidation of zinc oxide upon the switch to catalytic conditions. These drastic events are also accompanied by other gradual, structural changes. Understanding what happens during these events is key to develop tailored start‐up protocols that are aimed at maximal longevity and activity of the catalysts.