Radial Frequency Research Articles

Why and How is Burrow Ventilation Initiated? A Case Study of Polychaete Behavior in the Burrow at Different Temperatures

Bioirrigation is a process corresponding to animal-induced transport of porewater solute or exchange between interstitial and overlying waters. How and why the burrowing macrobenthos complete this process remain unclear. Here, we used two infaunal-behavior observation devices to investigate the ventilation behaviors of the benthic polychaete Perinereis aibuhitensis Grube, a species that is widespread along the Asian coast with a wide temperature range, at various temperatures (5°C, 10°C, 15°C, 20°C, and 25°C). The two typical movement behaviors of P. aibuhitensis, axial crawling and radial undulation, as well as associated parameters, were delimited and quantified. We found that the radial undulation frequency of P. aibuhitensis and the associated pumping rate (PR) increased significantly with temperature (T, 5-25°C); this relationship can be described by the regression equation PR = −0.0067T2 + 0.29T - 0.52 (R2 = 0.749, P < 0.05; n = 15). The relationship between axial crawling velocity (ACV) and temperature (T, 5-25°C) can be expressed by the regression equation ACV = -0.0001T3 + 0.0059T2 - 0.063T + 0.28 (R2 = 0.997, P<0.05; n = 15). In general, pumping efficiency increased as temperature decreased, implying that the polychaete increasingly conserved energy at lower temperatures. Peak pumping volume (4.36 L d-1) was observed at 25°C, as a result of radial undulations. Thus, we concluded that radial undulation was the primary movement that led to bioirrigation. The dissolved oxygen demand was the key factor driving the initiation of radial undulation, and the specific aim of radial undulation was to increase oxygen availability by pumping new seawater into the burrow. Thus, radial undulation is critical for polychaete survival. The dissolved oxygen threshold level at which pumping was initiated increased with temperature, suggesting more energy conserved at lower temperatures. This pumping strategy of P. aibuhitensis is consistent with optimality theory, and is here designated the “optimal dissolved oxygen obtainment strategy”.

KIC 5768203: A δ Sct Pulsator Modulated by Rotation and Spots

We perform a detailed analysis of the Kepler target KIC 5768203 based on the Kepler and Transiting Exoplanet Survey Satellite (TESS) data. Three independent frequencies are detected by Fourier analysis of the Kepler long-cadence data: two pulsation frequencies f P0 = 7.807874(2) day−1 and f P1 = 9.970035(6) day−1, which have amplitudes below 1.4 mmag in the Kepler band, and one modulation frequency f rot = 0.45813(1) day−1. Based on a period ratio of 0.7803, f P0 and f P1 are supposed to be radial frequencies. However, further confirmation is needed. Based on the triplets and phase variations of the two pulsation frequencies, the star is possibly a δ Sct pulsator in a binary system. The modulation frequency f rot and its four harmonics could be attributed to the stellar rotation and surface spots. With the rotation frequency f rot, the rotation velocity of the star is estimated to be 75(3) km s−1. By analyzing the phase diagram without pulsations, it is inferred that there are starspots (or clusters of starspots) of large area on the surface of KIC 5768203. These starspots are slowly evolving in position and brightness over the course of the Kepler long-cadence observations. The finding of the rotation frequency in the TESS data implies the long-term presence of starspots on the surface of KIC 5768203.

Scotopic Contour Deformation Detection Reveals Early Rod Dysfunction in Age-Related Macular Degeneration With and Without Reticular Pseudodrusen.

PurposeThe purpose of this study was to investigate scotopic contour deformation detection (sCDD), and its structural determinants, in participants with intermediate age-related macular degeneration (iAMD) with or without reticular pseudodrusen (RPD).MethodsForty-one participants (aged 58–89 years), including 9 with iAMD and RPD, 16 with iAMD only, and 16 controls, underwent functional testing. The sCDD was evaluated with radial frequency arcs presented at 4 loci: ±4 degrees and 8 degrees vertical eccentricity. Scotopic thresholds and dark adaptation (DA) were measured at the same loci. Retinal layers of spectral domain optical coherence tomography (SD-OCT) volume scans were segmented. To establish the concurrent validity of the functional test, we evaluated the fraction of variability in sCDD thresholds explained by SD-OCT data.ResultsThe iAMD group had significantly worse sCDD thresholds compared with controls (8 degrees inferior retina: P = 0.004 and the 4 degrees loci: P < 0.02 for both). Elevated sCDD thresholds were observed in iAMD and RPD eyes at loci with normal scotopic thresholds; the opposite was rarely encountered. Elevated sCDD thresholds were also observed in iAMD eyes with normal DA. Elevated sCDD thresholds were associated with increased age and presence of late AMD in the fellow eye. The optimal machine learning model predicted 16% of variability (cross-validated R2) in sCDD thresholds at 8 degrees.DiscussionA novel scotopic contour deformation task can provide unique information about rod dysfunction in participants with iAMD and RPD not observed with structural and other functional assessments. Rod dysfunction observed with scotopic contour deformation testing was associated with factors linked to risk of AMD progression.

An analytical approach to design horns and boosters of ultrasonic welding machines

This paper presents a new design approach for two main components of an ultrasonic plastic welding machine, booster and horn, based on an analytical model. The design procedure is developed due to the lack of a comprehensive and precise analytical model for rapid design and analysis of these components. The previous analytical models use the one-dimensional wave equation that causes significant errors in designing components with large lateral dimensions. Three-dimensional vibrations are considered for developing an analytical model using the apparent elasticity method. In this way, longitudinal frequency equations are coupled with radial frequency equations by mechanical coupling coefficients. Also, the damping of materials is taken into account. The model can be adapted to calculate the resonant length of the components or calculate the resonant frequency. To verify the model, the results are compared to a numerical simulation. The difference between analytical and numerical resonance frequency is less than 0.02%. Moreover, an experimental modal analysis is performed, which shows 0.9% error with analytical results.Article highlightsA new design approach for boosters and horns has been developed based on an analytical model.Three-dimensional vibrations are considered in the model using the apparent elasticity method.The accuracy of calculating resonant frequencies is more than one-dimensional design method.

Dynamic response characteristics of adjacent tunnel lining under blasting impact in subway connecting passage

The connecting passage between two adjacent tunnels is conducive to the rescue and evacuation of subway tunnels when disasters occur. The blasting method is usually used in the construction of connecting passage. The vibration caused by blasting construction may endanger the safety of subway tunnel structure. As a result, the influence of blasting pressure on the stability of subway tunnel lining structure during the excavation of connecting passage is studied, and the safe blasting construction distance is proposed, which is crucial to the safety of adjacent subway tunnel lining. This study takes the connecting passage of Wuhan Metro Line 8 as an example. Using Finite element software ANSYS/LS-DYNA, an accurate numerical calculation model of construction site is established. The nonlinear elastoplastic mechanical characteristics of soil, rock, and tunnel lining are simulated by Drucker Prager, Plastic Kinematic, and Johnson Holmquist Concrete constitutive material models, respectively. The credibility of the three-dimensional numerical calculation model and material constitutive model was proved by contrasting the field measured data of the connecting passage with the numerical calculated results. Analysis of numerical results, the axial and radial PPV, frequency, and Von Mises stress of subway tunnel lining are obtained. The influence of subway tunnel lining under adjacent blasting can be obtained by analyzing the distribution law of PPV and Von Mises stress. Non-static tensile strength is needed considering the high pressure and high strain rate process of concrete during blasting. By fitting the relationship between PPV and dynamic tensile stress, and referring to DIF parameters, the safety range of PPV in subway tunnel lining blasting is determined. The critical safety distance between blasting construction and tunnel lining is obtained by Sadovsky vibration velocity attenuation formula, which is used to guide the subsequent blasting excavation of continuous tunnels.

Short-range correlation effects in neutron star's radial and non-radial oscillations * *Supported by the National Key Research and Development Program of China (2017YFA0402600, 2016YFE0129300), the National SKA Program of China (2020SKA0120300) and the National Natural Science Foundation of China (11833003, 11947211, 119051)

In this study, we determine the influence of the nucleon-nucleon short range correlation (SRC) on static spherically symmetric neutron stars (NSs) from the perspectives of radial and nonradial oscillations for the first time. We revise the equation of state and coupling parameters in the relativistic mean field theory after considering the SRC effect, and select the hyperon coupling parameters as the SU(3) model. For the non-radial oscillations, the SRC effect decreases the -mode frequency by kHz. For the radial oscillations, it decreases the fundamental radial frequency by 0.75 ~ 0.85 kHz. Additionally, we refit the linear relationship between the average density and -mode frequency for SRC. Combining the characteristics of the radial and non-radial frequencies, we provide a view of inferring the maximum mass of NSs. Owing to the characteristics of the SRC influence on the radial frequency, we expect that the SRC can be tested by future observation and can also be used as a probe for the structure inside NSs.

Tunable Three-Body Interactions in Driven Two-Component Bose-Einstein Condensates.

We propose and demonstrate the appearance of an effective attractive three-body interaction in coherently driven two-component Bose-Einstein condensates. It originates from the spinor degree of freedom that is affected by a two-body mean-field shift of the driven transition frequency. Importantly, its strength can be controlled with the Rabi-coupling strength and it does not come with additional losses. In the experiment, the three-body interactions are adjusted to play a predominant role in the equation of state of a cigar-shaped trapped condensate. This is confirmed through two striking observations: a downshift of the radial breathing mode frequency and the radial collapses for positive values of the dressed-state scattering length.

Hiding the Rabbit: Using a genetic algorithm to investigate shape guidance in visual search.

During visual search, attention is guided by specific features, including shape. Our understanding of shape guidance is limited to specific attributes (closures and line terminations) that do not fully explain the richness of preattentive shape processing. We used a novel genetic algorithm method to explore shape space and to stimulate hypotheses about shape guidance. Initially, observers searched for targets among 12 random distractors defined, in radial frequency space, by the amplitude and phase of 10 radial frequencies. Reaction time (RT) was the measure of “fitness.” To evolve toward an easier search task, distractors with faster RTs survived to the next generation, “mated,” and produced offspring (new distractors for the next generation of search). To evolve a harder search, surviving distractors were those yielding longer RTs. Within eight generations of evolution, the method succeeds in producing visual searches either harder or easier than the starting search. In radial frequency space, easy distractors evolve amplitude × frequency spectra that are dissimilar to the target, whereas hard distractors evolve spectra that are more similar to the target. This method also works with naturally shaped targets (e.g., rabbit silhouettes). Interestingly, the most inefficient distractors featured a combination of a body and ear distractors that did not resemble the rabbit (visually or in spectrum). Adding extra ears to these distractors did not impact the search spectrally and instead made it easier to confirm a rabbit, once it was found. In general, these experiments show that shapes that are clearly distinct when attended are similar to each other preattentively.

Dynamical evolution of dark matter admixed neutron stars

We dynamically evolve for the first time dark matter admixed neutron stars with fermionic dark matter. These systems are mixtures of the ordinary nuclear matter of a neutron star and dark matter. To perform our dynamical evolutions, we derive the equations of motion, in conservation form, for spherically symmetric systems with an arbitrary number of perfect fluids. Using finite volume and high-resolution shock-capturing methods, we dynamically evolve the two-fluid case, with the first fluid modeling ordinary matter and the second fluid modeling dark matter. We use our dynamical solutions to study nonlinear stability, radial oscillation frequencies, and a dynamical formation process.

Radial Oscillations of Quark Stars Admixed with Dark Matter

We investigated compact stars consisting of cold quark matter and fermionic dark matter treated as two admixed fluids. We computed the stellar structures and fundamental radial oscillation frequencies of different masses of the dark fermion in the cases of weak and strong self-interacting dark matter. We found that the fundamental frequency can be dramatically modified and, in some cases, stable dark strange planets and dark strangelets with very low masses and radii can be formed.

CORALIE radial velocity search for companions around evolved stars (CASCADES)

Context. The advent of asteroseismology as the golden path to precisely characterize single stars naturally led to synergies with the field of exoplanetology. Today, the precise determination of stellar masses, radii and ages for exoplanet-host stars is a driving force in the development of dedicated software and techniques to achieve this goal. However, as various approaches exist, it is clear that they all have advantages and inconveniences and that there is a trade-off between accuracy, efficiency, and robustness of the techniques. Aims. We aim to compare and discuss various modelling techniques for exoplanet-host red giant stars for which TESS data are available. The results of the seismic modelling are then used to study the dynamical evolution and atmospheric evaporation of the planetary systems. Methods. We study, in detail, the robustness, accuracy and precision of various seismic modelling techniques when applied to four exoplanet-host red giants observed by TESS. We discuss the use of global seismic indexes, the use of individual radial frequencies and that of non-radial oscillations. In each case, we discuss the advantages and inconveniences of the modelling technique. Results. We determine precise and accurate masses of exoplanet-host red giant stars orbited by long-period Jupiter-like planets using various modelling techniques. For each target, we also provide a model-independent estimate of the mass from a mean density inversion combined with radii values from Gaia and spectroscopic data. We show that no engulfment or migration is observed for these targets, even if their evolution is extended beyond their estimated seismic ages up the red giant branch.

Parametric Mid-Spatial Frequency Surface Error Synthesis

Standard mid-spatial frequency tooling mark errors were parameterized into a series of characteristic features and systematically investigated. Diffraction encircled and ensquared energy radii at the 90% levels from an unpowered optical surface were determined as a function of the root-mean-square surface irregularity, characteristic tooling mark parameters, fold mirror rotation angle, and incident beam f-number. Tooling mark frequencies on the order of 20 cycles per aperture or less were considered. This subset encompasses small footprints on single-point diamond turned optics or large footprints on sub-aperture tool polished optics. Of the characteristic features, off-axis fabrication distance held the highest impact to encircled and ensquared energy radii. The transverse oscillation of a tooling path was found to be the second highest contributor. Both impacts increased with radial tooling mark frequency.

Shortening the Leuven Perceptual Organization Screening Test with item response theory and confirmatory factor analysis.

The Leuven Perceptual Organization Screening Test (L-POST) is a test for midlevel visual perceptual deficits after brain injury. Previous research demonstrated reliable test scores and valid test score interpretations. However, the test's duration (20-35 min) is too long for a screening approach for all patients in clinical practice. Our aim was to shorten L-POST to 10-15 min based on statistical criteria of the items. Data from 3,391 participants who completed L-POST were analyzed. L-POST consists of 15 subtests with five items each. Item Response Theory (IRT) was applied to guide the selection of the items. The highest correlation with full-scale subtest scores was observed when two items were selected for each subtest following an adaptive testing procedure. A pilot validation in a subsample of participants with low abilities demonstrated adaptive testing has reasonable sensitivity (80%) but limited specificity (55%) in classifying participants with impaired and unimpaired abilities. Subsequently, we reduced the number of subtests through factor analysis. We showed that the subtests using Radial Frequency Patterns as stimuli were redundant and could be combined in one subtest. We conclude that L-POST can be shortened to 26 items (7-14 min) and an adaptive item selection procedure could prove particularly useful for screening purposes. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Internal resonance and nonlinear dynamics of a dielectric elastomer circular membrane

Dielectric elastomers (DE) are widely used in several applications such as artificial muscles, sensors or energy harvesters. Their hyperelastic nature complicates their design because of the obtained rich dynamics. The electrical field applied in the material, couples the dynamics of these devices to the applied voltage through compliant electrodes. In this work, a circular DE membrane under mechanical and electrical excitations is analyzed in order to seek internal resonances capable of increasing its performance for future applications. The hyperelastic properties of the material and the Maxwell stresses are taken into account to derive the nonlinear governing equation. Analytical and numerical approaches are used to obtain the dynamic solution of the device under different prestretch and electrical conditions. The effect of the prestretch on the first transverse and radial natural frequencies is first calculated analytically and validated by a finite element software. One-to-one, two-to-one and three-to-one internal resonances are possible as the prestretch applied to the membrane is varied. Using a Galerkin procedure and a multiple scale technique, the frequency response curves are obtained for different applied voltages. The results are validated using a Runge–Kutta time discretization technique. Finally, the effect of the applied voltage is analyzed for the frequency response curves of the radial and transverse displacements.

Dynamics and fundamental frequencies of test particles orbiting Kerr–Newman–NUT–Kiselev black hole in Rastall gravity

The spacetime properties in the exterior of the Kerr–Newman–NUT–Kiselev black hole in the Rastall theory of gravity, through particle dynamics, are investigated with the aim to find possible degeneracy of the different black hole parameters. We show that the effective potential, the energy, and the angular momentum of a test particle moving in the spacetime of such a black hole strongly depend on the central black hole parameters. We also evaluate the innermost stable circular orbit radii of test particles and show how the spacetime parameters can act on them. Further, we show the results for the fundamental frequencies of test particles moving at small distances from the circular orbits in the equatorial plane. We demonstrate that change in the Rastall parameter $$\kappa \lambda $$ can make the radial epicyclic frequency to become zero at larger distances from the central source. We also notice that for the vertical epicyclic frequencies, in the case of the Kerr–Newman–NUT–Kiselev black hole in the Rastall theory of gravity lower frequencies, are observed as compared to the frequencies observed in the case of the Kerr black hole. Finally, we show that for the Kerr–Newman–NUT–Kiselev black hole in the Rastall gravity, the Keplerian frequencies are almost identical with the frequencies noticed in the case of the Kerr black hole and the difference between the two can only be observed in the regions in a very close vicinity to the central black hole, studied in the present work.

Advanced machine learning decision policies for diameter control of carbon nanotubes

The diameters of single-walled carbon nanotubes (SWCNTs) are directly related to their electronic properties, making diameter control highly desirable for a number of applications. Here we utilized a machine learning planner based on the Expected Improvement decision policy that mapped regions where growth was feasible vs. not feasible and further optimized synthesis conditions to selectively grow SWCNTs within a narrow diameter range. We maximized two ranges corresponding to Raman radial breathing mode frequencies around 265 and 225 cm−1 (SWCNT diameters around 0.92 and 1.06 nm, respectively), and our planner found optimal synthesis conditions within a hundred experiments. Extensive post-growth characterization showed high selectivity in the optimized growth experiments compared to the unoptimized growth experiments. Remarkably, our planner revealed significantly different synthesis conditions for maximizing the two diameter ranges in spite of their relative closeness. Our study shows the promise for machine learning-driven diameter optimization and paves the way towards chirality-controlled SWCNT growth.

Faraday waves in strongly interacting superfluids

We report on the observation of Faraday waves in a cigar-shaped Fermi superfluid of 6Li parametrically excited by modulating the radial trap frequency. We characterize the phenomenon as a function of the interaction parameter employing a Feshbach resonance. Starting from the BEC side of the resonance, we observe a reduction of visibility of the Faraday pattern as we approach unitarity, possibly due to the increased incompressibility of the system. We probe the superfluid excitation spectrum by extracting an effective 1D speed of sound for different values of the interaction parameter, in good agreement with numerical simulations. We also discuss the effects introduced by the finite size of the sample. Finally, we introduce a novel model based on Floquet theory that we employ to perform a stability analysis in the parameter space, showing the emergence of the Faraday waves as unstable solutions to a Mathieu-like equation.

Distinguishing signal strength and spatial structure in fMRI pattern analyses of human primary visual cortex

Multivariate pattern analyses are widely used in neuroimaging studies. But it is unclear what these analyses reveal about neural coding. Such approaches often obfuscate the link between neural measurements and the stimulus, greatly limiting their utility. Linear classification, a highly-popular approach, exploits the Euclidean distance among pattern vectors. Our recent theoretical work suggests that information regarding tuning properties is best captured by angular distances, not Euclidean distances. The goal of this experiment was to relate specific aspects of multivariate measurements to parametrically defined dimensions of visual stimuli. We used primary visual cortex as a model system to test the following predictions: (i) Euclidean distances conflate information regarding response amplitude and selectivity, (ii) angular distances best reflect information about selectivity, and (iii) data demeaning—a common preprocessing procedure—invalidates inferences regarding selectivity because it changes angular relationships among pattern vectors. fMRI BOLD activity was measured from 5 participants (7T, 32-channel coil, 1.2x1.2x1.2 mm resolution). Stimuli consisted of Cartesian sinusoidal gratings multiplied by flower-shaped apertures. The orientation of the “petals” was controlled by the phase of the radial frequency (RF) used to generate the aperture. In a fully crossed experimental design, the compound stimulus varied along three dimensions: grating orientation, contrast, and RF-phase, resulting in a total of 96 unique conditions. We found that the Euclidean metric was sensitive to stimulus contrast and relatively insensitive to grating orientation and aperture phase. Angular distances proved sensitive to grating orientation and aperture phase, and robust to changes in stimulus contrast. As predicted, data demeaning led to mischaracterizations of neural tuning. Finally, we used a biologically-inspired image-computable model to provide a theoretic account of these observations. Our results have fundamental implications for the interpretation of MVPA, and inform the development of data analysis strategies that are more readily interpretable in terms of the underlying neurophysiology.

Epicyclic oscillations of test particles near marginally stable circular orbits around charged Kiselev black holes

The marginally stable circular orbits (MSCOs) of test particles in the spacetime exterior to a charged Kiselev black hole are investigated for three characteristic values of the equation of state parameter ${\ensuremath{\omega}}_{q}$, namely (i) ${\ensuremath{\omega}}_{q}=\ensuremath{-}1/3$, (ii) ${\ensuremath{\omega}}_{q}=\ensuremath{-}1$, and (iii) ${\ensuremath{\omega}}_{q}=\ensuremath{-}2/3$, and for different values of the normalization factor $\ensuremath{\alpha}$ and electric charge $Q$ of the black hole. It is found that the presence of the quintessence field shifts outward the innermost stable circular orbits (ISCOs) around the Kiselev black hole, having the same charge parameter $Q$, as compared to the ISCOs around a Riessner-Nordstrom black hole, while the effect of the quintessence field on the outermost stable circular orbits (OSCOs) is just opposite to that on the ISCOs. Further, the radii of the photon circular orbits are also calculated for different ranges of the parameters $\ensuremath{\alpha}$ and $Q$. It is observed that the photon orbits are also shifted outward as the value of $\ensuremath{\alpha}$ increases. The radial and latitudinal epicyclic motion of test particles, which can be related to the quasiperiodic oscillations of test particles slightly above the MSCOs in the vicinity of the charged Kiselev black hole, is analyzed for the three different values of ${\ensuremath{\omega}}_{q}$. It is seen that the azimuthal and latitudinal frequencies coincide, and the radial epicyclic frequency is different in dependence on the spacetime parameters. In the case of ${\ensuremath{\omega}}_{q}=\ensuremath{-}1/3$, the azimuthal and latitudinal frequencies depend on the radial position $r$ of the particle, the charge $Q$, and the mass $M$ of the black hole, and do not depend on the factor $\ensuremath{\alpha}$. However, for ${\ensuremath{\omega}}_{q}=\ensuremath{-}2/3$ and ${\ensuremath{\omega}}_{q}=\ensuremath{-}1$, these two frequencies, along with the black hole parameters---i.e., $M$ and $Q$ and the radial position $r$---also depend on the factor $\ensuremath{\alpha}$. The radial epicyclic frequency for all the values of ${\ensuremath{\omega}}_{q}$ depends on $M$, $Q$, $r$, and also on the normalization factor $\ensuremath{\alpha}$. We also compare the epicyclic frequencies with that for an uncharged black hole. With the increase of electric charge, the ISCO becomes closer to the central object, and one can observe epicyclic frequencies closer to the central object, which makes the epicyclic frequencies larger. The ISCO gets larger as $\ensuremath{\alpha}$ increases, and thus the epicyclic frequencies can be observed away from the central object and would be smaller as compared to the case of a pure Riessner-Nordstrom black hole without quintessence. As the effect of the parameters $Q$ and $\ensuremath{\alpha}$ on the OSCOs is just opposite to that on the ISCOs, the epicyclic frequencies near the OSCOs behave the other way around.

Quasiperiodic oscillations in rotating Ellis wormhole spacetimes

We analyze the properties of the circular orbits for massive particles in the equatorial plane of symmetric rotating Ellis wormholes. In particular, we obtain the orbital frequencies and the radial and vertical epicyclic frequencies, and consider their lowest parametric, forced and Keplerian resonances. These show that quasi-periodic oscillations in accretion disks around symmetric rotating Ellis wormholes have many distinct properties as compared to quasi-periodic oscillations in accretion disks around rotating Teo wormholes and the Kerr black hole. Still we can distinguish some common features which appear in wormhole spacetimes as opposed to black holes. The most significant ones include the possibility of excitation of stronger resonances such as lower order parametric and forced resonances and the localization of these resonances deep in the region of strong gravitational interaction near the wormhole throat, which will lead to further amplification of the signal.