Frequency Of Breaks Research Articles

Searching for similarities in the accretion flow of Seyfert 1 galaxies and cataclysmic variables based on the flare profiles of IRAS 13224–3809, 1H 0707–495, Mrk 766, and MV Lyr

Aims. We studied the fast variability of three selected active galactic nuclei (AGNs), IRAS 13224−3809, 1H 0707−495, and Mrk 766, and the cataclysmic variable MV Lyr, which were observed by the XMM-Newton and Kepler spacecrafts, respectively. Our goal is to search for the common origin of the variability and to test the so-called sandwich model, in which a geometrically thick corona surrounds a geometrically thin disc. Context. We studied the substructures of the averaged flare profiles. The flare profile method identifies individual flares in the light curve, and averages them. The direct fitting of the profile substructures identified individual characteristic frequencies that are seen in standard power density spectra (PDS) as a break frequency or quasi-periodic oscillation. The credibility of the flare profile substructures is demonstrated by comparison with the autocorrelation function. Results. We found that the flare profiles of AGNs are similar to those of a cataclysmic variable in the low state. We explain this as a consequence of a truncated inner disc in a sandwich model. The same scenario is also able to explain the characteristic break frequencies in X-ray PDS, which are not seen in the optical. We also searched for substructures in the flare profile of IRAS 13224−3809. In addition to a permanently present main flare, we found that a transient side-lobe appears before the main flare and is only seen in a high-flux period. The complex flare profile of this AGN suggests that an additional source of X-rays appears during the high-flux period. We propose a scenario in which an accretion flow fluctuation enters the sandwich corona and propagates further to some very central part of the accretion disc.

Design and analysis of pneumatic composite phononic crystal

Tuning band gaps in soft phononic crystal by air pressure-induced deformation is a feasible method to manipulate elastic waves. In this paper, we design a pneumatic composite phononic crystal that incorporates a labyrinthine structure into the Helmholtz-type phononic crystal. By calculating the band gaps of the representative volume element (RVE) arranged in a two-dimensional triangular lattice, we find that this design effectively extends the transmission path of sound waves, achieving band gaps in the vicinity of the lower frequency range. We apply pressure to the scatterer’s pneumatic actuator to adjust its volume through the deformation of soft material, altering the air filling rate and enabling reversible adjustment of the frequency and width of band gaps. Nonlinear finite element simulations investigate the effects of different pressure levels on the band gaps. Furthermore, we explore bandgaps tuning in one-dimensional phononic crystals and the impact of various types of point defects on the transmission characteristics of phononic crystals. Results show that the pneumatic phononic crystal exhibits rich band gaps under air pressure loading, in which a low-frequency band gap exists, and is capable of reversible continuous tuning. This study provides valuable for manipulating elastic waves in periodic structures and designing soft acoustic devices.

Impact of Alignments on the Accuracy of Protein Subcellular Localization Predictions.

Alignments in bioinformatics refer to the arrangement of sequences to identify regions of similarity that can indicate functional, structural, or evolutionary relationships. They are crucial for bioinformaticians as they enable accurate predictions and analyses in various applications, including protein subcellular localization. The predictive model used in this article is based on a deep - convolutional architecture. We tested configurations of Deep N-to-1 convolutional neural networks of various depths and widths during experimentation for the evaluation of better-performing values across a diverse set of eight classes. For without alignment assessment, sequences are encoded using one-hot encoding, converting each character into a numerical representation, which is straightforward for non-numerical data and useful for machine learning models. For with alignments assessment, multiple sequence alignments (MSAs) are created using PSI-BLAST, capturing evolutionary information by calculating frequencies of residues and gaps. The average difference in peak performance between models with alignments and without alignments is approximately 15.82%. The average difference in the highest accuracy achieved with alignments compared with without alignments is approximately 15.16%. Thus, extensive experimentation indicates that higher alignment accuracy implies a more reliable model and improved prediction accuracy, which can be trusted to deliver consistent performance across different layers and classes of subcellular localization predictions. This research provides valuable insights into prediction accuracies with and without alignments, offering bioinformaticians an effective tool for better understanding while potentially reducing the need for extensive experimental validations. The source code and datasets are available at http://distilldeep.ucd.ie/SCL8/.

Nuclear abnormalities and DNA damage indicate different genotoxic stress responses of marsh frogs (Pelophylax ridibundus, Pallas 1771) to industrial and agricultural water pollution in South Bulgaria.

Amphibians are continuously exposed to pollutants and anthropogenic stressors in their natural habitats, representing a significant challenge to their survival. This study aimed to quantify the extent of DNA damage caused by chronic industrial and agrochemical surface water pollution in wild populations of the marsh frog (Pelophylax ridibundus). The observed genotoxic effects on the marsh frog DNA, manifesting as abnormalities in erythrocyte nuclei, micronuclei, and DNA strand breaks, demonstrate a clear cause-and-effect relationship with surface water parameters, heavy metals, metalloids, and pesticides. The most prevalent nuclear abnormalities observed were notched and blebbed nuclei and nuclear buds, indicative of chromosomal instability. The significant correlation between cadmium, lead, and copper contamination and the increased frequency of DNA breakage in the marsh frogs from the industrial site indicates that heavy metal contamination has a higher genotoxic potential than pesticide contamination. These findings underscore the vulnerability of amphibians inhabiting heavy metal-contaminated wetlands to genotoxic stress due to their lower tolerance to environmental genotoxins. Therefore, using in situ assays to detect erythrocyte nuclear abnormalities and DNA damage in P. ridibundus could serve as a reliable indicator of environmental quality and provide early detection of anthropogenic pollution.

Probing the Electric Field Response of a Water Molecule Confined in Small Carbon Nanocages: A Density Functional Theory Investigation.

We consider a water molecule under tight confinement in the small-sized fullerenes (C , C , C ) within the density functional theory (DFT) calculations with suitable exchange-correlation functionals. Such nanoscopic molecular cages provide an ideal setup to study their characteristic properties not present in the condensed phase. The water molecule entirely loses its feature of typical water when it is confined in small fullerenes of size equal to C or smaller, in which the asymmetric O-H stretching vibration occurs at a lower wavenumber than the symmetric stretching. We study the response of the confined water molecule to the applied electric fields in terms of change in geometrical parameters, NMR spin-spin coupling constants, dipole moment, HOMO-LUMO (HL) gap, and vibrational frequency shift. The electric field shielding property of small-sized fullerene cages is explored and found to be strongly correlated with the HL gap. Since the electric field modulates the gap to decrease generally, shielding efficiency varies with field strength, thereby making large fields better shielded than small fields for the small penetration factor at large fields. The results that hold significance for technological applications are discussed.

Automated geotechnical logging of core box images using machine learning

ABSTRACT Geotechnical characterization is contingent on reliable data to reduce uncertainty in the conditions of slope walls or underground workings. However, geotechnical data for greenfield and brownfield sites are often limited. The data that are available are often inconsistent and difficult to reliably use to inform the geotechnical domain model. SRK has developed machine learning workflows using deep learning for geotechnical classification of existing core box photographs to provide a reliable and objective data set that can be used to inform rock mass characterization and structural modeling. Conventional geotechnical parameters are often unsuitable for automation due to the reliance on subjective decisions by the logger for interval lengths or defining naturally open versus closed breaks. Three classification systems have been developed: the Core Damage Index (CDI), the Pseudo-RQD, and the Break Frequency. The CDI classifies discrete intervals within the photographs according to the average clast sizes relative to the core diameter to provide a high-resolution view of the variability of damage down a drill hole. Pseudo-RQD and Break Frequency are calculated by mapping the breaks and rubble zones observed on drill core images.

Dispersive properties of metamaterial beams with rod-like resonators: A coupled axial-flexural analysis

This paper addresses the propagation of coupled axial-flexural waves in metamaterial beams with rod-like resonators. Utilizing an exact frequency-dependent stiffness method, based on Euler–Bernoulli beam assumption for rods and host beam, and fully accounting for axial-flexural coupling phenomena, several adimensional parametric analyses are performed for investigating the dispersive properties of the metamaterial beams. The analyses reveal novel and relevant aspects unaddressed in previous studies. Firstly, they show that certain rod configurations lead to significant interference between flexural resonance and the band gaps opened by axial resonance, whereas other configurations enable flexural resonance to open substantial band gaps without interference from axial resonance. Results are complemented by 3D finite element analyses proving evidence of the findings and validating the method. Additional analyses demonstrate that adding a tip mass to the rods, while keeping the total mass of the resonator unchanged, can significantly reduce the opening frequency of the band gaps and can attenuate or remove the interference caused by flexural resonance within the band gaps opened by axial resonance; the rotational inertia of the tip mass can also play a significant role in removing flexural resonance interference. Notably, the paper also reveals that the attenuation phenomena for the coupled problem with a single set of rods are governed by the opening of weak band gaps, rather than by traditional band gaps; this aspect is elucidated by showing Bloch mode shapes of the infinite metamaterial beam and frequency response of the corresponding finite beam. Results and proposed design prove to be useful and promising for locally resonant beams featuring rod-like resonators, both as an alternative to traditional beam-like resonators and for their applicability in the 3D printing process of locally resonant structures, where rods serve as elastic elements in constructing the resonators.

Band Gap Engineering and Frequency Dispersive Dielectric Properties of Rare Earth (Sm3+) Modified Ba0.8Sr0.2TiO3 Ceramics for Potential Use as an Optoelectronic Materials

Lead free perovskite materials have the capability to be used in various multifunctional applications. In this regard, dielectric and light absorption properties of Sm modified Ba0.8-xSmxSr0.2TiO3 have been explored. The dielectric constant has been estimated to be 2788 for Ba0.77Sm0.03Sr0.2TiO3. The optical band gap of all prepared samples has been evaluated by employing Tauc plot method and observed that the band gap varies 3.13-2.97 eV with the increase in Sm concentration. In brief, the present study reports the physical properties of Ba0.8-xSmxSr0.2TiO3 ceramics which open window for possible use of it as lead-free optoelectronic material.

Electric Field Influence on CO Clathrate Hydrates.

We consider carbon monoxide (CO) confined in the hydrogen-bonded building blocks of sI and sII clathrate hydrates, viz., (512, 51262, 51264) cages, within the density functional theory-based calculations. We study their response to the applied electric fields in terms of changes in the geometrical parameters, dipole moment, HOMO-LUMO gap, and vibrational frequency shift. We examine the stability of CO clathrate hydrate building block cages and identify a possible indication of the field-induced release of CO.

Study on the folding damage mechanism of SiC fiber braided fabric based on synchrotron radiation CT and finite-element analysis

Silicon carbide (SiC) fiber exhibits high strength, thermal resistance, and chemical stability, but its insufficient flexural strength renders it unsuitable for use in flexible structural materials. In this study, the microstructure evolution and damage mechanisms of SiC fiber braided fabric were investigated at different braiding angles and folding stages using synchrotron micro computed tomography (µ-CT) and finite-element analysis. Results from synchrotron radiation CT scans indicate that, with an increase in the number of folding cycles, both fiber surface fractures and slippage gradually increased, leading to a looser internal structure and diminished fiber continuity. The SiC fiber braided fabric at 37.8° was predominantly influenced by the folding behavior, exhibiting a higher frequency of fiber breakages. Conversely, the 43.1° SiC fiber braided fabric was primarily affected by inter-bundle abrasion, resulting in looser fiber bundles and increased slippage. In the case of the 41.2° SiC fiber braided fabric, under the combined effects of friction and folding, the highest occurrences of fiber slippage and breakages were observed. Finite-element simulation results reveal that the stress at the folding site of the 40° braided fabric was higher than those of the 45° and 50° braided fabrics, confirming the experimental conclusion that the folding resistance of SiC fiber fabrics is poorest at a braiding angle of around 41° to 42°. This research is of significant importance for a deeper understanding of the folding performance and damage behavior of SiC fiber braided fabric, providing valuable insights for further optimizing material design and applications.

Localization and pauses duration in Russian iambic tetrameter in the poetry of A. S. Pushkin

This article is a continuation of a study dedicated to the role of pauses in the prosodic structure of the Russian iambic tetrameter. New data on the localization and duration of the pauses in Alexander Pushkin’s “Eugene Onegin,” as voiced by three speakers, corroborate previously identified patterns in the organization of poetic lines at the prosodic level. Pauses of varying durations, occurring with different frequencies at various junctures, emphasize the depth of the varying degree of internal division within a line. The method of multidimensional classification revealed five groups of pause durations, ranging from ultra-short to super-long. It was found that within a line, ultra-short and short pauses predominate, while longer pauses tend to occur more towards the middle and less towards the beginning. The absence or brevity of pauses near the end of a line highlights a more prolonged inter-line pause. Individual pause strategies manifest in the observance or omission of inter-line pauses, their duration, the frequency of prosodic breaks within a line, and the frequency of using pauses of a particular duration group. High correlation coefficients indicate a consistent use of pauses among the three speakers.

Stay focused! Exploring the compulsive nature of alcohol-related attentional bias in severe alcohol use disorder.

Prominent models postulate that alcohol-related attentional bias (AB), emerging from the overactivation of the reward system, plays a key role in severe alcohol use disorder (sAUD) and is independent from voluntary control. We determined whether AB is indeed compulsive or can be modulated by the control/inhibition system. Patients with sAUD (17 women, 13 men, mean age of 47, White) and matched healthy controls (16 women, 14 men, mean age of 44, White) performed a visual probe task with behavioral (reaction time) and eye-tracking (first fixation location and duration, second fixation location, dwell time) measures. They also performed an avoidance task, requiring to focus on a target by voluntarily inhibiting eye movements toward alcohol/nonalcohol/nonappetitive distractors and measuring overt (break frequency) and covert (fixational eye movements) attentional processes. Patients with sAUD exhibited an avoidance AB indexed by (a) reduced attentional resources dedicated to alcohol-related stimuli, namely, reduced dwell time (p = .040) and second fixation (p = .001) toward these stimuli; (b) increased inhibitory processes, namely, easier inhibition of saccades toward alcohol measured by lower break frequency (p < .001); and (c) covert eye movements posited further away from alcohol. In contradiction with theoretical models, our two tasks did not show any AB toward alcohol in sAUD. Instead, patients exhibited an avoidance AB indexed by increased inhibitory processes as well as reduced overt and covert attentional resources dedicated to alcohol-related stimuli. These results question the theoretical and clinical role of AB, as measured through reliable eye-tracking tasks, in sAUD. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Nonminimal coupling holographic superconductors

We explore a holographic superconductor model in which a real scalar field is nonminimally coupled to a gauge field. We consider several types of the nonminimal coupling function h(ψ) including exponential, hyperbolic (cosh), power-law, and fractional forms. We investigate the influences of the nonminimal coupling parameter α on condensation, critical temperature, and conductivity. We can categorize our results in two groups. In the first group, conductor/superconductor phase transition is easier to occur for larger values of α, while in the second group stronger effects of the nonminimal coupling makes the formation of scalar hair harder. Although the real and imaginary parts of conductivity are impressed by different forms of h(ψ), they follow some universal behaviors such as connecting with each other through Kramers–Kronig relation in ω → 0 limit or the appearance of gap frequency at low temperatures around ωg ∼ 8 Tc, which shifts to larger values by increasing the strength of α. Among all forms of h(ψ) we observe that h(ψ) = 1 + αψ2 gives us better information in wide range of nonminimal coupling constant and temperature. Choosing the best form of h(ψ), we construct a family of solutions for holographic conductor/superconductor phase transitions to discover the effect of the hyperscaling violation when the gauge and scalar fields are nonminimally coupled. we find that the critical temperature increases for higher effects of hyperscaling violation θ and nonminimal coupling constant α. By increasing these two parameters, we obtain lower values of condensation which means that conductor/superconductor phase transition will acquire easier. Furthermore, we understand that the hyperscaling violation affects the conductivity σ of the holographic superconductors and changes the expected relation in the gap frequency. Some universal behaviors like infinite DC conductivity are observed. In addition, we consider a five-dimensional Gauss–Bonnet (GB) black hole with a flat horizon. We find out that the critical temperature decreases for larger values of GB coupling constant, λ, or smaller values of nonminimal coupling constant, α, which means that the condensation is harder to form. Moreover, we study the electrical conductivity in the holographic setup. We observe that the gap frequency shifts to larger values for stronger λ, and becomes flat by increasing α.

Strong noninertial radiative shifts in atomic spectra at low accelerations

Despite numerous proposals investigating various properties of accelerated detectors in different settings, detecting the Unruh effect remains challenging due to the typically weak signal at achievable accelerations. For an atom with frequency gap ω0, accelerated in free space, significant acceleration-induced modification of properties like transition rates and radiative energy shifts requires accelerations of the order of ω0c. In this paper, we make the case for a suitably modified density of field states to be complemented by a judicious selection of the system property to be monitored. We study the radiative energy-level shift in inertial and uniformly accelerated atoms coupled to a massless quantum scalar field inside a cylindrical cavity. Uniformly accelerated atoms experience thermal correlations in the inertial vacuum, and the radiative shifts are expected to respond accordingly. We show that the noninertial contribution to the energy shift can be isolated and significantly enhanced relative to the inertial contribution by suitably modifying the density of field modes inside a cylindrical cavity. Moreover, we demonstrate that monitoring the radiative energy shift, as compared to transition rates, allows us to reap a stronger purely noninertial signal. We find that a purely noninertial radiative shift as large as 50 times the inertial energy shift can be obtained at small, experimentally achievable accelerations (a∼10−9ω0c) if the cavity’s radius R is specified with a relative precision of δR/R0∼10−7. Given that radiative shifts for inertial atoms have already been measured with high accuracy, we argue that the radiative energy-level shift is a promising observable for detecting Unruh thermality with current technology. Published by the American Physical Society 2024

Broadband multi‐carrier linear frequency modulation signal reception with subcarrier frequency offset deramp processing

AbstractIn this paper, a broadband multi‐carrier linear frequency modulation (LFM) signal reception method with subcarrier frequency offset deramp processing is proposed and investigated. The proposed frequency offset deramp processing is implemented by mixing the multi‐carrier LFM radar echo with a multi‐carrier LFM reference that has a different subcarrier frequency interval. With this design, the sampling rate of the radar receiver is remarkably reduced and crosstalk‐free separation of different subcarrier signals is easily conducted in the frequency domain. To fuse the multiple subcarriers and fill the frequency gaps, a sparse reconstruction method is employed to obtain the broadband response, which is essential for achieving high range resolution detection. The effectiveness of the proposed method is validated through an experiment in which the reception of an 8‐carrier LFM signal is conducted and a total bandwidth of 6 GHz after multi‐carrier fusion is demonstrated. An inverse synthetic aperture radar imaging experiment is also conducted with the results verifying the good potential of the proposed method in practical applications.

Searching for the mHz variability in the TESS observations of nova-like cataclysmic variables

We investigated the fast optical variability of selected nova-like cataclysmic variables observed by the satellite. We searched for break frequencies b $) in the corresponding power density spectra (PDS). The goal is to study whether these systems in an almost permanent high optical state exhibit preferred $f_ b $ around 1\,mHz. We selected non-interrupted light curve portions with durations of 5 and 10 days. We divided these portions into ten equally long light curve subsamples and calculated mean PDS. We searched for $f_ b $ in the frequency interval from log($f$/Hz) = -3.5 to -2.4. We defined as a positive detection when the $f_ b $ was present in at least 50&lt;!PCT!&gt; of the light curve portions with a predefined minimum number of detections. We have measured $f_ b $ in 15 nova-like systems and confirmed that the value of this frequency is clustered around 1\,mHz with a maximum of the distribution between log($f$/Hz) = -2.95 and -2.84. The confidence that this maximum is not a random feature of a uniform distribution is at least 96&lt;!PCT!&gt;. This is a considerable improvement on the previous value of 69&lt;!PCT!&gt;. We discuss the origin of these b $ in the context of the sandwich model in which a central hot X-ray corona surrounds a central optically thick disc. This scenario could be supported by a correlation between the white dwarf mass and $f_ b $; the larger the mass, the lower the frequency. We see such a tendency in the measured data; however, the data are too scattered and based on a low number of measurements. Finally, it appears that systems with detected $f_ b $ have a lower inclination than 60-75$^ circ $. In higher-inclination binaries, the central disc is not seen and the PDS is dominated by red noise. This also supports the inner disc regions as being the source of the observed $f_ b

Quantifying the role of electron plateau distribution on the chorus gap formation using one-dimension PIC simulations

Although ubiquitous in the Earth’s inner magnetosphere, how chorus waves with a gap in intensity near half the electron cyclotron frequency, 0.5fce, is formed remains to be understood. One hypothesis invokes the often-observed feature in electron phase space density where two anisotropic populations of warm and hot temperatures, respectively, are separated by a relatively isotropic beam-like component, called the parallel plateau distribution. According to linear theory, its mean velocity is such that the plateau population can lead to a sufficient cyclotron damping in a narrow frequency range near 0.5fce. To test this hypothesis more quantitatively, we carry out a series of one-dimensional particle-in-cell simulations in a parabolic magnetic field with observationally constrained plateau density and mean velocity. We find that even though the chorus generation involves nonlinear physics, the gap formation is largely determined by the linear properties of plateau electrons. In addition, given a sufficiently large plateau density with a right combination of warm and/or hot source populations, our simulations were able to generate lower-band-only chorus, upper-band-only chorus, banded chorus with partial damping at the gap, and banded chorus with a strong power gap. When it comes to comparing with observations, however, we find that (1) the minimum plateau density required to generate banded chorus is somewhat larger than that observed; (2) even with the largest plateau density used, the gap formation in the simulations is not consistent; and (3) most importantly, the dependence of the gap frequency on the plateau velocity in our parametric analysis differs quite substantially from that of the recent statistical results. Provided that the simplifying assumptions in our simulations remain valid, these discrepancies would indicate that the electron plateau distribution is not the major contributor to the chorus gap formation.

A CFD‐PBM‐ANN framework to simulate the liquid–liquid two‐phase flow in a pulsed column

AbstractCFD‐PBM numerical simulation is a powerful tool in the research of droplet swarm behavior. In this work, an artificial neural network (ANN) based droplet breakage frequency function is established based on the directly measured data from our previous studies. Then, the weights and biases of ANN are embedded into the CFD‐PBM code in the form of matrices and vectors. For the first time, a CFD‐PBM‐ANN simulation framework is established. Simulation results are in good agreement with the experimental data under different operation conditions. The cumulative droplet size distribution decreases with the increase of interfacial tension and pulse intensity. It is also found by the simulation that the droplet breakage frequency is relatively high at the edge of disc and doughnut plate, which is accordant with the distribution of turbulent energy dissipation and velocity gradient.

Influence of auditory-based cognitive training on auditory resolution, executive function, and working memory skills in individuals with mild cognitive impairment – a pilot randomized controlled study

Background Age-related central auditory processing disorder and mild cognitive impairment (MCI) can be concomitant in older adults, making it difficult to communicate, especially in challenging listening conditions. This preliminary study investigated the efficacy of auditory-based cognitive training on the auditory processing abilities and cognitive functions of older adults with MCI. Methods In this randomized controlled trial twenty-two older adults with mild cognitive impairment (MCI) were randomly assigned to either an experimental (n=11) or a control group (n=11). The experimental group received 15 cognitive training sessions through tasks involving the auditory domain. The outcome measures of this study included auditory resolution (Temporal gap detection, frequency discrimination, and modulation detection) and cognitive measures (Trail making tests and digit recall), which were administered at three-time points (before training, post-training, and follow-up). The linear mixed model computed the effects of training on the outcome measures. Results A significant improvement was observed in the modulation detection threshold between baseline and follow-up and between post-training and follow-up sessions. However, GDT and FD thresholds did not reveal any statistically significant difference. In the trail making test, Part B showed consistent significance across the time points, whereas Part A and the delayed recall task showed no significant difference. Conclusion Auditory-based cognitive training may improve auditory processing and executive function in older adults with mild cognitive impairment (MCI). Trial registration CTRI/2019/01/017073, registered on 14.01.2019

The coupled band gap of longitudinal wave in metamaterial-based double-rod containing resonators

This study investigates the coupled band gap and vibration propagation characteristics of elastic waves in a metamaterial elastic double-rod system with attached periodic resonators. We derive the band gap structure and vibration attenuation equations of double-rod structure using the spectral element method, Bloch’s theorem, and the transfer matrix method. The validity of the coupled band gap is confirmed through forced vibration response analysis. Furthermore, we examine the effects of various parameters on the double-rod system, revealing that coupled band gaps exist with the average vibration attenuation rates of −50.23 dB for rod one and −47.87 dB for rod two, respectively. Remarkably, by adjusting the double-rod parameters, both the band gap frequency range and vibration attenuation ability of the coupled band gap can be adjusted to meet specific engineering requirements in low-frequency regions. This research contributes to developing continuous mechanical structures featuring coupled band gaps.