Changes In Peak Frequency Research Articles

The development of aperiodic and periodic resting-state power between early childhood and adulthood: New insights from optically pumped magnetometers

Neurophysiological signals, comprised of both periodic (e.g., oscillatory) and aperiodic (e.g., non-oscillatory) activity, undergo complex developmental changes between childhood and adulthood. With much of the existing literature primarily focused on the periodic features of brain function, our understanding of aperiodic signals is still in its infancy. Here, we are the first to examine age-related changes in periodic (peak frequency and power) and aperiodic (slope and offset) activity using optically pumped magnetometers (OPMs), a new, wearable magnetoencephalography (MEG) technology that is particularly well-suited for studying development. We examined age-related changes in these spectral features in a sample (N=65) of toddlers (1–3 years), children (4–5 years), young adults (20–26 years), and adults (27–38 years). Consistent with the extant literature, we found significant age-related decreases in the aperiodic slope and offset, and changes in peak frequency and power that were frequency-specific; we are the first to show that the effect sizes of these changes also varied across brain regions. This work not only adds to the growing body of work highlighting the advantages of using OPMs, especially for studying development, but also contributes novel information regarding the variation of neurophysiological changes with age across the brain.

Origin of the broadband emission from the transition blazar B2 1308+326

Context. Transition blazars exhibit a shift from one subclass to the next during different flux states. It is therefore crucial to study them to understand the underlying physics of blazars. Aims. We probe the origin of the multi-wavelength emission from the transition blazar B2 1308+326 using the ∼14-year long γ-ray light curve from Fermi and the quasi-simultaneous data from Swift. Methods. We used the Bayesian block algorithm to identify epochs of flaring and quiescent flux states and modelled the broadband spectral energy distributions (SEDs) for these epochs. We employed the one-zone leptonic model in which the synchrotron emission causes the low-energy part of the SED and the high-energy part is produced by the inverse-Compton (IC) emission of external seed photons. We also investigated its multi-band variability properties and γ-ray flux distribution, and the correlation between optical and γ-ray emissions. Results. We observed a historically bright flare from B2 1308+326 across the optical to γ-ray bands in June and July 2022. The highest daily averaged γ-ray flux was (14.24 ± 2.36) × 10−7 ph cm−2 s−1 and was detected on 1 July 2022. For the entire period, the observed variability amplitude was higher at low (optical/UV) energies than at high (X-ray/γ-ray) energies. The γ-ray flux distribution was found to be log-normal. The optical and γ-ray emissions are well correlated with zero time lag. The synchrotron peak frequency changes from ∼8 × 1012 Hz (in the quiescent state) to ∼6 × 1014 Hz (in the flaring state), together with a decrease in the Compton dominance (the ratio of IC to the synchrotron peak luminosities), providing a hint that the source transitions from a low-synchrotron peaked blazar (LSP) to an intermediate-synchrotron peaked blazar (ISP). The SEDs for these two states are well fitted by one-zone leptonic models. The parameters in the model fits are essentially consistent between both SEDs, except for the Doppler-beaming factor, which changes from ∼15.6 to ∼27 during the transition. Conclusions. An increase in the Doppler factor might cause both the flare and the transition of B2 1308+326 from an LSP to an ISP blazar.

Novel multivariate methods to track frequency shifts of neural oscillations in EEG/MEG recordings

Instantaneous and peak frequency changes in neural oscillations have been linked to many perceptual, motor, and cognitive processes. Yet, the majority of such studies have been performed in sensor space and only occasionally in source space. Furthermore, both terms have been used interchangeably in the literature, although they do not reflect the same aspect of neural oscillations. In this paper, we discuss the relation between instantaneous frequency, peak frequency, and local frequency, the latter also known as spectral centroid. Furthermore, we propose and validate three different methods to extract source signals from multichannel data whose (instantaneous, local, or peak) frequency estimate is maximally correlated to an experimental variable of interest. Results show that the local frequency might be a better estimate of frequency variability than instantaneous frequency under conditions with low signal-to-noise ratio. Additionally, the source separation methods based on local and peak frequency estimates, called LFD and PFD respectively, provide more stable estimates than the decomposition based on instantaneous frequency. In particular, LFD and PFD are able to recover the sources of interest in simulations performed with a realistic head model, providing higher correlations with an experimental variable than multiple linear regression. Finally, we also tested all decomposition methods on real EEG data from a steady-state visual evoked potential paradigm and show that the recovered sources are located in areas similar to those previously reported in other studies, thus providing further validation of the proposed methods.

Inertial-Sensor-Based Monitoring of Sample Entropy and Peak Frequency Changes in Treadmill Walking during Recovery after Total Knee Arthroplasty

This study aimed to investigate whether sample entropy (SEn) and peak frequency values observed in treadmill walking could provide physical therapists valuable insights into gait rehabilitation following total knee arthroplasty (TKA). It was recognized that identifying movement strategies that during rehabilitation are initially adaptive but later start to hamper full recovery is critical to meet the clinical goals and minimize the risk of contralateral TKA. Eleven TKA patients were asked to perform clinical walking tests and a treadmill walking task at four different points in time (pre-TKA, 3, 6, and 12 months post-TKA). Eleven healthy peers served as the reference group. The movements of the legs were digitized with inertial sensors and SEn and peak frequency of the recorded rotational velocity–time functions were analyzed in the sagittal plane. SEn displayed a systematic increase during recovery in TKA patients (p < 0.001). Furthermore, lower peak frequency (p = 0.01) and sample entropy (p = 0.028) were found during recovery for the TKA leg. Movement strategies that initially are adaptive, and later hamper recovery, tend to diminish after 12 months post-TKA. It is concluded that inertial-sensor-based SEn and peak frequency analyses of treadmill walking enrich the assessment of movement rehabilitation after TKA.

EEG spectral and connectivity parameters as cognitive biomarkers in Parkinson disease

BackgroundCognitive decline is a common presentation of Parkinson’s disease (PD) and a continued search exists for a reliable biomarker for early identification and management of this clinical problem. The objective of this study is to select the most useful biomarker in assessment of PD-related cognitive decline. This cross-sectional study included 47 patients with PD and 47 matched healthy controls. All participants were assessed by quantitative electroencephalography (QEEG) spectral (relative power and background peak frequency) and connectivity measures (coherence and phase lag degree), in addition to clinical evaluation using Unified Parkinson’s Disease Rating Scale (UPDRS)and Modified Hoehn and Yahr staging scale and neuropsychological assessment of the patients using Montreal Cognitive Assessment (MoCA).ResultsPD patients showed significantly higher relative power in all frequency bands over the right temporal region with no significant changes in peak frequency, coherence and phase lag degree compared to healthy controls. PD patients with impaired cognition (MoCA < 26) had significantly lower global relative power, more marked in alpha and beta frequency bands compared to PD patients with normal cognition. Alpha and beta relative power in frontal and temporal regions showed significant correlation with different cognitive domains of MoCA score.ConclusionsQEEG measures especially spectral relative power could be used as adjunct to neuropsychological assessment in evaluation of PD-related cognitive decline.

Dynamic positioning filter design applied on the small ship

This paper investigates a filter design method for dynamic positioning control system based on the wave peak frequency tracking algorithm. The wave peak frequency varies randomly with the sea condition, ship speed, wave direction and other factors. The performance of the filter is greatly affected by the real-time recognition of the wave peak frequency. The wave disturbance model is indicated as an autoregressive moving average (ARMA) model and the recursive extended least squares (RELS) algorithm is proposed to identify the wave peak frequency with the auxiliary model idea. A filter with the wave peak frequency tracker is constructed to evaluate the effectiveness of the proposed filter. Ultimately, simulation results show that the proposed filter can effectively track the wave peak frequency and can still effectively reduce the influence of waves on the ship control system when the peak frequency changes.

Periodic and quasi-periodic one-dimensional phononic crystal biosensor: a comprehensive study for optimum sensor design.

The resonant acoustic band gap materials have introduced an innovative generation of sensing technology. Based on the local resonant transmitted peaks, this study aims to comprehensively investigate the use of periodic and quasi-periodic one-dimension (1D) layered phononic crystals (PnCs) as a highly sensitive biosensor for the detection and monitoring of sodium iodide (NaI) solution. Meanwhile, a defect layer is introduced defect layer inside the phononic crystal designs to be filled with NaI solution. The proposed biosensor is developed based on the periodic PnCs structure and quasi-periodic PnCs structure. The numerical findings demonstrated that the quasi-periodic PnCs structure provided a wide phononic band gap and a large sensitivity compared to the periodic one. Moreover, many resonance peaks through the transmission spectra are introduced for the quasi-periodic design. The results also show that the resonant peak frequency changes effectively with varying NaI solution concentrations in the third sequence of the quasi-periodic PnCs structure. The sensor can differentiate between concentrations ranging from 0 to 35% with a 5% step, which is extremely satisfying for precise detection and can contribute to a variety of issues in medical applications. Additionally, the sensor provided excellent performance for all the concentrations of the NaI solution. For instance, the sensor has a sensitivity of 959 MHz, a quality factor of 6947, a very low damping factor of 7.19 × 10-5, and a figure of merit of 323.529.

Peak Frequency Changes From HV Spectral Ratios in Central Italy: Effects of Strong Motions and Seasonality Over 12 Years of Observations

AbstractWe analyzed 12 years of continuous seismic data acquired by two seismic stations in Central Apennines (Italy) with the aim to investigate the temporal variations of H/V spectral ratios. The two stations are located in the epicentral areas of the main strong motion earthquakes occurred in Central Italy in the last 12 years (L’Aquila 06 April 2009, Mw 6.1; Amatrice 24 August 2016, Mw 6.0; Visso 26 October 2016, Mw 5.9, and Norcia 30 October 2016, Mw 6.5). H/V ratios are computed both on continuous and earthquakes data recorded by the two stations. H/V ratios are subjected to abrupt changes after strong earthquakes. The results highlight that after strong shaking, there are remarkable drops of the peak frequencies (7%–10% of reduction). After this sudden decrease, the peak frequency slowly recovers to the initial value in a time ranging from a few months to a few years. We also observe a moderate frequency variation (of order of 2%–3%) linked to seasonal variations: the peak frequencies increase in the spring‐summer months and decrease during the winter. The frequency changes after strong earthquakes have been interpreted in terms of velocity variations of the shallow layers. This effect must be taken into account for microzonation, geophysical, and engineering studies that are often carried out in the epicentral areas after strong earthquakes. H/V analysis over time proved to be a useful procedure for highlighting temporal changes relating to the properties of shallow layers of the propagation medium and could provide relevant information for the site characterization of permanent seismic stations.

Peak Frequency Decomposition: A Multivariate Method to Find Neural Sources of Peak Frequency Changes

Peak Frequency Decomposition: A Multivariate Method to Find Neural Sources of Peak Frequency Changes

Assessing focused wave impacts on floating wave energy converters using OpenFOAM

This study considers focused wave interactions with floating wave energy converters and represents an individual contribution to the CCP-WSI blind test series 2, in which the submitted results are compared against both physical and alternative numerical solutions for varying wave steepness achieved through changes in peak frequency. Reducing the time taken to provide reliable results is critical if computational fluid dynamics (CFD) is to become a routine design tool for offshore renewable energy devices. This can potentially be achieved by simplifying simulation set-up, and hence reduce the required man-hours, through standardised ‘best practice’ procedures. In order to achieve this, it is essential that the limitations of a numerical tool are well understood, and minimised. Therefore, this study aims to quantify the numerical reproduction of the focused wave event, and the motion of two different geometries predicted using a commonly used CFD methodology with waves generation achieved by way of linear superposition. The results imply that the error in peak values of heave and empty tank surface elevation are comparable, but the peak surge and pitch are substantially larger. This is likely due to a combination of numerical modelling errors, which must be addressed in future study.

Variations of global thunderstorm activity derived from the long-term Schumann resonance monitoring in the Antarctic and in the Arctic

The paper analyzes the records of the magnetic components of the Schumann resonance signals obtained at the Ukrainian Antarctic station “Akademik Vernadsky” (coordinates: 65.25° S, 64.25° W) from March 2002 to March 2019 and at Svalbard in the Arctic (coordinates: 78.15° N and 16.05° E) from October 2013 to June 2019. The time-course is studied of the monthly average intensities and peak frequencies of the first Schumann resonance maximum, as well as the background noise intensity at the first minimum. Both observed parameters demonstrate periodic seasonal variations. The intensities are in-phase in different hemispheres while the peak frequencies are in anti-phase. Another feature of the resonance signals is interannual trend of the resonance intensity and peak frequency observed in both hemispheres being synchronous with 11-year solar cycle. The background noise intensities demonstrate the absence of appreciable interannual variations. We propose the following interpretation of these results. Seasonal changes in peak frequencies are determined by the regular meridian drift of the world thunderstorm centers up to ±(18°–26°) in latitude from the equator. Seasonal variations of the intensity are controlled by changes of thunderstorm activity that increase of about 1.5 times during the boreal summer compared with the winter. World thunderstorm activity is practically independent on the phase of the solar cycle. The observed interannual trends in the parameters of the first Schumann mode are determined by the global changes in the lower ionosphere. They can be explained by increasing of the upper (magnetic) characteristic height by 2–3 km due to additional ionization during the years of maximum solar activity. Another explanation might be an increase of the lower (electric) characteristic height by 1–1.5 km during the years of the quiet Sun due to variation of the flux of galactic cosmic rays. Moreover, we showed that involvement of ionosphere conductivity profiles in the point source model accounting their seasonal drift provides reliable estimating the global thunderstorms’ centers activities. To explain a behavior of the intensity changes recorded in the Antarctic observatory a mechanism of additional modulation of the local resonant cavity parameters within the solar cycle is required.

Dry EEG in Sports Sciences: A Fast and Reliable Tool to Assess Individual Alpha Peak Frequency Changes Induced by Physical Effort.

Novel state-of-the-art amplifier and cap systems enable Electroencephalography (EEG) recording outside of stationary lab systems during physical exercise and body motion. However, extensive preparation time, cleaning, and limited long-term stability of conventional gel-based electrode systems pose significant limitations in out-of-the-lab conditions. Dry electrode systems may contribute to rapid and repetitive mobile EEG acquisition with significantly reduced preparation time, reduced cleaning requirements, and possible self-application by the volunteer but are known for higher channel failure probability and increased sensitivity to movement artifacts. We performed a counterbalanced repeated measure endurance cycling study to objectively validate the performance and applicability of a novel commercially available 64-channel dry electrode cap for sport science. A total of 17 healthy volunteers participated in the study, performing an endurance cycling paradigm comprising five phases: (I) baseline EEG, (II) pre-cycling EEG, (III) endurance cycling, (IV) active recovery, and (V) passive recovery. We compared the performance of the 64-channel dry electrode cap with a commercial gel-based cap system in terms of usability metrics, reliability, and signal characteristics. Furthermore, we validated the performance of the dry cap during a realistic sport science investigation, verifying the hypothesis of a systematic, reproducible shift of the individual alpha peak frequency (iAPF) induced by physical effort. The average preparation time of the dry cap was one-third of the gel-based electrode caps. The average channel reliability of the dry cap varied between 80 ± 15% (Phase I), 66 ± 19% (Phase III), and 91 ± 10% (Phase V). In comparison, the channel reliability of the gel-based cap varied between 95 ± 3, 85 ± 9, and 82 ± 9%, respectively. No considerable differences were evident for the comfort evaluations nor the signal characteristics of both caps. A within-volunteers repeated measure analysis of variance (RM-ANOVA) did not show significant effects of the electrode type on the iAPF [F(1,12) = 1.670, p = 0.221, = 0.122, Power = 0.222]. However, a significant increase of the iAPF exists from Phase II to Phases IV and V due to exhaustive physical task. In conclusion, we demonstrated that dry electrode cap is equivalent to the gel-based electrode cap based on signal characteristics, comfort, and signal information content, thereby confirming the usefulness of dry electrodes in sports science and other mobile applications involving ample movement.

Formant Modification through Vocal Production Learning in Gray Seals

Vocal production learning is a rare communication skill and has only been found in selected avian and mammalian species [1-4]. Although humans use learned formants and voiceless sounds to encode most lexical information [5], evidence for vocal learning in other animals tends to focus on the modulation pattern of the fundamental frequency [3, 4]. Attempts to teach mammals to produce human speech sounds have largely been unsuccessful, most notably in extensive studies on great apes [5]. The limited evidence for formant copying in mammals raises the question whether advanced learned control over formant production is uniquely human. We show that gray seals (Halichoerus grypus) have the ability to match modulations in peak frequency patterns of call sequences or melodies by modifying the formants in their own calls, moving outside of their normal repertoire's distribution of frequencies and even copying human vowel sounds. Seals also demonstrated enhanced auditory memory for call sequences by accurately copying sequential changes in peak frequency and the number of calls played to them. Our results demonstrate that formants can be influenced by vocal production learning in non-human vocal learners, providing a mammalian substrate for the evolution of flexible information coding in formants as found in human language.

Model-Based Analyses of Confined Polymer Electrolyte Nanothin Films Experimentally Probed by Polarized ATR–FTIR Spectroscopy

Orientational ordering within nanoscale (70–8 nm) thickness fluorinated ionomer films on Si substrates was investigated through the use of attenuated total reflection Fourier transform infrared (ATR–FTIR) spectroscopy in conjunction with electromagnetic field calculations. A spectral model was developed for Nafion thin films across the 1400–950 cm–1 region from frequency-dependent, isotropic optical constants derived from Kramers–Kronig analysis of ionomer transmission infrared spectra. The model considered infrared light propagation within the parallel boundary regions between the Ge ATR crystal, the ionomer film, and the Si substrate supporting the film. The calculations reproduced overall polymer thickness-dependent changes in peak frequencies and band shapes observed in experimental spectra recorded with p- and s-polarized light. General trends were traceable to effects of anomalous dispersion and electric field enhancement within the nanoscale gap separating the Ge and Si phases. However, optical eff...

Adjusting Flood Peak Frequency Changes to Account for Climate Change Impacts in the Western United States

AbstractOne consistent projection for the western United States has been for increasing peak streamflow as the global climate warms. Although past studies have characterized some aspects of future ...

Different maturational changes of fast and slow sleep spindles in the first four years of life

Objective/BackgroundMassive changes in brain morphology and function in the first years of life reveal a postero-anterior trajectory of cortical maturation accompanied by regional modifications of NREM sleep. One of the most sensible marker of this maturation process is represented by electroencephalographic (EEG) activity within the frequency range of sleep spindles. However, direct evidence that these changes actually reflect maturational modifications of fast and slow spindles still lacks.Our study aimed at answering the following questions:1. Do cortical changes at 11.50 Hz frequency correspond to slow spindles?2. Do fast and slow spindles show different age trajectories and different topographical distributions?3. Do changes in peak frequency explain age changes of slow and fast spindles? Patients/MethodsWe measured the antero-posterior changes of slow and fast spindles in the first 60 min of nightly sleep of 39 infants and children (0–48 mo.). ResultsWe found that (A) changes of slow spindles from birth to childhood mostly affect frontal areas (B) variations of fast and slow spindles across age groups go in opposite direction, the latter progressively increasing across ages; (C) this process is not merely reducible to changes of spindle frequency. ConclusionsAs a main finding, our cross-sectional study shows that the first form of mature spindle (i.e., corresponding to the adult phasic event of NREM sleep) is marked by the emergence of slow spindles on anterior regions around the age of 12 months.

Interstellar ice analogs: H2O ice mixtures with CH3OH and NH3in the far-IR region

Context. New spectroscopic observations in the far-infrared (IR) range are expected from future planned missions. Although water ice is the only species detected so far in interstellar ices in this range, the presence of ice mixtures requires laboratory characterization of the corresponding spectra.Aims. We present an investigation on far-IR spectra of binary ice mixtures relevant in various astrophysical environments. The foremost goal is to compare the spectroscopic features of the ice mixtures to those of pure ices, and to search for changes in peak frequencies, intensities, and band strengths of the main bands.Methods. Mixtures H2 O:CH3 OH and H2 O:NH3 of different ratios have been deposited on a diamond substrate at astrophysically relevant conditions. We measured the spectra in the near- and mid-IR regions to derive ice column densities that were subsequently used to calculate the apparent band strengths in the far-IR region. We also designed theoretical models to study these mixtures and to predict their spectra.Results. We recorded spectra of amorphous phases for H2 O:CH3 OH mixtures of different compositions, that is 1:1, 3:1, and 10:1 at 8 K, and compared these mixtures to those obtained after warming. This process involves the appearance of new spectral features and changes in band shapes and band strengths. We also compared the spectra to those of the pure species and to theoretical predictions. We measured apparent band strengths for all the observed features. For H2 O:NH3 mixtures, the ratios selected were 3:1, 1:1, and 1:3. In this case the spectral variations are even more marked than for the water:methanol samples. Conclusions. Band strengths in the far-IR are missing in astrophysics literature for ice mixtures. The results presented here are valuable for detecting the presence and composition of such mixtures from future space observations in this spectral region.

Subsurface imaging of metal lines embedded in a dielectric with a scanning microwave microscope**Official contribution of the National Institute of Standards and Technology; not subject to copyright in the United States.

We demonstrate the ability of the scanning microwave microscope (SMM) to detect subsurface metal lines embedded in a dielectric film with sub-micrometer resolution. The SMM was used to image 1.2 μm-wide Al–Si–Cu metal lines encapsulated with either 800 nm or 2300 nm of plasma deposited silicon dioxide. Both the reflected microwave (S11) amplitude and phase shifted near resonance frequency while the tip scanned across these buried lines. The shallower line edge could be resolved within 900 nm ± 70 nm, while the deeper line was resolved within 1200 nm ± 260 nm. The spatial resolution obtained in this work is substantially better that the 50 μm previously reported in the literature. Our observations agree very well with the calculated change in peak frequency and phase using a simple lumped element model for an SMM with a resonant transmission line. By conducting experiments at various eigenmodes, different contrast levels and signal-to-noise ratios have been compared. With detailed sensitivity studies, centered around 9.3 GHz, it has been revealed that the highest amplitude contrast is obtained when the probe microwave frequency matches the exact resonance frequency of the experimental setup. By RLC equivalent circuit modeling of the tip-sample system, two competing effects have been identified to account for the positive and negative S11 amplitude and phase contrasts, which can be leveraged to further improve the contrast and resolution.

ICONE23-1900 DEVELOPMENT OF NON-DESTRUCTIVE INSPECTION TECHNIQUE FOR WEDGE ANCHOR BOLTS USING AE SENSOR

A new non-destructive inspection technique with using acoustic emission (AE) sensor was developed for the purpose of overcoming problems originating in existing hammering test. The new technique enables us to obtain inspection results with no dependence on personal skills of a checker, and to judge the integrity of the bolts based on quantitative measurement results. The investigation of applying the new method to wedge anchor bolts is reported. From experimental results by using this technique, the trend of peak frequency changes obtained from concrete blocks with no crack has a clear tendency to increase with increasing tightening torque. In addition, the peak frequency obtained from the bolt installed in the cracked concrete block decreases compared with one in no-crack concrete block. These results indicate the possibility that both looseness of nut and degradations such as cracking in concrete could be detected by the new technique.

The effect of boundary proximity on the response of individual ultrasound contrast agent microbubbles

The effect of boundary proximity on ultrasound contrast agent microbubble emissions can play an important role in the context of both targeted microbubble imaging and contrast imaging of microvascular perfusion. In this study, individual microbubbles (n = 104) were insonicated as a function of distance from either a polystyrene membrane (OpticellTM) or a compliant agarose boundary up to offset distances of 1000 µm by use of an optical trapping setup. An ‘acoustic spectroscopy’ approach was employed, which entailed transmitting a sequence of tone bursts with centre frequencies ranging from 4 to 13.5 MHz to determine the frequency and amplitude of maximum radial response (fMR and AMR, respectively). For the OpticellTM case, microbubble response exhibited a distinctly oscillatory pattern with increasing offset distance, with an average maximal change in peak frequency and scattered pressure amplitude of 29.6% and 73.2%, respectively, as compared to their values adjacent to the boundary. For the agarose case, microbubbles exhibited an increase in fMR and a decrease in AMR with respect to their values in free space. Simulations indicate the oscillatory dependence on OpticellTM distance stems from wavelength-dependent interference phenomena. A recent analytical bubble-boundary model is in broad agreement with the relative AMR changes due to the more compliant agarose layer, however underestimates the change in relative fMR at the boundary.