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

Context. Large-scale equatorial Rossby modes have been observed on the Sun over the last two solar cycles. Aims. We investigate the impact of the time-varying zonal flows on the frequencies of Rossby modes. Methods. A first-order perturbation theory approach is used to obtain an expression for the expected shift in the mode frequencies due to perturbations in the internal rotation rate. Results. Using the time-varying rotation from helioseismic inversions we predict the changes in Rossby mode frequencies with azimuthal orders from m = 1 to m = 15 over the last two solar cycles. The peak-to-peak frequency change is less than 1 nHz for the m = 1 mode, grows with m, and reaches 25 nHz for m = 15. Conclusions. Given the observational uncertainties on mode frequencies due to the finite mode lifetimes, we find that the predicted frequency shifts are near the limit of detectability.

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A field investigation of source parameters for the sledgehammer

Geophysics ◽

10.1190/1.1443833 ◽

1995 ◽

Vol 60 (4) ◽

pp. 1051-1057 ◽

Cited By ~ 22

Author(s):

Dean A. Keiswetter ◽

Don W. Steeples

Keyword(s):

Source Parameters ◽

Peak Frequency ◽

Field Investigation ◽

Source Parameter ◽

Seismic Reflection Data ◽

Near Surface ◽

Reflection Data ◽

Frequency Changes ◽

Seismic Amplitudes ◽

Study Sites

We examined amplitude and frequency changes in shallow seismic‐reflection data associated with simple source‐parameter modifications for the sledgehammer. Seismic data acquired at three sites with different near‐surface geology show the potential effects of varying the hammer mass, the hammer velocity, the plate mass, and the plate area. At these study sites, seismic amplitudes depend on plate‐surface area and on hammer mass but not heavily on hammer velocity or plate mass. Furthermore, although the total bandwidth of the recorded data was independent of source parameter changes, the peak frequency at one site was increased approximately 40 Hz by increasing the area of the plate. The results indicate that the effects of modifying the source parameters for the sledgehammer are site‐dependent. The experiments described are quick, cheap, and simple, and can be duplicated by others at prospective sites to answer site‐specific questions.

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

Journal of Water Resources Planning and Management ◽

10.1061/(asce)wr.1943-5452.0000903 ◽

2018 ◽

Vol 144 (3) ◽

pp. 05017025 ◽

Cited By ~ 13

Author(s):

Edwin P. Maurer ◽

Gretchen Kayser ◽

Laura Doyle ◽

Andrew W. Wood

Keyword(s):

Climate Change ◽

United States ◽

Climate Change Impacts ◽

Peak Frequency ◽

Western United States ◽

Flood Peak ◽

Frequency Changes

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Hypoxia, temperature, and pH/CO2 effects on respiratory discharge from a turtle brain stem preparation

Journal of Applied Physiology ◽

10.1152/jappl.1998.84.2.649 ◽

1998 ◽

Vol 84 (2) ◽

pp. 649-660 ◽

Cited By ~ 24

Author(s):

Stephen M. Johnson ◽

Rebecca A. Johnson ◽

Gordon S. Mitchell

Keyword(s):

Brain Stem ◽

Respiratory Activity ◽

Bath Temperature ◽

Peak Frequency ◽

Chrysemys Picta ◽

Nerve Roots ◽

Increased Temperature ◽

Rhythmic Discharge ◽

Frequency Changes

Johnson, Stephen M., Rebecca A. Johnson, and Gordon S. Mitchell. Hypoxia, temperature, and pH/CO2 effects on respiratory discharge from a turtle brain stem preparation. J. Appl. Physiol. 84(2): 649–660, 1998.—An in vitro brain stem preparation from adult turtles ( Chrysemys picta) was used to examine the effects of anoxia and increased temperature and pH/CO2on respiration-related motor output. At pH ∼7.45, hypoglossal (XII) nerve roots produced patterns of rhythmic bursts (peaks) of discharge (0.74 ± 0.07 peaks/min, 10.0 ± 0.6 s duration) that were quantitatively similar to literature reports of respiratory activity in conscious, vagotomized turtles. Respiratory discharge was stable for 6 h at 22°C; at 32°C, peak amplitude and frequency progressively and reversibly decreased with time. Two hours of hypoxia had no effect on respiratory discharge. Acutely increasing bath temperature from 22 to 32°C decreased episode and peak duration and increased peak frequency. Changes in pH/CO2increased peak frequency from zero at pH 8.00–8.10 to maxima of 0.81 ± 0.01 and 1.44 ± 0.02 peaks/min at 22°C (pH 7.32) and 32°C (pH 7.46), respectively; pH/CO2 sensitivity was similar at both temperatures. We conclude that 1) insensitivity to hypoxia indicates that rhythmic discharge does not reflect gasping behavior, 2) increased temperature alters respiratory discharge, and 3) central pH/CO2 sensitivity is unaffected by temperature in this preparation (i.e., Q10 ∼1.0).

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

Frontiers in Neuroscience ◽

10.3389/fnins.2019.00982 ◽

2019 ◽

Vol 13 ◽

Cited By ~ 5

Author(s):

Selenia di Fronso ◽

Patrique Fiedler ◽

Gabriella Tamburro ◽

Jens Haueisen ◽

Maurizio Bertollo ◽

...

Keyword(s):

Peak Frequency ◽

Physical Effort ◽

Reliable Tool ◽

Frequency Changes ◽

Sports Sciences ◽

Alpha Peak

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Decrease in Volcano Jet Noise Peak Frequency from Crater Expansion

10.5194/egusphere-egu21-6746 ◽

2021 ◽

Author(s):

Kathleen McKee ◽

Eveanjelene Snee ◽

Sean Maher ◽

Cassandra Smith ◽

Kevin Reath ◽

...

Keyword(s):

Strouhal Number ◽

Satellite Data ◽

Jet Noise ◽

Peak Frequency ◽

Nozzle Geometry ◽

Jet Flows ◽

Crater Diameter ◽

Jet Velocity ◽

Frequency Changes ◽

Volcanic Jet

Volcanic jet noise is the sound, often below the human audible range (<20 Hz and termed infrasound), generated by momentum-driven fluid flow through a volcanic vent. Assuming the self-similarity of jet flows and audible jet noise extends to infrasonic volcanic jet noise, the Strouhal number, St=Djf/Uj, connects frequency changes, f, to changes in the jet length (expanded jet diameter, Dj) and/or velocity scale (jet velocity, Uj). We examine the infrasound signal characteristics from the June 2019 VEI 4 eruptions of Raikoke, Kuril Islands and Ulawun, Papua New Guinea volcanoes with changes in crater geometry. We use data from the International Monitoring System (IMS) infrasound network and pre- and post-eruption satellite data (RADARSAT-2 and PlanetScope imaging for Raikoke and Ulawun, respectively). During both eruptions we observe a decrease in infrasound peak frequency during the transition to a Plinian phase, which remains through the end of the eruptions. The RADARSAT-2 data show a qualitative increase in the crater area at Raikoke; quantitative analysis is limited by shadows. At Ulawun, however, we estimate an increase in crater area from ~35,000 m2 on May 25, 2019 to ~66,000 m2 on July 17, 2019. We assume a constant Strouhal number and use the crater diameter as a proxy for expanded jet diameter. Our analysis suggests that the increase in crater diameter alone cannot account for the decrease in peak frequency during the Ulawun eruption. This suggests that the jet velocity also increased, which fits satellite data, and or the fluid properties (e.g. particle loading, nozzle geometry and roughness, etc.) changed. This is reasonable as the Ulawun eruption went Plinian, which likely involved an increase in jet velocity and erosion of the crater walls. This is the first study to corroborate the decrease in infrasound peak frequency with documented increase in crater area. The fortuitous satellite overpass timing, clear skies, and high spatial resolution enabled the quantitative examination of the Ulawun eruption.

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The frequency gradient of human resting-state brain oscillations follows cortical hierarchies

eLife ◽

10.7554/elife.53715 ◽

2020 ◽

Vol 9 ◽

Cited By ~ 3

Author(s):

Keyvan Mahjoory ◽

Jan-Mathijs Schoffelen ◽

Anne Keitel ◽

Joachim Gross

Keyword(s):

Cortical Thickness ◽

Resting State ◽

Brain Area ◽

Peak Frequency ◽

Hierarchical Level ◽

Spatial Gradient ◽

Brain Oscillations ◽

Mixed Effect ◽

Frequency Changes ◽

Posterior Anterior

The human cortex is characterized by local morphological features such as cortical thickness, myelin content, and gene expression that change along the posterior-anterior axis. We investigated if some of these structural gradients are associated with a similar gradient in a prominent feature of brain activity - namely the frequency of oscillations. In resting-state MEG recordings from healthy participants (N = 187) using mixed effect models, we found that the dominant peak frequency in a brain area decreases significantly along the posterior-anterior axis following the global hierarchy from early sensory to higher order areas. This spatial gradient of peak frequency was significantly anticorrelated with that of cortical thickness, representing a proxy of the cortical hierarchical level. This result indicates that the dominant frequency changes systematically and globally along the spatial and hierarchical gradients and establishes a new structure-function relationship pertaining to brain oscillations as a core organization that may underlie hierarchical specialization in the brain.

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SEM image sharpness analysis

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100163174 ◽

1996 ◽

Vol 54 ◽

pp. 142-143

Author(s):

M. T. Postek ◽

A. E. Vladar

Keyword(s):

High Frequency ◽

Low Frequency ◽

Quantitative Information ◽

Primary Electron ◽

Image Sharpness ◽

Critical Dimensions ◽

Sem Image ◽

Frequency Changes ◽

Electron Microscopes ◽

Scanning Electron

Fully automated or semi-automated scanning electron microscopes (SEM) are now commonly used in semiconductor production and other forms of manufacturing. The industry requires that an automated instrument must be routinely capable of 5 nm resolution (or better) at 1.0 kV accelerating voltage for the measurement of nominal 0.25-0.35 micrometer semiconductor critical dimensions. Testing and proving that the instrument is performing at this level on a day-by-day basis is an industry need and concern which has been the object of a study at NIST and the fundamentals and results are discussed in this paper.In scanning electron microscopy, two of the most important instrument parameters are the size and shape of the primary electron beam and any image taken in a scanning electron microscope is the result of the sample and electron probe interaction. The low frequency changes in the video signal, collected from the sample, contains information about the larger features and the high frequency changes carry information of finer details. The sharper the image, the larger the number of high frequency components making up that image. Fast Fourier Transform (FFT) analysis of an SEM image can be employed to provide qualitiative and ultimately quantitative information regarding the SEM image quality.

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