Spatial and frequency coherence of oblique, one-hop, high-frequency paths

Abstract Evidence is presented supporting the view that high-frequency seismic noise decreases with increased depth. Noise amplitudes are higher near the free surface where surface-wave noise, cultural noise, and natural (wind-induced) noise predominate. Data were gathered at a hard-rock site in the northwestern Adirondack lowlands of northern New York. Between 15- and 40-Hz noise levels at this site are more than 10 dB less at 945-m depth than they are at the surface, and from 40 to 100 Hz the difference is more than 20 dB. In addition, time variability of the spectra is shown to be greater at the surface than at either 335- or 945-m depths. Part of the difference between the surface and subsurface noise variability may be related to wind-induced noise. Coherency measurements between orthogonal components of motion show high-frequency seismic noise is more highly organized at the surface than it is at depth. Coherency measurements between the same component of motion at different vertical offsets show a strong low-frequency coherence at least up to 945-m vertical offsets. As the vertical offset decreases, the frequency band of high coherence increases.

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Output Gap, Money Growth and Interest Rate in Japan: Evidence from Wavelet Analysis

Arthaniti-Journal of Economic Theory and Practice ◽

10.1177/0976747918800847 ◽

2018 ◽

Vol 18 (2) ◽

pp. 171-184

Author(s):

Aviral Kumar Tiwari ◽

Olaolu Richard Olayeni ◽

Reza Sherafatian-Jahromi ◽

Olofin Sodik Adejonwo

Keyword(s):

Interest Rate ◽

High Frequency ◽

Money Growth ◽

High Frequencies ◽

Time Frequency ◽

Long Run ◽

Direction Of Causation ◽

Cyclical Relationships ◽

Frequency Coherence ◽

The Relationship

This article investigated the relationship between output, money and interest rate, using wavelet tools for the period 1972–2017. Application of such tools is helpful in answering particularly two questions: first, what the strength and direction of the causal relationships between money, output and interest rate is, and second, whether the relationship is cyclical or anti-cyclical in nature. Findings from this article show that output and money are highly coherent in low, middle and high frequencies, and coherence increases while controlling for interest rate, with money growth as the leading variable most of the time across frequencies. Output and interest rate are equally highly coherent, mostly at high frequency and some bits of middle frequency; coherence increases with the control for money, and interest rate often times leads the relationship. Also, money and interest rate are coherent at low, middle and high frequencies with interest rate leading the relationship, and controlling the effect of output increases the coherence at some times and decreases at other times. There are observable evidences of both cyclical and anti-cyclical relationships among the variables. Policy decisions should be cautious of shortrun moves in order not to trigger undesired long-run outcomes since no difference is observed in the direction of causation over time–frequency. JEL: C49, E43, E52

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Motoneuron firing patterns underlying fast oscillations in phrenic nerve discharge in the rat

Journal of Neurophysiology ◽

10.1152/jn.00292.2012 ◽

2012 ◽

Vol 108 (8) ◽

pp. 2134-2143 ◽

Cited By ~ 24

Author(s):

Vitaliy Marchenko ◽

Michael G. Z. Ghali ◽

Robert F. Rogers

Keyword(s):

High Frequency ◽

Low Frequency ◽

Medium Frequency ◽

Adult Rats ◽

Time Frequency ◽

High Frequency Oscillations ◽

Novel Method ◽

Frequency Coherence ◽

Fast Oscillations ◽

First Time

Fast oscillations are ubiquitous throughout the mammalian central nervous system and are especially prominent in respiratory motor outputs, including the phrenic nerves (PhNs). Some investigators have argued for an epiphenomenological basis for PhN high-frequency oscillations because phrenic motoneurons (PhMNs) firing at these same frequencies have never been recorded, although their existence has never been tested systematically. Experiments were performed on 18 paralyzed, unanesthetized, decerebrate adult rats in which whole PhN and individual PhMN activity were recorded. A novel method for evaluating unit-nerve time-frequency coherence was applied to PhMN and PhN recordings. PhMNs were classified according to their maximal firing rate as high, medium, and low frequency, corresponding to the analogous bands in PhN spectra. For the first time, we report the existence of PhMNs firing at rates corresponding to high-frequency oscillations during eupneic motor output. The majority of PhMNs fired only during inspiration, but a small subpopulation possessed tonic activity throughout all phases of respiration. Significant time-varying PhMN-PhN coherence was observed for all PhMN classes. High-frequency, early-recruited units had significantly more consistent onset times than low-frequency, early/middle-recruited and medium-frequency, middle/late-recruited PhMNs. High- and medium-frequency PhMNs had significantly more consistent offset times than low-frequency units. This suggests that startup and termination of PhMNs with higher firing rates are more precisely controlled, which may contribute to the greater PhMN-PhN coherence at the beginning and end of inspiration. Our findings provide evidence that near-synchronous discharge of PhMNs firing at high rates may underlie fast oscillations in PhN discharge.

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Scale Interactions in Turbulence for Mountain Blowing Snow

Journal of Hydrometeorology ◽

10.1175/jhm-d-17-0179.1 ◽

2018 ◽

Vol 19 (2) ◽

pp. 305-320 ◽

Cited By ~ 6

Author(s):

N. O. Aksamit ◽

J. W. Pomeroy

Keyword(s):

High Frequency ◽

Complex Terrain ◽

Large Scale ◽

Quadrant Analysis ◽

Blowing Snow ◽

Near Surface ◽

Atmospheric Flows ◽

Surface Turbulence ◽

Frequency Coherence ◽

Snow Transport

Abstract Blowing snow particle transport responds to wind motions across many length and time scales. This coupling is nonlinear by nature and complicated in atmospheric flows where eddies of many sizes are superimposed. In mountainous terrain, wind flow descriptions are further complicated by topographically influenced or enhanced flows. To improve the current understanding and modeling of blowing snow transport in complex terrain, statistically significant timing and frequencies of wind–snow coupling were identified in high-frequency observations of surface blowing snow and near-surface turbulence from a mountain field site in the Canadian Rockies. Investigation of the mechanisms influencing near-surface, high-frequency turbulence and snow concentration fluctuations provided strong evidence for amplitude modulation from large-scale motions. The large-scale atmospheric motions modulating near-surface turbulence and snow transport were then compared to specific quadrant analysis structures recently identified as relevant for outdoor blowing snow transport. The results suggest that large atmospheric structures modulate the amplitude of high-frequency turbulence and modify turbulence statistics typically used to model blowing snow. Additionally, blowing snow was preferentially redistributed under the footprint of these same sweep motions, with both low- and high-frequency coherence increasing in their presence.

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