scholarly journals A Recurrent Increase of Synchronization in the EEG Continues from Waking throughout NREM and REM Sleep

2014 ◽  
Vol 2014 ◽  
pp. 1-10
Author(s):  
Ralf Landwehr ◽  
Andreas Volpert ◽  
Ahmad Jowaed
Keyword(s):  
Temporal Dynamics ◽  
Dominant Frequency ◽  
Subcortical Structures ◽  
Spectral Content ◽  
Waking And Sleep ◽  
Nonlinear Approach ◽  
Current State ◽  
Coupling Pattern ◽  
State Of Vigilance ◽  
Dominant Frequencies

Pointwise transinformation (PTI) provides a quantitative nonlinear approach to spatiotemporal synchronization patterns of the rhythms of coupled cortical oscillators. We applied PTI to the waking and sleep EEGs of 21 healthy sleepers; we calculated the mean levels and distances of synchronized episodes and estimated the dominant frequency shift from unsynchronized to synchronized EEG segments by spectral analysis. Recurrent EEG synchronization appeared and ceased abruptly in the anterior, central, and temporal derivations; in the posterior derivations it appeared more fluctuating. This temporal dynamics of synchronization remained stable throughout all states of vigilance, while the dominant frequencies of synchronized phases changed markedly. Mean synchronization had high frontal and occipital levels and low central and midtemporal levels. Thus, a fundamental coupling pattern with recurrent increases of synchronization in the EEG (“RISE”) seems to exist during the brain’s resting state. The generators of RISE could be coupled corticocortical neuronal assemblies which might be modulated by subcortical structures. RISE designates the recurrence of transiently synchronized cortical microstates that are independent of specific EEG waves, the spectral content of the EEG, and especially the current state of vigilance. Therefore, it might be suited for EEG analysis in clinical situations without stable vigilance.

scholarly journals Acoustic communication and the evolution of hearing in fishes

2000 ◽  
Vol 355 (1401) ◽  
pp. 1285-1288 ◽  
Author(s):  
Friedrich Ladich
Keyword(s):  
Inner Ear ◽  
Acoustic Communication ◽  
Acoustic Signals ◽  
Spectral Content ◽  
Auditory Thresholds ◽  
Selective Pressures ◽  
Vocal Signals ◽  
Species Specific ◽  
Hearing Abilities ◽  
Dominant Frequencies

Fishes have evolved a diversity of sound–generating organs and acoustic signals of various temporal and spectral content. Additionally, representatives of many teleost families such as otophysines, anabantoids, mormyrids and holocentrids possess accessory structures that enhance hearing abilities by acoustically coupling air–filled cavities to the inner ear. Contrary to the accessory hearing structures such as Weberian ossicles in otophysines and suprabranchial chambers in anabantoids, sonic organs do not occur in all members of these taxa. Comparison of audiograms among nine representatives of seven otophysan families from four orders revealed major differences in auditory sensitivity, especially at higher frequencies (> 1kHz) where thresholds differed by up to 50 dB. These differences showed no apparent correspondence to the ability to produce sounds (vocal versus non–vocal species) or to the spectral content of species–specific sounds. In anabantoids, the lowest auditory thresholds were found in the blue gourami Trichogaster trichopterus , a species not thought to be vocal. Dominant frequencies of sounds corresponded with optimal hearing bandwidth in two out of three vocalizing species. Based on these results, it is concluded that the selective pressures involved in the evolution of accessory hearing structures and in the design of vocal signals were other than those serving to optimize acoustic communication.

Experimental investigation on the characteristics of the dynamic rail pad force and its stress distribution in the time and frequency domain

2019 ◽  
Vol 234 (2) ◽  
pp. 201-213 ◽  
Author(s):  
Xu Zhang ◽  
Chunfa Zhao ◽  
Xiaobo Ren ◽  
Yang Feng ◽  
Can Shi ◽  
...  
Keyword(s):  
Stress Distribution ◽  
Frequency Domain ◽  
Maximum Stress ◽  
Field Tests ◽  
Service Condition ◽  
Field Testing ◽  
Dominant Frequency ◽  
Test Results ◽  
Parabolic Shape ◽  
Dominant Frequencies

The rail pad force and its stress distribution have critical influences on the performance and fatigue life of the rail, fasteners, and sleepers. The characteristics of the rail pad force and its stress distribution in the time and frequency domain obtained from field tests carried out using matrix-based tactile surface sensor are presented in this paper. The field testing involved rail pads under various axle-loads of running trains at different speeds. The influences that the train axle-load, the operational speed, and the rail pad stiffness have on the rail pad force and its stress distribution are analyzed. The test results indicate that the rail pad stiffness has a remarkable influence on the amplitude of the rail pad force but has little influence on its dominant frequencies. The first dominant frequency of the rail pad force is quite close to the passing frequency of the vehicle length. The stress distribution on the rail pad has a parabolic shape along the longitudinal and the lateral directions with the large stress appearing near the center of the rail pad, and is remarkably affected by the service condition of the rail pad. The maximum stress is about 2.5 to 3 times of the average stress, which is significantly greater than the nominal stress resulting from the assumption of uniform stress distribution.

Frequencies in vibrating wood – Does cell organization matter?

IAWA Journal ◽  
2019 ◽  
Vol 40 (1) ◽  
pp. 124-142
Author(s):  
Oliver Dünisch
Keyword(s):  
Spatial Organization ◽  
Ring Width ◽  
Spatial Arrangement ◽  
Cell Types ◽  
Dominant Frequency ◽  
Fast Fourier Transformation ◽  
Frequency Spectra ◽  
Laser Sensors ◽  
Vibrating Plates ◽  
Dominant Frequencies

ABSTRACT The relationship between the spatial organization of different cell types, of the xylem rays, and of the tree rings and the frequencies in vibrating softwoods and hardwoods was studied under controlled conditions. In total, the frequencies in 1007 standardized vibrating plates from 16 softwoods and 74 hardwoods were analysed using high resolution laser sensors (accuracy ± 0.02 μm, sampling frequency 30 kHz) for vibration measurements. Overlapping frequencies within the frequency spectra were identified by means of Fast Fourier Transformation analysis. With regard to the number of distinct frequencies within the spectra, four different vibration types were identified: type 1–one dominant frequency within the frequency spectra; type 2-two dominant frequencies within the frequency spectra; type 3-three dominant frequencies within the frequency spectra; type 4-no dominant frequencies within the frequency spectra. The presence of distinct frequencies was correlated with a highly organized spatial arrangement of tracheids in softwoods, with a storied arrangement of the xylem rays in hardwoods, and with low variation in tree-ring width in both softwoods and hardwoods. The grid size for repetition in these xylem structures influenced the frequencies of the vibrating wood in absolute numbers. The results indicate that the analysis of the anatomical structure of the wood can contribute to the grading of timber for its vibration characteristics, which is of special interest for the selection of resonance wood for musical instruments.

Frequency modulation within electrocardiograms during ventricular fibrillation

2000 ◽  
Vol 279 (2) ◽  
pp. H825-H835 ◽  
Author(s):  
Abhijit Patwardhan ◽  
Sachin Moghe ◽  
Ke Wang ◽  
Fabio Leonelli
Keyword(s):  
Ventricular Fibrillation ◽  
Body Surface ◽  
Dominant Frequency ◽  
The Body ◽  
Frequency Variation ◽  
Refractory Periods ◽  
Analysis Technique ◽  
Before And After ◽  
Average Variation ◽  
Dominant Frequencies

Periods of reentrant activation and effective refractory periods are correlated with dominant frequency or reciprocal of cycle periods during ventricular fibrillation (VF). In the present study, we used an analysis technique based on Wigner transforms to quantify time-varying dominant frequencies in electrocardiograms (ECGs) during VF. We estimated dominant frequencies within orthogonal ECGs recorded in 10 dogs during trials of 10 s of VF and in 9 dogs during trials of 30 s of VF. In four additional dogs, we compared dominant frequencies during 10 s of VF before and after administration of amiodarone. Our results showed the following. 1) There was substantial frequency variation or modulation within the ECGs during 10 and 30 s of VF, the average variation being ±15% from the mean frequency. Amiodarone decreased mean frequencies ( P < 0.05) as expected; however, amiodarone also decreased the variation in frequencies ( P < 0.05). 2) During 30 s of VF, the dominant frequencies increased continuously from 7.3 to 8.1 Hz ( P < 0.05). The increase in frequency was almost linear with a rate of 0.022 Hz/s ( r 2 = 0.93, P < 0.0005). 3) Modulation of frequencies during the first and the last one-half of 30 s of VF was not different. Average (in time) mean frequencies and modulation of frequencies were similar in all three ECGs. 4) Although the averages were similar, during any VF episode, dominant frequencies in ECGs recorded from different locations on the body surface were similar to each other at some times and markedly different from each other at other times. We conclude that during VF, 1) frequencies in ECGs vary considerably and continuously, and amiodarone decreases this variation; 2) mean frequencies increase linearly during first 30 s; 3) the variability in frequency does not change during 30 s; and 4) at any given time, the frequencies within spatially different body surface ECGs can be either similar or markedly different.

Earthquake source properties from analysis of dynamic ruptures and far-field seismic waves in a damage-breakage model

2020 ◽  
Vol 224 (3) ◽  
pp. 1793-1810
Author(s):  
Ittai Kurzon ◽  
Vladimir Lyakhovsky ◽  
Yehuda Ben-Zion
Keyword(s):  
Seismic Waves ◽  
Source Parameters ◽  
Dominant Frequency ◽  
Earthquake Source ◽  
Corner Frequency ◽  
Far Field ◽  
Rupture Directivity ◽  
Rupture Velocity ◽  
S Waves ◽  
Dominant Frequencies

SUMMARY We present results on earthquake source properties using simulations of dynamic rupture and radiated seismic waves in a continuum damage-breakage rheological model. The source properties are derived by (1) calculation of source parameters directly from the simulated ruptures and (2) observational processing of the far-field radiated waves. The seismic potency, moment, damage-related source term, rupture velocity and effective rigidity are estimated directly from the simulated sources, while the radiation pattern, dominant frequency, directivity, rupture velocity and seismic potency are calculated through analysis of the radiated waves. The potencies calculated directly from the sources are used to validate those estimated by wave analysis. The effective rigidity at the rupture zone during failure is about four times smaller than that of the intact surrounding rocks. Rupture velocity can be estimated by far-field measurements for sources with unidirectional ruptures with prominent rupture directivity. The dominant frequencies for P and S waves $f_d^S/f_d^P$ reflect clearly the rupture duration and have a ratio in the range 0.87–1.12. Seismic potencies obtained through processing the P or S waves have an overall ±15 per cent difference from the source reference values. The calculated values of the coefficient ${\rm{\kappa }}$, relating rupture length to corner or dominant frequency, have strong dependency on the source geometry. Using a strain-rate dependent ${\rm{\kappa }}$, we obtain much weaker dependencies of strain-drop on the dominant frequencies, $\Delta {\rm{\varepsilon }} \propto {( {{f_d}} )^{3/4}}$, than the classical cube-dependency between stress drop and corner frequency, and corresponding weak dependency of average slip on dominant frequency, ${\rm{\bar{D}}} \propto {( {{f_d}} )^{1/2}}$. The obtained analysis procedure and relations can be used to reduce the uncertainty of source properties derived from far-field seismic waves.

scholarly journals Dendroclimatology in Latin America, State of the Art and Contributions for Understanding Climate Variation

2020 ◽  
Author(s):  
Oscar D. Sánchez ◽  
Manuel E. Mendoza ◽  
Teodoro Carlón-Allende ◽  
José Villanueva-Díaz
Keyword(s):  
Latin America ◽  
Web Of Science ◽  
Temporal Dynamics ◽  
State Of The Art ◽  
Climatic Variability ◽  
Temperate Climate ◽  
Response Functions ◽  
The Past ◽  
Current State ◽  
Spatial And Temporal Dynamics

Dendroclimatology has gained relevance during the XXI century. We analyze the state of-the-art of dendroclimatology in Latin America during the past 28 years (1990 to 2019), identifying the current state and recent advances in the application of dendroclimatology in this region. We carried out a systematic review in ScienceDirect, Web of Science, and Scopus databases using Boolean operators to logically connect the keywords &ldquo;dendrochronology,&rdquo; &ldquo;dendroclimatology,&rdquo; &ldquo;trend,&rdquo; &ldquo;climatic variability,&rdquo; and &ldquo;climatic variability trend&rdquo;, for each country. Dendroclimatological research conducted in the region focused on climatic reconstruction and the evaluation of new tree species with dendrochronological potential, which increase in 2010, then there was a gap between 1995 and 1996, later increase to present. Dendroclimatological studies in Latin America have been mainly developed in temperate climate zones (82.4 %) followed by tropical or subtropical areas (17.6 %). Dendroclimatological research in Latin America has provided advances in the study of climate variability by defining response functions of tree rings to climate. The generated information allows for a better understanding of the spatial and temporal dynamics of climatic variability and about its effects on ecosystems and society. We also call for increased dendroclimatological research based on subtropical and tropical forests limited studied until today.

Influences of Rotational Speed Variations on the Flow-Induced Vibrational Performance of a Prototype Reversible Pump Turbine in Spin-No-Load Mode

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Xianghao Zheng ◽  
Yuning Zhang ◽  
Jinwei Li ◽  
Yuning Zhang
Keyword(s):  
Vibrational Level ◽  
Rotational Speed ◽  
Draft Tube ◽  
Dominant Frequency ◽  
Pump Turbine ◽  
Vortex Rope ◽  
Vibrational Levels ◽  
Load Mode ◽  
Swirling Vortex ◽  
Dominant Frequencies

Abstract During the spin-no-load mode, vibrational performance of the reversible pump turbine is an important criterion for the evaluation of the operational performances of the power station. In the present paper, the influences of rotational speed variations on the vibrational performances of the whole unit (including the top cover, the upper, and the lower brackets) are experimentally investigated with discussions of their sources and propagation characteristics. According to the whole vibrational levels and the dominant frequencies of the vibration signals obtained at the top cover, the investigated cases with different rotational speeds could be divided into three partitions with their main characteristics given as follows. In the first partition (with low rotational speeds), the vibrational level is quite limited, and its source is the pressure fluctuation generated by the swirling vortex rope in the draft tube. In the second partition (with medium rotational speeds), the vibrational level gradually increases and its source is the mechanical aspects of the impeller rotation. In the third partition (with high rotational speeds), the vibrational level is prominent with a prominent swirling vortex rope in the draft tube and intensive rotor–stator interactions in the vaneless space (VS). For the vibrations of the upper and the lower brackets, the vibrations mainly originate from the mechanical aspects of the impeller rotation and the amplitudes of the dominant frequency also increase with the increment of the rotational speed. Finally, differences between the vibrational performances of the spin-no-load mode and the generating mode are discussed.

An Investigation of the Scales in Transitional Boundary Layers Under High Free-Stream Turbulence Conditions

2002 ◽  
Author(s):  
Ralph J. Volino
Keyword(s):  
Boundary Layer ◽  
Free Stream ◽  
Dominant Frequency ◽  
Intermittent Flow ◽  
Self Similarity ◽  
Free Stream Turbulence ◽  
Transitional Boundary Layer ◽  
Streamwise Location ◽  
Transition Models ◽  
Dominant Frequencies

The scales in a transitional boundary layer subject to high (initially 8%) free-stream turbulence and strong acceleration (K as high as 9×10−6) have been investigated using wavelet spectral analysis and conditional sampling of experimental data. The boundary layer shows considerable evolution through transition, with a general shift from the lower frequencies induced by the free-stream unsteadiness to higher frequencies associated with near wall generated turbulence. Within the non-turbulent zone of the intermittent flow, there is considerable self-similarity in the spectra from the beginning of transition to the end, with the dominant frequencies in the boundary layer remaining constant at about the dominant frequency of the free-stream. The frequencies of the energy containing scales in the turbulent zone change with streamwise location and are significantly higher than in the non-turbulent zone. When normalized on the local viscous length scale and velocity, however, the turbulent zone spectra also show good self-similarity throughout transition. Turbulence dissipation occurs almost exclusively in the turbulent zone. The velocity fluctuations associated with dissipation are isotropic, and their normalized spectra at upstream and downstream stations are nearly identical. The distinct differences between the turbulent and non-turbulent zones suggest the potential utility of intermittency based transition models in which these zones are treated separately. The self-similarity noted in both energy containing and dissipation scales in both zones suggests possibilities for simplifying the modeling for each zone.

Effects of age, size and temperature on the advertisement calls of two Spanish populations of Pelodytes punctatus

2002 ◽  
Vol 23 (3) ◽  
pp. 249-258 ◽  
Author(s):  
◽  
◽  
◽  
◽  
Keyword(s):  
Body Size ◽  
Dominant Frequency ◽  
Advertisement Call ◽  
Male Body ◽  
Body Temperatures ◽  
Spectral Parameters ◽  
Advertisement Calls ◽  
Poor Predictor ◽  
Spanish Populations ◽  
Dominant Frequencies

AbstractAdvertisement calls of males from two Spanish populations of parsley frogs (Pelodytes punctatus) were recorded. Body size (SVL, mass) and calling temperature were measured, and age was determined through skeletochronology of phalanges. Calling males were 2-7 years old in Valencia. In Burgos, males were 1-6 years old and the age structure was highly skewed with more than 50% of the sample of males being 1 year old. The range of body temperatures of calling males was similar in both sites (10-15.1°C in Valencia, and 10-17.5°C in Burgos). Males called with the typical two-note advertisement call A-B, although in Burgos it was common to hear A-only calls. In both populations repetition of the second note was rare. Calls of both populations showed a negative correlation between temporal parameters (note duration, inter-note interval, pulse rate) and body temperature. On the other hand, spectral parameters (dominant frequencies and dominant frequency ranges) were not correlated to temperature and correlation with body size (SVL, mass) was non-significant. Age was not significantly correlated with dominant frequency or with any other measured call parameter. Call frequency in Pelodytes is a poor predictor of male body size and does not convey information on age. Thus, any size-related mating trends could result from non-static calling parameters such as call intensity, or from mechanisms of malemale competition (e.g. chorus attendance).

scholarly journals Seismic Vulnerability Index Calculation for Mitigation Purposes at Cilacap District

2021 ◽  
Vol 873 (1) ◽  
pp. 012005
Author(s):  
Robert Edison ◽  
Supriyanto Rohadi ◽  
Yusuf Perdana ◽  
Nelly Florida Riama ◽  
Dwikorita Karnawati
Keyword(s):  
Seismic Vulnerability ◽  
Natural Vibration ◽  
Soil Layer ◽  
Vulnerability Index ◽  
Dominant Frequency ◽  
Key Factors ◽  
Minimum Duration ◽  
Central Java ◽  
Maximum Amplification ◽  
Dominant Frequencies

Abstract Seismic vulnerability index is one of the key factors in mitigation that shows the vulnerability of the soil layer beneath when passed through with a wave, the more vulnerable the soil layer, the more damage it done when an earthquake happens. Seismic vulnerability is calculated using two variables, that is dominant frequencies and amplification that are obtained by analyzing HVSR curve. HVSR are used to determine the dominant frequency by determining the maximum amplification in that area. HVSR curve is obtained by measuring microbemor data in 163 spots with 30 minutes-minimum duration in Cilacap with a portable seismograph. Mierotremor is a natural vibration that is caused by continuous vibration that come from beneath the surface, sometimes mixed up by the vibrabon that is caused by human activities such as pipe-flow, vehicles, etc. Thus, the purposes of this research are to determine which area is more vulnerable than others, based on the seismic vulnerability index, so it could be a reference for regional development to classified is it safe or unsafe to build in that area, remembering Cilacap is one of the most developed Districts in Central Java.

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