Low-Frequency Seismic Noise Before and After the Sumatra Megaearthquake of December 26, 2004

2019 ◽  
Vol 485 (2) ◽  
pp. 395-400 ◽  
Author(s):  
G. A. Sobolev
Keyword(s):  
Seismic Noise ◽  
Low Frequency ◽  
Before And After

scholarly journals Low frequency seismic noise before and after the Sumatra megaearthquake December 26, 2004

2019 ◽  
Vol 485 (4) ◽  
pp. 497-501
Author(s):  
G. A. Sobolev
Keyword(s):  
Seismic Noise ◽  
Isotropic Turbulence ◽  
Seismic Station ◽  
Low Frequency ◽  
Oscillation Period ◽  
Motion Velocity ◽  
Standard Equipment ◽  
Seismic Stations ◽  
Before And After ◽  
Different Sources

The paper aims at detailed study of the structure of seismic noise before and after the Sumatra mega-earthquake with M = 9.1 of December 26, 2004. The records by IRIS seismic stations in the different regions of the world, equipped with STS-1 seismometers providing ground motion velocity recording in a broad range of periods from 0.2 to 360 s with the use of standard equipment, form the empirical base of the research. In the records by each station, the intervals free of the earthquakes, interference of manmade impacts, and noise enhancement due to cyclone propagation were selected. The noise bursts in the ranges 40-80, 80-160, and 160-320 s differ by the shape and time of occurrence suggesting different sources of their generation. The absence of the correlation between the noise recordings at the neighboring seismic stations spaced 102 - 103 km apart indicates the influence of local processes. The noise reflects turbulent processes in the Earth’s atmosphere whereas the exponential growth of the noise with the increase of the oscillation period is consistent with A.N. Kolmogorov’s theory of locally isotropic turbulence in the atmosphere. The noise amplitude after the Sumatra mega-earthquake with M = 9.1 of December 26, 2004 has increased by a factor of 1.5-2 in January 2005 compared to January 2004 irrespective of the location of a seismic station.

Effects of activation frequency and force on low-frequency fatigue in human skeletal muscle

1999 ◽  
Vol 86 (4) ◽  
pp. 1337-1346 ◽  
Author(s):  
Stuart A. Binder-Macleod ◽  
David W. Russ
Keyword(s):  
Healthy Subjects ◽  
Human Skeletal Muscle ◽  
Low Frequency ◽  
Variable Frequency ◽  
Activation Pattern ◽  
Constant Frequency ◽  
Mean Frequency ◽  
Before And After ◽  
Low Frequency Fatigue ◽  
Force Time

No comparison of the amount of low-frequency fatigue (LFF) produced by different activation frequencies exists, although frequencies ranging from 10 to 100 Hz have been used to induce LFF. The quadriceps femoris of 11 healthy subjects were tested in 5 separate sessions. In each session, the force-generating ability of the muscle was tested before and after fatigue and at 2, ∼13, and ∼38 min of recovery. Brief (6-pulse), constant-frequency trains of 9.1, 14.3, 33.3, and 100 Hz and a 6-pulse, variable-frequency train with a mean frequency of 14.3 Hz were delivered at 1 train/s to induce fatigue. Immediately postfatigue, there was a significant effect of fatiguing protocol frequency. Muscles exhibited greater LFF after stimulation with the 9.1-, 14.3-, and variable-frequency trains. These three trains also produced the greatest mean force-time integrals during the fatigue test. At 2, ∼13, and ∼38 min of recovery, however, the LFF produced was independent of the fatiguing protocol frequency. The findings are consistent with theories suggesting two independent mechanisms behind LFF and may help identify the optimal activation pattern when functional electrical stimulation is used.

Effect of Incisions in the Brainstem Commissural Network on the Short-Term Vestibulo-Ocular Adaptation of the CAT

1991 ◽  
Vol 1 (3) ◽  
pp. 223-239
Author(s):  
G. Cheron
Keyword(s):  
Low Frequency ◽  
Adaptive Plasticity ◽  
Training Procedure ◽  
Optokinetic Response ◽  
Mean Values ◽  
Ocular Reflex ◽  
Optokinetic Reflex ◽  
Before And After ◽  
Vestibulo Ocular Reflex ◽  
Vor Adaptation

This study was intended to test the adaptive plasticity of the vestibulo-ocular reflex before and after either a midsagittal or parasagittal incision in the brainstem. Eye movements were measured with the electromagnetic search coil technique during the vestibulo-ocular reflex (VORD) in the dark, the optokinetic reflex (OKN), and the visuo-vestibular adaptive training procedure. Two types of visual-vestibular combined stimulation were applied by means of low frequency stimuli (0.05 to 0.10 Hz). In order to increase or decrease the VORD gain, the optokinetic drum was oscillated either 180∘ out-of-phase or in-phase with the vestibular stimulus turntable. This “training” procedure was applied for 4 hours. Initial measurements of the VORD were normal with a mean gain value of 0.92 ± 0.08. After 4 hours of “training” with the out-of-phase condition (180∘), VORD gain reached mean values of 1.33 ± 0.11 (n = 6 cats). In the in-phase combination, the mean VORD gain decreased from 1.0 to 0.63 ± 0.02 (n = 2 cats). No significant change of VORD phase was found in any of the cats. Midsagittal or parasagittal pontomedullary brainstem incisions were performed in 4 cats. Recovery of the VOR was tested on the 2nd, 7th, and 30th day after operation. After the 30th day, recovery of the VORD gain stabilized at about 66% of the initial preoperative value. At this stage of the recovery, the optokinetic response (OKN) of the midsagittal-Iesioned cats was practically normal: in the parasagittal-Jesioned cats, the postoperative OKN responses were asymmetric. After stabilization of recovery, lesioned cats were trained with the same adaptation procedure. Although the direct effect of the visuo-vestibular combined stimulation during the training was still operative in all lesioned cats, the adaptive plasticity was completely abolished by the lesions. These results suggest that the commissural brainstem network may play a crucial role in the acquisition of the forced VOR adaptation.

High-frequency seismic noise as a function of depth

1991 ◽  
Vol 81 (4) ◽  
pp. 1101-1114
Author(s):  
Jerry A. Carter ◽  
Noel Barstow ◽  
Paul W. Pomeroy ◽  
Eric P. Chael ◽  
Patrick J. Leahy
Keyword(s):  
New York ◽  
High Frequency ◽  
Seismic Noise ◽  
Low Frequency ◽  
Time Variability ◽  
Orthogonal Components ◽  
The Difference ◽  
Frequency Coherence ◽  
Cultural Noise ◽  
Natural Wind

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.

Comparative study on effect of neutral spinal bath and neutral spinal spray on blood pressure, heart rate and heart rate variability in healthy volunteers

2018 ◽  
Vol 16 (2) ◽  
Author(s):  
Arundhati Goley ◽  
A. Mooventhan ◽  
NK. Manjunath
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Heart Rate Variability ◽  
Healthy Volunteers ◽  
Group Analysis ◽  
Low Frequency ◽  
Single Session ◽  
Arterial Blood ◽  
Before And After ◽  
Instantaneous Heart Rate

Abstract Background Hydrotherapeutic applications to the head and spine have shown to improve cardiovascular and autonomic functions. There is lack of study reporting the effect of either neutral spinal bath (NSB) or neutral spinal spray (NSS). Hence, the present study was conducted to evaluate and compare the effects of both NSB and NSS in healthy volunteers. Methods Thirty healthy subjects were recruited and randomized into either neutral spinal bath group (NSBG) or neutral spinal spray group (NSSG). A single session of NSB, NSS was given for 15 min to the NSBG and NSSG, respectively. Assessments were taken before and after the interventions. Results Results of this study showed a significant reduction in low-frequency (LF) to high-frequency (HF) (LF/HF) ratio of heart rate variability (HRV) spectrum in NSBG compared with NSSG (p=0.026). Within-group analysis of both NSBG and NSSG showed a significant increase in the mean of the intervals between adjacent QRS complexes or the instantaneous heart rate (HR) (RRI) (p=0.002; p=0.009, respectively), along with a significant reduction in HR (p=0.002; p=0.004, respectively). But, a significant reduction in systolic blood pressure (SBP) (p=0.037) and pulse pressure (PP) (p=0.017) was observed in NSSG, while a significant reduction in diastolic blood pressure (DBP) (p=0.008), mean arterial blood pressure (MAP) (p=0.008) and LF/HF ratio (p=0.041) was observed in NSBG. Conclusion Results of the study suggest that 15 min of both NSB and NSS might be effective in reducing HR and improving HRV. However, NSS is particularly effective in reducing SBP and PP, while NSB is particularly effective in reducing DBP and MAP along with improving sympathovagal balance in healthy volunteers.

Reversal of muscle fatigue during 16 h of heavy intermittent cycle exercise

2004 ◽  
Vol 97 (6) ◽  
pp. 2166-2175 ◽  
Author(s):  
H. J. Green ◽  
T. A. Duhamel ◽  
S. Ferth ◽  
G. P. Holloway ◽  
M. M. Thomas ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Muscle Fatigue ◽  
Intermittent Exercise ◽  
Low Frequency ◽  
Quadriceps Muscle ◽  
Stimulation Frequency ◽  
Peak Oxygen Consumption ◽  
Force Frequency ◽  
Reduction In Force ◽  
Before And After

This study examined the effects of extended sessions of heavy intermittent exercise on quadriceps muscle fatigue and weakness. Twelve untrained volunteers (10 men and 2 women), with a peak oxygen consumption of 44.3 ± 2.3 ml·kg−1·min−1, exercised at ∼91% peak oxygen consumption for 6 min once per hour for 16 h. Muscle isometric properties assessed before and after selected repetitions (R1, R2, R4, R7, R12, and R15) were used to quantitate fatigue (before vs. after repetitions) and weakness (before vs. before repetitions). Muscle fatigue at R1 was indicated by reductions ( P < 0.05) in peak twitch force (135 ± 13 vs. 106 ± 11 N) and by a reduction ( P < 0.05) in the force-frequency response, which ranged between ∼53% at 10 Hz (113 ± 12 vs. 52.6 ± 7.4 N) and ∼17% at 50 Hz (324 ± 27 vs. 270 ± 30 N). No recovery of force, regardless of stimulation frequency, was observed during the 54 min between R1 and R2. At R2 and for all subsequent repetitions, no reduction in force, regardless of stimulation frequency, was generally found after the exercise. The only exception was for R2, where, at 20 Hz, force was reduced ( P < 0.05) by 18%. At R15, force before repetitions for high frequencies (i.e., 100 Hz) returned to R1 (333 ± 29 vs. 324 ± 27 N), whereas force at low frequency (i.e., 10 Hz) was only partially ( P < 0.05) recovered (113 ± 12 vs. 70 ± 6.6 N). It is concluded that multiple sessions of heavy exercise can reverse the fatigue noted early and reduce or eliminate weakness depending on the frequency of stimulation.

Near-maximal voluntary hyperpnea and ventilatory muscle function

1984 ◽  
Vol 57 (6) ◽  
pp. 1742-1748 ◽  
Author(s):  
T. R. Bai ◽  
B. J. Rabinovitch ◽  
R. L. Pardy
Keyword(s):  
Muscle Function ◽  
Low Frequency ◽  
Normal Subjects ◽  
Pressure Time ◽  
Before And After ◽  
Expiratory Muscles ◽  
Four Levels ◽  
Frequency Relationship ◽  
Low Frequency Power ◽  
Relationship Of

Because of its potential relevance to heavy exercise we studied the ventilatory muscle function of five normal subjects before, during, and after shortterm near-maximal voluntary normocapnic hyperpnea. Measurements of pleural and abdominal pressures and diaphragm electromyogram (EMG) during hyperpnea and of maximum respiratory pressures before and after hyperpnea were made at four levels of ventilation: 76, 79, and 86% maximal voluntary ventilation (MVV) and at MVV. Measurements of pleural and abdominal pressures and diaphragm electromyogram (EMG) during hyperpnea and of maximum respiratory pressures before and after hyperpnea were made. The pressure-stimulation frequency relationship of the diaphragm obtained by unilateral transcutaneous phrenic nerve stimulation was studied in two subjects before and after hyperpnea. Decreases in maximal inspiratory (PImax) and transdiaphragmatic (Pdimax) strength were recorded posthyperpnea at 76 and 79% MVV. Decreases in the pressure-frequency curves of the diaphragm and the ratio of high-to-low frequency power of the diaphragm EMG occurred in association with decreases in Pdimax. Analysis of the pressure-time product (P X dt) for the inspiratory and expiratory muscles individually indicated the increasing contribution of expiratory muscle force to the attainment of higher levels of ventilation. Demonstrable ventilatory muscle fatigue may limit endurance at high levels of ventilation.

scholarly journals The Effect of 12 Hz Extremely Low-Frequency Electromagnetic Fields on Visual Memory of Male Macaque Monkeys

2021 ◽  
Author(s):  
Masoomeh Kazemi ◽  
◽  
Hamed Aliyari ◽  
Elaheh Tekieh ◽  
Hassan Tavacoli ◽  
...  
Keyword(s):  
Electromagnetic Fields ◽  
Visual Memory ◽  
Rhesus Macaques ◽  
Low Frequency ◽  
Serum Levels ◽  
Control Group ◽  
Behavioral Tests ◽  
Extremely Low Frequency ◽  
Before And After ◽  
Male Rhesus

Introduction: Today, humans leave in a world surrounded by electromagnetic fields. Numerous studies have been carried out to discover the biological, physiological, and behavioral effects of electromagnetic fields on humans and animals. Given the biological similarities between monkeys and humans, the goal of the present research was to examine Visual Memory (VM), hormonal, genomic, and anatomic changes, and changes of the amygdala function in the male rhesus macaques who exposed to extremely low-frequency magnetic fields (ELF/MF). Materials and methods: Four male Rhesus Macaques (Macaca mulatta) were used. For the behavioral tests the animals were needed to be fasting for 17 hours, and for the behavioral tests such as visual memory, cooperation of the animal was necessary. Using the radiation protocol, two of the monkeys were exposed to 12-Hz electromagnetic fields with a magnitude of 0.7 microtesla (electromagnetic radiation) four hours a day for a month. Before and after the exposure, a visual memory test was conducted using a coated device (visible reward) on a movable stand. Ten mL of blood was obtained from the femoral artery of the monkeys and half of it was used to examine cortisol serum levels using MyBioSource kits (made in the USA). The other half of blood samples were used to extract lymphocytes for assaying expressions of Glucocorticoid Receptor (GR) genes before and after radiation using the PCR method. Anatomic studies of the amygdala were carried out based on pre- and post-radiation Magnetic Resonance Imaging (MRI). Findings: Research results indicated that visual memory in male primates increased significantly at the 12Hz frequency. Hormonal analysis at the 12Hz frequency showed a decrease in cortisol serum levels. However, visual memory and serum cortisol levels did not change considerably in male primates in the control group. There was no considerable amygdala volumetric difference at the 12 Hz frequency. The expression of the GR genes decreased at 12Hz compared to the control group. Conclusion: In short, these results indicated that ELF may have a beneficial value for memory enhancement as indicated by the fact that exposure to the 12 HZ ELF can enhance visual memory. This may be due to a decrease in plasma cortisol, and/or expression of GR genes. Moreover, direct involvement of the amygdala in this regard cannot be recommended.

scholarly journals Effectiveness of Extremely Low Frequency Electromagnetic Field and Pulsed Low-Level Laser Therapy in Acute Stroke Treatment

2020 ◽  
Vol 7 (3) ◽  
pp. 127-131
Author(s):  
Farzad Ashrafi ◽  
Amir Rezaei ◽  
Arash Azhideh ◽  
Faraj Tabeie ◽  
Latif Gachkar ◽  
...  
Keyword(s):  
Electromagnetic Field ◽  
Medical Condition ◽  
Low Frequency ◽  
Cognitive Status ◽  
Low Level Laser Therapy ◽  
Stroke Treatment ◽  
Extremely Low Frequency ◽  
Level Laser ◽  
Significant Difference ◽  
Before And After

Introduction: Stroke is one of the most devastating neurologic conditions in the world. Despite all the efforts that have been made for effective treatment, the prevalence of this medical condition is still high. One of the new methods in the treatment of patients is the use of low power laser and pulsed magnetic fields. The previous studies investigated the effectiveness of these methods individually. However, the present study aimed to investigate their effectiveness in combination. Methods: We divided the patients into control (n=26) and experimental (n=26) groups. The primary variables included the Mini-Mental State Examination (MMSE) and the National Institute of Health Stroke Scale (NIHSS). The experimental group received extremely low-frequency electromagnetic field (EMF-ELF) treatment with 1 mT power and laser in rejection with a wavelength of 840 nm for 5 days and 45 min/d. Results: The variable measured during this study, in addition to comparing the results of the intervention between the control and experimental groups, showed a significant difference in all indicators before and after the intervention. The mean and standard deviations of the modified Rankin scale (mRS), functional status (Barthel’s index), and cognitive status (MMSE) (P<0.001) were signed between 2 groups. Conclusion: Laser and magnetic field combination can be effective in the treatment of stroke. Further studies are recommended to ensure a better comparison.

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