scholarly journals Краевые колебания нанолент графана

2018 ◽  
Vol 60 (5) ◽  
pp. 1029
Author(s):  
А.В. Савин
Keyword(s):  
Force Field ◽  
Frequency Spectrum ◽  
High Frequency ◽  
Low Frequency ◽  
Dispersion Curves ◽  
Linear Vibrations ◽  
The Mean

AbstractUsing the COMPASS force field, natural linear vibrations of graphane (graphene hydrogenated on both sides) nanoribbons are simulated. The frequency spectrum of a graphane sheet consists of three continuous intervals (low-frequency, mid-frequency, and narrow high-frequency) and two gaps between them. The construction of dispersion curves for nanoribbons with a zigzag and chair structure of the edges show that the frequencies of edge vibrations (edge phonons) can be present in the gaps of the frequency spectrum. In the first type of nanoribbons, two dispersion curves are in the low-frequency gap of the spectrum and four dispersion curves in the second gap. These curves correspond to phonons moving only along the nanoribbon edges (the mean depth of their penetration toward the nanoribbon center does not exceed 0.15 nm).

Effect of Inhalation of 30% Nitrous Oxide on Spectral Components of Heart Rate Variability in Conscious man

1993 ◽  
Vol 85 (4) ◽  
pp. 389-392 ◽  
Author(s):  
D. C. Galletly ◽  
P. D. Tobin ◽  
B.J. Robinson ◽  
T. Corfiatis
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Frequency Spectrum ◽  
High Frequency ◽  
Low Frequency ◽  
Spectral Components ◽  
Frequency Components ◽  
The Mean ◽  
Frequency Power ◽  
High Frequency Spectrum

1. Periodicities in cardiac interbeat interval may be resolved into discrete frequency components by applying Fourier analysis to heart rate time series. Low-frequency components (<0.15 Hz) are believed to be under parasympathetic and sympathetic control, whereas a higher frequency component in phase with respiration is believed to be entirely parasympathetic. The ratio of the power in the low-/high-frequency spectrum gives an estimate of sympathetic/para-sympathetic balance. 2. This study examined, using heart rate variability spectral analysis, the cardiac autonomic effects of breathing 30% N2O in normal subjects. While supine, the inhalation of N2O caused a significant fall in high-frequency power and a rise in the low-/high-frequency spectrum. During air breathing, tilting caused a significant rise in the mean blood pressure, heart rate, low-frequency power and low-/high-frequency spectrum. During N2O breathing, tilting caused a rise in the heart rate and the mean blood pressure, but no significant alteration in the power of individual spectral components. During tilting, the heart rate, the low-frequency and low-/high-frequency spectrum were less when breathing N2O than when breathing air. 3. These observations are consistent with the effect of N2O being an enhanced sympathetic balance of sinoatrial control, with the primary effect being through reduced parasympathetic tone. Enhanced sympathetic dominance of heart rate variability was seen on standing while subjects breathed air, but this effect was blunted with N2O.

Preferential acceleration of heavy ions from thermal velocities

1968 ◽  
Vol 46 (10) ◽  
pp. S638-S641 ◽  
Author(s):  
D. B. Melrose
Keyword(s):  
Frequency Spectrum ◽  
High Frequency ◽  
Heavy Ions ◽  
Crab Nebula ◽  
Low Frequency ◽  
High Frequency Waves ◽  
Hydromagnetic Waves ◽  
The Crab Nebula ◽  
Low Frequency Waves

The acceleration of ions from thermal velocities is analyzed to determine conditions under which heavy ions can be preferentially accelerated. Two accelerating mechanisms involving high-and low-frequency hydromagnetic waves respectively are considered. Preferential acceleration of heavy ions occurs for high-frequency waves if the frequency spectrum falls off faster than (frequency)−1. For the low-frequency waves heavy ions are less effectively accelerated than lighter ions. However, very heavy ions can be preferentially accelerated, the abundances of the very heavy ions being enhanced by a factor Ai over the thermal abundances. Acceleration of ions in the envelope of the Crab nebula is considered as an example.

A Novel Accelerometer Mounting Method for Sensing Performance Improvement in Acoustic Measurements From the Knee

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Goktug C. Ozmen ◽  
Mohsen Safaei ◽  
Lan Lan ◽  
Omer T. Inan
Keyword(s):  
Frequency Band ◽  
High Frequency ◽  
Low Frequency ◽  
Adhesive Tape ◽  
Spectral Centroid ◽  
Wearable Systems ◽  
Electrodynamic Shaker ◽  
3D Printed ◽  
The Mean ◽  
Sensing Performance

Abstract In this study, we propose a new mounting method to improve accelerometer sensing performance in the 50 Hz–10 kHz frequency band for knee sound measurement. The proposed method includes a thin double-sided adhesive tape for mounting and a 3D-printed custom-designed backing prototype. In our mechanical setup with an electrodynamic shaker, the measurements showed a 13 dB increase in the accelerometer's sensing performance in the 1–10 kHz frequency band when it is mounted with the craft tape under 2 N backing force applied through low-friction tape. As a proof-of-concept study, knee sounds of healthy subjects (n = 10) were recorded. When the backing force was applied, we observed statistically significant (p &lt; 0.01) incremental changes in spectral centroid, spectral roll-off frequencies, and high-frequency (1–10 kHz) root-mean-square (RMS) acceleration, while low-frequency (50 Hz–1 kHz) RMS acceleration remained unchanged. The mean spectral centroid and spectral roll-off frequencies increased from 0.8 kHz and 4.15 kHz to 1.35 kHz and 5.9 kHz, respectively. The mean high-frequency acceleration increased from 0.45 mgRMS to 0.9 mgRMS with backing. We showed that the backing force improves the sensing performance of the accelerometer when mounted with the craft tape and the proposed backing prototype. This new method has the potential to be implemented in today's wearable systems to improve the sensing performance of accelerometers in knee sound measurements.

Heart rate at 4 s after the onset of exercise in endurance-trained men

2014 ◽  
Vol 92 (6) ◽  
pp. 476-480 ◽  
Author(s):  
Divanei Zaniqueli ◽  
Elis Aguiar Morra ◽  
Eduardo Miranda Dantas ◽  
Marcelo Perim Baldo ◽  
Luciana Carletti ◽  
...  
Keyword(s):  
Heart Rate ◽  
Frequency Spectrum ◽  
High Frequency ◽  
Sinus Node ◽  
Low Frequency ◽  
Spectral Indices ◽  
High Frequency Band ◽  
Band Ratio ◽  
Endurance Runners ◽  
Vagal Influence

It has been suggested that the increase in heart rate (HR) at the onset of exercise is caused by vagal withdrawal. In fact, endurance runners show a lower HR in maximum aerobic tests. However, it is still unknown whether endurance runners have a lower HR at 4 s after the onset of exercise (4th-sec-HR). We sought to measure the HR at the onset of the 4 s exercise test (4-sET), clarifying its relationship to heart rate variability (HRV), spectral indices, and cardiac vagal index (CVI) in endurance runners (ER) and healthy untrained controls (CON). HR at 4th-sec-HR, CVI, and percent HR increase during exercise were analyzed in the 4-sET. High frequency spectrum (HF-nu), low frequency spectrum (LF-nu), and low frequency/high frequency band ratio (LF/HF) were analyzed from the HRV. ER showed a significantly higher HF, and both a lower LF and LF/HF ratio compared with the CON. ER presented a significantly lower 4th-sec-HR, although neither CVI nor HR increases during exercise were statistically different from the CON. In conclusion, ER presented a lower 4th-sec-HR secondary to increased vagal influence over the sinus node. CVI seems to be too weak to use for discriminating individuals with respect to the magnitude of HR vagal control.

A generalized mean-field model of the natural and high-frequency actuated flow around a high-lift configuration

2009 ◽  
Vol 623 ◽  
pp. 283-316 ◽  
Author(s):  
DIRK M. LUCHTENBURG ◽  
BERT GÜNTHER ◽  
BERND R. NOACK ◽  
RUDIBERT KING ◽  
GILEAD TADMOR
Keyword(s):  
High Frequency ◽  
Field Model ◽  
Mean Field ◽  
Low Frequency ◽  
Navier Stokes ◽  
Mean Field Model ◽  
High Lift ◽  
The Mean ◽  
Generalized Mean ◽  
Low Dimensional

A low-dimensional Galerkin model is proposed for the flow around a high-lift configuration, describing natural vortex shedding, the high-frequency actuated flow with increased lift and transients between both states. The form of the dynamical system has been derived from a generalized mean-field consideration. Steady state and transient URANS (unsteady Reynolds-averaged Navier–Stokes) simulation data are employed to derive the expansion modes and to calibrate the system parameters. The model identifies the mean field as the mediator between the high-frequency actuation and the low-frequency natural shedding instability.

scholarly journals Evolution of low-frequency contribution in emission of steep-spectrum radio sources

2014 ◽  
Vol 11 (S308) ◽  
pp. 631-635
Author(s):  
Alla P. Miroshnichenko
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Radio Spectrum ◽  
Unified Model ◽  
Linear Size ◽  
Radio Sources ◽  
Mean Values ◽  
Spectrum Radio ◽  
Size Characteristic ◽  
The Mean

AbstractWe consider evolution properties of galaxies and quasars with steep radio spectrum at the decametre band from the UTR-2 catalogue. The ratios of source's monochromatic luminosities at the decametre and high-frequency bands display the dependence on the redshift, linear size, characteristic age of examined objects. At that, the mean values of corresponding ratios for considered galaxies and quasars have enough close quantities,testifying on the unified model of sources. We analyse obtained relations for two types of steep-spectrum sources (with linear steep spectrum (S) and low-frequency steepness after a break (C+)) from the UTR-2 catalogue.

scholarly journals Influence of Autonomic Control on the Specific Intermittent Performance of Judo Athletes

2018 ◽  
Vol 64 (1) ◽  
pp. 99-109
Author(s):  
Bruno T. Campos ◽  
Eduardo M. Penna ◽  
João G.S. Rodrigues ◽  
Mateus Diniz ◽  
Thiago T. Mendes ◽  
...  
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Training Experience ◽  
Specific Performance ◽  
Before And After ◽  
Post Test ◽  
Judo Athletes ◽  
The Mean ◽  
Hrv Analysis ◽  
Different Levels

Abstract Judo is a high-intensity intermittent combat sport which causes cardiac adaptations both morphologically and related to the autonomic nervous system (ANS). Therefore, this study aims to verify the correlation between heart rate variability (HRV) at rest with performance in the Special Judo Fitness Test (SJFT) and whether groups with different RR values at rest show different performance in the SJFT and during post-test recovery. Sixteen judo athletes with 7.2 ± 3.9 years of training experience participated in the study. Before and after the SJFT execution HRV and lactate measurements were conducted. For HRV analysis, we used the mean interval RR, the standard deviation of the RR interval (SDNN), the root mean square of successive differences in RR intervals (RMSSD), the low frequency (LF) and high frequency (HF) in normalized and absolute units. The sample was split into two groups (low RR and high RR) to verify if this variable could differentiate between specific performance. For the SDNN, a significant and moderate correlation (r = 0.53) was found with the total number of throws and throws in the series A (r = 0.56) and B (r = 0.54) and for the RMSSD a correlation with throws during series B (r = 0.59) in the SJFT. However, the groups did not differ in performance and recovery. Therefore, HRV is related to intermittent judo performance; however, it cannot differentiate between judokas at different levels of performance.

scholarly journals High-Frequency Conductive Hearing following Total Drum Replacement Tympanoplasty

2020 ◽  
Vol 162 (6) ◽  
pp. 914-921 ◽  
Author(s):  
Marc D. Polanik ◽  
Danielle R. Trakimas ◽  
Nicole L. Black ◽  
Jeffrey T. Cheng ◽  
Elliott D. Kozin ◽  
...  
Keyword(s):  
High Frequency ◽  
Care Center ◽  
Tertiary Care ◽  
Surgical Techniques ◽  
Case Series ◽  
Low Frequency ◽  
Temporalis Fascia ◽  
The Mean ◽  
Hearing Outcomes ◽  
Conductive Hearing

Objectives Conventional reporting of posttympanoplasty hearing outcomes use a pure-tone averaged air-bone gap (ABG) largely representing a low-frequency sound conduction. Few studies report high-frequency conductive hearing outcomes. Herein, we evaluate high-frequency ABG in patients following temporalis fascia total drum replacement. Study Design Case series with chart review. Setting Tertiary care center. Subjects and Methods All patients who underwent type 1 tympanoplasty using a lateral graft total drum replacement technique between August 2016 and February 2019 were identified. Patients with pre- and postoperative audiograms were included. Low-frequency ABG was calculated as the mean ABG at 250, 500, and 1000 Hz. High-frequency ABG was calculated at 4 KHz. Pre- and postoperative ABGs were compared. Results Twenty-three patients were included, and the mean age at surgery was 44 years (range, 9-68 years). Perforation etiology was from trauma (n = 14) or chronic otitis media (n = 9). Preoperative mean low-frequency ABG was 27.8 ± 12.6 dB and mean high-frequency ABG was 21.5 ± 15.1 dB ( P = .044). Postoperatively, the mean low-frequency ABG was significantly reduced by 15.5 ± 13.3 dB ( P < .001) while the mean high-frequency ABG insignificantly changed (reduced by 2.6 ± 16.2 dB, P = .450). Conclusion In a series of patients undergoing temporalis fascia total drum replacement, low-frequency ABG improved; however, high-frequency conductive hearing loss persists. Conventional methods of reporting ABG may not identify persistent high-frequency ABG. These results merit further study across a range of tympanoplasty graft materials and surgical techniques.

Potentiation of transmission at Ia-motoneuron connections induced by repeated short bursts of afferent activity

1985 ◽  
Vol 54 (6) ◽  
pp. 1541-1552 ◽  
Author(s):  
B. M. Davis ◽  
W. F. Collins ◽  
L. M. Mendell
Keyword(s):  
High Frequency ◽  
Afferent Fiber ◽  
Low Frequency ◽  
Mean Amplitude ◽  
Medial Gastrocnemius ◽  
Epsp Amplitude ◽  
Ia Afferent ◽  
Enhanced Transmission ◽  
Test Stimulation ◽  
The Mean

Single medial gastrocnemius Ia-afferent fibers and motoneurons to which they projected were simultaneously impaled in anesthetized cats. Each Ia-afferent fiber was electrically stimulated once every 2 s with short high-frequency bursts (32 shocks at 167 Hz) followed by 1-11 test shocks. The resulting motoneuron excitatory postsynaptic potentials (EPSPs) were recorded and averaged in register. The interval between the end of one burst and the beginning of the next was 2 s; therefore, the amplitude of the first EPSP in the burst was considered to be a measure of efficacy of transmission 2 s after the burst. At most connections (23/29) the mean amplitude of the first EPSP in the burst was equal to or larger than the mean amplitude of control EPSPs produced by low-frequency (18-Hz) stimulation. Enhancement of transmission was maximum 50-100 ms after the burst, and the amplitude of the test EPSP delivered at this time was always greater than that of the control. The period of enhanced transmission appeared to decay more rapidly at connections with small EPSPs. The greatest amount of EPSP amplitude enhancement at 50 or 100 ms after the burst was observed at connections at which EPSP amplitude increased during the burst. The shape (rise time, half width) of potentiated EPSPs was the same as control EPSPs averaged during low-frequency (18-Hz) stimulation. Multiple shocks delivered at low frequency between bursts revealed that enhanced transmission following the high-frequency burst is very sensitive to the effects of low-frequency test stimulation. Furthermore, increasing the number of shocks during the interval between bursts reduced the enhancement of the first EPSP in the burst. We suggest that modulation of synaptic transmission after high-frequency bursts differs across Ia-motoneuron connections. These time-dependent changes associated with short bursts of firing (which are similar in frequency to those observed in Ia-fibers supplying hind-limb muscles during stepping) emphasize the necessity to consider the history of the discharge pattern of the group Ia fiber in assessing efficacy at individual Ia-motoneuron connections.

Electronic Picture in the Normal States of High-Tc Superconductors: From the Optical Viewpoint

1989 ◽  
Vol 156 ◽  
Author(s):  
S. Tajima
Keyword(s):  
Liquid Metal ◽  
Frequency Spectrum ◽  
High Frequency ◽  
Fermi Liquid ◽  
Low Frequency ◽  
High Tc Superconductors ◽  
High Tc ◽  
Electronic Model ◽  
Normal States ◽  
Highly Correlated

ABSTRACTThe specific features of the optical spectra in the high-Tc Cu-oxides are discussed. The low-frequency spectral behavior can be explained by the highly correlated electronic model, whereas in the high-frequency spectrum the behavior of the Fermi liquid metal shows up.

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