scholarly journals Multi-fluid Approach to High-frequency Waves in Plasmas. II. Small-amplitude Regime in Partially Ionized Media

2017 ◽  
Vol 837 (1) ◽  
pp. 80 ◽  
Author(s):  
David Martínez-Gómez ◽  
Roberto Soler ◽  
Jaume Terradas
Keyword(s):  
High Frequency ◽  
Small Amplitude ◽  
Partially Ionized ◽  
High Frequency Waves

Rapid-distortion turbulence models in the theory of surface-wave generation

1996 ◽  
Vol 329 ◽  
pp. 147-153 ◽  
Author(s):  
Cornelis A. Van Duin
Keyword(s):  
High Frequency ◽  
Small Amplitude ◽  
Turbulence Models ◽  
Mixing Length ◽  
Surface Gravity Wave ◽  
Physical Similarity ◽  
Specific Choice ◽  
Turbulent Air Flow ◽  
High Frequency Waves ◽  
Significant Underestimation

Turbulent air flow over a surface gravity wave of small amplitude is studied analytically on the basis of a family of rapid-distortion turbulence models. Results for the wave growth rate do not depend sensitively on the specific choice of these models. However, the agreement with results based on a so-called truncated mixing-length model (Belcher & Hunt 1993) is poor, despite physical similarity of the models. The present analysis also shows that the use of turbulence models based on rapid-distortion theory leads to significant underestimation of observed growth rates of high-frequency waves.

Amplification of Small-Amplitude High-Frequency Waves in a Reactive Mixture

SIAM Review ◽  
1989 ◽  
Vol 31 (3) ◽  
pp. 401-427 ◽  
Author(s):  
Y. S. Choi ◽  
Andrew Majda
Keyword(s):  
High Frequency ◽  
Small Amplitude ◽  
Reactive Mixture ◽  
High Frequency Waves

scholarly journals PROBING THE GRAVITATIONAL GEON

1996 ◽  
Vol 05 (04) ◽  
pp. 375-406 ◽  
Author(s):  
F.I. COOPERSTOCK ◽  
V. FARAONI ◽  
G.P. PERRY
Keyword(s):  
Spherical Shell ◽  
High Frequency ◽  
Small Amplitude ◽  
Gravitational Energy ◽  
Necessary Condition ◽  
Regularity Conditions ◽  
Field Equations ◽  
Nonsingular Solution ◽  
Tensor Spherical Harmonics ◽  
High Frequency Waves

The Brill-Hartle gravitational geon construct as a spherical shell of small amplitude, high frequency gravitational waves is reviewed and critically analyzed. The Regge-Wheeler formalism is used to represent the most general gravitational wave perturbations of the spherical background as a superposition of tensor spherical harmonics and an attempt is made to build a nonsingular solution to meet the requirements of a gravitational geon. The attempted constructs of gravitational and electromagnetic geons are contrasted. High-frequency waves are seen to be a necessary condition for the geon and the field equations are decomposed accordingly. It is shown that this leads to the impossibility of forming a spherical gravitational geon. The attempted constructs of gravitational and electromagnetic geons are constructed. The spherical shell in the proposed BrillHartle geon does not meet the regularity conditions required for a nonsingular source and hence cannot be regarded as an adequate geon construct. Since it is the high frequency attribute which is the essential cause of the geon nonviability, it is argued that a geon with less symmetry is an unlikely prospect. The broader implications of the result are discussed with particular reference to the problem of gravitational energy.

First VIKING results: high frequency waves

1988 ◽  
Vol 37 (3) ◽  
pp. 469-474 ◽  
Author(s):  
A Bahnsen ◽  
M Jespersen ◽  
E Ungstrup ◽  
R Pottelette ◽  
M Malingre ◽  
...  
Keyword(s):  
High Frequency ◽  
High Frequency Waves

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.

The effects of pH on force and stiffness development in mouse muscles

1987 ◽  
Vol 65 (8) ◽  
pp. 1798-1801 ◽  
Author(s):  
J. M. Renaud ◽  
R. B. Stein ◽  
T. Gordon
Keyword(s):  
High Frequency ◽  
Small Amplitude ◽  
Force Production ◽  
Muscle Length ◽  
Low Ph ◽  
Muscle Stiffness ◽  
Average Force ◽  
Cross Bridge ◽  
Effects Of Ph ◽  
Cross Bridges

Changes in force and stiffness during contractions of mouse extensor digitorum longus and soleus muscles were measured over a range of extracellular pH from 6.4 to 7.4. Muscle stiffness was measured using small amplitude (<0.1% of muscle length), high frequency (1.5 kHz) oscillations in length. Twitch force was not significantly affected by changes in pH, but the peak force during repetitive stimulation (2, 3, and 20 pulses) was decreased significantly as the pH was reduced. Changes in muscle stiffness with pH were in the same direction, but smaller in extent. If the number of attached cross-bridges in the muscle can be determined from the measurement of small amplitude, high frequency muscle stiffness, then these findings suggest that (a) the number of cross-bridges between thick and thin filaments declines in low pH and (b) the average force per cross-bridge also declines in low pH. The decline in force per cross-bridge could arise from a reduction in the ability of cross-bridges to generate force during their state of active force production and (or) in an increased percentage of bonds in a low force, "rigor" state.

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