Stimulated Brillouin scatter in a magnetized ionospheric plasma.

High power electromagnetic waves transmitted from the HAARP facility in Alaska can excite low-frequency electrostatic waves by magnetized stimulated Brillouin scatter. Either an ion-acoustic wave with a frequency less than the ion cyclotron frequency (f(CI)) or an electrostatic ion cyclotron (EIC) wave just above f(CI) can be produced. The coupled equations describing the magnetized stimulated Brillouin scatter instability show that the production of both ion-acoustic and EIC waves is strongly influenced by the wave propagation relative to the background magnetic field. Experimental observations of stimulated electromagnetic emissions using the HAARP transmitter have confirmed that only ion-acoustic waves are excited for propagation along the magnetic zenith and that EIC waves can only be detected with oblique propagation angles. The ion composition can be obtained from the measured EIC frequency.

The effect of strength training and reduced training on rotator cuff musculature.

OBJECTIVE: Elucidate the training frequency required to maintain strength gains acquired via short-term resistance training on the rotator cuff. DESIGN: Twenty-one participants performed 12 wk resistance training followed by 12 wk reduced training. Following the training phase (three rotator-cuff-specific exercises; three sessions/wk), participants were randomly assigned to one of three reduced training groups (2, 1 or 0 session(s)/wk). METHODS: Isokinetic testing was done at 0, 6, 12, 18 and 24 wk to obtain mean and peak torque (N m). Testing involved concentric and eccentric actions of internal and external rotation for both shoulders at 60 and 120 degrees /s. RESULTS: Training produced increases in mean and peak torque for all tests but the four of concentric external rotation. A control group performed no training, showing no changes in strength at 0, 6 and 12 wk. Reduced training (2 or 1 session(s)/wk) produced no decreases in peak or mean torque. Detraining (0 session/wk) produced mean torque decreases in four tests, with eccentric strength showing greater losses. CONCLUSIONS: A training frequency of 1 session/wk maintains rotator cuff strength gains in previously untrained subjects. Further, eccentric strength may be more susceptible to detraining. RelevanceThese findings have direct relevance to functional rehabilitation practices for the rotator cuff. They may aid in resistance training programming for athletes during the off-season or returning from injury, particularly those in overhand sports.