114,355 research outputs found
Effects of External Loads on Human Head Movement Control Systems
The central and reflexive control strategies underlying movements were elucidated by studying the effects of external loads on human head movement control systems. Some experimental results are presented on dynamic changes weigh the addition of aviation helmet (SPH4) and lead weights (6 kg). Intended time-optimal movements, their dynamics and electromyographic activity of neck muscles in normal movements, and also in movements made with external weights applied to the head were measured. It was observed that, when the external loads were added, the subject went through complex adapting processes and the head movement trajectory and its derivatives reached steady conditions only after transient adapting period. The steady adapted state was reached after 15 to 20 seconds (i.e., 5 to 6 movements)
Decay constants and radiative decays of heavy mesons in light-front quark model
We investigate the magnetic dipole decays of various
heavy-flavored mesons such as and
using the light-front quark model
constrained by the variational principle for the QCD-motivated effective
Hamiltonian. The momentum dependent form factors for decays are obtained in the frame and then analytically
continued to the timelike region by changing to in the form factors. The coupling constant for real
photon case is then obtained in the limit as , i.e.
. The weak decay constants of heavy pseudoscalar
and vector mesons are also calculated. Our numerical results for the decay
constants and radiative decay widths for the heavy-flavored mesons are overall
in good agreement with the available experimental data as well as other
theoretical model calculations.Comment: 9 pages, 3figures, added few more references, typos correcte
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