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Optical Doppler shift demonstration experiments are not a simple task since the light source cannot usually be moved in a sufficiently smooth and uniform manner to keep the level of noise well below of that of the signal. For that reason most demonstration experiments are usually performed with sound or with microwaves.Previous works have been reported using a moving mirror in order to produce a moving light source, but small perturbation of its trajectory, as small as the optical wavelength, can produce a large noise.Using a rotating mirror, in which one beam is reflected from the advancing side and the other beam is reflected from the receding part of a rotating mirror, can overcome many of the noise generating effects.In the present work we report the construction and operation of a demonstration apparatus for measuring optical Doppler shift based on a rotating mirror.

The possibility of producing radiative collapses in pinches is studied using a 1/2D numerical model with pure bremsstrahlung as the source of radiation, including anomalous resistivities and axial mass losses. The results of the model show the existence of both a lower and an upper limit value of the pinch current to produce collapses. It is also shown that a minimum initial pinch radius (which depends on the initial particle density) is required in order to obtain radiative collapses. The inclusion of axial mass losses makes the production of the collapse more difficult, because it enhances the anomalous resistivity heating.

The photostability and photophysical properties of the dimethyl ester of the mycosporine-like amino acid shinorine have been experimentally evaluated in aqueous solution and in the presence of direct micelles prepared with a cationic or an anionic detergent, respectively. In comparison with shinorine, the ester molecule increases the photostability, the fluorescence quantum yield and the fluorescence lifetime in water as well as in the micellar solutions. The effects are more pronounced in sodium dodecyl sulfate solutions and suggest that the electrostatic attractions with the micellar interface contribute to limit the movement of the molecules and influence the relative rate of their deactivation channels. However, the predominance of the nonradiative decay is maintained together with the UV photoprotective ability of this atypical mycosporine species.

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