Laser measurements of coral growth

Article Abstract:

An underwater laser apparatus was used to measure skeletal extension in the staghorn coral Acropora grandis Brook. Branches of coral were placed inside short plastic tubings and remained undisturbed for at least four weeks prior to measurement. Linear extension of the branch tip was determined from changes in the distances between lines in the diffraction pattern formed by a laser beam on a reference screen behind the coral. Distances were then converted to growth distances from a linear calibration.

Measurement, Growth, Growth (Physiology), Corals

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Hexagonal patterns in laser light

Article Abstract:

PbMg1/3Nb2/3O3 (PMN) crystal scatters low intensity laser light and forms hexagonal intensity patterns in a reproducible manner. This phenomenon cannot be explained by crystallographic-diffraction, as the patterns do not rotate when the crystal is rotated. The pattern formation is a photorefractive effect, caused by a change in refractive index due to the electric field of the light, and thermal defocusing provides the transverse nonlinearity for the pattern formation.

Observations, Laser beams, Photorefractive materials, Light scattering

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Problems with a giant laser project

Article Abstract:

The difficulties being experienced in the construction of the National Ignition Facility in the US are discussed. The project is expected to cost $4-billion rather than the $400-million proposed in 1990.

Design and construction, Science and technology policy, Buildings and facilities, United States. Department of Energy, Laser fusion, United States. National Ignition Facility

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