Particle sizing in fluoride glasses and fibers by scattering measurements.

Angular scattering measurements on fluoride glass fibers or bulk samples are reported. Patterns obtained on crystallites or bubbles give several peaks which are dependent on particle size and refractive index. Peak positions and scattering levels on the experimental curves are interpreted using Mie scattering theory. Particle sizing is possible and the refractive index can be estimated.

In situ monitoring of myocardial metabolism by laser fluorimetry: relevance of a test of local ischemia.

We have developed a hypoxia test by local ischemia, to be performed with a special probe adapted to an in situ NADH laser fluorimeter. Local ischemia is produced by pressurization on the organ surface in an area of approximately 0.2 mm2. In order to assess the method on open-chest rat hearts (ten), we used the following protocol: local ischemia tests (three), global anoxia (100% N2 ventilation), superimposition of local ischemia to global anoxia, and local ischemia tests during the period just prior to death and immediately thereafter. Three different responses were observed: large amplitude of compensated fluorescence (Fo) increase, medium amplitude of Fo increase, and no Fo increase. These responses were related to the metabolic state prior to the test (States 3, 4, and 5 of Chance's nomenclature). We have thus demonstrated the possibility of very rapidly determining the in situ NADH degree of reduction, without a destructive assay. Such a parameter may be of great relevance in heart surgery, as it might allow detection of potentially harmful situations, thereby enabling early and appropriate treatment.

In situ double-beam NADH laser fluorimetry: choice of a reference wavelength.

A double-beam laser fluorimeter, using a single optical fiber to guide the lights, was constructed for in situ and on-line monitoring of NADH concentration [( NADH]) from normally blood-perfused living tissues. The device was tested on an isolated blood-perfused rat heart system to determine the most efficient reference wavelength for the compensation of the hemodynamic artifact induced by blood circulation in the tissues on the fluorescence measure; 586 nm was found to be an accurate reference wavelength, and a mathematical relationship was established that allowed the digital treatment of the measured fluorescence to give a signal (compensated fluorescence) that varied only with [NADH] in the volume of tissue investigated.

Cancelling of Fresnel reflections in in situ, double beam laser, fluorimetry using a single optical fibre.

This paper describes several techniques used to cancel Fresnel reflection on the extremities of the optical fibre in in situ double beam laser fluorimetry when the single optical fibre is adopted. The reasons for the technical choices are exposed and the results on several media are presented (water, air, finger pad, rat heart).

Particle size analyzer.

A particle size analyzer using a gas laser as a source of coherent light crossing a sample is described. The particle size distribution is calculated from intensity variations within the diffraction pattern at infinity.

Using gas lasers in road works.

Descriptions of two devices using unique properties of gas lasers are given: an automatic elevation guidance system and an apparatus for measuring plane defects, both applied to road making or road control.