Quantum Theory of Massless Particles in Stationary Axially Symmetric Spacetimes.

Quantum equations for massless particles of any spin are considered in stationary uncharged axially symmetric spacetimes. It is demonstrated that up to a normalization function, the angular wave function does not depend on the metric and practically is the same as in the Minkowskian case. The radial wave functions satisfy second order nonhomogeneous differential equations with three nonhomogeneous terms, which depend in a unique way on time and space curvatures. In agreement with the principle of equivalence, these terms vanish locally, and the radial equations reduce to the same homogeneous equations as in Minkowski spacetime.

Diamond shaped optical fiber delivery system.

BACKGROUND: Optical fibers are generally used with a flat cut end. The adaptation of a coaxial exit of a refrigerated gas near the distal tip of the optical fiber cools the tissue where the laser beam is applied and reduces the injury of thermal effects on biological tissue. MATERIALS AND METHODS: We have changed the flat end geometry of the fiber's end to a pyramidal end shape (named: Diamond tip). In this project we have evaluated the new shape of the fiber's end using laboratory tests and in real conditions. We have examined the emission pattern in the air and in water as well as its performance in surgery. RESULTS: With the new shape better results were obtained: higher power density, more utilizations of the same fiber (after sterilization) resulting in economical savings. The diamond tip is characterized by greater mechanical resistance then conical tip delivery systems. The greater resistance of the Diamond tip prevents optical fiber breakage during surgery. The delivered system can be reshaped by a trained hospital physician and reused. Our experience shows that delivery systems intended by the producer to one use only can be converted, by reshaping their tips, to highly performing delivery systems, which can be reused many times. In addition less power was needed, with less tissue penetration. The thermal effect was minimized and higher mechanical resistance was achieved, which allowed reusing the fiber more than six times. The special structure of the faces of the optical fiber diamond tip eased its sliding. CONCLUSION: The Diamond tip is superior to other fiber end tips by having minimal thermal effects, higher mechanical resistance and by being reused many times.