Rapidity Of Release Research Articles

Resonant laser ionization of radioactive atoms

Intense radioactive ion beams are produced by the isotope separation on-line method. The resonance ionization laser ion source (RILIS) can provide the chemical selectivity to separate beams with reduced isobaric contamination. The hot cavity RILIS at ISOLDE (CERN) uses copper vapor laser pumped dye lasers for the resonant transitions. Up to now 22 elements have been ionized with efficiencies of the order of 10%. Additional elements have been ionized with similar RILIS set-ups at the Institute of Spectroscopy (Troitsk), IRIS (Gatchina), Mainz University and TIARA (Takasaki). Ideas are discussed for future developments of this type of RILIS, which could further improve the efficiency, selectivity, rapidity of release and stability of the operation. The RILIS can also be applied for atomic spectroscopy studies of exotic radioactive isotopes, which are produced at rates of few atoms per second only. An interesting parallel is shown to the atomic vapor laser isotope separation (AVLIS), a large-scale application of resonance ionization, which could be used for the isotope enrichment of macroscopic amounts: tens of kg per h.

Release of sodium fluoride from poly (L-lactic acid) implants characterized by thermal history.

The method of injection molding of the melt of poly(L-lactic (PLLA), Mw 11 730, containing 7.5% of particles of sodium fluoride smaller than 1 microm was employed to prepare cylinders of a diameter of 2 and 10 mm in length. These matrices with an insoluble active ingredient with an amorphous structure of the carrier obtained by rapid cooling of the melt were annealed at temperatures from 70 to 140 degrees C in the medium of a hot-air drying plant and liquid paraffin. It has been found that crystallization of PLLA manifested by the rapidity of release of sodium fluoride does not take place at a temperature of 70 degrees C; at a temperature of 75 degrees C the effect of annealing of polyester matrices on the decrease in the rapidity of sodium fluoride release was already perceptible. Also in annealing of matrices at temperatures of 120 and 140 degrees C an identical deceleration of sodium fluoride release as that at 75 degrees C took place; the rapidity of the development of an effective crystalline phase was higher at higher temperatures. The method of interval cooling with the first stage of slow cooling and the second stage of rapid cooling of the melt of PLLA with 15% sodium fluoride fixed the structure achieved till the moment of the change in the rapidity of cooling. This revealed the temperature range of the development of the effective crystalline phase from the viewpoint of sodium fluoride release lying between 92 and 122 degrees C.