الفهرس 
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Abstract
Calcified tissues representing three different matrices, namely enamel of human teeth, shells and eggshell, have been studied via Laser Induced Plasma Spectroscopy (LIPS) technique. The experimental CaII/CaI and MgII/MgI ratios have been measured, in view of the expected correlation between the extent of ionization caused by the laser induced shock wave (SW) and the hardness of the target. The ratio CaII/CaI between the ionic calcium line at 373.68 nm and the neutral line at 428.93 nm is obtained for enamel, shells and eggshell spectra, as well as the ratio MgII/MgI between the ionic magnesium line at 280.26 nm and the neutral line at 285.22 nm. The results show that such spectral lines intensities ratio differs for different matrices and is indeed related to the target material hardness. It is also found that the MgII/MgI ratio is preferable as anndicator of hardness since these lines are less affected by self absorption The SW front speed has been measured in the three cases and the obtained values confirm the proportionality to the target hardness. Theresults here obtained suggest the feasibility of the quantitative estimation of hardness for any other calcified tissues using this method The effects of LIPS experimental conditions on the measurement of the surface hardness of calcified tissues have been studied. Laser induced plasma spectra were obtained under two different experimental conditions. In the first nano and picoseconds lasers were used in a single pulse arrangement, while in the second single and double pulse regimes with nanosecond laser excitation were utilized. The results show that the onic to atomic intensity ratios are higher in case of ultrashort laser pulses for both Ca and Mg spectral lines. This effect has been justified in view of the repulsive force of laser induced shock waves which depends clearly on the target surface hardness and on the laser irradiance. The lectron densities ratio (pico/nano) is shown to be strongly depending on he laser irradiance too. In case of calcium, single pulse ratios are higher than the double pulse while there is no appreciable difference between both in case of magnesium. The results here obtained suggest that double pulse nanosecond arrangement and the choice of minor element are the best experimental conditions for estimating the surface hardness via LIPS spectra. To validate this method it has been applied on two previously measured groups of teeth enamel, the first is of ancient Egyptians and the second is of Nubians and Ugandans. The results support the usefulness of his method for similar real life applications. The method has been also applied in poultry science to assess the age of broiler breeders by measuring the hardness of their eggshell. Satisfactory results have been obtained for two different broiler breeder strains. However, it was not possible to differentiate between the two strains according to the relevant eggshell surface hardness.