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AimsCalcific aortic valve stenosis (CAVS) is characterized by a fibrocalcific process. Studies have shown an association between CAVS and the activation of platelets. It is believed that shear stress associated with CAVS promotes the activation of platelets. However, whether platelets actively participate to the mineralization of the aortic valve (AV) and the progression of CAVS is presently unknown. To identify the role of platelets into the pathobiology of CAVS.

The interaction between metaphosphate chains and the metal ions Ca2+ and Eu3+ has been studied in water by Eu3+ luminescence, infrared absorption, and 31P NMR spectroscopy. Two main families of sites could be identified for the metal ions in the aqueous polyphosphate colloidal systems: (1) cagelike sites provided by the polyphosphate chain and (2) a family which arises following saturation of cagelike sites. Occupation of this second family leads to supramolecular interactions between polyphosphate chains and the consequent destabilization of the colloidal system. In the polyphosphate-Ca2+ system, this destabilization appears as a coacervation process. Equilibrium existing between colloidal species as a function of the compositions could be reasoned based on the spectroscopic measurements. The determination of coordination numbers and the correlation of the results with the observation of coacervates show that Eu3+ luminescence properties can be used to probe in a unique way the coacervation process.

The mechanism of the Yb 3ϩ →Er 3ϩ energy transfer as a function of the donor and the acceptor concentration was investigated in Yb 3ϩ -Er 3ϩ codoped fluorozirconate glass. The luminescence decay curves were measured and analyzed by monitoring the Er 3ϩ ( 4 I 11/2 ) fluorescence induced by the Yb 3ϩ ( 2 F 5/2 ) excitation. The energy transfer microparameters were determined and used to estimate the Yb-Er transfer rate of an energy transfer process assisted by excitation migration among donors state ͑diffusion model͒. The experimental transfer rates were determined from the best fitting of the acceptor luminescence decay obtained using a theoretical approach analog to that one used in the Inokuti-Hirayama model for the donor luminescence decay. The obtained values of transfer parameter gamma ͓␥͑exp͔͒ were always higher than that predicted by the Inokuti-Hirayama model. Also, the experimental transfer rate, ␥ 2 (exp), was observed to be higher than the transfer rate predicted by the migration model. Assuming a random distribution among excited donors at the initial time (tϭ0) and that a fast excitation migration, which occurs in a very short time (t Ӷ␥ Ϫ2 ), reducing the mean distance between donor ͑excited͒ and acceptor, all the observed results could be explained.