A relationship between macroradical decay kinetics and α-segmental dynamics in glassy amorphous polymers

For a series of five amorphous polymers with a broad range of T_g values the kinetics of macroradical decay was measured by ESR technique and evaluated by the second-order kinetic model. It was found that the temperature T_tr of the transition between two regions of different reactivity in free radical decay reaction agrees quite well with the temperature parameter T₀ of the Vogel-Fulcher-Tamman-Hesse (VFTH) equation for α-segmental dynamics. This parameter represents the onset of α-segmental mobility in glassy state below T_g. A nontraditional way of the estimation of T₀ values for α-segmental dynamics through study of the macroradical decay in glassy state of amorphous polymers has been suggested. © 1996 John Wiley & Sons, Inc.     

Imaging and correlation used for guided laser lithotripsy

High-speed imaging of phenomena akin to laser lithotripsy is performed. A new method for guiding laser light for the stone destruction is proposed. This is based on a combination of signals obtained from the correlation of fluorescent and ballistic images.     

Brown colour of ruby

The defects characteristic of brown pure ruby crystals coloured by specific growth conditions, annealing and irradiation are described. The comparsion of UV- and X-rayed crystals is given. Brown or yellow colour is attributed to the O⁻ centre which is formed by the electron transfer from O²⁻.     

Temperature distribution in growing semi-transparent crystals (II). Comparison of theory with experiments

Calculated temperature difference between the liquid/solid interface and bulk of the melt was compared with the wide-angle scattering (celluae density) of Al₂O₃ and YAG crystals. Celluae free coloured crystals were grown using higher energy losses from the upper part of the crystal and the melt. Colourless crystals were successfully grown under opposite conditions. The results are in accordance with the calculated temperature differences which are proportional to the actual temperature gradient at the interface.