By the second half of the twentieth century, a new branch of materials science had come into being - crystalline materials research. Its appearance is linked to the emergence of advanced technologies primarily based on single crystals (bulk crystals and films). At the turn of the last century, the impending onset of the "ceramic era" was forecasted. It was believed that ceramics would play a role comparable to that of the Stone or Bronze Ages in the history of civilization. Naturally, such an assumption was hypothetical, but it showed that ceramic materials had evoked keen interest among researchers. Although sapphire traditionally has been considered a gem, it has developed into a material typical of the "ceramic era." Widening the field of sapphire application necessitated essential improvement of its homogeneity and working characteristics and extension of the range of sapphire products, especially those with stipulated properties including a preset structural defect distribution. In the early 1980s, successful attainment of crystals with predetermined char- teristics was attributed to proper choice of the growth method. At present, in view of the fact that the requirements for crystalline products have become more str- gent, such an approach tends to be insufficient. It is clear that one must take into account the physical-chemical processes that take place during the formation of the real crystal structure, i.e., the growth mechanisms and the nature and causes of crystal imperfections.
When Curious George's new bath toys go down the drain, it's time to call the plumber. With some amazing tools (and George's help), the toys are found and the pipes are cleared. When a second drain disaster occurs, George tries fixing it on his own, "without "the same success. Ultimately, George learns that the best way to keep the plumbing system working is to prevent clogs in the first place . . . "and "to invest in extra large (and extra fun) bath toys. George's latest adventure includes fun facts about how water gets to your house along with a coloring and tool-labeling activity.