Grown crystal

Quartz. When colorless, quart2 [14808-60-7] is also known as rock crystal. When irradiated, it becomes smoky from a color center associated with a ubiquitous Al impurity at about the 0.01% level. The name citrine [14832-92-9] is used when quart2 is colored by Fe, and irradiation of this can produce the purple-colored amethyst [14832-91-8] under certain circumstances (2). Although not signiftcandy lower priced than the natural materials, synthetic citrine and amethyst ate used in jewelry because of the abiUty to provide matched sets of stones from large, up to 7-kg, hydrothermaHy grown crystals. 

XII. Antimony Of various new papers on the crystal growth of SbSI, the one by Ishikawa et al. (425) is worth mentioning, since it describes a new device especially designed to avoid formation of hollows in vapor-grown crystals. 

The ribosome is a unique cellular machine in that its main functional component is RNA whereas proteins seem to play only a structural role. For a long time, it has been debated whether RNA or proteins contribute most to the ribosome s function. With the determination of high-resolution crystal structures, this question could finally be answered. Clearly, these structures have revolutionized the field of ribosome studies. Already in the 1980s, Yonath and coworkers had grown crystals of active ribosomes that diffracted to about 0.6 nm (6 A) (1 A = 0.1nm) resolution. However, owing to the large size of the ribosome of about 2 500 000 Da (lDa=lgmoP), the ribosome structure was not solved to atomic resolution until tbe year 2000. 

The use of constraints and restraints arise from unrealistic bond lengths and angles. It is a reasonable use of statistical analysis to include prior information in a refinement procedure, and geometry is one such restraint/constraint. Poor geometries are often a consequence of missing data down one axis, invariably the result of the missing cone or lack of an epitaxially grown crystal. This lack of data has a profound effect on the refinement process... 

Preparation of solution-grown crystals (including so-called single crystals ) of linear polymers [2-4,8,10-13]... 

A major weakness in the calculations described above is that they can only be used to represent vapor grown crystals. In crystals grown from solution, the solvent can greatly influence the crystal habit as can small amounts of impurities. Several investigators (68. 69 accounted for discrepancies between observed crystal habit and those obtained using attachment energies by assuming preferential solvent (or impurity) adsorption on crystal faces. 

In this study, D-SCMC seed crystals were put in a racemic SCMC supersaturated solution in a batchwise agitated vessel and growth rates in longitudinal and lateral directions and the optical purity of D-SCMC crystals were measured. The growth rates and optical purity were discussed considering surface states of grown crystal observed by a microscope. The kinetics of crystal growth were measured and a model of inclusion of impurity was proposed. 

Figure 8. Optical purity of grown parts of the crystal on whidi some fines stuck before and after dipping test Q, before dipping tests and Q, after dipping test a, photographic picture of surface of grown crystal before and after 2 h of dipping test and b, data.

Chayen, N. E. and HeUiwell, J. R. (1999). Space-grown crystals may prove their worth. Nature, 398, 20. 

That is, the concentration of trace element i in the crystal is the same as that in the initial melt because an incompatible trace element would build up and a compatible trace element would be depleted at the interface until the concentration in the newly grown crystal is the same as that in the initial melt. 

Watson E.B. and Eiang Y. (1995) A simple model for sector zoning in slowly grown crystals implications for growth rate and lattice diffusion, with emphasis on accessory minerals in crustal rocks. Am. Mineral. 80, 1179-1187. 

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