Crystal formation growth

Bisphosphonates (etidronate, pamidronate, til-udronate) are effective because of their inhibition of crystal formation, growth and dissolution, such as must occur in bone mineralisation and demineralisation. The response is dose-related and remission after a course may last up to two years. Calcition (which inhibits bone resorption) has been largely superseded by the bisphosphonates but is useful to reduce bone blood flow before operation. 

Jones R, Tredgold R H, Hoorfar A, Allen R A and Hodge P 1985 Crystal-formation and growth in Langmuir-Blodgett multilayers of azobenzene derivatives—optical and structural studies Thin Solid Films 134 57-66... 

Crystal Formation There are obviously two steps involved in the preparation of ciystal matter from a solution. The ciystals must first Form and then grow. The formation of a new sohd phase either on an inert particle in the solution or in the solution itself is called nucle-ation. The increase in size of this nucleus with a layer-by-layer addition of solute is called growth. Both nucleation and ciystal growth have supersaturation as a common driving force. Unless a solution is supersaturated, ciystals can neither form nor grow. Supersaturation refers to the quantity of solute present in solution compared with the quantity which would be present if the solution were kept for a veiy long period of time with solid phase in contac t with the solution. The latter value is the equilibrium solubility at the temperature and pressure under consideration. The supersaturation coefficient can be expressed... 

Most investigators have focused their attention on a differential segment of the zone between the feed injection and the crystal melter. Analysis of crystal formation and growth in the recoveiy section has received scant attention. Table 22-4 summarizes the scope of the literature treatment for center-fed columns for both solid-solution and eutectic forming systems. 

Brown, C.M., Ackemiann, D.K., Puricli, D.L. and Finlayson, B., 1991. Nucleation of calcium oxalate monoliydrate use of turbidity measurements and computer-assisted simulations in characterising early events in crystal formation. Journal of Crystal Growth, 108, 455 64. 

The promoter may slow down, or otherwise influence crystal formation and growth, or produce lattice defects. These effects may lead either to a higher activity per unit area or to a higher specific surface area. 

Although crystals can be grown from the liquid phase—either a solution or a melt—and also from the vapour phase, a degree of supersaturation, which depends on the characteristics of the system, is essential in all cases for crystal formation or growth to take place. Some solutes are readily deposited from a cooled solution whereas others crystallise only after removal of solvent. The addition of a substance to a system in order to alter equilibrium conditions is often used in precipitation processes where supersaturation is sometimes achieved by chemical reaction between two or more substances and one of the reaction products is precipitated. 

Figure 7.6. Part of a current-time record during a mononuclear layer-by-layer growth of a quasiperfect Ag( 100) crystal face with a circular form in the standard system Ag(100)/6 MAgN03 at T7 = -6 mV and T = 318 K. Surface area A = 3 X 10 cm . Current density i = 1 mA/cm. The current spikes indicate the formation, growth, and decay of new layers. (From Ref. 34, with permission from the Electrochemical Society.)...

Mechanism of Action Inhibits formation, growth, and dissolution of hydroxyapatite crystals and their amorphous precursors by chemisorption to calcium phosphate surfaces ... 

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