Crystallization front

What next The situation is replete with possibilities. If the growing electrodeposit is inadequately supplied with metal ions, the nature of the further growth depends on how easily different parts of the electrode secure the supply of ions used to build up the crystal surface. One is talking of the logistic differences between different parts of the advancing crystal front. 

By a similar usage in petrology, a euleeltc is a discrete mixture of two or more minerals, in definite proportions, which have simultaneously crystallized front the mutual solution of their constituents The eutectic point is the lowest temperature at any given pressure at which the above physical-chemical process may lake pluce, The eutectic ratio is the ratio hy weight of two minerals dial originate bv the above process. 

To presume that thermal insulation is always necessary is false. For example, when cryogenic fluids arc transported from a supply suurce to a vessel, even in bright sunshine, it is usually most economical not to insulate the line at all. The reason for this Is twofold (I) lor the short time of transport the area of the pipe exposed to the surt is much smaller than the area that would be exposed if it were insulated and (2i the heat that would be in the insulation when the transport starts would have to be removed by the cryogenic fluid. The combination of these two factors often makes the use of insulation undesirable for this type of cold fluid transport system. Moreover, the rapid formation of ice crystals front moisture in the air constitutes a thermal insulation. 

The nature of the lower vesicular zone is not particularly dependent on flow thickness beyond size compression due to lava overburden. As bubbles rise to escape the rising lower crystallization front, the size of the largest bubble caught depends on the velocity of the front, and once the velocity (slowing with the square-root of time like a cooling half space) is reduced below the Stokes velocity of the smallest bubbles in the distribution, all can escape and the lower boundary of the massive zone (Sahagian et al. 1989) is defined at that point. This is true of any flow thickness, so that the only factor that controls the nature of the lower vesicular zone (relative to that of the upper vesicular zone, which is much more complex) is the overlying pressure of the lava. A thicker flow would result in proportionally smaller size mode, which is the basis of the entire analysis for paleoelevation. 

As the front descends and slows further, bubbles that started lower in the flow have time to reach the front. These bubbles may have escaped the lower crystallization front and had time on their way upward to interact and coalesce the larger bubbles catching and joining with smaller ones with lower terminal Stokes velocities. These coalesced bubbles reach the upper crystallization front and lead to the formation of a highly vesicular zone that includes the largest bubbles in the flow. Below that zone, only the smaller... 

Tc 600°C), at which crystallization occurs. The released latent heat raises the local temperature further, and thermal conduction maintains self-sustaining explosive transformation until the crystallization front has propagated down the thermal gradient to a point below Tc. Pulsed electron beam heating experiments indicate that a-Si melts at 1170°K (Baeri et al., 1980). 

The thermomicroscopic differentiation between two phases that are known to be related either by polymorphism or dynamic isomerism is elegantly straightforward. The two phases should be melted side by side between a microscope slide and a cover slip, and then allowed to crystallize. Two possibilities exist for the subsequent crystallization events. In the case of polymorphism, the crystal fronts from the two melts will grow at a constant velocity until they come into contact, at which point one phase will grow through the other, due to a solid-solid transformation to the stable phase at that temperature. In the case of dynamic isomerism, the two crystal fronts would slow down as they approach each other, and in the so-called zone of mixing (McCrone 1965) a eutectic could appear. 

Figure 5 Ice nucleation on smooth a-AhOs (0001) at -27 C. A. water droplets and ice crystal front. B-C. Ice nucleation of adjacent water droplets by propagation of ice pods along surface. D. Aftermath of nucleation showing ice crystals on surface.

When crystallized front hot t Hj solution. selenium forms dark red tmimhicent crystal. i-omorph <[Pg.316]

Additive and impurity rejection at the growing crystal front leads to uneven distribution in a crystalline polymer. This redistribution process has been studied by UV and fluorescence microscopy and by an electron microscope with energy dispersive x-ray analysis. In polymer samples which are quenched after rapid crystallization, the additive distribution is kinetically determined and may be modeled in a computer as a three-dimensional zone-refining process. In annealed polymer samples, low molecular weight additives are uniformly concentrated in the amorphous phase. The additive distribution reflects that of crystalline material within the polymer. Antioxidant and uv stabilzer redistribution probably does not have a major effect on polymer stability, but the redistribution of partially oxidized, impure polymer may be important... 

Hydrochloride, CjpH CljNjOj, PJ IBS, R 18553, Arret, Biox, Brel, Dissenten, For in sec, Imodium, lmosec, Lopemid, Lopemin, Loperyt, Suprasec, Tebloc. Crystals front isopropanol, mp 222 -223. Practically insol in water at physiological pH (0.002%). Stable, can be stored for several years under normal conditions not hygroscopic not affected by light. LDW in mice (mg/kg) 75 s.c. 28 i.p. 105 orally in rats (mg/kg) 185 orally (Niemegeers). therap cat Ant idiarrheal. 

Methochloride, CggHyCINO, I-(3-eyctohexyt-3-hydroxy-3-phenylpropyl)-l-methylpyrrolidinlum chloride, tricyclamol chloride, Etorine chloride, Lergine chloride, Tricotoid chto. ride. Crystals front nitroethane, mp 159-164°. Moderately sol in water, alcohol. Practically insol in ether. 

Aggregates of dark red crystals front carbon disulfide + petr ether, mp 171 (preliminary sintering). Absorption max (chloroform) 521, 486, 453 nm. 

In blends of a crystaUizable polymer with an amorphous one, the morphology is largely determined by the type of segregation of the amorphous component. Crystallization in a miscible blend involves two types of polymer transport diffusion of the crystaUizable component towards the crystallization front and simultaneous rejection of the amorphous component. This latter phenomenon is called segregation it can take place at three different levels interspherulitic, interfibrillar and interlamellar (Figure 3.3). 

E is the kinetic energy supply required to move the dispersed droplet along with the motion of the crystallizing front = 2/3 Q2 Hr2 Pp... 

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