The Melting Regime

The lace breaks into Irregularly shaped Hnine form in the pieces With diameters approximately 

Sheet or ribbon of the dispersed phase forms in the matrix. 

The size and concentration of holes becomes sufficient tor a lace structure to be 

Drop and cylinder breakup form the final spherical particles. 

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O Hara, M. J. (1985). Importance of the shape of the melting regime during partial melting of the mantle. Nature, 314, 58-62. 

The shape of the melting regime and the generation of diverse melt compositions... 

Plank T. and Langmuir C. H. (1992) Effects of the melting regime on the composition of oceanic cmst. J. Geophys. Res. 

Another problem with the transport models is that they assume complete equilibrium between melt and solid throughout the melting regime. This implies that the solid residues at the top of the column (e.g., near the Moho), should be in chemical equilibrium with MORE. However, another key observation of MORBs is that they are out of equilibrium with abyssal peridotities near the Moho for both major and trace elements. A quick fix for the transport models is to assume that melts remain in chemical equilibrium up to some depth and then melt fractionally for the remaining distance (e.g., see Kelemen et al., 1997). However, different attempts to explain both U-series and stable elements in melts and residues in the single-porosity transport models has motivated much of the development of the two-porosity models in next section. 

Dynamic melting models produce all correlated excesses at the bottom of the melting regime and require melt transport rates sufficient to transport radium from the bottom of the melting regime on timescales short compared to the half-life of radium (1,600 yr). 

Beyond Semidilute Solutions. Further increase of concentration gives the concentrated regime and the melt regime. Beyond the semidilute regime, the minimal model mentioned above is not adequate, because the volume fraction is now finite and it really exerts entropic forces (53). If the static model is not in a good shape, it should be clear that we do not have a reliable minimal model for dynamics of nondilute solutions. We must take into account entanglement and direct friction as well as the hydrodynamic interactions. Thus, from the statistical thermodynamic point of view, real understanding of many polymer chain systems is still beyond our reach. 

However, the main domain of iq>pl>< ution of the RPA is not the semi-dilute regime (where inside each blob, an ideal chain pictuie is not acceptable) but rather the melt regime, where the total concentration is... 

Figure 5.17 [5] compares the torque as a function of time in a batch intensive mixer for non-reactive and reactive blends of polystyrene/ethylene-propylene rubber. These results are typical for a relatively slow interfacial reaction. As the room temperature pellets of the blend are added to the hot mixer, the mixing torque rises rapidly in the melting regime. The torque for both blends then begins to fall as the temperature increases and the polymers soften. In the case of the non-reactive blend, the torque continues to fall and levels out to a reasonably constant value. However, in the case of the reactive blend there is a second peak in the torque due to the chemical reaction. The interfacial chemical reaction builds molecular weight, and in some cases may result in local crosslinking. This increases the viscosity of the blend relative to a non-reactive blend. 

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