Crushing statements

Considering the set PO points presented in Table 4.5, the following statement can be made there exists no mixture composition with a higher robustness coefficient and, simultaneously, a higher crushing strength than a PO mixture composition. 

Like dissolves like a substance is most soluble in that solvent to which it is most closely related in structure. This statement serves as a useful classification scheme for all organic molecules. The solubility measurements are done at room temperature with 1 drop of a liquid, or 5 mg of a solid (finely crushed), and 0.2 mL of solvent. The mixture should be rubbed with a rounded stirring rod and shaken vigorously. Lower members of a homologous series are easily classified higher members become more like the hydrocarbons from which they are derived. 

Inspite of the last statement, continuous operation of spouted beds normally does require the separation of product from over- and undersized agglomerates both off-scale material streams, the oversized after crushing to below maximum product size, are recirculated (Fig. 7.89b). 

To this day, we still hear people claim that in vitro testing of materials alone shows that they are suitable for use in chronically implanted devices. Others continue to say that I proved the materials are biocompatible and biostable, so I don t have to do any device testing. This statement can be very far from the truth. In vitro testing has its place, primarily to screen materials and processes for further testing. In some cases where no suitable in vitro test exists, one may be forced to develop accelerated in vivo materials tests. Once the preliminary testing is accomplished, however, one must test the device per se in animals. A biocompatible material does not necessarily make a biocompatible device. The same may be said about biostability. These statements are true because shape, size, surface finish, interactions between the materials in the device, etc., all can affect its biocompatibility and biostability. But even well-performed animal studies may not unveil previously unknown mechanisms, because animals do not perfectly mimic the human in vivo environment. An excellent example of this is the subclavian crush in humans (clamping a lead between the clavicle and first rib), which is impossible to discover in animals with no clavicles. With the right protocol for the device in question, only postmarket surveillance appropriate for the device in question can determine for certain that the device does or does not meet expectations. 

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