Stress testing degradants characterization

The forced degradation studies should be part of impurity characterization. When identification of the impurity is not feasible, incorporate the description of unsuccessful experiments (including those conducted in stress-testing studies) in the text of the application. The most frequently encountered protein variants include truncated fragments, deamidated, oxidized, isomerized, aggregated forms, and mismatched disulfide links. 

For non-compendial procedures, the performance parameters that should be determined in validation studies include specificity/selectivity, linearity, accuracy, precision (repeatability and intermediate precision), detection limit (DL), quantitation limit (QL), range, ruggedness, and robustness [6]. Other method validation information, such as the stability of analytical sample preparations, degradation/ stress studies, legible reproductions of representative instrumental output, identification and characterization of possible impurities, should be included [7], The parameters that are required to be validated depend on the type of analyses, so therefore different test methods require different validation schemes. 

Determination of these soil properties are well established with recent advances in the formulation of nonlinear hysteretic constitutive relations for soils and the characterization of stiffness degradation of saturated sands and clays with cycles of loading. The increasing interest in seafloor slope stability problems imder wave and earthquake loadings has also emphasized the need for data from cyclic tests simulating stress conditions on slopes. The application of cyclic test techniques in relation to the latter developments are discussed with reference to both test results and associated analytical approaches. 

Let us turn our attention to the deformation curve encountered in sample testing in the uniaxial extension at a constant relative strain rate, de/dt. Let the curve be plotted in e-a coordinates, where o is the stress applied to the initial section of the sample (Figure 5.10a). If the material is brittle, the failure can occur already within the initial Hookean portion of the curve characterized by a linear dependence between e and a. The collapse will then occur before the proportional limit, Op, has been reached. If the material is plastic, the increase in the stress slows down and the transition to a plastic flow occurs once the yield point, Of, has been reached. The increase in the stress then progresses at a slower rate, and the so-called strain hardening takes place. A subsequent fast increase in a in these coordinates corresponds to the formation of a neck. After that, o reaches a particular maximum and tear takes place. This stress maximum (per initial cross section) is referred to as the temporary resistance to degradation, Og. This parameter can be determined experimentally under the most simple and reproducible conditions, and for this reason, it is used as the standard characteristic in a number of strength theories. In addition to this characteristic, one also often uses the maximum deformation, 5 = and the thinning, that is, the decrease in cross-sectional area, [Pg.200]

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