Strain reversal

Escherichia coli WP2 uvrA, WP2, other strains, reverse mutation DNA strand breaks, cross-links or related damage, Chinese hamster V79 lung cells in vitro°... 

ECR, Escherichia coli (other miscellaneous strains), reverse + + 200 Mohn etal. (1981)... 

If a piezoelectric plate (Fig. 6.1), polarized in the direction indicated by P, carries electrodes over its two flat faces, then a compressive stress causes a transient current to flow in the external circuit a tensile stress produces current in the opposite sense (Fig. 6.1(a)). Conversely, the application of an electric field produces strain in the crystal, say a negative strain reversal of the field causes a positive strain (Fig. 6.1(b)). The changes in polarization which accompany the direct piezoelectric effect manifest themselves in the appearance of charges on the crystal surface (see Eq. (2.71)) and, in the case of a closed circuit, in a current. 

Coupling of highly conductive CNT network with a soft polymer matrix with large coefficient of thermal expansion (CTE) leads to a new class of electrothermal CNT-polymer composite actuators,which generates significant strains reversibly at applied electric fields at least two orders of magnitude lower than those reported for electrostrictive polymer nanocomposites. 

As discussed in Chapter 2, the moleeular structure of polymers, whether glassy or semi-crystalline, incorporates a signifieant component of disordered material containing a certain fraction of free volume or a liquid-like material environment, depending on the thermal history of the polymer. The subject of this chapter is the small-strain reversible response of sueh polymeric materials and structures under stress that we refer to as linear viscoelasticity. 

Equation (1) represents a curved transition from a straight-Une asymptote with slope Eo to another asymptote with slope bEo (Figure 1 Unes (a) and (fi) respectively). <70 and So are the stress and the strain at the point where two asymptotes of the branch under consideration meet (Figure 1, point A), while Or and denote the stress and the strain at the point where the last strain reversal with stress of equal sign took place (Figure 1, point B). The shape of the transition curve allows a good representation of the Baushinger effect. This is a function of the curvature parameter R and depends on the strain difference between the current asymptote intersection point and the previous... 

In order to tackle difficulties such as those discussed in the previous section, Dodd and Restrepo-Posada (1995) introduced the idea of major, minor and simple reversals, whilst Balan et al. (1998) distinguished reversals into complete and incomplete, with a value of 2fy being adopted as a threshold parameter. For the Monti-Nuti model, Attolico et al. (2000) proposed that whenever small strain variations take place, the model should follow the backbone curve before the last strain reversal. 

The cumulative strain, due to creep strain reversals arising from power changes, may however be the critical factor in determining the endurance of the can. 

A second important parameter of the fatigue is the frequency, v, of the cycle. The frequency, which is the reciprocal of the period, t, and is shown in Fig. 10(a), describes the number of strain reversals that occur per unit time—typically, per second. The fatigue process is often... 

Factorization of the function concentrated polystyrene solution, time-strain factorability is not valid at short times after the imposition of the step shear. An accurate K-BKZ constitutive equation for shearing flows of this material will be much more complex than that for melt I. Furthermore, in strain histories in which a strain reversal takes place, such as constrained recoil (Wagner and Laun, 1978) or double-step strains with the second strain of sign opposite the first (Doi, 1980 Larson and Valesano, 1986), good agreement... 

Typically, beams or columns with low axial compression exhibit predominantly tensile yielding. Therefore, the monotonic curve provides a reasonable envelope to the cyclic response in the tension range, while compressive behavior deviates. In columns with high compression stress levels and high confinement ratios, reinforcing bars may be subject to strain reversals of almost equal magnitude. In that case the stress level for a given strain may substantially exceed the stress indicated by the monotonic behavior (Priestley et al. 1996). 

Parent Strain Reversion Compensatory mutations Occurrence PS assay ... 

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