Domain reorientation

A second type of behavior existing in the PLZT s is the linear (Pockels) effect which is generally found in high coercive field, tetragonal materials (composition 3), This effect is so named because of the linear relationship between An and electric field. The truly linear, nonhysteretic character of this effect has been found to be intrinsic to the material and not due to domain reorientation processes which occur in the quadratic and memory materials. The linear materials possess permanent remanent polarization however, in this case the material is switched to its saturation remanence, and it remains in that state. Optical information is extracted from the ceramic by the action of an electric field which causes linear changes in the birefringence, but in no case is there polarization reversal in the material. 

Brown, M. E., Hollingsworth, M. D., Stress-induced domain reorientation in urea inclusion-compounds. Nature 1995, 376, 323-327. 

In practice, with most PZT compositions, Eq. (6.78) may underestimate the energy released because domain reorientation associated with ferroelasticity will contribute significantly to the charge developed (cf. Fig. 6.13). However, the magnitude and duration of the applied force must be such that the changes in polarization due to ferroelasticity are reversible if the output of the igniter is not to deteriorate with usage. 

Edema factor of anthrax is one of the three exotoxins produced by the bacteria. The primary sequence is only slightly homologous to other adenylyl cyclases. When it enters the host cells, edema factor acts as an adenylyl cyclase and transforms ATP to cAMP efficiently. The structme of CaM-edema factor of anthrax complex has been obtained (Figure 9). In the CaM-edema factor complex, only the C-terminal lobe binds two calcium ions while the N-terminal lobe is empty. CaM remains extended and is deeply inserted between the catalytic and the a-helical domains of this exotoxin with a large number of residues of CaM iuvolved in the interaction. CaM binding results in a large domain reorientation of edema factor. The helical domain of edema factor undergoes a 15 A translation and a 30° rotation. The CaM inserted site is far from the catalytic site and the... 

Ilin S, et al. Domain reorientation and induced fit upon RNA binding solution structure and dynamics of ribosomal protein Ell from Thermotoga maritima. ChemBioChem. 2005 6 1611-1618. 

Measured RDC values are representative averages of the whole ensemble of dipolar interactions within protein molecules in solution. Such an ensemble should include all protein conformers interconverting at time scales faster than the inverse of RDC values HD). For instance, the observed dipolar coupling is affected by the intemuclei or bond vectors that stretch and vibrate on a femtosecond to nanosecond (fs-ns) time scale, the protein domain reorientation on a nanosecond to microsecond (ns-ps) time scale, and conformational change that ranges from nanoseconds, e.g., unstructured terminus, to milliseconds. It is nearly impossible to describe protein structure and dynamics using RDC values without any assumptions. Some approximations have to be made in interpreting RDC measurements. 

Bertini I, Del Bianco C, Gelis I et al (2004) Experimentally exploring the conformational space sampled by domain reorientation in calmodulin. Proc Natl Acad Sci USA 101 6841-6846... 

Acceptors, e.g, replacing Zr"" with Fe with the concomitant formation of oxygen vacancies. Domain reorientation is limited, and hence acceptor additives lead to poorly developed hysteresis loops, lower k, low tan 5, low compliance, and high aging rates. Typical applications are in high-power devices such as sonar and ultrasonic transducers. 

DeRouchey, J., Thum-Albrecht, T., Russell, T.P., Kolb, R. Block copolymer domain reorientation in an electric field an in-situ small-angle x-ray scattering study. Macromolecules 37, 2538 (2004)... 

The main difference between primary ferroics and those of the higher orders is related to the fact, that at least one pair of the domains in the primary ferroics has opposite direction of order parameter, while the same pair in the higher-order ferroics can be induced by corresponding set of external fields. For example, in ferrobielectric, the domain pairs have the same orientations of polarization P, so that field-induced domain reorientation can be represented via induced polarization difference as follows ... 

Another distinguishing feature of ferroelectric behavior is the polarization versus electric field P—B) hysteresis loop. The hysteresis loop results from the domain reorientation which occurs as the electric field direction is varied. The size and shape of the loop is determined by the magnitude of the dipole moment of the unit cell and the domain-switching characteristics of the material. Hysteresis loop behavior is measured using either a Sawyer—Tower circuit or a Diamant—Pepinsky bridge. Details of the construction and operation of a Sawyer—Tower circuit are given in Reference 24. Thin film properties have also been measmed with these two devices, and in addition, a commercially available measurement system has been widely used. ... 

Reece, M.J. and Guiu, F., 2002, Toughening produced by crack tip stress induced domain reorientation in ferroelectric and/or ferroelastic materials. Philosophical Magazine A82 29 38. 

Under a strain below 40%, both domains tend to align perpendicular to the stress direction, and the individual mesogens are aligned parallel to the stress direction. At a strain above 40%, however, both the liquid crystalline smectic domains and the hard segment domains reorient parallel to the stress direction this is shown schematically in Figure 2.24. 

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