Orientability, mechanical

McGregor, J. H and Teska, W. R. 1989. Olfaction as an orientation mechanism in migrating Ambystoma maculatum. Copeia 1989,779-781. 

With regard to male behavior, several recent reports have delineated the time course of maturation of male sexual response, its diel periodicity and circadian regulation, and behavioral tactics employed by males in orienting to females. As in other insects, cockroaches integrate visual and olfactory cues, but the orientation mechanisms have been little studied, especially under natural conditions. In... 

Keywords Electric field Block copolymers Microdomain orientation In situ SFM Orientation mechanism... 

Since the nanocrystallites were separated from the substrate with a layer of amorphous carbon, one might think that the ordered arrangement of the nanocrystallites was due to an auto-orientation mechanism, which operated at all stages of the growth of the ordered nanocrystalline forms of the films of the zirconia-based solid electrolyte. 

Figure 6.10. Effect of polarized light on oriented DHI 34/LC (nematic) assemblies. Ey is the extinction when the polarized light is parallel to the electric vector of the light (Ei perpendicular). Molecules were oriented mechanically in the nematic phase. E or T refers to the extinction measured for 34 or 46 with parallel (or perpendicular) light in the nematic ZLI-2452 (Merck) phase (Type I).

One interesting aspect of these and other studies which may be worth emphasising is that the same ultimate surface condition may arise with either burnished powder or certain bonded films. It appears that the same orientation mechanism can occur with or without the presence of a binder. On that basis the function of at least the softer binders would be simply to retain the molybdenum disulphide in position while the running-in or burnishing is taking place. This subject is further discussed later. 

However, in any conformation the chain as a whole has a dipole moment m being the vector sum of dipole moments Mq of all its polar groups. The rotating moment exhibited by the dipole p in the electric field, can lead to the orientation of p in the field direction through rotation of the chain molecule as a whole (large-scale motion). In this case, the mechanism of the appearance of the polarization and macroscopic solution anisotropy may be called orientational mechanism. 

Fig. 58a, b. Possible polarization mechanisms of a chain molecule in the electric field, a Kinetically flexible chain (deformational mechanism) b kinetically rigid chain (orientational mechanism)... 

As frequency increases, all dispersion curves decrease to virtually zero. This indicates that EB is produced by the dipolar-orientational mechanism whereas the anisotropy of the dielectric polarizability of the macromolecules is virtually imper-ceptile in the Kerr effect. The displacement of curves towards higher frequencies with... 

The orientational mechanism of EB in solutions of r id-chain polymers and the possibility of determining rotatory diffusion constants of their molecules from dispersion curves may be utilized for the characterization of equilibrium conformational properties of their drains. The theory of rotational friction of kinetically rigid molecules developed by Hearst makii% use of the statistics of worm-like chains can be employed for this purposes. The results of this theory for the two limiting cases of molecular conformation refering to the slightly bent rod and the worm-like coil are expressed by Eqs. (27) and (28) (Sect. 2.3). 

However, this mechanism of motion does not provide any great contribution to the Kerr effect since the dispersion curves of EB fall to virtually zero (Fig. 60). This difference may be interpreted by the proportionality of the orientational EB of a ripd-chain polymer to the square of the number of monomer units in segment whereas increment Ae/c related to the orientational mechanism is proportional to S (see Sects. 5.8 and 5.9). Hence, in the case of dielectric polarization the part played by the deformational mechanism as cmnpared to the orientational mechanian can be more important than in the case of EB. 

Hence, when i ing from the orientational mechanism of EB to tlK deformationai mechanism coefficient C in Eq, (84) decreases and continues to decrease with the introduction of higher modes of intramolecular motion. 

By means of Eqs. (85a)-(85c), (92), (93), (104), and (106) for the three contributions to the molecular Cotton-Mouton constant arising from the orientational mechanism of birefringence in the magnetic field, we obtain... 

Fig. 37a,b. Schematic view of the orientation mechanism in all optical poling with azo dye molecules (a) and electron transition diagram between fundamental and excited singlet states (b). In the case of azo dyes, the trans-cis isomerization is achieved through both one- and two-photon excitations [144]... 

In accordance with the discussion of Figures 9.25c and d, they reflect a sUghtly positive orientation for PHB and PLA in the matrix and an opposite orientation for the two polymer components (PHB negative, PLA positive) in the islands . These figures clearly demonstrate that the polarization spectra recorded with a single-element detector cannot discriminate between the different orientation mechanisms in the phase-separated, anisotropic structure of this polymer blend. 

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