Array reorientation

Figure 2-4. A simplified scheme of the proposed water-gated mechanism of proton translocation. Each numbered state shows haem a and the binuclear site (left and right rectangles, respectively) the A-propionate of haem is shown schematically. Three water molecules (oxygen in red hydrogen in yellow) are shown to mediate Grotthuss proton transfer from the glutamic acid (GLU-OH) to the propionate or the binuclear site, respectively. In state 1, an electron is transferred to haem a. The formed electric field between the redox sites orientates the water molecules towards the propionate (state 2). In state 3, electron transfer to the binuclear site is accompanied by proton transfer via the propionate a proton is deposited above haem and the glutamate is reprotonated via the D-pathway (state 4). The switch of electric field orientation reorientates the water array towards the binuclear site (state 5). Finally, a proton is transferred to this site, and the first proton is ejected (state 6). Reprotonation of the glutamate transfers the system back to state 1. For details, see the text and ref. 17.

For stems, it is well known that externally applied cytokinins inhibit elongation and induce thickening. In early work, the synthetic molecules, kinetin and benzimidazole, were found to elicit reorientation of pre-existing random or transverse CMTs into longitudinal arrays... 

Mechanical Steering. The simplest method of beam steering is to use a mechanism to reorient a transducer (usually a circular aperture) to a predetermined set of orientations so as to capture the required two-dimensional data set. This approach was dominant at first however, in the last 15 years, electronically steered systems have become, by far, the most popular. Mechanical systems usually use either a single-element transducer or an annular array transducer (Fig. 25.8). Tlie former will have a fixed focus while the latter does allow the focal point to be moved electronically. This will be discussed more fiilly later. 

Figure 5.9a illustrates the focused spot patterns produced by such microlens arrays when no voltage was applied. Arrays of uniform bright spots generated by positive lenses were observed. The light-intensity profile of spot A was measured at different voltages, V = 0, 40, 60 V ms/ respectively (Figure 5.9b). At V = 0, the peak intensity was the strongest. As the applied voltage increased, the LC directors in the polymer cavities reoriented toward the electric field and the curvature of the refractive index profile gradually...

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