Crystal-like domains

Comparing with conventional amorphous organic semiconductors [16], it is characteristic that conjugated polymer films consist of crystal-like domains, in which jt-conjugated chains are stacked closely, and an amorphous domain, in which polymer chains are disordered [115]. In crystal-like domains, band-like carrier transport that is similar to that of molecular crystals should be possible. However, hopping transport influenced by structural disorder is the dominant process in the amorphous domains. The total carrier transport process is dominated mainly by that in amorphous domains, resulting in bulk carrier transport characteristics similar to those of amorphous organic semiconductors. 

Gomis-Ruth FX, Gohlke U, Betz M, Knauper Y, Murphy G, Lopez-Otin C, Bode W. The helping hand of collagenase-3 (MMP-13) 2.7 A crystal structure of its C-terminal haemopexin-like domain. J Mol Biol 1996 264 556-566. 

While there is at present no full understanding as to why plastocyanin should require two sites for reaction, there is now much evidence detailing this two-site reactivity. Moreover, the recent X-ray crystal structure of ascorbate oxidase (which has 4 Cu atoms per molecule) has indicated a plastocyanin-like domain, with the two type 3 Cu s (in close proximity with the type 2 Cu) located at the remote site. Fig. 2 [5]. Since electrons are transferred, from the type 1 Cu to O2 bound at the type 3 center this structure defines two very similar through-bond routes for biological electron transfer. 

The recent X-ray crystal structure of ascorbate oxidase [6] has indicated the relative positions of type 1, 2 and 3 Cu centers. The type 1 center is in a plastocyanin like domain, and is the primary acceptor of electrons from substrate. The shortest pathway for electron transfer from the type 1 to type 3 Cu s is the bifurcated path via Cys508 and either His 507 or His509. The two histidines are part of the plastocyanin-like domain, and serve also to coordinate the type 3 Cu s, Fig. 2. The His507 to Cys508 bonding is similar to that of Tyr83... 

However, if an LC substance is heated, it will show more than one melting point. Thus, liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional liquid and a solid crystal. For instance, an LC may flow like a liquid but have the molecules in the liquid arranged and/or oriented in a crystal-like way. There are many different types of LC phases that can be distinguished based on their different optical properties (such as birefringence). When viewed under a microscope using a polarized light source, different liquid crystal phases will appear to have a distinct texture. Each patch in the texture corresponds to a domain where the LC molecules are oriented in a different direction. Within a domain, however, the molecules are well ordered. Liquid crystal materials may not always be in an LC phase (just as water is not always in the liquid phase it may also be found in the solid or gas phase). 

Figure 13.11 (a) Thread-like domains in a nematic liquid crystal of thickness 100 j,m viewed under... 

Thus observation of ferroelectric domain reversal induced by indirect electron beam irradiation in LiNb03 bulk crystals represents a pronounced fdb effect. The reversed structure represents domain clusters consisting of multiple string-like domains with nanometer radius and 350 pm lengths. Fabricated one- and two-dimensional domain configurations could be used for a broad range of new 2-D as well as potential 3-D nonlinear photonic devices. 

In Table 10.2 below we summarize the calculated values of the shape invariant r 2//m and aspect ratio rm/lm of string-like domains in different fe crystals formed under the fdb conditions. The experimental parameters used for these calculations are U = 3kV (applied voltage), R = 50 nm (typical radius of curvature of the tip apex), d = 0.5 nm (distance between the tip apex and the sample surface). The calculated aspect ratios rm/lm are quite different for the chosen fe. 

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