Symmetrical extended arrays

The thin filament (about 7 nm in diameter) fies in the 1 band and extends into the A band but not into its H zone (Figure 49-2). Thin filaments contain the proteins actin, tropomyosin, and troponin (Figure 49-3). In the A band, the thin filaments are arranged around the thick (myosin) filament as a secondary hexagonal array. Each thin filament lies symmetrically between three thick filaments (Figure 49-2, center mid cross-... 

For a such case, linear arrays of electrodes may be used however, this will lead to extended structures when using, e.g., more than four electrodes. Instead of using such unidirectional motion, the droplet may be moved in circular fashion by a square-like 2x2 array of electrodes. Indeed, faster mixing times compared with simple droplet merging can be achieved, albeit not faster than for the respective four-electrode linear structure. Actually, a small portion of the droplet remains unmixed. This was explained as due to the droplet pivoting around the array center. For this reason, a non-symmetric array (2 x 3) was developed as mentioned below. 

Modern devices use photodiodes or CCD arrays (Sect. 4.5.2) instead of photoplates. With a diode width of 25 p.m, the peak of a symmetric line profile extending over 3—5 diodes can be determined by a least-squares fit to a model profile within 1—5 xm, depending on the S/N ratio. When the array is placed behind a spectrometer with a dispersion of 1 mm/nm, the center of the line can be determined within 10 nm. Since the signals are read electronically, there are no moving parts in the device and any mechanical error source (backlash) is eliminated. 

In this chapter we study the phenomenon of optical cross-talk between pairs and between arrays of cylindrically symmetric or slowly varying fibers. Crosstalk arises because the fields of a fiber extend indefinitely into the cladding and interact with any other fiber which may be present. This interaction excites the fields of the second fiber, which in turn interact with the fields of the first fiber. Consequently there will be an exchange of power between the two fibers as the fields propagate. The amount of cross-talk, or power exchange, depends on the overlap of the fields of the two fibers. In ray language, cross-talk is associated with frustrated internal reflection or, equivalently, optical tunneling. 

The addition of homopolymers further enhances the tolerance of mismatching and allows chemical epitaxy of stractures more complex than the typical bulk phases of block copolymers. Stoykovich et al. introduced a ternary blend to further extend their surface-directed method. Such a blend system enables the block copolymer lamellae to conform to substrate stripe arrays with sharp bends. In the imblended block copolymer S3 tem, a high strain builds up in the polymer film at sharp comers of the chemical pattern because the comer-to-comer distance is much larger than the natural periodicity of the block copolymer. Successful replication of arrays of tilt boundaries with 45° and 90° angles was observed as a result of the redistribution of the homopolymer. (The polymer blend includes 20% PMMA homopolymer, 20% PS homopolymer, and 60% symmetric PS-b-PMMA.) Homopolymers are depleted above commensurate regions and concentrated above the distorted regions of the pattern to reduce the strain from incommensurability. 

---