Lamellar pattern

Figure 1.20 Periodic concentration profile of a regular multi-lamellar pattern in a rectangular interdigital micro mixer, determined by photometric-type analysis [119].

The lipid molecule is the main constituent of biological cell membranes. In aqueous solutions amphiphilic lipid molecules form self-assembled structures such as bilayer vesicles, inverse hexagonal and multi-lamellar patterns, and so on. Among these lipid assemblies, construction of the lipid bilayer on a solid substrate has long attracted much attention due to the many possibilities it presents for scientific and practical applications [4]. Use of an artificial lipid bilayer often gives insight into important aspects ofbiological cell membranes [5-7]. The wealth of functionality of this artificial structure is the result of its own chemical and physical properties, for example, two-dimensional fluidity, bio-compatibility, elasticity, and rich chemical composition. 

Fig. 9. Flectronmicrograph (Pt/C replica) showing epitaxial association of poly-L-alanine and R-quartz. Note the lamellar pattern and the insertion of new lamellae due to dispersion bonding forces. A smooth chain-folded surface, as shown in (a) is developed. In contrast a rough-chain-folded surface (b) is developed in Fig. 10. Start and termination of a peptide chain is indicated in (a) and (b) by an x (after Seifert99 10°))...

Yamamoto, T., Domon, T., Takahashi, S., Islam, N., and Suzuki, R. (2000b). Twisted plywood structure of an alternating lamellar pattern in cellular cementum of human teeth. Anat. Emhryol. 202, 25-30. 

Lamellar patterns formed via the side-by-side arrangement of linear polyphenylenes68 and columns... 

The lamellar pattern is believed to be due to the differential rates of fibrillar formation during daily growth cycles [277,278]. Differential compaction of the fibrils provides variations in fibrillar bonding, and determines accessibility or permeability into the inner areas of the fiber. The lumen is the central opening in the fiber that spans its length from base nearly to the tip. It contains the dried residues of cell protoplasm, the only source of noncellulose materials in the fiber other than those in the primary wall. A thin cell wall (lumen wall) provides the inner cell boundary. The lumen opening occupies about 5% of the cross-sectional area of the mature fiber. 

Figure 5 Murine stratum comeum normal full thickness. Powder diffraction patterns obtained from mouse SC at 25°C. The upper figure shows the small-angle lamellar pattern produced by the intercellular lipid domains, with a repeat period of 131 2 A. The lower figure shows the wide-angle pattern produced by the lipid alkyl chains and the comeocyte envelope. See text. (Data from White et al., 1988.)...

Thus, three mechanisms of alignment—one for frequencies and temperatures at which molecular stresses dominate, and the other two at conditions where stresses from the lamellar pattern dominate—can rationalize the alignment behavior of the low-molecular-weight PS-... 

Not only are disclination lines aligned along the field direction, but also wall defects are anisotropically distributed in the aligned sample. This is best understood by first defining a rotation axis for a wall defect. A rotation plus a translation is required to map the lamellar pattern on one side of a wall defect to the other. I refer to this rotation axis as the rotation axis for the wall. If the wall contains its rotation axis, it is a bend wall, and if the axis is perpendicular to the wall, it is of twist character. The wall is of mixed character if the rotation axis is in between. In the field-aligned sample, the rotation axes of the wall defects are aligned predominantly along the direction of the applied field, e.. Thus, walls with normals parallel to S. have primarily twist character, and walls with normals nearly perpendicular to S. have primarily bend character. Examples of bend walls are indicated in Fig. 28a. 

Wall defects may also interact indirectly with distortions in the lamellar pattern (Fig. 35c and d). A simple example involves a perpendicular bisector wall. The perpendicular bisector wall bisects the angle between the lamellae on both sides of the wall. Many walls of this type can be observed in block copolymer samples. The continuity of the lamellar pattern across the wall makes this a particularly favorable (low-energy) wall defect. As a bisector wall defect approaches a region of distortion, the coherence of the lamellar pattern is lost because the wall is no longer a perpendicular bisector of the lamellar pattern. Alternatively, the wall will distort in order to maintain the perpendicular bisector condition, resulting in an increase in the wall area. Either way, the energy of the wall defect is increased. 

Observed changes in the physicochemical and micellar properties of the pyrro-lidinium imidazoUum or alkylammonium alkylcarboxylates protic ionic liquid surfactants in mixtures with water can be linked to the nature of the cation. Figure 7.14 shows, for example, lamellar patterns bilayer systan of diisopropylammonium octanoate in water (50 % w/w). By comparison with classical anionic surfactants having inorganic counterions (LP, Na. ..), these monomers exhibit a higher ability to aggregate in aqueous solution, demonstrating their potential applicability as a surfactant. 

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