Lamellar arrangement

A typical lamellar arrangement of the rods is formed in which the benzenoid n-systems lie flat on the surface. The nature of the substrate surface is, however, crucial. If the corresponding polyphenyle-neethynylenes 21 are deposited onto mica surfaces and the resulting patterns visualized by AFM, one detects micrometer long needles, whose width corresponds to the length of the polymers (Figure 2).181... 

Each sphere has a lamellar structure and a single preferred orientation but shows systematic variations in the optical extinction patterns, which indicate some variation from a strictly lamellar arrangement this is most noticeable at the poles of spheres. As they grow and meet obstructions to their enlargement in particular directions, their extinction behavior becomes increasingly complex, especially when the pitch nears solidification and the complete mosaic structure is formed. 

The medium may have a marked effect on the shape of receptor molecules itself. Shape modifications could strongly influence their substrate binding properties, for instance in the case of amphiphilic cyclophane receptors subjected to hydrophobic-hydrophilic factors in aqueous solution. Such medium effects in action are visualized by the solid state structures of two different forms of the water-soluble hexasodium salt of the macrobicyclic cyclophane 66, which could be crystallized in two very different shapes an inflated cage structure 71 building up cylinders disposed in a hexagonal array and a flattened structure 72 stacked in molecular layers separated by aqueous layers in a lamellar arrangement [4.73]. These two... 

The current observations confirm previous studies on beechwood and sprucewood holocellulose (7,10,19). The attack of the hemicellulose proceeds from the primary wall/Si as well as from the tertiary wall into S2 the pit chambers constitute preferred paths of enzyme diffusion into the walls. Also, substances of the middle lamella, especially in the cell corners, are removed by the xylanase and the mannanase treatments. Parallel to the removal of hemicelluloses, the fibrillar structure of the cellulose and its lamellar arrangement in transections of cell walls became obvious. In samples treated with cellulases, the cellulose fibrils were often completely hydrolyzed in the Si layer, occasionally accompanied by complete dissolution of cell-wall portions. This is also in conformity with the previous conclusion that the cellulases hydrolyze highly ordered zones of cellulose and remove hemicelluloses by hydrolysis or by detachment. 

Fig. 4 Influence of molecular weight Mw on (a) lamellar arrangement and (b) diffraction patterns of polyethylene (c) comparison of the diameter Dk of molecular coils and of the long period L of the lamellar structure (after Michler [12])...

We now turn to the case of block copolymers. Early work by Shull [20] considered a lamellar arrangement parallel to the walls only. From such calculations, one obtains a unified treatment of both the weak and the strong segregation limit within mean field theory, and a detailed description of the order parameter profiles across the thin film emerges. 

Under defined conditions, the toughness is also driven by the content and spatial distribution of the -nucleating agent. The increase in fracture resistance is more pronounced in PP homopolymers than in random or rubber-modified copolymers. In the case of sequential copolymers, the molecular architecture inhibits a maximization of the amount of the /1-phase in heterophasic systems, the rubber phase mainly controls the fracture behavior. The performance of -nucleated grades has been explained in terms of smaller spherulitic size, lower packing density and favorable lamellar arrangement of the /3-modification (towards the cross-hatched structure of the non-nucleated resin) which induce a higher mobility of both crystalline and amorphous phases. 

The above results show that while total lipid extracts do not necessarily form the same lamellar arrangement observed in intact stratum comeum, it is... 

The formation of shear bands under compression is found in crystalline polymers when loaded at temperatures lower than 0.75 T. Under such a condition the shear bands interact with certain morphological features such as spherulite boundaries or lamellar arrangements inside the spherulites. The band initiation stress, ct, increases and the strain at break, Cp, decreases with decreasing temperature and increasing stiffness of the tested polymer, i.e. increasing degree of crystallinity. 

Hansen A, Zielinski BS (2005) Diversity in the olfactory epithelium of bony fishes development, lamellar arrangement, sensory neuron cell types and transduction components. J Neurocytol 34 183-208... 

Hansen A, Rolen SH, Anderson K, Morita Y, Caprio J, Finger TE (2003) Correlation between olfactory receptor cell type and function in the channel catfish. J Neurosci 23 347-359 Hansen A, Anderson KT, Finger TE (2004) Differential distribution of olfactory receptor neurons in goldfish structural and molecular correlates. J Comp Neurol 477 347-359 Hansen A, Zielinski BS (2005) Diversity in the olfactory epithelium of bony fishes development, lamellar arrangement, sensory neuron cell types and transduction components. J Neurocytol 34 183-208... 

In addition to the characterization of the lamellar arrangement in processed polymers, as discussed above, AFM is useful to analyze changes in surface morphology and roughness owing to surface treatments. For example, Vancso and coworkers reported on an early AFM study of the surface morphology of commercial polymer films. The effects of various oxidizing treatments and of metallization of PP have been unraveled. In this study the thickness and orientation of the exposed lamellae were determined [161]. 

C line widths of erthythrocyte membrane 48 lipids are typical for a lamellar arrangement but for endoplasmic reticulum membranes lipid line widths are small and characteristic of Isotropic phases. 

Sometimes, depending on the system and conditions, the duplex oxide-sulphide layer will appear as a lamellar arrangement, as in the case of iron. " With nickel, however, the sulphide forms in a more massive, less organized arrangement. In either case, the sulphide probably forms as a continuous network to account for the high ionic conductivity of the duplex layer. 

Figure 6.9 Lamellar arrangement of PE0/V20s.nH20 composite. (Reprinted with permission from Chemistry of Materials, Intercalation of poly(ethylene oxide) in vanadium pentoxide (V2O5) xerogel by Y. J. Liu, D. C. DeCroot, J. L. Schindler et al., 3, 6. Copyright (1991) American Chemical Society)...

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