Alignment random parallel

FIGURE 13 3 (a) In the absence of an external magnetic field the nuclear spins of the protons are randomly oriented (b) In the presence of an external magnetic field Xq the nuclear spins are oriented so that the resulting nuclear magnetic moments are aligned either parallel or antiparallel to Xq The lower energy orientation is the one parallel to Xq and more nuclei have this orientation... 

When peptides containing four cysteine residues in the molecule are randomly oxidized, three different disulfide isomers can be formed (Scheme 1), isomer 1 with the disulfides aligned in parallel manner, isomer 2 with crossed disulfides and isomer 3 with sequential disulfides these isomers are also named in a more descriptive manner as the ribbon, globule and string-of-beads isomers. 28 The preferred formation of one of the isomers strongly depends upon the sequential topology of the cysteine residues, but also upon the sequence composition that may favor more or less globular structures with hydrophobic cores. 

Both XRD and TEM investigations show that the incorporation of F127 (ratio F127/SS = 0.005) in a prehydrolysed solution of TEOS leads to the formation of highly ordered composite films, when deposited by dip coating. Once F127 is removed, the pores consist of channels aligned preferentially parallel to the substrate surface in random directions. Peaks... 

While all vibrational transitions arg allowed by Eq. (1), the intensity of a mode is governed by the (Q c.j term which expresses the component of the neutron momentum transfer along the direction of the atomic displacements. To an extent, this feature can be exploited with substrates such as Grafoil which have some preferred orientation. By aligning Q parallel or perpendicular to the predominant basal plane surfaces, the intensity of the "inplane" and "out-of-plane" modes, respectively, can be enhanced. In practice, while this procedure can be useful in identifying modes (9), the comparison with calculated intensities can be complicated by uncertainties in the particle-orientation distribution function. In this respect, randomly oriented substrates are to be preferred (10). 

The distance that separates the two molecules goes from 10 to 60-100 A. Below 10 A, electron transfer may occur between the two molecules, inducing an energy transfer from donor to acceptor, k2 values hold from 0 to 4. For aligned and parallel transition dipoles (maximal energy transfer) k2 is 4, and if the dipoles are oriented perpendicular to each other (very weak energy transfer), k2 is 0. When k2 is not known, its value is considered to be equal to 2/3. This value corresponds to a random relative orientation of the dipoles. 

It is clear that the cubic unit cell is very large and accommodates more than 100 molecules. It can be assumed that the molecules are aligned in parallel in micelles or in bundles, and the preferred direction is randomly oriented in dynamic equilibrium. The lattice elements form a three-dimensional cubic lattice with a long-range order. 

Orientation of hllers in directions other than perpendicular to the permeant how signihcantly reduces the effect of aspect ratio. When the hller sheets are aligned perfectly parallel to the direction of permeation, similar to the parallel model, the permeability of the composite system nearly approaches that of a monolithic polymer, that is, the barrier improvement is nearly zero. Thus, for a practical system, considering the possible orientation of hllers in every direction, the actual tortuosity will be less than that obtained by Eqn (8.12). To account for such a random orientation of the GO hller sheets, an order parameter S is dehned as expressed by Eqn (8.13) (Bhardwaj, 2001). 

There are two other examples of fluid orientation that are closely related to uniform parallel alignment. In the first case, the director also lies parallel to the cell surfaces. However, the director orientation in the plane parallel to the cell walls is not uniform rather, it changes randomly over dimensions on the order of micrometers. This orientation is known as random parallel alignment (see Fig. 4B). 

Guyon et al did not state the exact nature of the liquid-crystal orientation with films evaporated at = 0°. Meyerhofer has measured random parallel alignment for = 0° evaporations. A reasonable conclusion that can be drawn from the data is that, when in contact with mesomorphic fluids, freshly evaporated SiOx films produce parallel alignment in liquid crystals through physicochemical forces. At the present time, it is still not clear whether the directionality induced in the liquid crystal by obliquely fevaporated SiOx film is caused by the sawtooth model or some other anisotropic property of the SiOx. 

Figure 15.25 shows the result for the initial muon spin polarization perpendicular to the Z -axis. When the muon spin is polarized parallel to the Z>-axis, the amplitude of the oscillating signal becomes very small (about 20% of that of the perpendicular orientation) [30]. This suggests tiiat the spin orientation in different domains is not aligned randomly and is most likely along the b-axis. Recent FM resonance experiments by... 

It is not very difficult to appreciate that if polymer molecules are aligned as in Fig. 18.10 then a much higher tensile strength will be obtained if a test is carried out in the X-X direction as opposed to the Y-Y direction. It is also not difficult to understand why such a material has a lower impact strength than a randomly coiled mass of molecules (Fig. 18.10) because of the ease of cleavage of the material parallel to the X-X direction. 

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