Stripe model

An unusual feature of the cuprate superconductors is the anomalous suppression of superconductivity in La2 Ba Cu04 and related phases when the hole concentration X is near 1/8. A possible explanation is a dynamical modulation of spin and charge giving antiferromagnetic stripes of copper spins periodically separated from the domains of holes. Neutron-diffraction evidence has been presented in the case of Laj g Nd() Sr CuO (x = 0.12) which is a static analogue of the dynamical stripe model (Tranquada et al., 1995). It appears that spatial modulations of spin and charge density are related to the superconductivity in these oxides. 

Fig.l. Stripe models for 1/3 doping.18 Arrows indicate correlated Ni magnetic moments circles indicate oxygen sites filled circles indicate locations of doped holes on oxygen sites. Bold dashed lines indicate positions of domain walls, while bold solid lines outline a magnetic unit cell. The two-magnon Raman process is shown also bold arrows demonstrate spins on adjacent sites and curved lines indicate broken magnetic bonds. 

To verify the syimnetry and identify the sensitivity of CBED to CO syimnetry, dynamic simulations using the Bloch wave method were examined to see the difference between the two models. The atomic positions within the unit cells for the two models from RadaeUi etal. are very close to each other. To avoid the possible pseudo-symmetry generated in the Bi-stripe model, dynamic simulations from the CO stmctures described by the Wigner-crystal model and Bistripe model are calculated and compared for the thickness of 300 nm in Figure 15(d) and (e). The difference between the two simulations is that the G-M lines exist in four (303) reflections and 2n +, 0, 0) reflections simulated by the Wigner-crystal model, as they are in the experimental CBED patterns, but do not show up in four (303) reflections simulated by the Bi-stripe model. 

Fig. 14 Left Schematic diagrams of the stripe model (a vertical stripes, bihorizontal stripes). Circles indicate Cu sites in hole-doped stripes, and arrows indicate magnetic moments on undoped Cu sites. Right Simulations of the constant-energy slices using the stripe model [7]. The h and k directions are rotated by tt/4 from the usual directions...

Figure 15 Symmetry identification of iow-temperature charge-ordered Lao.ssCao.eeMnOs. (a) the experimentai CBED pattern from a singie crystai domain in Lao.ssCao.ByMnOs recorded at 99K and aiong the [010] zone axis, (b) schematic illustration of charge ordering models, (c) the line extinction across a series of odd-indexed reflections along the reciprocal 2 direction in the experimental pattern, (d) and (e) Simulated CBED patterns from the CO structures described by the Wigner-crystal and Bi-stripe models (b) for the thickness of 300 nm...

Note that the width of the stripe, modeled by Takeuchi and Fuller (2008), is 10 times less than the width of the shaded domain in Figure 5.31. 

S. R. Lee and J. S. Kim, On the sublimit solution branches of the stripe patterns formed in counterflow diffusion flames by diffusional-thermal instability. Combust. Theory Model. 6(2) 263-278,2002. 

Figure 9.22. Scanning force microscopy images of polyethylene films formed on a model planar chromium polymerization catalyst. The small white stripes are lamellar crystals. These form the well-known spherulite superstructure upon crystallization from the...

A very different model of tubules with tilt variations was developed by Selinger et al.132,186 Instead of thermal fluctuations, these authors consider the possibility of systematic modulations in the molecular tilt direction. The concept of systematic modulations in tubules is motivated by modulated structures in chiral liquid crystals. Bulk chiral liquid crystals form cholesteric phases, with a helical twist in the molecular director, and thin films of chiral smectic-C liquid crystals form striped phases, with periodic arrays of defect lines.176 To determine whether tubules can form analogous structures, these authors generalize the free-energy of Eq. (5) to consider the expression... 

The pattern of protection is shown in Fig. 8. The striped lines show those regions in which amide exchange is retarded by binding. The hatched area is the area predicted from the Poulos model to be solvent accessible. The area predicted by Poulos is indeed protected. However, the protected area also... 

Figure 5. Photograph of a lysozyme model showing the position of antigenic site 3 on the molecule relative to sites 1 and 2. The side chains of the residues comprising the sites are outlined. The residues constituting site 3 are shown as striped areas. This view Is taken by rotating the model 125° anticlockwise on the vertical axis relative to the view shown In Figure 5. From this perspective only parts of site 1 can be seen, which are the residues Lys-13, Arg-5, and Arg-125 (speckled areas). Of site 2, only Trp-62 can be seen (dotted areas). Site 3 showed the same directional preference (Lys-1l6 to Lys-33) toward rabbit and goat antisera.

Fig. 9a and b. Aldoxime-receptor binding model. The maximum contour of the sweet aldoximes is striped. Unflgured is that of the bitter analogs, a The view from the C1 atom to the direction of L-axis. b The view from the upside. 521 (reproduced with permission from the American Chemical Society)... 

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