Reflection layered structure

Figure 15. Arrangement of the Mn - O layers and separating sheets according to Giovanoli [3]. The layer structure can be (a) completely ordered or (d) completely disordered (turbostratic disorder). The cases (h) and (c) represent situation between the two extremes, (b) Disorder of the interlayer atoms or molecules but an ordered stacking of the Mn - O layers with constant layer distance, (c) Disorder of the interlayer atoms and an incommensurate shift of the complete Mn - O sheet within the layer plane, resulting in an incommensurate superstructure along the r -direction (perpendicular to the layer) and in a diffuse distribution of the electron density in this layer, resulting in a lower contribution of this layer to the 0 0 / reflections. (Adapted from Ref. [47]).

In situ Fourier transform infrared and in situ infrared reflection spectroscopies have been used to study the electrical double layer structure and adsorption of various species at low-index single-crystal faces of Au, Pt, and other electrodes.206"210 It has been shown that if the ions in the solution have vibrational bands, it is possible to relate their excess density to the experimentally observed surface. 

Smectic phases are more highly ordered than nematic phases, and with an ordering of the molecules into layers. There are a number of different smectic phases which reflect differing degree of ordering. Crystal smectic phases are characterised by the appearance of inter-layer structural correlations and may in some cases be accompanied by a loss of molecular rotational freedom. 

The flexibility of polyoxovanadate species [VxOy]" to adopt a wide variety of structural configurations, such as rings, chains, and layers, is reflected in their predominance in a wide variety of hybrid solids. For example, approximately sixteen distinct hybrid vanadium oxides based solely on V205 layers, with about nine different layer types, have currently been synthesized [34—47]. Layered structures of... 

A breakthrough came in 1988 when Hamada et al. demonstrated that a dye layer with a relatively low optical absorbance and high reflectance at the recording wavelength could be interposed between the substrate and reflecting layer of a CD-ROM type structure, and, with appropriate optimization of the optical properties, this would record and reproduce in accordance... 

The reflection spectrum of the atmosphere is a measure of the albedo of the planet (Figure 10.4) and, despite the strong methane absorption in the red, Titan s disc looks orange principally due to scatter from the surface of dense methane-hydrocarbon clouds. Scatter from aerosol particles within the thick clouds obscures the surface of the moon although the radar analysis reveals considerable Chapman layer structure within the atmosphere and some interesting surface features. 

Evidence for a layered structure is provided by X-ray reflection. For the oxide film present at point A in Fig. 5.4, a thickness of 10.8 nm and a density of 2.1 gcnT3 has been determined. While the film present at point B shows an angular reflectance that could best be fitted assuming a double layer structure with a thin (2.9 nm), dense (2.1 g cm-3) oxide at the silicon interface and a thick (10.2 nm), less dense (1.75 g cm-3) oxide on top. The density value found for the top oxide is in good agreement with density values obtained for thick (100 nm) anodic oxides using gravimetric methods. 

Figure 1. Schematic view of the one-dimensional layered structure. The vertical lines denote discontinuities of refractive index distribution. The monochromatic plane wave is incident in the y direction with the electric field amplitude The amplitudes of reflected and transmitted waves are ref and, respectively.

Time-resolved techniques are very powerful for examining structures where the useful information is contained in the normally reflected signal. Frequency analysis of a reflected broadband signal can also be used for film characterization (Wang and Tsai 1984 Lee et al. 1985). But in many other problems, especially in materials science, there is a great deal of information contained in the way that the coefficient of reflection changes with angle of incidence. It is therefore important to understand the behaviour of the reflectance function R(d) of a layered structure. 

The elasticity of the protein layer structure is supposed to act against the tendency of an emulsion or foam to collapse because it allows the stretching of the interface. This behaviour is most commonly observed for globular proteins, which adsorb, partially unfold, and then develop attractive protein-protein interactions (Dickinson, 1999a Wilde, 2000 Wilde et al., 2004). The strength of such an adsorbed layer, reflected in the value of the elastic modulus, and the stress at which the structure breaks down, can be successfully correlated with stability of protein-based emulsions and (more especially) protein-based foams (Hailing, 1981 Mitchell, 1986 Izmailova et al., 1999 Dickinson, 1999a). 

Figure 2 illustrates the X-ray powder diffraction patterns for the as -synthesized and the calcined heterostructures. Both diffraction patterns show a 001 reflection indicating the presence of a layered structure with a basal spacing 36.8 A respectively 32.9 A. However, a decrease of 4 A in the gallery height, along with a small loss of crystallinity, can be observed upon calcination. 

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