Anisotropic structure

Left Fig. 8. Schematic illustration of angular-resolved EEL spectra for CNT with anisotropic structure. 

The structural features of most niobium oxychlorides known to-date are summarized in Table 6.1. The use of a combination of chloride and oxide hgands leads to compounds with unique structure types [41], characterized by a remarkable variety of cluster frameworks, ranging from discrete cluster units to chains, layers, and three-dimensional nets, some topologies of which are unprecedented in compounds containing octahedral clusters. Most of the niobium oxychlorides known to date have anisotropic structures (the exceptions are Cs2LuNb,5Cli70 and PbLusNbsClisOg). 

Moriya et al. first demonstrated that anisotropic structure in blends can be generated by applying ac electric fields to solvent-free blends of PEO and PS [60]. A similar morphology transformation induced by electric fields has been detected in PEO/PS/cyclohexane systems [61-63]. During solvent evaporation,... 

This property is readily established from the definition of Fourier transform and convolution. In scattering theory this theorem is the basis of methods for the separation of (particle) size from distortions (Stokes [27], Warren-Averbach [28,29] lattice distortion, Ruland [30-34] misorientation of anisotropic structural entities) of the scattering pattern. 

Rigid Structural Entities. If the initial structure is described by rigid, anisotropic structural entities which are oriented at random, the evolution of anisotropic scattering is readily studied by means of the methods presented in Chap. 9. A practical example is the study of growing orientation in fiber-reinforced materials. 

If the intended evaluation can be carried out on isotropic material, and thus the observed anisotropy is rather an obstacle than an advantage, the fiber pattern can be isotropized (cf. Sect. 8.4.2). This may, in particular, be helpful if lamellar structures are analyzed. If the focus of the study is on the anisotropic structure, the multidimensional CDF (cf. Sect. 8.5.5) may be a suitable tool for analysis. Several studies have demonstrated the power of the CDF method for the study of structure evolution during straining [174,177,181-183],... 

By electromechanical interferometry, it was demonstrated that the anisotropic structure of high-density brush films is clearly reflected on their elastic properties [150]. Changes in the thickness of a graft film induced by an applied electric field (electrostriction) were measured by a Nomarski optical in-... 

Subsequent studies revealed, for the first time, the anisotropic structure of the vortex, and the interactions among vortices that give rise to a well-defined, oriented lattice structure aligned with the crystallographic orientations of 2//-NbSe2 (Hess et al, 1990a). For details, see Hess et al. (1991). 

When an expl is pressed in a die by means of a ram, the friction of the walls tends to cause press and density gradients. In addition, the one-dimensional compression can result in an anisotropic structure and produce pellets with residual strains. Where dimensional stability, uniformity and high density are essential to performance, hydrostatic pressing and isostatic pressing have been used. In both of these processes, the expl is compressed by the action of a fluid, from which it is separated by a rubber (or other elastomer) film... 

Fourier transform infrared spectroscopy (FTIR) was also used to study the anisotropic structure of polyimide films. This work was based on the fact that there are characteristic absorptions associated with in-plane and out-of-plane vibrations of some functional groups, such as the carbonyl doublet absorption bands at 1700-1800 cm . The origin of this doublet has been attributed to the in-phase (symmetrical stretching) and out-of-phase (asymmetrical stretching) coupled... 

Above it was pointed out that in unmixed rare gases binary absorption does not exist because of the inversion symmetry of like pairs. For like molecular pairs inversion symmetry does in general not exist because of the anisotropic structure and vibrational excitations of the individual molecules. In Chapter 5, we will show that in pure hydrogen gas, for example, the translational spectrum arises mainly from orientational ( magnetic ) transitions the translational spectrum of H2-H2 is discernible in Fig. 3.10 at low frequencies (0 < v < 250 cm-1). The translational peak is weak if compared to the strong So(J) lines near 354 and 587 cm-1, but its strength is comparable to those of the dissimilar rare gas pairs, Fig. 3.1. The translational H2-He pair spectra are somewhat stronger, Fig. 3.12,... 

Hollow fiber membranes are primarily homogeneous. In use, their lower permeability is compensated for by large surface per unit volume of vessel. Fibers are 25-250 pm outside dia, wall thickness 5-50 pm. The cross section of a vessel for reverse osmosis may have 20-35 million fibers/sqft and a surface of 5500-9000 sqft/cuft of vessel. Recently developed hollow fibers for gas permeation processes have anisotropic structures. 

The membrane cast from chloroform-formic acid mixtures had an anisotropic structure with a 0.9-1.2 p active layer and a 40 p porous support layer. At a water flux of 139 1/m2 day (kg/cm2 at 20 °C), the membrane showed 99.4 % rejection of cytochrome C and 72.7% of Vitamine B12. At 3980 1/m2 day water flux level, the rejection for bovine serum hemoglobin (MW, 66000 68000), cytochrome C, and Vitamine Bl2 were, 95.6, 79.4, and 39.8%, respectively. 

Nonporous, dense membranes consist of a dense film through which permeants are transported by diffusion under the driving force of a pressure, concentration, or electrical potential gradient. The separation of various components of a mixture is related directly to their relative transport rate within the membrane, which is determined by their diffusivity and solubility in the membrane material. Thus, nonporous, dense membranes can separate permeants of similar size if their concentration in the membrane material (that is, their solubility) differs significantly. Most gas separation, pervaporation, and reverse osmosis membranes use dense membranes to perform the separation. Usually these membranes have an anisotropic structure to improve the flux. 

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