Isotropic anisotropic

The flux of F radicals to tire wafer is nearly isotropic. Anisotropic etching is due to ions tliat are incident on tire wafer essentially perjDendicular to tire surface (see above). 

Fourier transformed to yield a ID isotropic spectrum. Alternatively, the isotropic echoes can be extracted and arranged in ID or 2D arrays, leading to ID DOR-like or 2D isotropic-anisotropic correlation spectra. The STARTMAS method is, however, quite sensitive to pulse imperfections and misadjustments, and unfortunately does not apply to spin I > 3/2 because the k ratio is negative in that case [202],... 

Bianchi et al. (19) spun fibers from isotropic and anisotropic solutions of cellulose (D.P. 290) in LiCl (7.8%)-DMAC solutions. The fiber mechanical properties increased throimh the isotropic-anisotropic transition with elastic moduli as high as 22 GPa (161 g/d) being obtained. 

The ternary phase diagram shown in Fig. 9b for the schizophyllan-water system has two more phase regions the isotropic-anisotropic (cholesteric)-anisotropic triphasic region (IAA) and the anisotropic-anisotropic biphasic region (AA). This was the first observation of the complex phase diagram as had been predicted by Abe and Flory, but the diagram quantitatively departs from their prediction in the positions and sizes of the regions [76]. 

Mesoporous dp = 2. .. 50 nm Carrier in liquid Affinity ligand in solid matrix anisotropic, isotropic track-etched immobilized in isotropic porous membrane isotropic, anisotropic Dialysis Carrier-mediated separation Ultrafiltration Electro- ultrafiltration... 

Figure 43 (A) 3D 31P 27Al MQMAS pulse sequence and (B) spectrum providing isotropic/anisotropic and bonding characterisation of the Al-O-P...

The changes undergone by US on interacting with a solid, and the information that can thus be obtained from the solid, have been measured mainly through the US velocity and attenuation under resonant conditions. The ultrasonic parameters to be used and their processing are dictated by the final information required. Thus, the resistance to deformation is obtained by calculating the elastic moduli, the number and nature of which are a function of the nature of the solid (e.g. isotropic, anisotropic). However, equations relating the acoustic measurement to sample density, dimensions, material microstructure and thickness can usually be derived from simple parameters such as US velocity... 

Sluckin adopted a quasi-equilibrium thermodynamic approach to understanding the effect of a strain rate field on the isotropic-anisotropic transition in polymer solutions. He derived a Clausius-Clapeyron-like equation which connects the shift in the critical polymer mole fraction C, and Cj, which are concentrations of isotropic and nematic phases, respectively, to the applied strain rate. 

The presence of anisotropic interactions in solids leads to a greater variety of 2D sequences. One of the simplest is the isotropic/anisotropic correlation, where high resolution is achieved in one dimension while preserving anisotropic information in the second dimension. The dipshift and J-resolved experiments correlate isotropic chemical shift with dipolar and J-coupling information respectively. In these sequences the... 

Such cross-polarisation procedures to enhance the signal intensity of Si are expected to be of use in making two-dimensional isotropic-anisotropic correlation spectroscopy more accessible to systems without protons. 

Identification of many particles and aerosols can be made using direct microscopic examination coupled with a knowledge of the collection circumstances. Particle features such as transparent/opaque, colorless/colored, rounded/angular, isotropic/anisotropic, density, and refractive index may all be determined in this way. When these properties are combined with the... 

Poly(2,5-di-n-dodecyl-l,4-phenylene) of 73000-94000 show a single anisotropic liquid crystalline mesophase in the molten state and macromolecules with Mw 44000—73000 gave coexisting isotropic/anisotropic phases [17]. 

In one study, a model for elastin, the main protein that confers elasticity on solid structures in mammals, had its mobility investigated by examining 1H-13C and 1H dipolar couplings extracted from isotropic-anisotropic correlation experiments.29 The elastic properties of elastin are almost certainly conferred by molecular degrees of freedom, so such studies are important in understanding how this material works in Nature. The motional amplitudes determined from these experiments were found to depend upon the degree of hydration, with the mean square fluctuation angles found to be 11-18° in the dry protein and 16-21° in the 20% hydrated protein. 

We have seen that it can be difficult to reach the critical concentration required to observe an isotropic-anisotropic transition because concentrated suspensions of colloids are not always stable. However, orientation of flexible polymers as well as of anisotropic particles in suspension can be induced by flow, a phenomenon that has long been observed, reported, and studied. This phenomenon is especially strong when a pretransitional effect exists, which can be easily observed by the naked eye on a sample that is shaken between crossed polarizers (see for example the section on clays). In these systems, birefringence is induced via mechanical forces, like the shear stresses in a laminar flow ( Maxwell-dy-namo-optic effect ). 

Furthermore with free-space methods, broadband characterisation under various incident angles, polarisations and temperature conditions can be made on isotropic, anisotropic or bi-anisotropic materials. 

Isotropic Isotropic Anisotropic Anisotropic Anisotropic Anisotropic Isotropic (upper) Isotropic (upper)... 

Fig. 9. Two-dimensional isotropic-anisotropic chemical shift conelation spectrum of L-tyrosine, showing the isotropic projection and the assignment of the peaks to each site in the molecule. A set of 6S sign were digitized at rates of 12 kHz over a range of angles. Experimental data were then interptdated over a regular grid ctnnpos of 128 X 256 points and Fourier transformed. (Adapted with permission from Frydman et al. )...

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